Climate Monitoring and 

Diagnostics Laboratory 

No. 22 

Summary Report 1993 

U.S. DEPARTMENT 

OF COMMERCE 

NATIONAL 

OCEANIC AND 

ATMOSPHERIC 

ADMINISTRATION 

ENVIRONMENTAL 

RESEARCH 

LABORATORIES 
Climate Monitoring 

and Diagnostics Laboratory 

No. 22 

Summary Report 1993 

James T. Peterson, Editor 

Rita M. Rosson, Assistant Editor 

Boulder, Colorado 

December 1994 

U.S. DEPARTMENT OF COMMERCE 

Ronald H. Brown, Secretary 

National Oceanic and Atmospheric Administration 

D. James Baker, Under Secretary for Oceans and Atmosphere/Administrator 

Environmental Research Laboratories 

James L. Rasmussen, Director 
NOTICE 

Mention of a commercial company or product does not constitute an endorsement by NOAA Environmental 

Research Laboratories. Use for publicity or advenising purposes of information from this publication concerning 

proprietary products or the tests of such products is not authorized. 

For sale by the National Technical Information Service, 5285 Pon Royal Road 

Springfield, VA 22161 

tt 
Contents 

CMDL Organization, 1993 ............................................................................................................................... v1 

CMDL Staff, 1993 ............................................................................................................................................ vii 

CMDL Station Information .... ................................. .......................................................................................... v111 

Preface ............................................................................................................................................................. ix 

1. Observatory Operations Division ................................................................................................................ 1 

1.1 . Maun a Loa . ... .... ... . ... . .. .. .. . . . . ... ...... ............ .. ... .. . .. . . .. . .. ... . ... .. . .......... .. ... .. . .. . . . .. . . . . . .. .. .... .... .. . .. . . . ... .. . . . . .. 1 

1.1.1. Operations . . ... .. . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .. . . .. . . . . . .. . . . . .. .. . .. . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . .. .. . .. . .. .. . 1 

1.1.2. Programs .... ..................................................................................................................... ...... 1 

1.2. Barrow .............................................................................................................................................. 8 

1.2.1. Operations .. .... ...... ... ........................ ... .. . .. .. .. . ...... ... ... ..... .... ... .... .. ... . ... .. . . ... ...... ....... .. . . . . .. .. . .. .. . 8 

1.2.2. Programs .... .... ...... ... .. ....................... .. ....... .. . .. .. .. ... ... ..... ... . ... .... .. ... . ... . . . . . .. .. .... ... ... . ... .. . .. ... . . . .. 8 

1.3. Samoa............................................................................................................................................... 11 

1.3.1. Operations .. .... ....................................................................................................................... 11 

1.3.2. Programs ............................................................................................................................... 11 

1.4. South Pole ................................................................................ ...... ............. .. ................................... 14 

1.4 .1. Operations .. .... ....... .. . ... .. .. .... ............ ... . .. .. . .. . .. .. ... . .. . .. . .... ... .. . .. ... . . . .. . .. . .. . . . . . . .. . .. . .. . .. . . .. . . . . . . . . . . . . . 14 

1.4 .2. Programs . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

1.5. Reference .............. ........................................................... ............................................... ................. 15 

2. Carbon Cycle Division................................................................................................................................ 18 

2. 1. Continuing Programs . ..... ...... .. ...... ........... .. . ... .. . .. .. . . .. . . ... . . . .. . .. ... ... ..... ... . . . . .. ... .. . . .. . . . ..... .. . . . .. . . . . . . . .. . . . . . . 18 

2. 1.1. In Situ Carbon Dioxide Measurements ..... ............................................................................. 18 

2. 1.2. Flask Sample Carbon Dioxide Measurements ........ ................... ...... .................................. ... .. 19 

2. 1.3. In Situ Methane Measurements ........................................................................................... .. 20 

2.1.4. Flask Measurements of Methane ........................................................................................... 22 

2.1.5. In Situ Carbon Monoxide Measurements................................................................................ 24 

2.1.6. Flask Measurements of Carbon Monoxide.............................................................................. 25 

2.1 .7. CO Standards................................................................. ........................................................ 26 

2.1.8. New Air Srunpling System ........................ ............................................................................. 26 

2. 1.9. Aircraft Project . .. .. .. . ... . ... . .. ... . .. . .. ... .. . . . ... ... . . ... .. ... . .. ... ........ .. . .. .. . .. . ... . . . . .. . . .. ... . . . ... ... . . . . . .. . . .. . . . . .. 26 

2. 1.10. Tall Towers Program........................................... ............................... ... ................................. 27 

2.2. References ........................................................................................................................................ 30 

3. Aerosols, Radiation, Ozone, and Water Vapor Division.............................................................................. 31 

3. 1. Continuing Programs . ....................................................................................................................... 31 

3.1.1. Surface Aerosols .................................................................................................................... 31 

3.1.2. Lidar Observations of Aerosols .............................................................................................. 36 

3.1.3. Total Ozone Observations...................................................................................................... 36 

3.1.4. Validation of Satellite Insrument Ozone Data......................................................................... 40 

3.1.5. Umkehr Observations............................................................................................................. 40 

3 .1.6. Calibration of CMDL Dobson Spectrophotometers ... .. ... ... ... ..... ... ... .............. ... .. ... .. .. .. ...... ... .. 40 

3.1 .7. Tropospheric Ozone ....... ......................................................................................................... 41 

3.1.8. Ozonesonde Observations...................................................................................................... 42 

3. 1.9. Stratospheric Water Vapor..................................................................................................... 44 

3. 1.10. Surface Radiation................................ ................................................................................... 45 

3 .1.11 . Solar Radiation Facility .. ... . .. ... ... .. . ... .. .. .... .. .. .. .. .. ... ... .. .. . ... ... ........... .. ... .. . .. . . . . ... . . .. . . .. . . . .. . .. . .. .. . 4 7 

3.2. Special Projects .............................................. ................... ......................... .............. .. .. .. ........... .. . ... .. 48 

3.2.1. An Analysis of 10-Day Isentropic Flow Patterns for Barrow, Alaska: 1985-1992 ................... 48 

3.2.2. Aerosol Measurements at MLO During MLOPEX .......................... ....................................... 49 

3.2.3. Water Vapor and Ozone Profiles Over the Tropical Pacific During CEPEX ........................... 54 

3.3. References ................................................................................................. ....................................... 55 

111 
4. Acquisition and Data Management Division ........................................................................................... ... 57 

4.1. Continuing Prograrns ..................................................................................................................... ... 57 

4.1.1. Station Climatology ................................................................ ........................................... ... 57 

4.1.2. Data Management .............................................................................................................. ... 65 

4.2. Special Project: Boundary Wind and Temperature Study at MLO, 1992-1993 ............................... ... 65 

4.3. References ........................................................................................................................................ 71 

5. Nitrous Oxide and Halocarbons Division.................................................................................................... 72 

5. 1. Continuing Prograrns ........................................................................................................................ 72 

5.1. 1. Flask Sarnples ...................................................................................... .. ....................... ........ 72 

5.1.2. RITS Continuous Gas Chromatograph Systems...................................................................... 73 

5.1.3. Low Electron Attachment Potential Species (LEAPS)............................................................ 74 

5.1.4. Alternative Halocarbon Measurements................................................................................... 75 

5.1.5. Gravimetric Standards............................................................................................................ 81 

5.2. Special Projects ................................................................................................................................ 83 

5.2. 1. Aircraft Project: Stratospheric Photochemistry, Aerosols, and 

Dynarnics Expedition (SPADE)........................................................................................... 83 

5.2.2. Automated Four-Channel Field Gas Chromatographs............................................................. 88 

5.3. References .............................................................................................................................. ...... .... 90 

6. Cooperative Prograrns ................................................................................................................................ 92 

Evaluation of Arctic Meteorological Buoys 

G.F. Appell............................................................................................................................ 92 

Global Precipitation Chemistry Program Measurements at Mauna Loa Observatory 

R.S. Artz, W.C. Keene, and J.N. Galloway.............................................................................. 94 

Global Atrnosphesric 02'N2 Measurements from Isotope Ratio Mass Spectrometer Analysis 

M.L. Bender, J.T. Ellis, and M.O. Battle............................................................................... . 95 

Latitudinal Profiles of Selected Trace Gases 

D.R. Blake and F.S. Rowland................................................................................................. 97 

Antarctic UV Spectroradiometer Monitoring Prograrn: Contrasts in UV Irradiance 

at the South Pole and Barrow, Alaska 

C.R. Booth, T .B. Lucas, J.R. Tusson JV, J.H. Morrow, and T. Mastechkina ............................ 98 

Exarnination of the Mauna Loa Roberston-Berger Meter Data For Calibration Inconsistencies 

J. DeLuisi. .... . .... .. .. .... .. .. .. . .. .. .. . .. . .. .. . .. . .. . .. .... . .. . .. .. .. .. . .. . .. . .. .. . .. .. . .. . . . .. . . .. .. . .. .. . .. . . . .. .. .. .. .. .. . .. .. . .. . . 101 

Comparison of Mauna Loa Observatory and Hilo Radiosonde Meteoroogcial Measurements 

E.Foltz.................................................................................................................................. 103 

lntercomparison of Stable Isotope Measurements of C02 

RJ. Francey, C.E. Allison, L.P. Steele, RL. Langenfelds, ED. Welch, J.W.C. White, 

M. Tro/ier, P.P. Tans, and K.A. Masarie ........................................................................... 106 

Barrow, The Westernmost Magnetometer Site in the STEP Polar Network 

K. Hayashi............................................................................................................................. 111 

Total Nitrate Variation at Mauna Loa 

BJ. Huebert and J.A. Heath................................................................................................... 112 

Trends of CO at Hawaii: Seasonal Cycles and Decreasing Concentrations 

M.A.K. Khalil and RA. Rasmussen........................................................................................ 114 

Radioactivity in the Surface Air at BRW, MLO, SMO, and SPO during 1993 

RJ. Larsen and C.G. Sanderson............................................................................................. 118 

Exposure Experiment, South Pole 

J.E. Mak, C.A.M. Brenninkmeijer, and J.R. Southon ........................................................ ...... 120 

Correlations in Short-Term Variations in Atmospheric Oxygen and Carbon Dioxide 

at Mauna Loa Observatory 

A.C. Manning and R.F. Keeling ............................................................................................. 121 

iv 
Artificial Windshielding of Precipitation Gauges in the Arctic 

R.J. McClure .......................................................................................................................... 124 

Lidar Measurements of Stratospheric Ozone, Temperature, and Aerosol Profiles al 

MaunaLoa 

l.S. McDermid, M. Schmoe, E.W. Sirko, and T.D. Walsh........................................................ 125 

Strontium-90 Deposition at SMO and MLO Through 1990 

M. Monetti .. ... .. ... .. . ... ..... ........... ......... ... . ... .. . .. .... ..... .. . ..... .. ...... ... .. . .. ... .. . . . .. . .. .. . . .. . .... . .. . .. . . .. ... . . 128 

Results from the Mauna Loa Ultrahigh Resolution Infrared Solar Spectrometer 

F .J. Murcray, S.J. David, R.D. Blatherwick, D.G. Murcray, and A. Goldman .. ...................... 130 

UV-B Optical Depths al Mauna Loa: Relative Contribution of Ozone and Aerosols 

P .J. Neale, DL. Correll, V.R. Goodrich, and D.R. Hayes, Jr. ................................................ 132 

Advanced Global Atmospheric Gases Experiment (AGAGE) 

R.G. Prinn, R.F. Weiss, F N. Alyea, D.M. Cunnold, P.J. Fraser, 

L.P. Steele, and P.G. Simonds.......................................................................................... 135 

The I3C/I2C of Atmospheric Methane 

P. Quay, J. Stutsman, and D. Wilbur.... .................................................................................. 137 

Point Barrow Geomagnetic Observatory 

J.F. Scarzello ...... .. . ... ... .. .. ... . .. ........... ... .... . . .. . .. ... .. .. ... . ..... . ... ... . .. . . .. . .. .. ... . . . .. ... .. . ... .... .. . . . . . . . . .. . . . 139 

USGS Barrow Observatory 

J. Townshend............... .......................................................................................................... 140 

A New Rugged dHigh Sensitivity Radon Monitor for Remote Stations 

S. Whittlestone and S. Ryan............................ ........................................................................ 141 

7. International Activities, 1993 ..................................................................................................................... 144 

8. Publications and Presentations by CMDL Staff, 1993 ................................................................................ 146 

9. Acronyms and Abbreviations ..................................................................................................................... 150 

v 
CMDL Organization, 1993 

The CMDL organization structure features five divisions organized 

according to scientific discipline as follows: (1) Carbon Cycle; (2) Nitrous 

Oxide and Halocarbons; (3) Aerosols, Radiation, Ozone and Water Vapor; 

(4) Acquisition and Data Management; and (5) Observatory Operations. 

The Office of the Director includes administrative and special project staff. 

At the end of 1993 , the laboratory staff consisted of 47 civil service 

personnel (excluding part-time student assistants). 30 CIRES/University of 

Colorado personne l, and two NOAA Corps officers as wen as severa l 

visitors and people on special appointments. 

Director, CMDL 

Dr. Eldon E. Ferguson 

(303) 497-6966 

Chief Scientist Deputy Director Administrative Officer 

Dr. David Hofmann Dr. James T. Peterson Ms. Donna J. Leise 

(303) 497-6663 (303) 497-6668 (303) 497-6070 

I I 

Carbon Cycle Nitrous Oxide and 

Halocarbons 

Dr. Pieter Tans 

(303) 497-6678 Dr. James W. Elkins 

(303) 497-6224 

I I 

Aerosols, Radiation, Observatory Operations Acquisition and Data 

Ozone, and Water Vapor Management 

Dr. David Hofmann Mr. Bernard G. Mendonca Mr. Gary A. Herbert 

(303) 497-6663 (303) 497-6733 (303) 497-6842 

Barrow Observatory 

/ 

Mauna Loa Observatory Samoa Observatory 

~ South Pole Observatory 

Mr. Daniel J. Endres Dr. Russell C. Schnell Mr. Mark A. Winey Lt. Katharine A. McNitt 

(907) 852-6500 (808) 961-3788 (684) 622-7455 (303) 497-6650 

vi 
Director's Office 

Eldon Ferguson, Director 

James T. Peterson, Deputy Director 

Donna Leise, Administrative Officer 

Sandra Howe, Administrative Assistant 

Carole Brandes, Secretary 

Rita Rosson, Editorial Assistant 

Denise Theede, Program Support Technician 

Special Projects 

Shuji Aoki, Visiting Scientist 

Howard Bridgman, Visiting Scientist 

Xing Sheng Li, Visiting Scientist 

Craig Quincy, Contractor 

Patrick Sheridan, CIRES 

Aerosols, Radiation, Ozone & \Vater 

Vapor Division 

David Hofmann, Chief 

Jill Foose, Secretary 

Jennifer Barnett, Physical Science Aid 

Barry Bodha ine, Meteorologist 

Paul Chilson , Physical Science Aid 

Mark Clark, C!RES 

John DeLuisi, Meteorologist 

Scan Dougherty, Physical Science Aid 

Ellswonh Dutton, Meteorologist 

Robert Evans, CIRES 

Douglas Garcia, Summer Aid 

Jason Gingerich, Physical Science Aid 

Helena Gonzalez-Jorge, Guest Worker 

Jason Gump, ClRES Student 

Robert Grass, CIRES 

Rudy Haas, Mathematician 

Bradley llaltcr, ClRES 

Joyce Harris, Physical Scientist 

Gloria Koenig, Physical Scientist 

Walter Komhyr, CIRES 

Thomas Kotsines, Engineering Technician 

Jeffrey Lathrop, Physical Scientist 

Kent Leonard, CIRES 

David Longenecker, CIRES 

Charles Myers, Engineering Aid 

Donald Nelson, Meteorologist 

John Ogren, Physical Scientist 

Samuel Olunans, Physicist 

Micheal O'Neill, CfRES 

Greg Orleans, Phyical Science Aid 

Gina Palmer, Physical Science Aid 

forank Polacek, Ill, Engineering Technician 

Dorothy Quincy, CIRES 

Scott Sanberg, Electronic Technician 

CMDL Staff, 1993 

Herman Sievering, Guest Worker 

Robert Stone, CIRES 

David Theisen, Physical Science Aid 

Holger Vllmel, CIRES 

Byron Wells, Physical Science Aid 

James Wendell, Electronic Technician 

Atmospheric Radiation Monitoring 

Division 

Gary Herbert, Chief 

Linda (Craig) Sachetti , Secretary 

Mark Bieniulis, CIRES 

Thomas Mefford, CIRES 

Kenneth Thaut, Electronic Technician 

Carbon Cycle Division 

Pieter Tans, Chief 

Debra Hansen , Secretary 

Peter Bakwin, Physicist 

Phillipe Ciais, NRC 

Thomas Conway, Research Chemist 

Wyatt Coy, ClRES 

Mario DiCino, Physical Science Aid 

Ed Dlugokencky, Research Chemist 

Laurie Geller, CIRES Student 

Douglas Guenther, ClRES 

Korie Handwerger, CIRES Student 

Duane Kitzis, CIRES 

Patricia Lang, Physical Scientist 

Lisa Lindstrom, CfRES Student 

Kenneth Masarie, CIRES 

Mark Ohan, CIRES Student 

Paul Novelli, CIRES 

Zhiqing Shao, Visiting Scientist 

Norman Siner, Physical Science A id 

Michael Stavish, CO-OP 

Kirk Thoning, Physicist 

Michael Trolier, INSTAAR 

Aaron Troyer, CIRES Student 

Jennifer Vaughan, CIRES Student 

Lee Waterman, Research Chemist 

Ni Zhang, CIRES 

Conglong Zhao, CIRES 

Nitrous Oxide and Halocarbons Division 

James Elkins, Chief 

Debra Hansen, Secretary 

Hans Auer, CIRES Student 

Thomas Baring, CIRES 

Diana Barnes, Guest Worker 

James Butler, Research Chemist 

Scou Cummings, CIRES 

vii 

Jeannie Dolan, C.U. Work Study 

Geoffrey Dutton, CllU:S 

Fahim Ghafoori, C.U. Work Study 

Jonathan Gilligan, CIRES 

Arnold Hayden, CIRES Student 

Dale Hurst, NRC Associate 

Bryan Jordan, C.U. Work Study 

Kristen Kauffman, C.U. Work Study 

Jilrgen Lobert, CIRES 

Loreen Lock, C.U. Work Study 

Angelo Madonna, Physical Science Aid 

Steve Montzka , Research Chemist 

Richard Myers, Physical Science 

Technician 

Phuong Nguyen, CIRES Student 

Matthew Nowick, CIRES Student 

William Sturges, CIRES 

Thomas Swanson, CIRES 

Thayne Thompson, Physicist 

Joshua Trought, CCI-IE Student 

Jennifer Vaughn, C.U. Work Study 

Michael Volk, CIRES 

Observatory Operations Division 

Bernard Mendonca, Chief 

I .inda (Craig) Sachetti . Secretary 

Daniel Endres, Station Chief, n arrow 

Bradley llalter, Physical Scientist 

Russell Schnell, Director, Mauna Loa 

Judith Pereira, Program Support Technician 

John Dams, Physical Scientist 

John Chin, Physicist 

Thomas Defooor, Electronic Engineer 

Melody Keaunui, Clerk 

Darryl Kuniyuki, Electronic Engineer 

Steven Ryan, Physical Scientist 

Robert Uchida, Electronic Technician 

Alice Wall, Physical Science Aid 

Alan Yoshinaga, Chemist 

Carl Farmer, Station Chief, Samoa 

Mark \Viney, Electronic Engineer/Staiton Chief 

Dale Tysor, :\OAA Corps, South Pole 

Katherine, McNitt, NOAA Corps 

Raymond Dunn, Electronic Engineer 

Carl Groeneveld, :\OAA Corps 

Thomas Jacobs, :\OAA Corps 

Donald Neff, Physicist 
Name: 

Latitude: 

Longitude: 

Elevation: 

Time Zone: 

Office Hours: 

Telephone 

Office hours: 

Fax: 

Postal Address: 

Commerce 

Observatory 

Freight Address: 

Commerce 

Name: 

Latitude: 

Longitude: 

Elevation: 

Time Zone: 

Office Hours: 

Telephone: 

Office hours: 

CMDL Boulder 

After hours: 

Fax: 

Postal Address: 

Freight Address: 

CMDL Station Information 

Barrow (BRW) Mauna Loa (MLO) 

71.323 19.539 

156.609 155.578 

8 m 3397 m 

GMT -9 GMT-10 

8:00 am-5:00 pm 8:00 am-5:00 pm 

(907) 852-6500 (808) 961-3788 

(907) 852-4622 (808) 961-3789 

Officer in Charge U.S. Dept. of 

NOAA/ERL/CMDL NOAA - Mauna Loa 

Pouch 8888 P.O. Box 275 

Barrow, AK 99723 Hilo, HI 96720 

Same as above U.S. Dept. of 

NOAA - Mauna Loa Observatory 

154 Waianuenue Ave. 

Hilo, HI 96720 

Samoa (SMO) 

-14.232 

170.563 

77m 

GMT-11 

8:00 am-5:00 pm 

0 11 (684) 622-7455 

011 (684) 699-9953 

011 (684) 699-4440 

South Pole (SPO) 

-89.997 

-102.0 

2841 m 

GMT + 12 

8:00 am - 5:00 pm 

Rel ayed through 

U.S. Dept. of Commerce Officer in Charge 

NOAA - CMDL Samoa Observatory 

Pago Pago, American Samoa 96799 

PSC 468 Box 402 

FPO AP 96598-5402 

Same as above Same as above 

viii 

NOAA/CMDL Clean Air Facility S-257 

South Pole, Antarctica 
Preface 

This report presents the major accomplishments of the National Oceanic and Atmospheric 

Administration/Climate Monitoring and Diagnostics Laboratory (NOAA/CMDL) for calendar year 

1993. This is the 22nd consecutive annual report issued by this organization and its ARL/GMCC 

predecessor since formation in 1972. 

CMDL is located in Boulder, Colorado, with observatories at Barrow, Alaska; Mauna Loa, 

Hawaii; Cape Matatula, American Samoa; and South Pole, Antarctica. It is one of twelve 

components of the Environmental Research Laboratories within NOAA 's Office of Oceanic and 

Atmospheric Research. The collected plans and accomplishments of all Environmental Research 

Laboratories are jointly published in two separate volumes: the ERL Programs and Plans document 

and the ERL Publication Abstracts. This CMDL document supplements the two ERL publications 

by providing a more detailed view of the CMDL programs during 1993. 

This report is organized into six major sections: Observatory Operations; Carbon Cycle 

Division; Aerosol, Radiation, Ozone, and Water Vapor Division; Acquisition and Data Management 

Division; Nitrous Oxide and Halocarbons Division; and Cooperative Programs. The body of the 

report is followed by a list of Publications and Presentations of CMDL personnel for 1993. 

Inquires and/or comments are welcomed and should be addressed to: 

Director, R/E/CG 

Climate Monitoring and Diagnostics Laboratory 

U.S. Department of Commerce/NOAA 

325 Broadway 

Boulder, Colorado 80303-3328 

(303) 497-6074 

ix 

1. Observatory Operations Division 

1.1. MAUNA LOA OBSERVATORY 

R.C. SCHNELL 

1.1.1. OPERATIONS 

MLO is undergoing an evolution in data gathering and 

data transmission brought on by the availability of 

inexpensive and reliable PCs and the Internet. In 1993 

MLO continued the process of expanding the number of 

measurements accessible in essentially real time via 

Internet and/or telephone modems. With the planned 

connec tion of the carbon cycle measurements to Internet 

in late 1994 and the halocarbons in 1995, the process 

will be near completion. Thus, by the end of 1995 all 

the continuous, automatic MLO measurements will be 

monitored (and in some cases, instruments adjusted) by 

Pls from their office computers wherever in the world 

they may be. Because of this movement to PC-based 

data monitoring systems at MLO, the venerable CAMS 

units are being replaced. With the upgrading of the 

carbon cycle C02 systems, the CAMS era at MLO will 

come to an end. 

Early in the year, the MLO outdoor electrical upgrade 

was completed and accepted coincident with a major 

upgrade of Hawaiian Electric's Hawaii Island generating 

capacity. Together, these new facilities reduced the 

number of power interruptions at MLO from 25 in January 

to 2 in February. Power problems were thought to be bad 

memories until July 24 when a lightning strike traveled 

backward through the now well-grounded MLO system and 

burned out about a dozen instruments. On a positive note, 

the breakers on the hot side worked in this lightning strike. 

The situation is now being monitored and isolating some 

sections of the grounding network should lightning damage 

occur again may be considered. 

A major staff change occurred in June when the 

electronic engineer, who ran the MLO lidar program for 

13 years, moved to a management position with the 

NOAA Space Environment Laboratory in Boulder. He 

was replaced in July by a physical scientist from the 

University of Michigan, Ann Arbor, in a smooth 

transition. 

The JPL ozone lidar me asurement system (part of the 

NDSC program) arrived on site in July in two 13-m (40 

ft) trailers that were installed on a cement pad 

immediately east of the AEC building. The lidar is 

operated by one of a rotating crew of three from JPL, 

Pasadena, California, who spend 3-4 weeks per shift in 

Hawaii. The JPL lidar group works closely with the 

NOAA lidar group in conducting coincident aerosol and 

temperature profiles. The JPL ozone profiles are 

compared with the weekly MLO ozonesonde profiles 

with generally excell ent agreement. 

Electrical power with 14 separate circuits (including 

2 RV and 2 at 220 V) has been installed at the base of 

the Cape Kumukahi lighthouse tower, and four air lines 

run to the top of the 18-m (60-ft) tower. Air Cadet 

pumps (one of which is pumping continuously) are 

mounted under a movable metal cover at the tower base 

and are used for the URI and SIO oxygen flask sampling 

programs. A 15 m x 15 m fenced enclosure is planned 

for construction just south of the tower to protect 

trailers and containers brought to Cape Kumukahi for 

future marine boundary layer measurement programs. 

Through an arrangement with Western Pacific 

Communications, Hilo, a radio telephone transceiver 

station was installed at MLO. This prov ides MLO, JPL, 

and· HAO vehicles with uninterrupted telephone 

communications on the Saddle and Observatory Roads, 

including the portion of the Saddle Road down to the 

Kona Coast. This communication link will be a 

valuable safety asset during the NDSC building 

construction phase. 

The transfer of the NDSC land from the state of 

Hawaii to NOAA was approved by the Department of 

Land and Natural Resources. Complete and cl ear title 

to the 4-acre parcel should occur in 1994 or early 1995. 

In September, commercial bike tours began operating on 

the Observatory Road. The tours consist of a van 

depositing mountain bikes and riders at MLO from where 

they coast approximately 51 km down to Kona. MLO is 

working with these companies (now numbering two) to 

make the ir riders visible to Observatory Road vehicle 

traffic. Early groups were riding black bikes, wore black 

T-shirts and helmets, and coasted head-down in the center 

of the road. Now at least they wear orange vests, white 

helmets, and are told to be aware of vehicle traffic. 

MLO was host to 399 signed-in visitors in 1993. 

Countries represented were Canada, Japan, China, 

Germany, Burkin a-Faso, Switzerland, France, Togo, 

Australia, Brazil, Russia, Iran, England, Denmark, 

American Samoa, Mexico, Singapore, Italy, Holland, 

New Zealand, Norway, and Sweden. This was in 

addition to visitors from 26 states. Most of the visiting 

scientists were given a tour and reprints of the most upto-date CMDL data plots MLO had available. MLO 

keeps a store of color plots on hand for such occasions. 

1.1.2. PROGRAMS 

Tabl e 1.1 summarizes the programs in operation at 

MLO during 1993. Relevant details of note on the 

respective programs are as follows: 

Carbon Dioxide 

The CMDL Siemens Ultramat-3 IR C02 analyzer and 

the SIO Applied Physics IR C02 analyzer were operated 

in parallel without major problems throughout the year. 
TABLE 1.1. Summary of Measurement Programs at MLO in 1993 

Gases 

C02 

co 

CH4 

Surface 0 3 

Total 0 3 

03 profiles 

Program 

N20, CFC-I I, CFC-12, CFC-113, 

CH3CCl3, CCl4 

N10. CFC-I I, CFC- 12, CFC- 11 3, 

CH3CCl3, CCl

4, HCFC-22, HCFC-141 b, 

HCFC-142b, CH3Br, CH3CI, CH2

Cl2, 

CHCl3, C2HCl3, c2c1 • • H-1301, H-12 11 

CFC-I I, CFC- 12, CFC-113, N20, 

CCl4 , CH3CC13, 

N20 

Radon 

Aerosols 

Condensation nuclei 

Optical propenies 

Stratospheric and upper tropospheric aerosols 

Black carbon 

Solar Radiation 

Globa l irradiance 

Direct irradiance 

Diffuse irradiance 

Terrestrial (IR) radiation 

Turbidity 

Column water vapor 

Meteorology 

Air temperature 

Instrument 

Siemens Ultramat-3 IR analyzer 

0.5-L glass fl asks, through analyzer 

Trace Analytical RGA3 

reduction gas analyzer no. RS 

2.5-L glass flasks, MAKS pump unit• 

3-L evacuated (KUM) 

Carle automated GC no. 6 

Dasibi ozone meter 

Dobson spectrophotometer no. 76 

Dobson spectrophotometer no. 76 

(automated Umkehr method) 

Balloonbome ECC sonde 

300-mL stainless steel fl asks 

850-mL stainless steel flasks 

HP5890 automated GC 

Shimadzu automated GC 

Two-filter system 

Pollak CNC 

TS! CNct 

Four-wavelength nephelometert: 

450, 550, 700, 850 nm 

Lidar, 694.3 nm 

Aethalometer 

Eppley pyranometers wilh Q, 

OG 1, and RG8 filters 

Eppley pyrhel iometer (2) with Q filter 

Eppley pyrheliometer with Q, OG I, 

RG2, and RG8 filters 

Eppley/Kendall active cavity radiometer 

Eppley pyrgeometer with shading disk 

and Q filLert 

Global downwelling IR pyrgeometer 

J-202 and J-3 14 sunphotometers with 

380-, 500-, 778-, 862-nm narrowband filters 

PMOD three-wavelength sunphotometert: 

380, 500, 778 nm; narrowband 

Two wavelength track ing sunpholometer: 

860-, 940-nm 

Aspirated therrnistort, 2- and 40-m heights 

(removed October 1993) 

Aspirated therrnistort, 2-, 9-, 37-m heights 

(added October 1993) · 

Max.-min. thermometers, 2-m height 

2 

Sampling Frequency 

Continuous 

I pair wk'1 

Continuous (5192) 

I pair wk'1 

I pair wk'1 

1 sample (24 min)"1 

Continuous 

3 day·1, weekdays 

2 day·1 

I wk' 1 

I sample wk'1 

I sample mo· 1 

I sample h'1 

I sample h'1 

Continuous integrated 

30-min samples 

I day·1 

Continuous 

Continuous 

I profile wk' 1 

Continuous 

Continuou s 

Continuous 

3 day· 1 

I mo·1 

Continuous 

Continuous (11/93) 

3 day·1, weekdays 

Continuous 

Continuous ( 4/92) 

Continuous 

Continuous 

l day-I 
TABLE 1.1. Summary of Measurement Programs at MLO in 1993--Continued 

Program 

Meteorology - Continued 

Temperature gradient 

Dewpoinl temperature 

Relative humidity 

Pressure 

Wind {speed and direction) 

Wi nd {speed and direction) 

Planetary boundary layer meteorology 

(PBL MEl) 

Precipitation 

Total precipitable water 

Precipitation Chemistry 

pl-I 

Conductivity 

Coopera tive Programs 

C02 (SIO) 

C02, nc, N2 0 (SIO) 

C02 , CO, Cl-14, 13C/12C (CSIRO) 

Cl14, Cl-13CCl3, CH3Cl, F-22, F-12, F-11, F-113 

CO, C02, N20, CHC13, CC14 (OG!Sl) 

0 2 analyses (SIO) 

0 2 analyses (URI) 

Cll4 (13Cf12C) (Univ. of Washington) 

Total suspended particles (DOE) 

Ultraviolet radiation (Smithsonian) 

Ultrav iolet radiation (ARL) 

UV solar radiation (ARL) 

Ultraviolet radiation (Univ. of Hawaii) 

Solar aureole intensity (CSU) 

Precipitation collection (DOE) 

Precipitation collection for organic acid 

analysis (Univ. of Virginia) 

Wet-dry deposition (ISWS, NADP) 

Aerosol chemistry (Univ. of Calif.-Davis) 

Various trace gases (OGISl) 

Sulfate, nitrate, aerosols (URI) 

Instrument 

Aspirated thermistorst, 2- and 40-m heights 

(removed October 1993) 

Aspirated thermistorst, 2-, 9-, 37-m heights 

(added October 1993) 

Dewpoinl hygrometert, 2-m height 

TSL 2-m height 

Capacitance transducert 

Mercurial barometer 

Bendix Aerovanet, 8.5- and 40-m heights 

(40-m Aerovane removed October 1993) 

8.5-, 10-, and 38-m heights {added October 1993) 

Wind vane, cup anemometer, and aspirated RTD 

thermometer {direction, speed, temperature at 

3-, 5-, 10-, 20-, 30-, and 40-m levels) 

(removed October 1993) 

Rain gauge, 20-cm 

Rain gauge, 20-cm:t 

Rain gauge, tipping buckett 

Foskell IR hygrometert 

pH meter 

Conductivity bridge 

Applied Physics IR analyzer 

5-L evacuated glass flasks• 

Pressurized glass flask sample 

Pressurized stainless steel flasks 

5-L glass fla sks through tower line and pump unit• 

(started June 1993) 

3-L glass flasks through tower line and pump unit 

(sta rted June 1993 at KUM) 

35-L evacuated flask 

High-volume sampler (1 filler wk·t) 

Eight-wavelength UV radiometer: 290-325 nm; 

narrowband 

Robertson-Berger UV radiometer {erythema) 

Yankee Environmental UVB pyranometer 

(280-320 nm) 

Robertson-Berger UV radiometer (erythema) 

{started June 1993) 

Multi-aperture tracking photometer: 

2, 5, 10, 20, 30' fields of view 

Exposed collection pails 

Aerochemetric automatic collector 

{terminated August 1993) 

Aerochemetric automatic collector and 

weighing-bucket rain gauge 

Programmed filter sampler 

Stainless steel flasks• 

Filter system 

3 

Sampling Frequency 

Continuous 

Continuous 

Continuous 

Continuous 

Continuous 

5 wk·I 

Continuous 

Continuous 

Continuous 

5 wk-t 

1 wk-t 

Continuous 

Continuous 

Daily 

Daily 

Continuous 

1 pair wk-t 

1 mo- 1 

3 wk·t 

3 (2 mo)"t 

2 (2 mo)" 1 

1 mo- 1 

Continuous 

Continuous 

Continu ous 

Continuous (10/92) 

Continuous 

Continuous 

Integrated monthly sample 

Collec1ion after each 

rain event 

Integrated 7-day sample 

Integrated 3-day sample 

1 continuous and 1 downslope sample (3 days)" 1 

I set wk·t (3 flasks) 

Daily, 2000-0600 LST 
TABLE I. I. Summary of Measurement Programs at MLO in 199>--Continued 

Program Instrument Sampling Frequency 

Cooperative Programs - Continued 

Radon (ANSTO) Aerosol scavenging of Rn daughters Continuous; integrated 

30-min samples 

Solar spectra (Univ. of Denver) 

All instruments are at MLO unless indicated. 

*MLO and Kumukahi 

FTIR spectrometer 

tData from this instrument recorded and processed by microcomputers. 

i Kulani Mauka 

Routine maintenance and calibrations were undertaken 

on both instruments as scheduled. An SIO electronic 

engineer upgraded the SIO C02 data acquisition system 

on March 24-26. Data are now recorded on a Brown 

strip chart recorder and stored on a PC hard disk. 

Hourly average C02 values are printed out at MLO. 

The prel iminary average MLO C02 concentration for 

1993 was 356.8 ppm. The C02 annual growth rate 

between 1992 and 1993 was approximately 0.6 ppm . 

Compared with the 1990- 1991 growth rate of 1.3 ppm 

per year, and the 1991 - 1992 growth rate of 0.8 ppm per 

year, this indicates a continue d slowdown in the C02 

growth rate measured at MLO. 

Outg assing from the volcanic vents at the Mauna Loa 

caldera and along the northeast rift zone at Mauna Loa 

continued to cause periodic observable disturbances in 

some of the C02 data record. As in prior years, these 

venting events occurred mostly between midnight and 

0800 LST of the following day, during the downslope 

wind regime. The err atic C02 concentration data 

resulting from these venting events were easily 

idcnti fied by visually scanning chart records or by 

utilizing a computerized data-screening procedure, and 

thus they have been separated from the clean-air record 

without difficulty. Such venting episodes were detected 

mainly on the basis of criteria for C02 concentration, 

C02 variability, and wind sector. The criterion for the 

C02 standard deviation screening was 1.0 ppm, which is 

the value suggested by Thoning e t al. ( 1989]. 

The frequency of monthly occurrences of observable 

outgassing from volcanic ven ts on Mauna Loa for 1993 

are listed in Table 1.2, and the annual number of events 

for the past 6 years are listed in Table 1.3. 

I wk"1 

The weekly C02, CH4 , and other gas sampling 

programs, using flask s at MLO and at Cape Kumukahi, 

were carried out according to schedule throughout the 

year, without major problems. 

The flask sampling procedure at MLO was changed as 

of November 19, 1993: 

• For the through analyzer sampling, the 0.5 -L 

greased-type flasks were replaced with 0.5 L Teflon 

0-ring-type flasks. 

• For the MAKS sampling, the 0.5-L Te flon 0 -ring 

flasks were replaced with 2.5-L Te flon 0 -ring 

flask s. 

Carbon Monoxide 

A Trace Analytical RGA3 Reduction Gas Analyzer for 

the continuous measurement of CO mixing ratios was 

in stall ed in May 1992 and continues to work well. 

System operations and chromatographic data logging 

are hand led by an HP3396A integrator. 

Methane 

The Carle automated GC system, Carle 6, was in 

continuous operation throughout the year providing CH4 

data on the basis of a grab air sample being t aken every 

24 minutes. The instrument func tioned well during the 

year. 

The CH4 data continued to show clearly defined 

cycles of varying frequencies. The typical diurnal cycle 

was well correlated with upslope and downslope winds, 

with the marine boundary layer air having the hi gher 

CH4 concentrations. There were also multi day or 

synoptic-scale CH4 cycles observed that apparently 

TABLE 1.2. Estimated Mauna Loa Venting Episodes (Total Time in Hours) at MLO in 1993* 

Jan. Feb. March April May June July August Sept. Oct. Nov. Dec. Yea r 

0 4 0 4 4 2 0 10 28 

•Criteria: C0 2 SD ~1.0 ppm ; wind direction sector 135" -225"; wind speed 1.35 m s·I. 

4 
TABLE 1.3. C02 Venting Events From 1988 Through 1993 

Year 

1988 

1989 

1990 

1991 

1992 

1993 

Total Time (Hours) 

200 

84 

48 

26 

23 

28 

relate to different air mass source regions. The average 

MLO CH4 concentration for 1993 was - 1728 ppb with 

the maximum occurring in November (- 1750 ppb) and 

minimum in August (-1720 ppb). 

Ozone Monitoring 

The 1993 MLO ozone monitoring program consisted 

of three measurement foci: continuous surface ozone 

monitoring using a Dasibi model 1003-AH UV 

absorption ozone monitor; total and Umkehr ozone 

profile measurements using computer-based automated 

Dobson instrument 76; and ozone profile measurements 

based on weekly ascents of balloonborne ECC 

ozonesondes released from the NWS station al the Hilo 

Airport. In addition lo the daily automated Umkehr 

measurements and 5-day-a-week total ozone 

measurements, five special early-morning AD-CD direct 

sun observations were completed in 1993. The Dasibi 

ozone monitor p erformed in a fully satisfactory manner 

and provided a continuous, high-quality record of 

station-level ozone concentrations for the entire year. 

Ha/o ca rbons and Nitrous Ox ide 

The RITS system had its annual major maintenance in 

September 1993. During this time, shutoff solenoid 

assembl ies and regulator warmers were added to the 

CALI and CAL2 tanks. Persistent leaks necessitated 

the replacement of various valves in the stream select 

unil and a brass actuator in the HP-GC. A new air 

compressor was installed lo replace one that burned out 

because of the leaks. 

In general, the RITS computer continued lo 

experience hangups throughout the year. A bad power 

supply was replaced in May. Program edi ting to cul 

down printing and data handling problems have not 

solved the computer "glitches." 

Radon 

The CMDL-DOE radon program completed its third 

year of operation and collected the first full year of 

improved data since the instrument background was 

reduced by applying epoxy over welds inside the 

instrument. The current background is 8 counts per 30 

minutes. A re-examination of the 1991-1992 data 

suggests that the background was 26 counts per 30 

minutes over lhal period. The 1993 data show excellent 

agreement with the ANSTO r adon monitor data. 

5 

Radon concentrations on January 6 reached their 

highest levels in the 3 years of radon monitoring al 

MLO, with half-hour averages greater than 2800 mBq 

m·3. This coincided with the high post-frontal wind 

flows from a storm on January 4-6. 

Aerosol Monitoring 

The TSI unit is a continuous expansion CNC in which 

condensation occurs in butyl alcohol vapor in a chamber 

and single particle counting statistics are used as a basis for 

the CN concentration calculations. The instrument has 

continued lo display higher counts than the Pollak counter 

since its return from the manufacturer in 1991. 

The aethalometer performed satisfactorily collecting 

black carbon data. There was some local contamination of 

the data during the early parl of the year when the 

observatory electrical upgrade contractor was using di esel 

equipment on site. 

The four-wavelength nephelome ler went down on 

January 17 because of a faulty automatic air/filter 

valve. While awaiting arrival of a replacement valve 

from Boulder, maintenance was performed on the 

circuitry. The system was brought back into service on 

February 26. The system performed without any 

problems the remainder of the year. 

Solar Radiation 

With the inclusion of the EKO sunpholometer on the 

spar in March, MLO is now measuring turbidity in more 

channels than ever before. The EKO is at MLO on a 

test basis and will be removed in 1994. Using two 

handheld sunpholometers, the PMOD sunphotometer, 

two water vapor meters with two channels each, and the 

EKO sunphotometer, MLO monitors in three channels al 

380 nm, three channels at 500 nm, one channel al 675 

nm, two channels al 778 nm, one channel al 862 nm, 

two channels al 870 nm, and two c hanne ls al 940 nm. 

This is a total of 14 channels al 7 separate wavelengths. 

Diffuse pyranomeler no. 12562, which had developed 

a negative offset, was replaced with no. 8031 on 

January 26. A pyrgeomeler (global downwelling IR) 

began operation for the first time al MLO on November 

l . Thirty-five handheld sunpholomeler instrument 

calibrations were performed during the year. 

A new data acquisition system was installed on 

October 12 based on Campbell Scientific modules that 

allow for direct access via a phone modem or RS232 

porl. All the sol ar radiation in struments on the 

radiation lower, the diffuse pyranomeler, the CN 

counter, and the nephelometer are now being monitored 

with this system al a 3-min time res olut ion. When 

instruments are accessed remote ly by phone, data are 

sent at 3-s intervals and plotted using Campbell 

Scientific software. 

Meteorology 

The standard meteorological monitoring equipment 

was down for a few days after the observatory lOok a 
direct lightning hit on July 24. It took about a week for 

all meteorological systems to become fully restored. 

There were no changes in the meteorological program 

other than the data system changes noted under the 

Computer/Network heading. The PBL system functioned without problems through 1993. The system 

measures wind speed, wind direction, and temperature 

at the 3-, 5-, 10-, 20-, 30-, and 40-m levels. 

Precipitation Chemistry 

The MLO modified program of precipitation 

chemistry collection and analyses was continued 

throughout 1993 within the basic MLO operational 

routine. This program consists of collection of a 

weekly integrated precipitation sample from the Hilo 

NWS station and collection of precipitation event 

samples at MLO. Analyses of these samples are 

undertaken in the Hilo laboratory for pH and 

conductivity . 

C omputersl Net work 

This is the year that Internet access was established, 

and it is rapidly transforming MLO operations. There is 

a direct link from the Hilo office to the University of 

Hawaii, and then to MLO via microwave. The PBL 

system was the first instrument to send data to Hilo and 

Boulder via the Internet. Other projects that followed 

included sending the JPL and CMDL lidar data through 

fiber optic links to the main MLO building. 

Ozonesonde data are also sent over the Internet on a 

weekly basis. With direct toll-free E-mail access 

available on Internet, this powerful form of 

communication is heavily utilized by MLO staff, thus 

cutting down on long-distance toll charges. MLO does 

not have access to FTS. 

The Hilo office has networked all of its PCs and uses 

Windows for Workgroups for its main operating system. 

For connection to the VAX, the PCs also run Decnet 

(Pathworks) and TCP/IP protocols. The VMS operating 

system on the VAX was upgraded to version 6. 

October was the last month of operation for the M03 

CAMS. It was removed on November 1 and replaced by 

the new PC-based meteorology data system. October 

was also the last month in which CAMS recorded solar 

radiation data; the ASR CAMS was replaced by a 

Campbell Scientific data system on November 1. The 

ASR CAMS is still connected to the aerosol instruments 

as a backup to the CSI system and wi II operate at least 

through 1994. 

Lidar 

Lidar operations continued on a regular weekly basis 

from February 1, 1993, through the end of the year. 

During January the repair of the laser power supply was 

completed. In October and November a new computer 

system (Gateway 80486 DX, 33 MHz) for controlling 

the laser and the data acquisition electronics replaced 

the old computer. The laser power supply was modified 

6 

to accept a trigger from the new computer. A new 

digital I/O board provides this trigger and is the 

interface with the data acquisition electronics. The 

instrument now runs automatically but still requires the 

operator to monitor the laser power and adjust it 

periodically. The raw data are displayed in real time 

and can be used to adjust the laser. The control and 

analysis software has been written in Turbo Pascal to 

run on the new computer. 

Observations of the decay of the Mount Pinatubo 

aerosols continued, allowing comparisons to be made 

with the El Chichon eruption. In Figure 1.1 the 

integrated aerosol backscatter is shown for the period 

from 1980 to present. The complete ruby lidar record at 

MLO extends back to December 1974. The backscatter 

is integrated from slightly below the tropopause to well 

above the stratospheric aerosol layer. 

The period from 1989 to 1991 would appear to show 

measurements of the stratospheric background level. 

No significant eruptions took place during that time, 

and the level appears constant. The average integrated 

aerosol backscatter is 0.69 x 10-4 sr·l. After subtracting this level from the data, decay lifetimes of 7 .4 

months and 11.5 months were calculated for Pinatubo 

and El Chichon aerosols, respectively. 

Outgassing of Mauna Loa Volcano 

Trace gas and aerosol measurements made at MLO 

have been analyzed in a special study aimed at 

characterizing the quiescent volcanic plume coming 

from the 6-km-distant summit of Mauna Loa volcano. 

The volcano has long been recognized as a source of 

C02 and aerosols. Previous studies have been 

concerned with identifying and eliminating this 

contamination from the climatological baseline record. 

In this study, minute-scale variability in the 

atmospheric C02 concentration was used to identify the 

presence of the volcanic plume at night in the 

I SL Jielens 

I I Alaid fl Clllchon RuiZ ,..,..,,,....... ""-U>o 

J0-5 • .• .. - · ~- - ~ . 

80 82 84 86 88 90 92 94 96 

Year 

Fig. 1.1. Stratospheric column integrated aerosol backscallcr 

measured with the MLO ruby lidar since 1980. Between I 980 

and 1982 the data arc monthly averages; after 1982 eac h 

observation is shown. 
downslope wind. The excess concentration of gases and 

aerosols above background levels was calculated for 

each hour in which the plume was present. The 

frequency of night-time hours in which the plume was 

detected varied between 50% and about 5%. In the 

months after the 1984 eruption, the plume C02 

occasionally saturated the analyzer output; an 

extrapolation model suggests that hourly excess C02 

may have r eached levels greater than over 600 ppm 

above baseline. The excess C02 was greatest when 

winds blew from the direction of the summit (180° to 

190°), with a small, sympathetic peak when winds came 

from east of 130° (Figure 1.2). The plume was 

frequently trapped beneath the night-time surface 

temperature inversion and had a scale height of tens of 

meters. The average strength of the plume at MLO 

followed the evolution of the temperature inversion, 

forming after sunset, gradually intensifying, and 

reaching a stable maximum between 0100 and 0600 

LST. 

Excess C02 was measured in the plume throughout 

the 1958-1993 period of record. The amount of C02 

was greatest shortly after eruptions (1950, 1975, 1984) 

and decreased exponentially in the following years, as 

may be observed in Figure 1.3. The rate of decrease 

following the 1984 eruption was about 6 times greater 

than that after the 1975 eruption. The post-1958 rate of 

decrease was similar to that after 1975. The onset of 

enhanced outgassing was delayed by 65 days following 

the 1975 eruption and by less than 20 days following 

the 1984 eruption. Neither eruption was preceded by 

any outgassing activity that could have been used to 

predict the eruption. 

Excess aerosol particles were present throughout the 

1974-1993 period of record as shown in Figure 1.4. In 

the post-1975 period, high CN levels were present. 

After the 1984 eruption, CN levels dropped by a factor 

of 5 and continued to fall through 1993. Two brief dips 

that occurred in 1986-1987 and 1990-1991 coincided 

with periods when geodetic observations showed that 

'E 10 0. 

,e, 1 - N 1978 0 

(.) 0.1 Cll 

..... 

Qi 

0 

Wind Direction (deg) 

Fig. 1.2. Yearly average excess C02 between 2000 and 0759 

LST in 10° wind direction bins between 1978 and 1992. Excess 

C02 was normali zed to a standard sampling height of 23 m. 

Winds outside of 10° to 260° blew too infrequently to yield 

statistically signficant excess C02 values. 

7 

e 

0. 

0. 

-

N 

0 0.1 

(..) 

IV 

~ 

Q) 0.01 0 

0.001 

58 62 66 70 74 78 82 86 90 94 

Year 

Fig. 1.3. Monthly average excess C02 between 2000 and 0759 

LST normalized to a standard sampling height of 23 m. The 

1975 and 1984 eruptions are denoted by vertica l lines. Data 

prior to 1976 were derived from hand-scaled data obtained by 

the SIO; the rest were derived from computer-digitized NOAA 

data. 

the gradual inflation of the summit either halted or was 

temporarily reversed. Light scattering aerosols were 

detectable only between 1977 and 1980 and to a lesser 

degree in 1983. The magnitude of large aerosols in the 

plume was consistent with the visual thickness of the 

plume at the vent (Figure 1.4). 

Seven additional MLO data sets were examined for a 

volcanic plume component: H20 (1974-1993), CH4 (1987-

1993), S02 (1988-1992), Aerosol black carbon (1990-

1993), radon (1991-1993), CO (1992-1993), and H2 (1992-

1993). None of these species were present in the plume 

down to the detection limits of the analysis technique. 

M' 1Q3 

E: 

~ .. z 102 

(..) 

~ 

Qi 101 

0 

100 . 

-- i 

z 10·6 ~ . Qi . 0 10-7 

74 76 78 80 82 84 86 88 90 92 94 

Year 

Fig. 1.4. Monthly average excess aeroso ls between 0000 and 

0759 LST measured from a sampling height of 13 m. The fits 

are 12-mo running means. Excess CN are shown by small ovals 

with a lower limit of detection of 1 cm·3. Excess 550 nm light 

scattering (squares) less than I x 10·7 m-t is plotted as I x 

10-7 m·l. The large solid ovals within the light scattering data 

indicate the visual thickne ss of the fume at the caldera vent 

estimated from aerial photographs (on a scale of 0 to 5) and 

then linearly scaled between I x 10·7 and I0-6 m·t. 
Cooperative Programs 

MLO cooperative programs are listed l ast in Table 

l . l ; new programs and changes in existing programs are 

presented below. 

The only major new program instituted at the MLO 

mountain site in 1993 was the University of Hawaii UV 

radiation measurement (Robertson-Berger meter) 

installed on June 18, 1993. This instrument has 

telephone access, and the data are also available on the 

MLO VAX through Interne t. 

At the MLO Cape Kumukahi lighthouse tower site, 

SIO and URI staff inst alled four Dekobon 6-mm (1/4 in) 

air sampling lines up to the top of the 18-m tower on 

June 25-27. Individual Air Cadet pumps are used to 

draw air through the air intake lines. The sample air 

will be used for the new SIO and URI oxygen flask 

sampling programs initiated in June 1993. 

SIO upgraded the SIO C02 data acquisition system at 

MLO on March 24-26. The data are now recorded on a 

Brown stripchart recorder and stored in a PC hard disk. 

The hourly average C02 values are printed out on the 

PC printer at the observatory. 

The formation of 3He (WHOI), 0 2/N2 fl ask sampling 

(NCAR), and University of Washington aerosol 

chemistry programs were discontinued in 1993. 

1.2. BARROW OBSERVATORY 

D. ENDRES 

1.2.1. OPERATIONS 

h was a relatively quiet year for CMDL programs at the 

BRW Observatory during 1993. Cooperative programs 

experienced some minor changes with the addition of new 

programs and changes in continuing programs. Barrow 

continues to serve as a training center for SPO personnel. This 

year the NOAA Corps officer was in Barrow for training during 

May and June. The SPO technician was in SMO for training 

because of scheduling conflicts. 

The biggest problem during the winter months involved 

access Lo the station. Once the road drifted over with snow, it 

received no maintenance due to the high cost of snow removal. 

Access was accomplished by snowmachine, skiing, or walking. 

There were fewer polar bear sightings this year than last. 

During the swnmer months, a gate was installed across the 

road to keep the amount of local traffic to a minimwn. 

Plans for a new observatory building were completed during 

1992 and are on site. NOAA facilities funding has not yet been 

secured for construction. 

Both GSA vehicles continued to run well. An agreement 

with the DEW Line allows us use of one stall in the garage to 

park vehicles. The stall is used for the truck during the day and 

snowmachines overnight. The Skandic snow machine had the 

engine rebuilt after it blew a piston. 

Water pipes in the bathroom at the house froze and had Lo be 

repaired this year. All the plwnbing was moved so that all the 

8 

pipes are now inside the house or in heated channels and no 

further freeze-ups are expected. In December the NWS hired a 

Seattle contractor to hook up the NOAA housing compound to 

the local utility system. The plans called for several hundred 

meters of unheated pipe with 10 mm of insulation to be 

installed and water to be circulated through it. The pipe froze 

two times in the first 24 hours and was disconnected. Future 

plans call for an upgrade sometime in 1995. 

A tape back-up was installed in the station computer to save 

on the nwnber of disks used in backing up the hard drive. A 

storm with westerly winds caused several power outages during 

the fall. It was an unusual storm with wet, heavy snow. 

During 1993, BRW was visited by 88 registered guests. This 

list included guided tours, researchers, and interested 

individuals. Visitors from Japan, Russia, Canada, and the 

South Pole were all involved in research at BRW. U.S. 

Government agencies were represented by NOAA/NOS, the 

USGS, Army Corps of Engineers, ONR, the Navy, and the Air 

Force. Personnel from eight universities were involved m 

research as well. Twenty-five states were represented. 

1.2.2. CMDL PROGRAMS 

Table 1.4 summarizes the 1993 measurement programs al 

BRW. Operational highlights are as follows: 

Aerosols 

The TSI CNC continues to measure higher levels of 

condensation nuclei than the Pollak. The reason for the 

difference is still under investigation. Because of this 

difference, independent data sets are maintained for both 

instruments. Both instruments ran all year with no major 

problems. 

Backscatter, as measured by the nephelometer, continues to 

show the seasonal trends associated with arctic haze. 

Springtime highs and summer lows characterize the BRW data. 

Intermittent problems with the nephelometer were solved 

during the first quarter of the year by replacing all l.C. chips on 

board 7. 

The aethalometer data acquisition system clock began to lose 

time early this year and a replacement laptop computer was 

ordered. Time loss of up to 20 seconds per day was noted. 

The laptop computer was replaced and a newer version of the 

software was installed. 

A new data Jogging system was installed for the solar 

radiation program with aerosols sharing the hardware. For 

more detail see the Solar Radiation section. 

Solar Radiation 

The BRW Observatory solar program consists of a 

downward facing albedo rack approximately 75 m behind the 

station and 1.75 m above the surface with a quartz pyranometer 

and a pyrgeometer. An upward facing quartz pyranometer, an 

RG8 pyranometer, and a tracking NIP are mounted on the 

Observatory roof. Located in the Dobson dome is a filter 

wheel NIP with Quartz, OG I, RG2, and RG8 filters. 

Observations begin in January when the sun returns and cease 

when the sun sets in November. 
TABLE 1.4. Summary of Measurement Programs at BRW in 1993 

Gases 

C02 

C02, CH4 , CO 

CH4 

Surface 0 3 

Total 0 3 

Program 

N10. crC-11, CFC-12, CFC-113, 

Cll3CCl

3, CCl4 

N10. crC-11, CFC- 12, CFC- 11 3, 

CH3CCl

3, CCl4 , HCFC-22, HCFC-141 b, 

HCFC-142b, CH3Br, CH3CI, CH2Cl2. 

CIIC13, C2HCl3, C2Cl

4, H-1301, H-121 1 

crC-1 1, CFC- 12, CFC-1 13, N10 

CCl4, CH3CCl3 

N20 

co 

Aerosols 

Condensation nuclei 

Optic a I properties 

Black carbon 

Solar Radiation 

Global irradiance 

Direct irradiance 

Albedo 

Terrestrial (IR) Radiation 

Upwelling and down welling 

Meteorology 

Air temperature 

Dewpoint temperature 

Pressure 

Wind (speed a nd direction) 

Precipitation 

Cooperative Programs 

Total surface particulates (DOE) 

Precipitation gauge (USDA) 

Magnetic fields (USGS) 

Various trace gases (OGIST) 

C02. 13C, N10 (SIO) 

CH4 (Un iv. of Calif., Irvine) 

Earthquake detection 

(Univ. of Alaska) 

Instrument 

Siemens Ultramat 5E analyzer 

3-L glass fl asks 

0.5-L glass flasks, through analyzer 

0.5-L glass flasks, P3 pump unit 

Carle automated GC 

Dasibi ozone meter 

Dobson spectrophotomete r no. 91 

300-mL stainless steel flasks 

850-mL stainless steel fl asks 

HP5890 automated GC 

Shimadzu automated GC 

Trace Analytical GC 

Pollak CNC 

T.S.I. CNC 

Fou r-wavelength nephelometer 

Aethalometer 

Eppley pyranometers with Q and RG8 filters 

Tracking NIP 

Eppley pyrheliometer with Q, OG 1 

RG2, and RG 8 filters 

Eppley pyranometer 

Eppley pyrgeometers 

Thermistor, 2 levels 

'Max.-min. thermometers 

Dewpoint hygrometer 

Capacitance transducer 

Mercurial barometer 

Bendix Aerovane 

Rain gauge, tipping bucket 

High-volume sampler (1 filter wk-I) 

Nipher shie ld, Alter shield, 2 buckets 

3-Component fluxgate magnetometer and total field 

proton magnetometer 

Declination/inclination magnetometer sample 

Stainless steel flasks 

5-L evacuated glass flasks 

Various stainless steel flasks 

Seismograph 

9 

Sampling Frequency 

Continuou s 

1 pair wk-I 

1 pair wk-I 

1 pair wk-I 

1 sample (12 min)·I 

Continuous 

3 day·l 

1 sample wk-I 

1 sample mo-I 

1 samp le h-1 

1 sample h-1 

1 sample (6 min)·I 

1 day·1 

Continuous 

Continuous 

Continuous 

Continuous 

Continuous 

Discrete 

Continuous 

Continuous 

Continuous 

1 day·1 

Continuous 

Continuous 

Discrete 

Continuous 

Continuous 

1 mo·I 

Continuous 

6 sets mo·I 

1 set wk-I (3 flasks set·I) 

1 pair wk-1 

1 set (3 mo)·I 

Continuous, check 

site 1 wk-1 
TABLE 1.4. Summary of Measurement Programs at BRW in 1993---Continued 

Program Instrument Sampling Frequency 

Cooptrativt Programs • Continued 

13CH4 ( 13C/12C) (Univ. ofWashing1on) 

UV monitor (NSF) 

35-L stainless steel flasks 

UV spectrometer 

I (2 wk)-1 

I scan per 0.5 hou r 

Magnetic fi elds (NAVSWC) 3He sensors Continuous 

Sound Source (DOE) RASS 

Ice Buoys (NOS) Ice buoys 

0 2 in air (Univ. of Rhode Island) 3-L glass flasks 

The tracking NIP was installed in February and collected 

data until the end of the solar season with only minor 

problems. Most of the problems-were caused by corrosion 

in the cable because of the salt air. The clutch in the 

tracker was repaired when it was found to be loose and 

causing tracking errors. 

The biggest change in the solar program was the 

installation of a Campbell Scientific Instruments (CSI) data 

collection system. A comparison between the CSI and the 

CAMS was performed for a month, with favorable results, 

and the CAMS was retired. Data from the CSI can be 

accessed by field personnel and a higher level of data 

quality can be assured. 

Epply blowers were installed on the roof PSPs to assist 

in keeping snow and ice from collecting on the domes. The 

new blower system works well and has reduced the 

maintenance needed to keep the domes ice free. 

Carbon Cycle 

C02 NDIR. C02 mixing ratios for the BRW Observatory 

show the same temporal distribution as in previous years. 

Winter highs of 360 ppm are seen with summertime lows of 

345 ppm. A Siemens Ultramat 5E continues to be the station 

instrument and responds well to changes in atmospheric C02. 

During early March a power outage damaged the analyzer, 

and it was returned to Boulder for repairs. It was returned to 

BRW and put back into operation by the end of March. 

During July the drive assembly for the Linseis recorder 

began sticking at lower voltage levels. The necessary parts 

were ordered, but before they arrived the chart recorder failed 

completely. The recorder unit was repaired and placed back in 

operation by the end of August. 

Methane. For the past few years BRW CH4 data has shown 

a decrease in the growth rate. During late 1992 and early 1993 

the growth rate actually exhibited a negative trend. This trend 

continued during 1993. Yearly cycles are seen with mixing 

ratios of between 1750 ppbv and 1950 ppbv. 

During July the Carle GC electrometer board failed and was 

replaced. The system ran for the rest of the year with no 

problems. 

Carbon Monoxide. A Trace Analytical GC has collected 

CO data at BRW since the fall of 1991. Like CH4, the growth 

for CO has shown a marked decrease. Flask data are available 

10 

I hr-I 

Continuous 

I pair (2 wk)-1 

from 1990 on. Annual average mixing ratios of approximately 

150 ppbv are measured with data ranging between 250 ppbv 

and 75 ppbv. 

In January the CO program was modified to run with three 

calibration gases to correct for any non-linearity in the 

detector. The Hg lamp was replaced in July after it dropped 

below acceptable output limits. 

Flask Samples. The Carbon Cycle Division (CCD) 

flask samples were collected with few problems during 

1993. Data concerning the CCD flasks can be found in 

section 2.1.6. Whole air collected using the various glass 

flasks is analyzed for CO, CH4 , and C02. 

A problem was discovered in the data when MAKS flas; 

data are compared with CMDL 3-L data. The problem wa 

discovered in 1992 and is still under investigation by 

CMDL personnel in Boulder. 

Meteorology 

September ushered in an ice storm that coated the 

streets of Barrow with ice. Temperatures remained cold 

enough that there was no melting. A storm in October 

brought enough snow to allow station personnel to ski 

to work but within 2 days was blown away by the high 

winds and the ice was uncovered. 

Problems were corrected with the TSL hygrothermometer. The instrument performs an auto-balance, 

which cleans the mirror, and should return to a zero 

value. The dewpoint assembly was replaced in May and 

no further problems occurred. 

CAMS 

CAMS ran without any significant problems for the 

entire year. However, plans are being made by most 

groups in Boulder for the next generation data 

acquisition system. CAMS is approaching the end of its 

useful life and alternative collection schemes must be 

implemented. 

Ozone 

Surface Ozone. Surface ozone is measured with a Dasibi 

ozone monitor. The Dasibi measures continuously and ran all 

year with only routine cleaning of the absorption tubes. Data 
continues to show trends of past years; i.e., springtime lows 

and highs during the dark winter months. 

Dobson. Dobson 91 is the instrument in BRW and 

observations are made from February until October. A semiautomated data acquisition system was added to the Dobson in 

May and has proven to be quite useful. Station personnel can 

now see real time ozone amounts as measured by the Dobson 

in Dobson Units (milli-atmo-centimeters). 

N,O and H alocarbons 

Gas Chromatographs. System lock-ups continued to 

plague the system during 1993. The only cure was to cycle the 

power. Batteries in the UPS for the DAS were found to be old 

enough that two of the four would no longer hold sufficient 

charge to run the system in the event of a power outage. The 

batteries were replaced. A suspected bad disk drive was 

replaced in August when several disks were found to be devoid 

of data. Leaks in the pneumatic lines caused the most 

problems and occurred on several occasions. The detector for 

channel B was replaced late in the year. 

Flask Samples. Flask samples were collected as available 

and scheduled. Data concerning the flasks can be found in the 

Nitrous Oxide and Halocarbons section (5.1.4). 

Cooperative Projects 

Only programs with problems or unusual occurrences are 

mentioned in this section. 

University of Rhode Island. A series of flask samples were 

collected during 1993 to test the feasibility of collecting whole 

air for analysis uf OifN2 and C02. Data collected by 

measuring 02 can yield vital information regarding the fate of 

fossil fuel C02 as well as ocean fertility. The test was 

successful and a regular schedule of sample collecting has 

begun. 

DOEIEML. Air filters collected at BRW were sent to 

DOE/EML on a weekly basis for analysis because of an 

explosion at a nuclear fuel processing plant near Tomsk in the 

former Soviet Union. A signal was detected in Barrow. 

DOE/Sandia National Laboratory. Preliminary site choice 

was made for the DOE CART/ARM site near Barrow. In 

cooperation with the North Slope Borough, Department of 

Wildlife Management, a 12-18 month test of the sound source 

for the RASS began in July. The test will show if there are any 

effects on local wildlife because of the high level of sound 

generated. 

USDAISCS. In July a gust of wind destroyed one of the 

longest running cooperative programs at the BRW 

Observatory. The Wyoming rain gage was knocked down 

when a gust of wind measuring 30 m s·l (66 mph) hit it during 

July. The warm summer temperatures caused a deeper melt 

than normal and the anchor bolts gave when the wind hit. 

There are no plans to fix the gage. 

USGS. BRW personnel have assumed the duties of 

calibration for the USGS Magnetic Observatory. A new MOA 

with USGS was negotiated (see Section 6.0, page 140). The 

Barrow Magnetic Observatory is one of thirteen observatories: 

three in Alaska, seven in the contiguous U.S., and one each in 

Hawaii, Puerto Rico, and Guam. Six sets of absolute 

11 

measurements are made once each month to determine the 

horizontal and vertical intensity and the declination. These 

numbers are then used to calibrate the continuous measuring 

instruments at the site. 

NOAA/Navy Joint Ice Center. Several ice buoys were 

installed for a Jong-term calibration study. There is a question 

about the long-term-stability of the sensors and BRW was 

chosen as the most suitable location to test the sensors. Data 

are collected on a laptop computer and downloaded by 

personnel from the National Ocean Service in Silver Spring, 

Maryland. 

1.3. SAMOA 

M. Winey 

1.3.1. OPERATIONS 

There was a personnel change at the observatory 

during the year. The SMO station chief ended a 4-year 

term and went to a teaching position at the American 

Samoa Community College. The e lectronic techni cian 

was then installed as station c hief and an environmental 

engineer was hired. 

The most exciting and disturbing event of the year was 

the burglary of the main observatory building. A safe that 

contained money and paper work was stolen. The 

perpetrators were caught, but none of the stolen property 

was recovered. A new safe was cemented into the floor of 

the office. Some structural changes were also made to the 

building to improve security. 

Two hurricanes made close calls early in the year. 

Minor damage was incurred and was easil y repaired by 

station personnel. These storms were a reminder of the 

past few years when two hurricanes did extensive damage. 

The two observatory vehicles were a constant source of 

trouble throughout the year. Both the van and the truck 

neared 100,000 miles of use. Repairs became more 

frequent and more complex, greatly inconveniencing the 

staff. Toward the end of the year the process began to 

replace the truck. 

The backup generator logged many hours during power 

blackouts. One major breakdown occurred but was 

successfully repaired by the staff. A modification was 

made to prevent overheating becaue of water loss in the 

radiator; when the generator overheated once before, the 

result was a Sl2,000 overhaul. 

Major remodeling of house T-7 occurred once the 

environmental engineer and family moved in. They did all 

the work themselves and greatly improved the appearance 

of the place. Unfortunately, a few termi tes were seen. 

Poison was applied in an effort to kill the termites, but this 

measure has not always been successful in the past. 

1.3.2. PROGRAMS 

Table 1.5 summarizes the programs at SMO for 1993. 

Further descriptions of some of the programs follow. 
TABLE 1.5. Summary of Measurement Programs at SMO in 1993 

Surface 03 

Total 0 3 

Program 

N20, CFC-I I, CFC-12, CFC-I 13, 

CH3CCl3, CCl4 

N20, CFC-I I, CFC-12, CFC-I 13, 

CH3CCl3, CCl4 , HCFC-22, HCFC-14 I b, 

HCFC- l 42b, CH3Br, CH3CI, CH2Cl2, 

CHC13, C2HCl3, C2Cl4 , H-1301, H-1211 

CFC-I I, CFC-12, CFC-113, N20, 

CCl

4 , CH3CCl3 

N20 

Aerosols 

Condensation nuclei 

Solar Radiation 

Global irradiance 

Direct irradiance 

Meteorology 

Air temperature 

Dewpoint temperature 

Pressure 

Wind (speed and direction) 

Precipitation 

Precipitation Chemistry 

Anions (NO), S04) 

Cooperative Programs 

C02, t3C, NzO (SIO) 

GAGE project: CFC- I I, CFC-I 2, 

NzO, CH3CCl3, CCl4 (SIO) 

Various trace gases (OGISl) 

Bulk deposition (EML) 

Hi-vol sampler (EML) 

Hi-vol sampler (SEASPAN Project) 

CH4 ,(llC/IZC ratio) (Un iv. of Wash.} 

Light hydrocarbons (UC!) 

Oz (URI) 

Oz (SIO) 

Instrument 

Siemens Ultramat-5E analyzer 

0.5-L glass flasks, through analyzer 

2.5-L glass flasks, MAKS pump unit 

Dasibi ozone meter 

Dobson spectrophotometer no. 42 

300-mL stainless stee l flasks 

850-mL stainless steel flasks 

HP5890 automated GC 

Shimadzu automated GC 

Pollak CNC 

G.E. CNC 

TSI CNC 

Eppley pyranometers with Q and RGS filters 

Eppley pyrheliometer with Q filter 

Eppley pyrheliometer with Q, OG I, 

RG2, and RGS filters 

Thennistors (2) 

Max.-min. thennomcters 

Polished mirror 

Capacitance transducer 

Mercurial barometer 

Bendix Aerovane 

Rain gauge, tipping bucket 

Rain gauge, plastic bulk 

Dionex QIC ion chromatograph 

5-L evacuated glass flasks 

HP5880 gas chromatograph 

Stainless steel flasks 

Plastic bucket 

High-volume sampler 

High-volume sampler 

30-L pressurized cylinder 

1-L evacuated stainless steel flasks 

2.5-L glass flasks 

3-L glass flasks 

12 

Sampling Frequency 

Continuous 

I pair wk"

1 

I pair wk'1 

Continuous 

4 day·l 

1 sample wk-I 

I sample mo·l 

1 sample h-1 

1 sample h·I 

1 day·l 

Continuous 

Continuous 

Continuous 

Continuous 

Discrete 

Continuous 

I day-I 

Continuous 

Continuous 

I wk·l 

Continuous 

Continuous 

I day-I 

1 day·t (CMDL) 

I set wk·l (3 flasks set·I> 

1 h·l 

I set wk·I (3 flasks set·I> 

Continuous (I bucket mo·l) 

Continuous (I filter wk·l) 

Continuous (I filter wk·I) 

Biweekly 

3-4 flasks qtr·I 

2 pair mo·I 

2 sets mo·l (3 fl asks set· I> 
Carbon Dioxide 

The continuous C02 analyzer ran faithfully through the 

year with only one short period of downtime. Data quality 

was very high. 

The most difficult task of the year was to replace the 

sample lines that run up the side of the 18-m mast. The 

wind-induced vibrations in the Dekoron tubing caused 

cracks and eventually breakage in several places. With the 

use of climbing gear, the station chief replaced all four 

lines that extended to the top of the mast. Further restraint 

was added to the lines to reduce vibration and hopefully 

prevent future problems of this sort. 

The glass fittings on the through-analyzer flask filling 

apparatus were replaced with Teflon fittings. 

A by-pass valve was added to the no. 2 air line upstream 

of the analyzer. The valve will be open for about an hour 

every 2 weeks for filling flasks for two cooperative 

projects. One set of flasks will come from SJO and the 

other from URI. 

Surface Ozone 

The Dasibi ozone monitor was down for several months 

when it became Jost in the mail on its way in for repairs. A 

replacement Dasibi was installed toward the end of the year 

and worked well after overcoming a small difficulty. The 

new monitor had water condensation inside the intake line 

and in the instrument causing erratic output. To take care 

of this problem, the intake line was insulated and warmed 

with heat tape lo prevent condensation. 

The data recorded by CAMS was frequently interrupted 

because of the sensitive nature of the signal-receiver board. 

This problem was due to the lack of reliable pOWl'I for 

CAMS. Some improvement was made when a power 

connection was made to the UPS in the Ekto building. 

Total Ozone 

The Dobson ran well. The instrument was sent to Hawaii 

for 2 weeks of intercomparison calibration. When the 

Dobson was returned, a member of the Aerosols, Radiation, 

Ozone, and Water Vapor Division installed a digital 

encoder. The encoder is connected to a computer that 

records the r-dial numbers and calculates the total ozone. 

This improved setup has relieved the staff of the tedious 

process of writing the data on paper forms. 

Halocarbons and Nitrous Oxide 

When operating properly, the dual GC system produces 

reliable data. There was one small problem and one big 

problem to contend with during the year. One of the ECD's 

went bad and had to be replaced, but the old one had to be 

sent back first. Once the replacement arrived, a successful 

installation was made quickly with little difficulty. 

Computer hang-ups were a far more perplexing problem. 

In the beginning of the year the system was running day 

after day with virtually no down time (this can be credited 

to the previous installation of a UPS). The computer then 

started to hang-up for no apparent reason. The suspected 

cause for the malfunction was replaced but this didn't help 

13 

much. The hard drive was reformatted and the programs 

reinstalled, again this didn't help. At year's end, it was 

almost a daily ritual to reboot the stalled system. 

Aerosols 

After a period of good side-by-side comparison between 

the TSI and GE, the GE was retired. The TSJ performed 

well with only a few small problems. The Pollak counter 

also worked reliably throughout the year. 

Water condensed inside the TSI and displaced the 

alcohol. This was remedied by pouring out the liquid and 

filling the instrument with pure butanol. 

The ammeter connected to the Pollak had to be replaced 

when the needle began to respond sluggishly. Other than 

that, the Pollak had a good year as usual. 

Solar Radiation 

The solar radiation instruments arc usually very 

dependable and this year was no exception. The only 

problem was a leak in the seal around the dome of the Qpyranometer. In an attempt to pinpoint the leak, a little air 

pressure was applied to the instrument; a little too much air 

pressure was used and the whole dome popped off. Since 

there was no damage to the dome, it was reattached and put 

back into service leak free. 

M eleorology 

Everything went well for the meteorological system 

during the year. However, two occurrences deserve 

mention. (1) The wind speed reported by the Aerovane was 

too low. After verifying the integrity of the electronics, a 

new Aerovane was installed and tested. From then on, the 

wind-speed indications were reliable. (2) When the 

registered dewpoint temperatures indicated below-zero 

readings, the mirror assembly was replaced and the 

problem solved. 

CAMS 

For the most part, CAMS did its job of collecting data. 

The early part of the year was marked by several 

interruptions because of power problems that resulted in 

board failures inside the M03 and ASR CAMS units. This 

problem was relieved by upgrading the 182-m (600-ft) 

extension cord that connected the CAMS units to the UPS 

in the Ekto building. Even after this improvement, all the 

CAMS units still experienced occasional auto-restarts but 

these were few and far apart. 

Cooperative Programs 

The SIO GC produced consistent data during the year. The 

ignitor in the FID failed and had to be replaced. This fairly 

delicate operation was performed successfully with only a very 

short period of interruption in the data. The UPS kept the 

system going continuously by protecting the equipment from 

the unreliable power supplied locally. To ensure continued 

UPS operation, a fresh set of batteries was installed. 

The SEASPAN system is another one of those projects 

that rarely has a problem, but during this year, the big, 
heavy blower had to be swapped out two times. There was 

a spare on hand the first time so there was very little down 

time, but the second time the replacement had to be 

shipped. This resulted in several months of down time. 

Two new cooperative flask programs were added during 

the year. One is for SIO and the other for URI. 

1.4. SOUTH POLE OBSERVATORY 

K. MCNITT 

1.4.1. OPERATIONS 

SPO is part of a l arger U.S. Antarctic presence that 

works in conjunction with NSF and ASA to conduct 

research at the Amundsen-Scott South Pole Station. 

SPO is just one of many projects at the geographic 

South Pole where the elevation is 2835 m above sea 

level and the average temperature is -49°C. 

Because airplanes can only land at the Pole during the 

relatively warm months of October through February, 

the station is physically "closed" for 8 months each 

year, with the exception of one mid-winter "airdrop" 

resupply in June. Data are transferred digitally via 

satellite throughout the year; however, air samples 

taken during the austral winter cannot be returned for 

analysis until the following spring. Of the 28 

winterovers for the 1992-1993 season, four were NOAA 

employees. Along with the CMDL programs, ERL 

Environmental Technology Laboratory studied atmospheric boundary layer interactions and changes in 

relation to ozone-hole development. 

Most of the CMDL projects are housed in the Clean 

Air Facility (CAF), an elevated building located 90 m 

grid northeast of the main station's fuel arch. As 

described in previous CMDL Summary Reports, the 

CAF is reaching its projected lifetime .and is scheduled 

for replacement. Consequently, many upgrading 

projects for the CAF were left unresolved. But 

regardless of this, a concerted effort to improve the 

safety and efficiency of the current building was made. 

Because the wind blows predominantly from the grid 

north or northeast, a "Clean Air Sector" has been 

designated into which excursions are prohibited wi thout 

permission. This Clean Air Sector is marked and 

includes the area grid north of the CAF from 340° to 

110°. 

CMDL's meteorological instruments are mounted on 

the walk-up Met. Tower, less than 100 m from the CAF, 

and operations for the balloon program take place in 

three locations: the main station science building, the 

cargo arch, and the Balloon Inflation Tower (BIT). 

Power outages were rare this year, but science 

demands continued to exceed "clean" power supplied by 

the CAF UPS. UPS-fed receptacles were identified and 

labeled to prevent accidental overloads, and the backup 

batteries were replaced. ASA electricians rewired the 

14 

fire alarm system and rectified potentially dangerous 

wiring schemes in the building. 

1.4.2. PROGRAMS 

Table 1.6 is a summary of the measurement programs 

at SPO during 1993, and Table 1.7 is a discrete 

measurements summary the 1992-1993 winterover year. 

Carbon Cycle Division 

The Siemans continuous C02 analyzer ran without 

significant problems, although occasional repair of the 

chart recorder was necessary when the electronics were 

damaged by static discharge, and there was a period of 

several weeks at the beginning of the season when no 

chart paper was available. 

Sample flask pairs were filled through the analyzer 

once per week and through a portable MAKS unit twice 

per month. The most significant improvement in the 

SPO carbon cycle program this year was the switch 

from the "greased connection" flasks to the flasks with 

Teflon valve seals. The analyzer manifold was 

modified to fill the new flasks in series, and the new 

MAKS unit required no modification. 

Aerosols 

The MRI four-wavelength nephelometer was off-line 

for 1 month at the beginning of the season while waiting 

for a replacement filter wheel motor; otherwise, the 

nephelometer and the TSI condensation nucleus counter 

ran continuously without extraordinary problems. 

Discrete observations with the Pollak condensation 

nucleus counter took place twice daily for comparison 

with the TSI instrument. 

Solar and Terrestrial Radiation 

During the summer, all Eppley pyranometers, 

pyrgeometers, and the tracking pyrheliometer ran 

continuously without significant problems. Discrete 

observations with the filter wheel NIP took place three 

times daily. After sunset in March, the short-wave 

instruments were taken off-line for the winter. One upfacing and one down-facing pyrgeometer remained. The 

down-facing instrument was off-line for 5 months 

because of damage received during an apparent power 

surge. 

Ozone and Wat er Vapor 

The Dasibi ultraviole t absorbtion ozone monitor no. 

322833 replaced instrument no. 5229 after 2 weeks of 

intercomparisons. The only remarkable problem with 

the new analyzer was the self-destruction of its pump 

that was replaced when small plastic shavings were 

discovered behind the exhaust outlet and the flow rate 

dropped below an acceptable level. 

Discrete observations with the Dobson ozone 

spectrophotometer took place during the summer 
TABLE 1.6. Summary of Measurement Programs at SPO in 1993 

Gases 

C02 

COz, CH4 

Program 

Surface 03 

Total 0 3 

Ozone profiles 

Water vapor 

N20, CFC-I I, CFC-12, CFC-113, 

CH3CCl

3, CCJ4 

N20, CFC-I I, CFC-12, CFC-1 13, 

CH3CCl3, CCl

4 • HCFC-22, HCFC-14 lb, 

HCFC- 142b, CH3Br, CH3CI, CH2CJ

2, 

CHCl3, C2HCl

3, C2C14, H- 1301, H-1211 

CFC-I I, CFC-12, CFC-113, N20, 

CH3CCl3, CCl4 

Aerosols 

Condensation nuclei 

Optical properties 

Solar Radiation 

Global irradiance 

Direct irradiance 

Albedo 

Terrestrial (IR) Radiation 

Un welling and downwelling 

Meteorology 

Air temperature 

Pressu re 

Wind (speed and direction) 

Frost-point temperature 

Cooperative Programs 

C02, tlC, NzO (SIO) 

Total surface particulates (DOE) 

Various trace gases (OGIST) 

Interhemispheric 13C/14C (CSIRO) 

0 2, N2 (Scripps) 

Isotope production (LLNL) 

Instrument 

Siemans IR analyzer 

2.S-L glass flasks, through analyzer 

2.S-L glass flasks, MAKS pump unit 

Dasibi ozone meter 

Dobson spectrophotometer no. 82 

Balloonbome ECC sonde 

Balloonbome sonde 

300-mL stainless steel flasks 

850-mL stainless steel flasks 

Shimadzu automated GCs 

Pollack CNC 

TSI CNC 

Four-wavelength nephelometer 

Eppley pyranometers with Q and RGS filters 

Eppley pyranometer with Q filter 

Net radiometer 

Eppley pyrheliometer with Q, OG I, RG2, 

and RGS filters 

Eppley pyrheliometers with Q and 

RGS filters 

Eppley pyranometers with Q and RGS filters 

filters, downward facing 

Eppley pyrgeometers 

Platinum resistor, 2- and 20-m heights 

Capacitance transducer 

Mercurial barometer 

Bendix Aerovane 

Hygrometer 

S-L evacuated glass flasks 

High-volume sampler 

Stainless-steel flasks 

S-L glass flasks 

Air sampling pump and flasks 

Pressurized cylinders 

15 

Sampling Frequency 

Continuous 

I pair twice mo·! 

I pair twice mo·1 

Continuous 

3 day·• 

I wk·l, summer, autumn, 

winter; I (3 day)·I, spring 

10 times yr• 

I sample mo·l 

I sample mo-I 

I sample h·I 

2 day·t 

Continuous 

Continuous 

Continuous, summer 

Continuous, summer 

Continuous, summer 

2 day·• 

Continuous, summer 

Continuous, summer 

Continuous 

Continuous 

Continuous 

I timewk·l 

Continuous 

Continuous 

2 mo·l (3 flasks sample·!) 

Continuous 

(4 filters mo·l) 

I week·! (2 flasks set ·I), 

summer only 

I or 2 flasks mo·t 

I mo·l (3 flasks set·!) 

NIA; checked once mo·l 
TABLE 1.7. South Pole Discrete Measurements Summary for the 1992-1993 Winterover Year 

1992 1993 

Nov. Dec. Jan. Feb. March April May June July Aug. Sept. Oct. 

CMDL Programs 

Dobson obs. 451 594 397 225 51 90 93 45 72 214 

Pollak obs. 135 149 149 124 168 162 156 156 156 165 165 162 

Filter wheel NIP 42 41 72 46 8 6 

Smithsonian model 21 26 43 31 19 15 

comparison (radiation) 

Meteorology obs. 30 31 31 28 31 30 31 30 31 31 30 31 

C02 flasks T.A. 10 6 8 6 10 8 10 8 8 10 8 8 

C02 flasks MAKS 4 4 8 2 4 4 4 4 4 4 4 4 

NOAH fl asks 10 6 8 10 2 2 2 2 2 2 

Balloons 0 3 9 3 3 5 5 5 4 4 5 9 11 I I 

Balloons H20 2 2 

Cooperative Programs 

CSIRO C02 fl asks 2 2 

OGC trace gases 10 6 6 

Scripps C02 flasks 6 6 6 6 6 

Scripps 0 2 and N2 flasks 3 2 3 2 

DOE radionuclies filte rs 4 4 4 4 4 

months when the sun was sufficiently high above the 

horizon and then in the darkest winter months during each 

full moon. Dobson no. 82 replaced no. 80 after extensive 

intercomparisons. This year marked the first year of 

observations with the new electronic shaft encoder and 

computerized data acqu1s1t1on system that worked 

wonderfully and also drastically reduced the time required 

for digital transfer of data to Boulder. 

The ozonesonde and water vapor programs had a very 

successful season despite early troubles with the 

ozondesonde solutions and faulty connections in the 

telemetry cables. On October 6, 1993, one of our 

ozonesondes recorded an all-time low, total ozone value of 

90 Dobson units. Data from this fli ght were supported by 

Dobson observations performed on the same day. 

Rubber balloons were l aunched from the BIT platform 

during the summer months. Water vapor flights and winter 

ozonesonde flights required the larger plastic balloons that 

were filled in the cargo arch and launched from the cargo 

yard. Launches usually occured once per week except 

during the months of stratospheric ozone depletion 

(August-November) when the schedule was changed to 

every 3 days. 

This year several successful dual launches with the ASA 

Meteorological Department (MET) were completed. There 

are many advantages to dual launches: Helium and MET 

balloons are conserved, the plastic balloons reach higher 

altitudes than the MET rubber balloons, and flight 

monitoring is easier with the MET automated tracking 

system than with the NOAA manual system. The CMDL 

antenna and the ASA MET antenna coexist in the radome 

on top of the BIT with very few instances of interference. 

16 

2 2 2 I 

6 

6 6 6 6 6 6 6 

3 3 2 3 3 3 2 

4 4 4 4 4 4 4 

The only interference that occurred was during the summer 

months when winds were light and the MET balloon rose 

straight overhead, causing their antenna to point directly at 

ours. The two antennas cannot physically bump into each 

other. 

Nitrous Oxides and Halocarbons Division 

The two Shimadzu Mini-2 electron capture gas 

chromatographs were inspected and upgraded during the 

summer by staff from the Nitrous Oxides and Halocarbons 

Division, adding "watchdog valves" to the gas standards 

and rurming new sample lines up the meteorological tower. 

For the remainder of the year, the GCs measured one 

sample from the sampling stack on the CAF ·roof and one 

from the middle of the tower. 

Sample flask pairs were filled with ambient air once per 

week during the summer and once per month during the 

winter. 

Meteorology 

A faulty power supply was the cause of questionable data 

during days 93212-93222. Otherwise, continuous temperature, wind, and pressure data were recorded without 

significant problems. Manual weather observations took 

place daily at midnight UT and data were compared with 

those collected by the ASA MET Department. 

Data Acquisition 

This was the l ast year of operation for most of the CAMS 

units that ran continuously without unexpected problems, 

except for occasional eccentricities when updating the date 

or time. 
Cooperative Program s 

CSIRO . Long-term monitoring of the ratio 13C/t2C 

in atmospheric C02 for use in a 2-D global carbon cycle 

model. One glass flask \Vas pressurized with ambient 

air per month, two during even numbered months. A 

new (portable) pump arrived during the summer and 

operations were trouble-free. 

OGIST. Seasonal trends in the amount of chlorineand bromine-containing trace gases in the Antarctic. 

Two flasks per week were fi lled with ambient air. No 

extraordinary problems were encountered . 

SCRIPPS. Long-term monitoring of C02, 13C/12C 

ratio, and N20. Twice per month, three evacuated glass 

flasks were exposed to ambient air. No significant 

problems occurred. 

SCRIPPS. Long-term monitoring of 02 and N1. 

Three glass flasks were pressurized with ambient air 

once per month. Reduced flowrates and broken 

stopcocks were a problem at the beg inning of the 

season, but the last several months of sampling went 

smoothly. 

LLNL. Quantification of the production rate of 

radiocarbon by galac tic cosmic rays. Seven air-filled 

cylinders were placed on platforms approximately 800 

m downwind of the main station. The cylinders were 

17 

inspected and c leared of snow periodically; no other 

operations were required. 

DOE. Long-term monitoring of the spatial and 

temporal distribution of specific and anthropogenic 

radionuclides in surface air. The DOE pump ran 

continuously wi thout significant problems; filt ers were 

replaced fou r times per month. 

M isce //a11eo us 

The University of Rome lidar and the U.S. Navy 

ceilometer are no longer CMDL cooperative proj ec ts, 

but assistance was given to the ASA science technicians 

with operations and maintenance of both instruments. 

CMDL st aff recovered snow stakes throughout the year 

to help representatives from U.S. Army Cold Regions 

Research and Engineering Laboratory determine the 

amount of snow accumulation around the South Pole 

Stat.ion . 

1.5. REFERENCE 

T hon ing, K.W., P.P. Tans, and W.D. Kornh yr, Atmospheric 

carbon dioxide al Mauna Loa Obse rvatory, 2, An:ilysis of 

the NOAA G:>.ICC data. 1974-1985, J . Geoplrys. Res., 

94(06), 8549-8565, 1989. 
2. Carbon Cycle Division 

P.S. BAKWIN (EDITOR), T.J. CONWAY, E.J. DLUGOKENCKY, D .W. GUENTHER, D. KITZIS , P.M. LANG, 

K.A. MASARIE, P.C. NOVELLI, K.W. THONING, P.P. TANS, AND L.S. WATERMAN 

2.1. CONTINUING PROGRAMS 

2 .1.1. IN SITU CARBON DIOXIDE MEASUREMENTS 

The mixing ratio of atmospheric C02 was measured 

with continuously operating NDIR analyzers at the four 

CMDL observatories during 1993 as in previous years. 

Monthly and annual mean C02 concentrations (in the 

WMO 1985 mole fraction scale (X85)) are given in 

Table 2.1. These values are provisional, pending final 

calibration of station standards. Preliminary selected 

monthly-average C02 mixing ratios for the entire record 

through 1993 are plotted versus time for the four 

observatories in Figure 2.1. 

The C02 in situ systems operated during 1993 from a 

low of 86.2% at BRW to a high of 97.5% of the year at 

MLO. SMO and SPO were operational 96.5% of the 

time. This is based on the number of valid hourlyaveraged C02 mixing ratios that were calculated for the 

year, taking into account missing data because of 

reference gas calibrations during the year. The major 

Joss of data at BRW was due to a mechanical failure in 

the C02 NDIR analyzer in February that was corrected 

in late March. 

The growth rates of C02 as measured by the in situ 

observatory systems, returned to more normal values 

ftcr showing smaller than average growth rates in 

1992. Figure 2.2 shows the instantaneous growth rate at 

the four CMDL observatories for 1980 through 1993. 

The B RW growth rate, which typically has greater 

fluctuations than the other sites, appeared to reach its 

lowest value in mid-1992, before any of the other sites. 

.. TABLE 2.1. Provisional 1993 Monthly Mean C02 Mixing 

Ratios From Continuous Analyzer Data (ppmv, Relative 

to Dry Air WO X85 Mole Fraction Scale) 

Month BRW MLO SMO SPO 

Jan. 362.45 356.79 355.38 354.04 

Feb. 361.81 357.13 355.34 354.22 

March 363.43 358.23 355.93 354.06 

April 363.03 359.14 355.59 354.17 

May 363.22 360.05 354.67 354.31 

June 360.51 359.37 355.42 354.58 

July 351.55 357.22 355.4 1 355.05 

Aug. 347.69 355.31 356.10 355.50 

Sept. 349.14 353.81 355.74 355.72 

Oct. 354.12 354.03 355.82 355.72 

Nov. 358.41 355.20 356.14 355.75 

Dec. 360.17 356.70 356.63 355.55 

Year 357.96 356.92 355.68 354.89 

l6s.---

360> CMauna Loa 

I 

' 0 <>Barrow 

mr >t-io. Samoa 

- · South Pole 

''°t l : • 

E' i.ol 0. ' 8 ' N }<() ' ~ 

0 

u i 

mf 

18 

J.30 

JU '" .. 

: . . : 

320 7 ) 7S n 79 II SJ SS 87 19 91 93 9S 

Year 

Fig. 2.1. Preliminary selected monthly mean C02 mixing 

ratio s at the four CMDL observatories. 

The minimum appeared to propagate sou thward with 

lesser magnitude, reaching SPO last by the first quarter 

of 1993. 

New data acquisition systems arc planned for the 

eventual replacement of the CAMS units at the four 

observatories. Five Hewlett Packard UNIX workstations were purchased in 1993 that wi II take over the 

task of controlling data acquisition not only for the C02 

in situ system, but for the CH4 and CO in situ 

.. '--~---~--~-------

Legend 

- Barrow 

·· ~fauna Loa 

Samoa 

· South Pole 

198> 1951 1912 1983 19&4 t98S 1986 1911 1918 1989 1990 1991 1992 1993 199-1 199.S 

Year 

Fig. 2.2. The variation of the C02 mixing ratio growth rate for 

1980-1993. The curves are the time derivatives of the 

deseaonalized, smoothed daily mean data for the four CMDL 

observatories. 
chromatograph systems as well. These computers, with 

associated equipment, are scheduled to be installed at 

the observatories starting in 1994. These types of 

systems will be compatible with the computer systems 

used in the Boulder laboratory for flask sample analysis 

and reference gas calibrations, so that software will be 

identical for all analysis systems throughout the Carbon 

Cycle Division. 

2.1.2. 

l\IENTS 

F LASK SAMPLE CARBON DIOXIDE MEASURE· 

Carbon dioxide measurements of air samples 

collected throughout the CMDL cooperative flask 

sampling network during 1993 continued to provide 

evidence for recent unexplained variations in the global 

carbon cycle. Provisional mean C02 mixing ratios for 

1993, along with revised values for 1991 and 1992, are 

r eported for 32 sites in Table 2.2. This is the first full 

TABLE2.2. Provisional 1991-1993 Annual Mean 

C02 Mixing Ratios From Network Sites 

C02 (ppm) 

Code Station 1991 1992 1993 

ALT Alert, N.W.T., Canada 357.3 357.5 357.7 

ASC Ascension Island 353.9 355.2 355.8 

BAL Balli<: Sea 359.9 

BME Bermuda (east coast) 356.1 357.1 356.8 

BMW Bermuda (west coast) 356.6 356.3 357.3 

BRW Barrow, Alaska 357.6 357.5 358.2 

CBA Cold Bay, Alaska 357.3 357.3 357.8 

CGO Cape Grim, Tasmania 352.8 353.6 354.5 

CHR Christmas Island 355.4 356.5 357.3 

CMO Cape Meares, Oregon 356.7 356.4 358.5 

GM! Guam, Mariana Islands 356.J 356.4 356.6 

HBA Halley Bay, Antarctica 353.2 354.6 355.1 

ICE Vestrnanaeyjar, Iceland 357.4 

IZO Jzaiia Observatory, Tenerife (] 356.2 357.5 

KEY Key Biscayne, Florida 356.5 357.3 358.4 

KUM Cape Kumukahi, Hawaii 355.8 356.3 357.1 

MBC Mould Bay, Canada 357.6 357.4 357.8 

MHT Mace Head, Ireland [] 356.l 356.7 

MID Midway Island 357.0 356.8 357.5 

MLO Ylauna Loa, Hawaii 355.6 356.5 356.9 

NWR Ni wot Ridge, Colorado 356.1 356.9 357.4 

PSA Palmer Station, Antarctica 353.2 354.2 355.J 

QPC Qinghai Province, China [] 356.6 357.3 

RPB Ragged Point, Barbados 355.9 356.0 356.7 

SEY Mahe Island, Seychelles 353.9 354.9 356.0 

SHM Shemya Island, Alaska 356.7 357.2 357.7 

SMO American Samoa 354.2 354.9 355.6 

SPO South Pole, Antarctica 353.1 354.1 354.8 

STM Ocean Station M 356.5 356.6 357.5 

SYO Syowa Station, Antarctica 353.3 354.2 354.5 

TAP Tae-ahn Peninsula, S. Korea 359.7 360.5 360.4 

UUM Ulaan Uul, Mongolia 356.6 357.1 

Square brackets indicate insufficient data to calculate annual mean. 

year of data from the Baltic Sea (BAL) and Vestmanaeyjar, 

Iceland (ICE). Three new sites were added to the network 

in 1993: Hegyhatsal, Hungary (HUN); Wendover, Utah 

(UTA); and Gozo, Malta (GOZ). 

The selection of new network sites continues to be 

motivated by the need to include measurements from 

continental regions in gl obal carbon cycle analyses. 

Three examples of this strategy are shown in Figure 2.3, 

where the C02 data for Ulaan Uul, Mongolia (UUM); 

Tae-ahn Peninsula, South Korea (TAP); and Qinghai 

Province , China (QPC) are plotted. The r emote desert 

site at UUM and the high plateau location of QPC 

appear to be excellent sites for sampling well-mixed 

continental air, unaffected by local vegetation or 

pollution sources of C02. The coastal site at TAP is 

more heavily influenced by local anthropogenic sources, 

as evidenced by the higher variability, but it has already 

y ielded useful information relevant to regional CH4 

emissions [Dlugokencky et al., 1993]. 

19 

Sampling was temporarily discontinued in the Pacific 

Ocean from the Blue Star Line ships Southland Star, 

PAC (August) and Wellington S tar, PAW (July), and in 

the South China Sea from the Chevron ship Carla A. 

Hills, SCS (February). Pacific Ocean sampling was 

restarted in October from the Blue Star Line ship 

California Star and given the 3-letter code OPC. 

Sample collection resumed in the South China Sea from 

aboard the Great Promise in November, retaining the 

same site code, SCS. 

The lower-than-average rate of increase of atmospheric 

C02 observed in 1992 continued in 1993. The C02 data for 

Mould Bay and South Pole are shown as examples in 

Figures 2.4 and 2.5. An analysis of the flask network data 

through 1992 yielded a globally-averaged C02 growth rate 

of 0.6 ppm yr-1 from 1991 to 1992 [Conway et al., 1994]. 

UU\! (44°N, I I 1°E) 

'E 37u 

§ 36J 

19~: 

· .. 

!992 

Year 

. . 

" 00 11 

!/'; . ,,c Cll',$00,. ., .. . ... .. 

!993 

'•' 

Fig. 2.3. C02 mixing ratios determined for flask samples 

collected at Ulaan Uul, Mongolia (UUM); Tae-ahn Peninsula, 

South Korea (TAP); and Qinghai Province, China (QPC) from 

1991 through 1993. The square symbols represent the average 

C02 mixing ratios for two flasks collected in series. 
300 .i'i t\ it: ~ ' : . : 

355 

~ 

. , : . :• 350 '• : ; 1, H I• 

:' I ;; .. 1 

0 345 ~ f • ; 

u 340 : ~ '• I' ~ 335 ·! I 

. ~ 

81 82 83 84 85 815 ,,, 88 89 90 111 92 93 

Year 

Fig. 2.4 . C02 mixing ratios measured in flask samples 

collected at Mould Bay, Canada (MBC). The square symbols 

repre sent the average va lue for two flasks collected in series 

The smooth curve represents the deseasonalized ong-ter~ trend. Note the near-zero increase in 1992 and the slight 

increase in 1993. 

87 88 89 90 111 92 93 

Year 

Fig. 2.5. C02 data and long-term trend for SPO. Note that the 

1992-1993 growth rate decl ine is not as pronounced as at 

\1ould Bay. 

The average growth rate for the latitude band from 30° to 

90°N, based on data through the end of 1992, was 

essentially zero. The global and semihemispheric growth 

rates through 1993 are given in Table 2.3. 

The globally-averaged COi increase from 1992 to 

1993 was only -0.7 ppm, about half the aver age 1981-

1991 annual increase. Most of the change in the 1992-

1993 global growth rate compared with 199 1-1992, is 

due to a recovery of the growth rate from 30 ° to 90°N to 

0.7 ppm yr-1 . The COi growth r ates for the othe r 

semihemisphe res during 1992-1993 were nearly equal to 

or slightl y less than during 1991-1992 . The variation 

with time of the globall y-averaged COi growth rate is 

shown in Fi gure 2.6. The uncertaint y of this c urve is 

- 0.2 ppm yr· l from 1981 to 1987, and - 0.1 ppm yr· l 

thereafter. For the last 6 m onths of 1993, this curve is 

less certain because the end of the curve is poorly 

constra ined until several months of 1994 data are 

TABLE 2 .3. Semihemisphcric and Globally 

Averaged COi Growth Rates (ppm yr I) 

Period 30-90"S 0-30"S 0-30"1\ 30-90"1'\ Global 

198 1-1991 1.43 1.48 1.51 1.59 1.50 

199 1-1992 0.93 0.89 0.62 0.09 0.64 

1992-1993 0.87 0.82 0.59 0.67 0.74 

20 

81 82 83 84 . 85 88 ,,, 88 89 90 111 92 93 

Year 

fig. 2.6. The globally averaged C02 growth rate obtained 

from the flask network data. Because this curve is based on 

data only through the end of 1993, the last 6 months mu st be 

vi ewed with cauti on. Preliminary 1994 data suggest that the 

uptu rn of the growth rate in 1993 will conti nue into 1994. 

included. A preliminary look at available 1994 data 

suggests that the upturn of the COi growth rate at the end 

of 1993, evident in Figure 2.6, will continue into 1994. 

2.1.3. I N S ITU MF.TIIA'.'IE MEASU REMENTS 

During 1993, in situ measurements of atmospheric 

CH4 continued with a frequency of 60 samples per day 

at MLO and BRW. The precision of the measurements 

(-0.2%) is limited in part by variations in laboratory 

temperature that affect the flow rate of the flame 

ionization detector (FID) fu e l, Hi . In Figure 2.7, 

re fe rence peak heights arc plotted for a 2-wk period at 

MLO. A distinct diurnal cycle is evident. This is 

obs erved because the Hi cylinder is stored in an 

attached , but unheated portion of the MLO laboratory , 

where temperature mearly tracks the outside 

temperature. The low pressure setti ng of the cylinder 

regulator dete rmines the Hi flow rate at the FID, and is 

sensitive to temperature. Fortunately, the temperature 

ch ange is slow enough that the measure-ments are not 

affected too severely. At BR\V, variations in re ference 

peak hei ght are even larger than at MLO, but these 

probably cannot be fully explained by variations in 

laboratory tem perature . A temperature controlled, 

hea ted module is being built where high-precision 

pr essure regulators wil l be housed, and these will 

determin e the gas flow rates without the effects of 

varyin g room temperature. The gas sample valve wi ll 

be moved from the GC oven into the heated module. 

The benefi t o f this is that the GC oven can then be used 

to bake out the sili ca gel and molecular sieve columns 

at much higher temperatures than curren tly achievable 

with the valve inside the oven since the valve can be 
21 400 

J: 21200 oi 

-~ 21000 

~ 

~ 20800 a.. 

v 20600 u 

c: 

~ 20400 

~ 

~ 20200 

20000 

l. .;_I ' ~.· 

,J'. .~th '.! . ·~·r :" , ,, • ~. ~· f J i • 

2 3 4 5 6 7 8 9101112131 4 15 

December 1993 

Fig. 2.7. Methane reference gas peak heights, in counts (where 

1 count = 0.125 m V), for a 2-wk period at MLO. Peak heights 

were quantified with an HP3393A integrator. 

damaged by heating above 150'C. A GC containing 

these modifications should be installed at MLO during 

1994. 

Edited, unconstrained, daily mean CH4 mixing ratios 

are shown in Figure 2.8a for BRW and 2.8b for MLO. 

Features in the data in 1993 are similar to previous 

years. At MLO, CH4 is highly variable on time scales 

. of days to weeks because of variations in atmospheric 

transport [Harris et al., 1992). At BRW, most of the 

highest values arc because of local CH4 emissions. At 

both observatories, CH4 is lower during summer than 

during winter because of chemical destruction by 

hydroxyl radical. Methane seasonal cycles at MLO and 

BRW are explored in more detail below. 

In Figure 2.9a, stand ard deviations from the daily 

means are shown for MLO. The maximum frequency 

.,.:.•1 FEB '-HA :.PR t·'A.1 JJJ .l.l ;. iJ SEP CCT r1:J~ DEC 

1 ,-,,o 01 __, 

' I i - l 'f-0 A I ~ I'' I ' • I, 1 

~ •''0 \'r\, ')\ ij\fu11\ I, l,il J\,q . /\. 1~ ', ,1 11vv·.'i1..,"j t I •' ·I',\/· ., . I\ 1; ' • I\ I\ v 172C I r '-. 1 ~ r '" I~·~' • · ' (• • • "\ , I 

' I I II I ... : 1 I ·'. I .. 

_)...', =Ee u.i,q ;.;:q V.l.f JJ., .J..\.. :. Jj SE;> OCT ., • c:E:C 

1993 

Fig. 2.8. Daily mean CI-14 mixing ratios in ppb for (a) BRW 

and (b) MLO for 1993. The data arc unconstrained, but have 

undergone a quality control step to ensure that the analytica l 

instrument was working optimally when they were obtained 

[Masarie et al., 1991). 

21 

0.05 

0.04 

0.0.3 

0.02 

0.01 

0.05 

>.. 

u 0.04 

c 

v 

:::> 0.0.3 

O"' 

v 

'-

u.. 0.02 

0 .01 

0 5 10 15 20 25 

Standard Deviation (ppb) 

Fig. 2.9. (a) Histogram of standard deviations for MLO daily 

means calculated from hourly aveuges. (b) Same u a, but data 

were constrained to time periods between 0000 to 0700 LST to 

capture downslope conditions. In both cases, there is one 

datum lying outside the range plotted. 

occurs at s -4.5 ppb, and the distribution has a 

relatively long tail. The shape of the distribution 

depends on the instrument prec1st0n and natural 

variations in the CH4 mixing ratio at the sampling site. 

At MLO a diurnal cycle in the methane mixing ratio 

sometimes exists with a peak-to-peak amplitude of -10 

ppb because of the upslope and downslope wind regimes 

[Peterson and Rosson, 1993). Daily means were also 

calculated for times of predominantly downslope 

conditions (0000-0700 LST) that represent free 

tropospheric air. The associated standard deviations are 

shown in Figure 2.9b. Note that the maximum in the 

distribution shifts to s -2.5 ppb, close to the instrument 

precision, and much of the long tail is no longer 

present. Still, the distribution is not Gaussian. This 

results because natural variations in CH4 mixing ratios, 

due to vari ations in transport, are still present. 

The CH4 time-series is a combination of three 

primary factors: (1) a long-term trend because of the 

small imbalance between CH4 sources and sinks; (2) an 

annual cycle because of the seasonality of some CH4 

sources and the CH4 photochemical sink; and (3) shortterm variations occurring on time scales of days to 

weeks due to variations in atmospheric transport at the 
sampling sites. These components were separated for 

analysis by first fitting a quadratic polynomial to the 

data to represent the Jong-term trend and a series of 

four harmonics to represent the average seasonal cycle. 

(1) 

• L. [a2i + 2 sin (27tit) + a2i + 3 cos (27tit)] l•I 

Di gital filtering of the residuals is applied to determine 

short-term variations (filter cut off = 4.56 cycles yr· I) 

and interannual variations in the Jong-term trend (filter 

cut off = 0.55 cycles yr-1). 

The average, detrended seasonal cycles for BRW (a) 

and MLO (b) arc shown as the solid curves in Figure 

2. 10. These curves show only the fundamental and 

harmonic frequencies. The filled circles arc de trended 

monthly means (± 1 s) determined from a smooth curve 

fitted to daily means. At MLO, the average position of 

the seasonal maximum was at the end of November, and 

the seasonal minimum was during the first week of 

August. The average peak-to-peak seasonal cycle 

amplitude was 25.l ppb. At BRW, the average position 

.30 

20 ,........ 

.D 10 0.. 

0.. 0 ...__,. 

\-r~ - - 1"" v 

u 

-20 

-.30 (a) 

.30 

20 ,........ 

.D 10 0.. 

0.. ++- 0 ...__,. 

~ 

I - 10 u 

-20 

- 30 (b) 

J F M A M J J A S 0 N D 

f-ig. 2.10. Average seasonal cycles fo r BRW (a) and MLO (b) 

determined from the fundamental and harmonic frequencies in 

eq. I. Detrended monthly means are also shown (±Is); these 

were dete rmined from the smooth ·curve fits to comple te data 

records for each site. 

22 

of the seasonal maximum was at the b eginning of 

February, and the minimum occurred on average at the 

end of June. The average seasonal-cycle ampl itude at 

BRW was 47.2 ppb. Minimum values at both sites 

occurred during the summer when the photochemical 

sink was most active. The minimum at BRW preceded 

MLO by about 6 weeks. This is probably due to the 

seasonality of CH4 emissions from borcal wetlands that 

become active during early summer and reach their peak 

emissions during late summer, somewhat canceling the 

effect of chemical destruction. Although the emissions 

from boreal wetlands and rice agri culture also play a 

part in determining the phase and amplitude of the CH4 

seasonal cycle at MLO, the e ffect is smaller due to the 

large distances between MLO and the source regions. 

2.1.4. FLASK '1EASUREl\IENTS OF METll ANE 

During 1993, the determination of the global 

d istribut ion of atmospheric CH4 continued at 37 

sampling sites of the Carbon Cycle Division's 

cooperative air sampling network. The gaps in the data 

records (see section 2 .1.2) prevent us from including 

annual means for shipboard samples coll ected in 1993. 

Sampling was started at three new sites during the year: 

Hegyhatsal, Hungary, HUN (March), Wendover, Utah, 

UTA (May), and Dwcjra Point, Gozo, Malt a, GOZ 

(October). Two of the sites arc continental (HUN and 

UTA), and they should provide interesting new data to 

complement the other sites in the CMDL predominantly 

ocean-based network. Provision al annual mean values 

for 1993 are given in Table 2 .4. 

One of the best known constraints on understanding 

the global atmospheric CH4 budget is the rate of 

growth. Because of the importance of C H4 as a 

greenhouse gas, variat ions in the trend have been 

newsworthy, especially during 1992 to 1993 when 

dramatic changes in growth rate were observed [Steele 

e t al., 1992; Dlugokencky e t al., 199411, b]. The CH4 

growth rates for the northern and sou thern hemispheres 

determined from the smoothed CMDL fl ask sample data 

are shown in Figure 2. 11. In both hemispheres, a longterm decrease in the rate of increase was observed . In 

addition, significant interannual va riations were also 

present. 

In the southern hemisphere, the re was a large increase 

in the growth rate during 1988- 1989. Such changes can 

be explored quantitatively using mass balance 

equations. For the southern hemisphere , the rate of 

increase in CH4 is given by 

dS/dt = Q5 + f(N-S) -kS (2) 

where S and N arc the burdens for the southern and 

northern hemispheres, Q5 is the CH4 source strength in 

the southern hemisphere, f is the rnverse of 

interhemispheric exchange time (-1 yr· I), and k is the 
inverse of the methane lifetime (-0.1 yr· I). The second 

de ri vative is: 

d2S/dt2 = df/d t(N-S) + fd(N-S)/dt + 

(3) 

dQ5/dt -kdS/dt -Sdk/dt. 

Except for the first term on the right-hand side, all of the 

terms in eq. 3 can be estimated from the measurement data, 

and d2S/dt2 is determined by taking the derivative of the 

growth rate curve in Figures 2.1 1 and 2.12. In 1988-1989, 

it was -10 ppb yr-2 or 14 Tg yr2. The difference in 

hemispheric burdens is determined as the difference 

between the annual means for each hemisphere, which is 

about 90 ppb or 125 Tg. It was assumed that this 

difference does not vary with time, although interannual 

variations in this parameter have been observed [Steele el 

al., 1992). The last three terms on the right-hand side of 

eq. 2 were interpreted as the fall off in the southern 

hemisphere growth rate, determined as twice the coTABLE 2.4. Provisional 1993 Annual Mean CH4 

Mixing Ratios From the Flask Network Sites 

Code Station CII4 (ppm) 

ALT Alert, N.W.T., Canada 1799. 1 

ASC Ascension Island 1678.2 

BAL Baltic Sea 1810.3 

BME Bermuda (cast coast) 1773.6 

BMW Bermuda (west coast) 1772.8 

DRW Barrow, Alaska 1807.0 

CBA Cold Bay, Alaska 1792.9 

CGO Cape Grim, Tasmania 1667.6 

CHR Christmas Island 1693.3 

CMO Cape Meares, Oregon 1782.1 

GMI Guam, Mariana Islands 1723.6 

GOZ Dwejra Point, Gozo, Malta [) 

IIUN 1-legyhatsal, 1 lungary [) 

ICE Vestmanaeyjar, Iceland 1793.2 

ITN WITN, Grifton, N. Carolina 1810.7 

IZO lzaiia Observatory, Tenerife 1754.l 

1113A Halley Bay, Antarctica [) 

KEY Key Biscayne, Florida 1750.9 

KUM Cape Kumukahi, Hawaii 1745.5 

MOC Mould Bay, Canada 1803.2 

MHT Mace Head, Ire! and 1787.3 

MID Midway Island 1760.0 

MLO Mauna Loa, Hawaii 1727.1 

NWR Niwol Ridge, Colorado 1760.6 

PSA Palmer Station, Antarctica 1668.3 

QPC Qinghai Province, China 1764.7 

RPU Ragged Point, Barbados 1733.7 

SEY Mahe Island, Seychelles 1687.2 

SGI South Georgia Island [) 

SllM Shemya Island, Alaska 1794.6 

s:-.10 American Samoa 1672.5 

SPO South Pole, Antarctica 1666.7 

SThl Ocean Station M 1796.6 

SYO Syowa Station, Antarctica 1677.2 

TAP Tae-ahn Peninsula, S. Korea 1833.9 

UTA Wendover, Utah [) 

UUM Ulaan Uul , Mongolia 1797.0 

Square brackets indicate insufficient data to calculate annual mean. 

23 

J:. 

-~ 

0 

.... 

CJ' 

:i 

u 

20 

5 

--NH 

······· ·SH 

0 ····························· 

63 64 65 66 67 66 89 90 91 92 93 

YEAR 

Fig. 2. 11 . Instantaneous growth ra te curves a ve raged ove r the 

northern (solid line) and southern hemispheres (dashed line). 

efficient a3 from a fit of eq. 1 to the smoothed southern 

hemisphere data. This gives -0.S ppb yr-2 or 

-0.7 Tg yr-2. Filling in these values in eq. 3 suggests 

that an enhancement by about 12% over average 

interhemispheric transport is necessary to explain the 

observation. S leele et al. [1992) suggested that 

increased interhemispheric transport occurred in 1988-

1989 because of a La Nina event. La Nina events are 

char ac teri zed by relatively cold surface temperatures in 

the equatorial Pacific and positive westerly wind 

anomalies at 200 mbar in the central, equatorial Pacific. 

Such conditions may be conducive to enhanced 

transport of trace gases between the hemispheres. Since 

CH4 mixing ratios are always greater in the northern 

hemisphere than the southern hemisphere, such 

increased transport would lead to an apparent increase 

m the growth rate m the southern hemisphere. 

20 --.-

15 ~ 

.... 

>.. 10 .....___ 

.D 

a. 5 a. 

.__. 

w 0 ..... 

~ -5 I 

..... 

3 

0 

-10 

a:: 

(..'.) -15 <J 

- 20 

-25 

83 R'1 R"> 86 P,7 RR 89 90 91 92 9 .) 

YEAR 

Fig. 2.12. Derivative of the southern hemisphere growth rate 

curve shown in Figure 2. 11 (dashed line). The positi ve 

deviations are u sed to evaluate th e left h and side o f equati on 3 

(section 2.1.4). 
This hypothesis is supported by an observed 

simultaneous decrease in the growth rate in the northern 

hemisphere by a similar amount. 

The effects of a change in interhemispheric transport on 

the hemispheric growth rates were investigated with a 2-

box model, with one box for each hemisphere. In the 

model, sources and sinks were constant, but the 

interhemispheric exchange term was increased by 10% 

during 1988 and then returned to normal in 1989. The 

growth rate for the model result is shown in Figure 2.13. 

The apparent decrease in growth rate in the year following 

the increased inter-hemispheric exchange occurs in the 

model result, and the observation, as the trend, comes back 

to its average value. 

During 1991, another large oscillation in the growth 

rate was observed, but a La Nina was not. Enhanced 

interhemispheric transport may h ave resulted because of 

the effects of aerosol injected into the atmosphere by 

the eruption of Mount Pinatubo [Pitari, 1993]. The 

change in f required to explain the measurements was 

about 18%. A corresponding change in growth rate in 

the northern hemisphere was not observed, suggesting 

tha t if interhemispheric exchange was responsible for 

the change in southern hemispheric growth rate at that 

time, there must have been a significant change in 

northern hemisphere sources or sinks. 

During 1992 and 1993, the CH4 growth rate in the 

southern hemisphere decreased dramatically. The 

increase in CH4 during 1992 wa~ (5.0 ± 0.8) ppb and 

(3.6 ± 1.0) ppb during 1993. These values compare 

with a trend of (10.6 ± 0.1) ppb yr· I averaged over the 

full measurement period (1983-1993 ). The cause of this 

decrease is sti ll unknown . In part it is a response to the 

large increase in growth rate just prior to this, but CH4 

st able isotope data [Lowe et al. , 1994] indicate th at 

decreased emissions of fossil CH4 in the northern 

>- 18 ......... 

.D 

a. 

a. 16 

<I> 

0 

a:: 14 

:5 

~ 12 ~ 

0 

<I> 

c 10 

0 

r. 

<I> 8 ~ 

· .. 

--NH 

······-· SH 

83 84 85 86 87 88 89 

YEAR 

'· 

90 91 92 93 

Fig 2.13. Growth rate curves determined from a 2-box model 

where interhemispheric transpo rt was increased by 10% during 

1988 and then returned to norma l in 1989. All other source and 

sink terms in the model remained constant. 

24 

hemisphere [Dlugokencky et al., l 994a] and decreased 

biomass burning in the tropics may have played a 

significant role. 

2.1.5. I N SITU CARBON MONOXIDE MEASUREMENTS 

Quasi-continuous in situ measurements of CO were 

made at BRW during 1993 using the gas chromatographmcrcuric oxide reduction detector previously described 

[Pete rson and Rosson, 1993]. The only difference in 

the analysis procedure in 1993 compared with previous 

years was to change the calibration approach from a 2-

point linear (two standards) to a 2-point piecewise 

linear calibration (three standards). The standardization 

procedure and the reference gases were changed on 

January 16, 1993. The new reference gases had CO 

mixing ratios of 77.4, 150.9, and 224 .2 ppb CO. As 

before, all standards were referenced to the CMDL CO 

standard scale [Novelli et al., 1991]. The instrument 

was operational 98% of the time. 

Preliminary CO hourly-average mixing ratios 

measured in situ during 1993 are compared with those 

for 1992 (Figure 2.14a,b). These data have not been 

filtered for background conditions (i.e., constrained by 

wind speed or direction). The time series exhibits 

periods of low vari ability punctuated by short-term 

increases or decreases. These events reflect the 

influence of local sources and the tran sport of air 

parcels from other locations. The seasonal cycle is 

typical of CO in the high northern l atitudes. Both years 

show max imum CO mixing ra tios in late winter and 

early spring, and a minimum occurs in summer. The 

annual mean CO mixing ratio de termined from the in 

situ measurements made at BRW during 1993 was 134.6 

ppb . In spite of the hi gh frequency variation seen in the 

in situ record, this annual average agrees well with that 

• 5() 

. .,, 

350~ ~ })).... . .. 

~ r.. .= ... ;..~ : 

·~ !00 ~ ~~.; ~.... . • 

.:5-) :-

~:o -

J~r.. 

g ml 

_g. 25':>~ :: ·•• . 

o 2C-,;.. ~1'L -Ill....._ u :~J ~~ ...., ..... -....,," : ' 

:o,

5-J~ 

- ~ 

.! '~ FS.:3 I!~~ .l.~ VJ,) JJ J J.J.. !Jj SC::;. 0:~ 

: 993 

(o) 4 

'o) 

fig. 2.14. (a) Prel iminary in situ hourly average CO mixing 

ratios at BRW in 1992. (b) Prelimin ary in situ hourly ave rage 

CO mixing ratios at BRW in 1993. 
TABLE 2.5. Flask Network Sites for CO Analysis 

and Preliminary Annual Mean CO Levels (ppb) 

Code Station 

ALT Alert, N.W.T., Canada 

ASC Ascension Island 

BAL Bailie Sea 

BME Bermuda (east coast) 

BMW Bermuda (west coast) 

BRW Barrow, Alaska 

CBA Cold Bay, Alaska 

CGO Cape Grim, Tasmania 

CHR Christmas Island 

CMO Cape Meares, Oregon 

GMI Guam, Mariana Islands 

GOZ Dwejra Point, Gozo, Malta 

ICE Heimaey, Iceland 

ITN WJTN, Grifton, N. Carolina 

IZO Izaiia Observatory, Tenerife 

KEY Key Biscayne, Florida 

KUM Cape Kumukahi , Hawaii 

MDC Mould Bay, Canada 

MHT Mace Head, Ireland 

MID Midway Island 

MLO Mauna Loa, Hawaii 

NWR Niwot Ridge, Colorado 

QPC Qinghai Province, China 

RPI3 Ragged Point, Barbados 

SEY Mahe Island, Seychelles 

SMO American Samoa 

TAP Tae-ahn Peninsula, S. Korea 

UTA Wendover, Utah 

UUM Ulaan Uul, Mongolia 

First 

Latitude Sample• 

82'N April 1992 

S'S Feb. 1989 

55'N Aug. 1992 

32'N June 199 1 

32'N July 1991 

71 'N July 1988 

55'N April 1992 

41 'S June 1991 

2' N Dec. 1989 

45' N Jan. 1992 

13'N Oct. 1989 

36'N Oct. 1993 

63' N Oct. 1992 

35'N July 1992 

28' N Nov. 1991 

25'N Aug. 1991 

20' N June 1989 

76'N Feb. 1992 

54'N June1991 

28'N Jan. 1992 

20' N July 1989 

40'N Dec. 1988 

36'N July 1991 

13 'N March 1993 

4'S Sept. 1990 

14'S Sept. 1988 

36'N Nov. 1990 

40'N May 1993 

44 'N Jan. 1992 

Annual 

Meant 

132.8 (3.5) 

74. 1 (3.9) 

184.5 (17) 

128.4 (6.4) 

128.0 (5.0) 

134.2 (3.2) 

133.8 (4.3) 

50.7 (0.8) 

72.9 (2.1) 

137.0 (3.6) 

86.0 (3.0) 

131.5 (2.6) 

174.1 (14) 

106.7 (3.7) 

100.3 (4.3) 

101.8 (4.5) 

131.1 (3.4) 

126.1 (3.4) 

113.4 (5.2) 

88.5 (4.8) 

117.7 (5.4) 

116.2 (7.6) 

92.5 (2.8) 

80.5 (2.5) 

55.3 (1.9) 

233.7 (28) 

151.5 (6.7) 

*The month and year air samples were first collected in a glass 

flask fitted with Teflon 0-ring stopcocks and analyzed for CO. 

tPreliminary 1993 mean mixing ratios and the standard error are 

taken from a smooth curve fit to the measured CO in flask samples 

as described in Novelli et al., 1991. 

determined from weekly flask samples that are collected 

to represent background conditions (Table 2.5). 

The unfiltered annual mean for in situ measurements 

made in 1993 was lower than that determined for 1992 

(145.4 ppb). This decrease is consistent with the global 

CO decrease observed tn the flask data (see section 

2.1.6). 

In si tu measurements of CO at MLO continued during 

1993. The analysis system was similar to that described 

previously [Peterson and Rosson, 1993). Calibration is 

conduc ted usin3 a 2-point piecewise linear calibration 

scheme. The three standards were changed on 

December 15, 1993; their CO values were 74.5, 137.4, 

and 178.6 ppb. The system operated about 94% of the 

time; some additional data was lost because of problems 

related to data 'storage. The annual mean value for 1993 

calculated from the in situ data (92.3 ppb) is not 

significantly different than the value determined from 

the weekly flask samples (88 .5 ± 4.8 ppb). 

25 

2.1.6. FLASK MEASUREMENTS OF CARBON MONOXIDE 

Carbon monoxide mixing ratios were measured in a 

subset of flasks collected as part of the cooperative 

flask sampling program. Measurements were made 

when glass flasks fitted with Teflon 0-ring stopcocks 

were used to collect the air sample. Table 2.5 lists the 

land-based sites where CO was measured in 1993, the 

date of the first CO measurement, and where possible, 

the 1993 annual mean value for the site. Samples for 

CO were also collected on trans-Pacific and South 

China Sea cruises through June 1993 (data not 

presented). In earl y 1994 these programs resumed (see 

section 2.1.2). Analysis of air from flasks for CO and 

Hi were made on a semi-automated Trace Analytical 

ROA. Methane, CO, and H2 analyses used a common 

reference gas (AAL-1 7270, 112.9 ppb CO). The 

response characteristics of the instrument used for flask 

analyses were non-linear over the range of atmospheric 

values. Preliminary CO mixing ratios were calculated 

using AAL-17270 as an internal reference, final values 

were determined using a 6-8 point calibration curve [as 

described in Peterson and Rosson, 1993; Novelli et al., 

1994a). The precision of the CO method, estimated as 

the difference of mixing ratios determined for each 

flask in a simultaneously collected pair of flasks, was 

typically 2 ppb or better. An automated flagging 

routine was installed with flagged flask pairs having a 

difference of greater than 3 ppb. Hydrogen was 

referenced lo an arbitrary scale awaiting the preparation 

of accurate standards. 

Annual mean CO values for 1993 were calculated for 

stations that had samples collected during the whole the 

year (Table 2.5). These mean values were calculated 

from a curve fit to the complete time series, the 

smoothed curve reduces the effects of any particular 

sample on the whole data set. The data are smoothed in 

time using algorithms developed at CMDL [Th oning et 

al., 1989]. 

Mixing ratios of CO determined in flask samples were 

used to determine the distribution of CO from June 

1990 to June 1993. Locations were used that had at 

least 2 y\!ars of measurements before June 30, 1993. 

This included 10 fixed sites and 17 shipboard sites from 

the Wellington Star (a similar shipboard sampling 

program aboard the Southland Star is described by Lang 

et al. (1992]). Each of these 27 sites showed a decrease 

in CO over the 3-yr period. The data from each site was 

smoothed in time as described previously, and a 

meridianal curve was fit to each biweekly period. 

These curves represent the surface presented in Figure 

2.15. 

These smoothed data were combined to calculate a 

quasi-global average CO mixing ratio (inset, Figure 

2.15). There was a slow decrease in CO levels during 

1990 and 1991, then CO levels dropped sharply in 1992 
JOO 

AVERAGE CO TREND 

,, ·::LS] a. 

--" 200 

~ 70 

-2' 91 92 93 

8 YEAR 

:00 

0 

-~-

Fig. 2.15. Three-dimensional representation of the distribution 

of CO in the marine boundary layer. The surface represents 

data smoothed in time and latitude for the period June l, 1990, 

to June 30, 1993. The inset shows the average CO mixing ratio 

during this period. 

and the first half of 1993. Possible reasons for this 

change include decr~ases in CO emissions because of 

decreases in fossil fuel combustion and biomass 

burning, or an increase in CO oxidation from increased 

levels of OH [Bakwin el al., 1994; Novelli el al., 

1994b]. 

2.1.7. CO STANDARDS 

The primary CMDL CO standards were prepared 

gravimetrically and then propagated to a set of working 

standards [Novelli el al., 1991]. These working 

standards were also calibrated against three CO-in-air 

standards prepared by the CMDL Nitrous Oxide and 

Halocarbon Di vision in March 1992 using gravimetri c 

methods. The differences in CO values assigned to the 

working standards using different reference gases were 

less than 1% [Novelli et al., 1994a]. 

The CMDL CO standards were compared with 

standards used by the NASA-Langley, Differential 

Absorption CO Measurement Group (Hampton, 

Virginia) and the Fraunhofer Institute (IFU) (GarmischPartenkirchen, Germany). The intercalibration of eight 

standards having CO levels between 100 and 165 ppb 

indicated agreement between CMDL and NASA of 

better than 2%. Calibration of six standards by CMDL 

and IFU having CO mixing ratios between 50 and 200 

ppb indicated agreement to better than 4% . The details 

of the intcrcalibrations and their results are presented in 

Nove lli et al. [1994a]. 

2.1.8. NEW AIR SAMPLil'G SYSTEM 

A new system was developed that will assure good 

measurements of the stable isotopic composition of 

oxygen in C02 (1 80/170) in flasks previously 

compromised by water condensation. The unit, dubbed 

the Airkit, houses a thermoelectric cooled water 

condenser with a micro-controlled air sampling system 

that eliminates most manual operations by the sample 

taker. Preliminary laboratory tests indicate good 

180/170 values from a very wet airstream. This system 

will be field tested in the coming year at SMO. 

2.1.9. AIRCRAFT PROJECT 

The aircraft project was started in 1992 to measure 

C02. CH4 , and CO gradients, and seasonal cycles from 

the boundary layer to the mid-troposphere. By 

sampling the free troposphere, mid-continent trace gas 

values can be measured without being affected by 

localized sources and sinks. These values can then be 

used to limit the number of regional source-sink 

scenarios that need to be considered in inversemodeling studies. In addition, if the C02 values are 

measured often enough, a seasonal cycle can be 

constructed. The seasonal cycle variation with altitude 

indicates the rate at which mixing ratio changes 

propagate upwards. This vertical mixing rate 

information can also help constrain the models by better 

defining atmospheric circulation. 

26 

In 1993, vertical profiles of C02, CH4 , and CO were 

sampled at least every 2 weeks over Carr, Colorado 

(40.9°N, 104.8°W), using a previously-developed 

automated sampling system in a light, single engine 

aircraft (Cessna T-1 82). The profiles consist of 20 

sampl es each, generally taken mid-morning between 

about 2 and 6 km above sea level (which is about 0.5 to 

4.5 km above ground level at Carr). Winds below the 

boundary layer are usually from the south at less than 5 

m s·l, and winds above the boundary I ayer are usually 

from the north or west at more than 10 m s· l. Figure 

2.16 shows the results from a typical flight. Where 

sample pairs were taken at a given altitude to test pair 

agreement, the line plots the average of the pair values. 

All three trace gases show decreasing mixing ratios with 

increased height since there are anthropogenic sources 

but few sinks at ground level during the winter. The 

8 8 8 

6 6 6 

'E 

~ I 1 

" 4 " 4 " 4 "O "O "O 

& ·~ & 0 0 0 

2 

~-~-~ OL---'--- 0~-~--

356 357 358 1744 1768 1791 101 116 132 

C02 (ppm) CH, (ppb) co (ppb) 

Fig. 2.16. Typical profil es o f C02 , CH4 , and CO versus height 

(km) over Carr, Colorado, December 14, 1993. 
increase in mixing ratios for all three gases between 

about 3.0 and 5.5 km, and particularly the wellcorrelated increase at 4 km, may indicate an urbanpolluted a ir mass that has been transported to the 

sampling site. Trajectory analysis from the previous 

year during this season suggests that the air aloft is 

transported from the west and crosses the California 

coast anywhere between San Francisco and the Mexican 

border. Although profiles over Carr are often 

interrupted by these polluted air masses, the gradients 

and seasonal trends remain consistent over multiple 

fl ights. 

Sampling at the Carr site began in November 1992, so 

with over a year of data available at the end of 1993, a 

seasonal cycle can be estimated for any given altitude 

range. Figure 2 .1 7 shows the C02 data for 1993 in a 1-

km wide band centered at 3 km above sea level. The 

overlaid curve is the sum of the first two harmonics of 

the fitted seasonal cycle using the same fitting 

techniques as are used for network flask data. 

Figure 2. 18 shows seasonal cycle plots for 1-km wide 

bands centered at 3-, 4-, 5-, and 6-km above sea level. 

The plot shows two significant feat ures. The first is a 

decrease in seasonal cycle amplitude of about 0.6 ppm 

between the 3- and 6-km bands that gives a consistent 

p icture of decreasing source-sink effects with increasing 

altitude. The second feature is a delay of about 6 weeks 

in the onset of spring draw-down between the lowest 

and highest alt itudes. This information can be used to 

help constrain the vertical m1xmg rate of the 

troposphere in this region as an additional constraint for 

global circulation models. 

In addition to data collection, work continued on 

sampling methods in 1993. A new version of the 

automated sampling system was developed using twovalvc flasks that may be flushed with sample air before 

fillin g. The previous design had only one valve per 

flask and relied on evacuating the flask before 

sampling, a process that was subject to contamination 

and leaks. Also in 1993, attempts were made to use 

E' 

a. 

a. 

~ 

0 

~ 

365 

360 . • • 

J F M A M J J A S 0 N D 

1993 

Fig. 2.17. C02 seasonal cycle at 3-km he ight over Carr, 

Colorado, for 1993 . 

27 

E' 

a. 

..:; 

.Q 

-e 

O' 

c 

·;; .E 

0 

u 

360 

358 

356 

354 

--3 km 

············ 4 km 

- -- - · 5 km _,,,_ ... 6 km 

J F M A M J J A S 0 N D 

1993 

Fig. 2.18. C02 seasonal cycle at 3-, 4-, 5-, and 6-km height 

over Ca rr, Colorado, for 1993. 

different models of light aircraft (Cessna T-210) to 

reach higher into the troposphere, up to 8.5 km above 

sea level. Early efforts were plagued by contamination 

from the plane engine exhaust, but this work will 

continue. The first version of the sampling system was 

also flown in a Russian AN26 aircraft over Bennett 

Island (150°E, 76°N) in an attempt to measure possible 

local CH4 emissions. Although the sampling system 

performed well overall, a leak in the pump head 

contaminated the results. The visit to Russi a was also 

used to lay the groundwork for a 2-yr biweekly 

sampling program over Yakutsk (129°E, 62°N) to beg in 

in 1994. 

2.1.10. TALL TOWERS PROGRAM 

There are 2 full years of continuous C02 data from 

the 610-m tall TV tower in eastern North Carolina 

(35°2 1'55"N, 77°23'38"W, 9 m above sea level). For 

measurements at 496 m above the ground , the rate of 

data return is about 85%. There are also measurements 

at 51 and 123 m. Some statistics of the data for June 

1993 through May 1994 are given in Table 2.6 (data for 

June 1992 through May 1993 are given in Peterson and 

Rosson [1993)). In addi tion, flask samples for CO, 

CH4 , and isotope (13C/12C and 18Q/16Q in C02) analysis 

are collected from the 496-m level once each week. 

In Figure 2.19 the daily afternoon (1500-1700 LST) 

mean C02 mixing ratios at 496-m height on the North 

Carolina tower are plotted with the flask data from the two 

Bermuda sites (BME and BMW). The difference between 

the mixing ratios at these locations gives an approximate 

measure of the afternoon drawdown or increase in C02 

within the atmospheric boundary layer at the tower site 

because of regional surface fluxes. In winter, the afternoon 

means at 496 m on the tower are generally 2-5 ppm higher 

than at Bermuda, likely reflecting small net respiration and 

C02 emissions from fossil fuel combustion around the 

tower site. In summer, afternoon means at the tower 
TABLE 2.6. Statistics of Daily Mean and Median C02 Mixing Ratios at the 

51-, 123-, and 496-m levels on the North Carolina Tower 

51 m 123m 496m 

Month Mean Median Mean Median Mean STDV Median LQ UQ N• 

1993 

June NA NA 361.87 36 1.67 355.35 2.84 355.48 353.46 357.82 22 

July 370. 11 369.16 361.52 36 1.47 353.80 3.80 353.85 351.10 356.46 31 

Aug. 364.45 364.35 355.90 354.98 350.76 4.38 35 1.80 347.24 354.56 26 

Sept. 370.20 366.24 363.07 361.92 355.83 4.45 354.88 353.50 358.46 29 

Oct. 365.79 363.09 362.15 360.94 356.96 4.83 355.81 353.74 359.00 11 

Nov. 368.83 368.52 366.59 364.81 362.22 3.78 362.29 359.20 364.59 27 

Dec. 369.59 369.73 368.00. 367.99 364.83 2.77 364.99 362.43 367.18 29 

1994 

Jan. 369.89 369.68 368.94 368.12 365.99 3.23 365.49 364.42 367.19 20 

Feb. 370.80 369.46 369.07 367.27 366.23 4.32 364.89 363.21 367.43 28 

March 368.80 369.83 367.17 366.90 365.15 2.15 364.77 363.77 366.14 25 

April 369.71 368.83 367.05 366.51 363.42 2.49 363.74 361.67 364.99 29 

May 366.28 366.35 363.49 363.38 360.63 2.94 360.99 359.47 362.02 26 

LQ and UQ indicate lower and upper quartiles, respectively. 

NA indicates data not available. 

•Number of days used in the average. 

are typically 2-10 ppm lower than at Bermuda, 

indicating rapid daytime photosynthesis in the v icinity 

of the tower. Occasionally (i.e., a few times per 

summer), unusually low C02 mixing ratios are observed 

in the flask samples from Bermuda. For example, air 

samples taken at BME and BMW on September 3 and 4, 

1992, res pee ti vely (plotted as triangles in Figure 2.19), 

show values 5-10 ppm below those obtained for 

~ ~ ~ ,~ 1m ~ ~ 1m ~ ~ ~ ~ ~ 

-- ~ ~ ~ - ~ -~ ~ ~ -- Fig. 2.19. Daily afternoon ( 1500-1700 LST) C02 mixing ratios 

at 496 m on the North Carolina tower (points) and CMDL flask 

data from Bermuda (open symbols). The large crosses denote 

monthly medians (horizontal bars) and inner quartiles (vertical 

bars) of the tower data, and the solid line is a smoothed fit 

[Thoning et al., 1989] to the Bermuda data (circles), with points 

lying more than two standa rd deviations from the curve plolled 

as triangles. 

28 

the previous and subsequent weeks. These low values 

fall within the range of afternoon m ixing ratios 

observed during the same period at the tower, 

suggesting that the samples may reflect transport of 

low-C02 air from the continental boundary layer to 

Bermuda. Isobaric back trajectory analysis (J. Harris, 

personal communication, 1993) shows rapid (1-2 day) 

transport of air from the southeast United States to 

Bermuda during this period. 

The isotopic composition of C02 carbon in flask 

samples collected at 496-m height is shown in Figure 

2.20, plotted against the reciprocal of C02 mixing ratio. 

In this plot the intercept (l/C02 = 0) gives a measure of 

the isotopic composition of the C02 source or sink that 

causes the observed variations in C02 mixing ratio. 

Cold and warm season data show significantly different 

relationships. During the cold season the C02 source 

has an isotopic composition of -28.2 (±1 .0, 1 standard 

deviation)%o, close to the value for the global average 

fossil fuel source of -28.5 %0 [Andres et al., 1995]. This 

result indicates that reg ional sources are dominated by 

fossil fuel combustion during the colder half of the 

year. In the warm season a much heavier (-22.8 

(±1.0)%0) C02 flux signature is indicated by the isotope 

measurements, consistent with the increased 

contribution of biological processes. 

The relationship between CO and C02 in flask 

samples taken weekly from the 496-m level are shown 

in Figure 2.21. Carbon monoxide is a product of 

incomplete combustion of organic material (fossil fuel 

and biomass) and is also formed in the atmosphere from 

the photooxidation of CH4 and other hydrocarbons. 

Carbon monoxide is removed from the troposphere 
C02 (ppm) 

370 365 360 355 350 345 340 

Flask data: 920730·940511 0 

0 

0 

·7.5 o.··· .... ·· ,-... a 0 

0 0 

......... 

0 

'-' 

u 

'.'.? ·8 .0 

'O 

·8.5 + 

0.00270 0.00275 0.00280 0.00265 0 00290 

1 /C02(ppm- 1) 

Fig. 2.20. The relationship between snc and C02 in flask samples 

from 496 m on the North Carolina tower. Cold season 

(:-.lovember-April, pluses and solid line) and warm season 

(May-October, circles and dashed line) data are plotted separately. 

The intercepts of orthogonal distance regression [Press et al., 1992) 

lines are -28.2 ± l .09'oo (r2 = 0.95, n = 43) for the cold season, and 

-22.8 ± l .O'!'oo (r2 = 0.95, n = 27) for the warm season. 

ma inly by reaction with the hydroxyl radical , and the 

lifetime of CO in the troposphere at the latitude of the 

tower ranges from around 1 month in summer (when OH 

is most abundant) to greater than 12 months in winter 

[Novelli el al., 1992]. A strong linear relationship 

exists between CO and C02 at the tower in winter 

(November-March, slope = 12.7 (±0.8) ppb CO/ppm 

C02. r2 = 0.93 , with three outliers removed based on 

examination of the residuals). The photochemical 

sources and sinks of CO, and the biogenic sources and 

sinks of C02, are slow in winter and the relationship in 

Figure 2.21 likely reflects a combustion source for both 

species. The slope of the relationship is about 60% of 

that expected from CO and C02 emission inventories 

for fossil fuel combustion in the Uni ted States [J. 

Logan, personal communication, 1993; Bakwin el al., 

1994]. probably because the source of C02 from soil 

respiration is not zero in winter. In summer, biogenic 

sources and sinks of C02 dominate fossil fuel sources, 

and no discernible relationship between CO and C02 

was found. 

A significant linear relationship · was observed 

between CO and CH4 in all seasons (Figure 2.22). The 

slope for wintertime data only is indistinguishable from 

the slope for all of the data, but the correlation is 

somewhat better in winter (r2 = 0.81 for winter, r2 = 

0.54 for all data). This result probably reflects 

29 

250 

,...... 

-g_ 200 

a.. 

0 

u 

150 

100 

Flask data: 920730-940518 

0 

0 

0 0 

340 345 

0 

0 0 

0 

0 

0 

0 

0 

++ 

0 

+ 

0 

0 

• 

0 

350 355 360 

C02 (ppm) 

• 0 + + 

+ + 

+ 0 0 

0 

• 

365 370 

Fig. 2.21. The relationship between CO and C02 in flask samples 

taken weekly from the 496 m level on the North Carolina tower. 

Winter (November-February, pluses) and non-winter (circles) data 

are plotted separately, and the slope of an orthogonal distance 

regression to the wintertime data only (with three outliers (stars) 

excluded on the basis of examination of the residuals) is 12.7 ± 0.8 

pph/ppm (r2= 0.93, n = 32). 

1860 

1640 

,....._1820 

.D 

a. 

a. 

'-' 

1800 

• I 

u 

1760 

1760 

1740 

Flask data: 920730·940516 

0 

0 

0 

00 

0 

0 + 

co 0 00 

+ 0 0 

+ 0 

+ + 0 

100 150 

.. 

+ 00 

0 

0 0 

+ 0 + 

+ 

ol» o 

8 

G. 0 

+ 0 

+ 0 

+ 

200 

co (ppb) 

<(, * 

... + 

+ 

0 

+ 

0 

.. 

Fig. 2.22. The relationship between CH4 and C02 in flask 

samples from 496 m above the surface. Winter 

(November-February, pluses) and non-winter (circ les) data are 

plotted separately. The orthogonal distance regression line is 

fit to all of the data, and the slope is 0.70 ppb/ppb (r2 = 0.66, n 

= 144). Three data points (stars) were excluded from the 

wintertime data analysis on the basis of the CO versus C02 

relationship (see Figure 2.21). 
colocated industrial sources for CO and CH4 (e.g., 

population centers). Apparently , regional biogenic 

sources and sinks for CH4 are small relative to urbanindustrial sources. 

2.2. REFERENCES 

Andres, R.J., G. Marland, T. Boden, and S. Bischoff, Carbon 

dioxide emissions from fossil fuel combustion and cement 

manufacture 175 1-1991 and an estimate of their isotopic 

composition and latitudinal distribution, in The Carbon Cycle, 

Procedings .. 1993 Global Change Institute, Snowmass, CO, July 

19-30, 1993, Cambridge Univ. Press, in press, 1995. 

Bakwin, P.S., P.P. Tans and P.C. Novelli, Carbon monoxide 

budget in the no rthern hemisphere, Geophys. Res. Lei/., 21, 

433-436, 1994. 

Conway, T.J., P.P. Tans, L.S. Waterman, K.W. Thoning, D.R. 

Kitzis, K.A. Masarie, and N. Zhang, Evidence for interannual 

variability of the carbon cycle from the NOAA/CMDL global 

air sampling network, J. Geophys. Res., 99, 22 ,83 1-22,855, 

1994. 

Dlugokencky, E.J., J.M. Harris, Y.S. Chung, P.P. Tans, and I. 

Fung, The relationship between the methane seasonal cycle 

and regional sources and sinks at Tae-ahn Peninsula, Korea, 

Atmos. Environ., 27A, 2115-2120, 1993. 

Dlugokencky, E.J., K.A. Masarie, P.M. Lang, P.P. Tans, L.P. 

Steele, and E.G. Nisbet, A dramatic decrease in the growth 

rate of atmospheric methane in the northern hemisphere 

during 1992, Geophys. Res. Le i/., 21, 45-48, 1994a. 

Dlugokencky , E.J., L.P. Steele, P.M. Lang, and K.A. Masarie, 

The growth rate and distribution of atmospheric methane, J. 

Geophys. Res., 99, 17,021-17,043 1994b. 

Harris, J.M., P.P. Tans, E.J. Dlugokencky, K.A. Masarie, P.M. 

Lang, S. Whittlestone, and L.P. Steele, Variations in 

atmospheric methane at Mauna Loa Observatory related to 

long-range transport, J. Geophys. Res., 97, 6003-60 I 0, 1992. 

Lang, P.M .. L.P. Steele, L.S. Waterman, R.C. Martin, K.A. 

Masarie, and E.J. Dlugokencky, NOAA/CMDL atmospheric 

methane data for the period 1983- 1990 from shipboa rd flask 

sampling, NOAA Tech. Memo. ERL CMDL-4, 88 pp., NOAA 

Environmental Laboratories, Boulder, CO, 1992. 

30 

Lowe, D.C, C.A.M. Brenninkmeijer, G.W. Brailsford, K.R. 

Lassey, and A.J. Gomez, Concentration and tJC records of 

atmospheric meth ane in New Zealand and Antarctica: 

evidence for changes in methane sources, J. Geophys. Res., 

99, 16,913-16,925, 1994. 

Masarie, K.A., L.P. Steele, and P.M. Lang, A rule-based expert 

system for evaluating the quality of long-term in situ, gas 

chromatographic measurements of atmospheric methane, 

NOAA Tech. Memo. ERL CMDL-3, 37 pp., NOAA 

Environmental Research Laboratories, Boulder, CO, 1991. 

Novelli, P.C., L.P. Steele, and J.W. Elkins, The development 

and evaluation of a grav imetric reference scale for 

measurements of atmosphe ri c carbon monoxide, J. Geophys. 

Res .. 96, 13,109-13,121, 1991. 

Novelli, P.C., L.P. Steele, and P.P. Tans, Mixing ratios of 

carbon monoxide in the troposphere, J. Geophys. Res .. 97, 

20,731-20,750, 1992. 

Novelli , P.C., J.E. Collins, Jr., R.C. Myers, G.W. Sachse, and 

!-I.E. Scheel, Re-evaluation of the NOAA/CMDL carbon 

monoxide reference scale and comparisons to CO reference 

gases at NASA-Langley and th e Fraunhofer Institute, J. 

Geophys. Res., 99, 12,833-12,839, I994a. 

Nove ll i, P.C., K.A. Masarie, P.P. Ta n s, and P.M. Lang, Recent 

changes in atmospheric carbon monoxide, Science, 263, 

1587- 1590, 1994b. 

Peterson, J.T .. and R.M. Rosson, Climate Monitoring and 

Diagnostics Laboratory, No. 21, Summary Report 1992, 131 

pp., NOAA Environmental Research Laboratories, Boulder, 

co. 1993. 

Pitari, G., A numerical study of the possible perturbation of 

stratospheric dynamics due to Pinatubo aerosols: 

Implications for tracer tran sport, J. Atmos. Sci .. 50, 2443-

2461, 1993. 

Press, W.11., S.A. Teukolsk y , W.T. Vetterling, and B.P. 

Flannery, Numerical Recipes in C, 994 pp., second edition, 

Cambridge Un iversity Press, Cambridge, 1992. 

Steele, L.P., E.J. Dlugokencky, P.M. Lang, P.P. Tans, R.C. 

Martin, and K.A. Masarie, Slowing down of the global 

accumulation of atmospheric methane during the 1980's, 

Nature, 358, 3 13 -316, 1992. 

Thoning, K.W., P.P. Tans, and W.D. Komhyr, Atmospheric 

carbon dioxide at Maun a Loa Observa tory, 2, Analysis of the 

NOAA GMCC data 1974-1985, J . Geophys. Res., 94, 8549-

8576, 1989. 
3. Aerosol, Radiation, Ozone, and Water Vapor Division 

B. BODHAINE, E. DUTTON, R. EVANS, R. GRASS, J. HARRIS, D. HOFMANN, W. KOMHYR, 

D . NELSON, J. OGREN, ANDS. OLTMANS 

3.1. CONTINUING P ROGRAMS 

3 .1.1. SURFACE AEROSOLS 

3 .1.1.1. BASELI NE OBSERVATIONS 

Operations 

The aerosol monitoring program at BRW, MLO, and 

SPO continued during 1993 as in previous years. CN 

concentration was measured continuously with TSI 

(butanol-based) CN counters at BRW, MLO, and SPO. 

Daily calibration points were provided by Pollak CN 

counters at all stations. Aerosol scattering extinction 

coefficient (O'sp) at 450-, 550-, 700-, and 850-nm 

wavelengths was measured continuously at BRW, MLO, 

and SPO with four-wavele ngth nephelometers. Aerosol 

absorption coefficient has been measured continuously 

using aethalometers at BRW since April 1988, MLO 

since April 1990, and at SPO during December 1986-

December 1991. 

Figure 3.1 shows daily geometric means of CN 

concentration (lower portion of each plot), O'sp (middle 

portion of each plot), and Angstrom exponent (upper 

portion of each plot) at the BRW, MLO, and SPO 

stations for 1993. Two independent values of Angstrom 

exponent (a.) were calculated from the 450-, 550-, and 

700-nm channels of O'sp data using the relation a. = -6 

log O'sp/6log A., where a. is Angstrom exponent and A. is 

wavelength. These averages were calculated only if 

data for all three wavelengths were available. A 

graphical presentation of the monthly geometric means 

of the entire data record for BRW, MLO, and SPO is 

shown in Figure 3.2. Monthly geometric means of the 

1993 aerosol data are listed in Table 3.1. 

Discussion 

The BRW data in Figure 3.1 show a O'sp maximum of 

about 3 x 10-5 m· I during spring, typical of the wellknown Arctic haze. Minimum values of O'sp below I0-6 

m-1 occurred in July-August. The BRW long-term 

record shown in Figure 3.2 clearly shows this annual 

cycle in O'sp • with springtime monthly means of about 

I0-5 m-1 and summertime monthly means of about 10·6 

m-1. The BRW CN record shows a more variable 

semiannual cycle with a maximum that usually 

coincides with the maximum in Osp and a secondary 

maximum in late summer or early fall. The 1993 annual 

geometric mean for CN is 195 cm·3 (compared with 228 

cm-3 for 1992) and the annual mean for O'sp (550 nm) is 

4.85 x 10·6 m·l (compared with 4.62 x l0-6 m·l) for 

1992. Note that the G.E. counter CN record is shown as 

a solid line and the TSI counter CN record is shown as a 

31 

dashed line. The individual squares plotted on the CN 

graph are monthly means of Pollak counter 

observations. These are shown separatel y because the 

TSI and Pollak counter give independent data sets, 

whereas the G.E. counter was calibrated using the 

Pollak counter data. Gaps in the data are apparent 

because of the averaging process that excludes data if 

local pollution is evident or if wind direction is not 

from the clean a ir sector. The BRW aerosol data set 

was presented by Bodhaine [ 1989] and Quakenbush and 

Bodhaine [1986]. 

The MLO O'sp data shown in Figure 3.1 arc typical of 

the long-term record, with the highest values in April 

and May, and lower values in fall and winter. Large 

events are apparen t in the springtime, caused by the 

long-range transport of Asian desert dust in the upper 

troposphere to the vicinity of Hawaii. As discussed in 

the 1988 Summary Report [Elkins and Rosson, 1989), 

O'sp values were generally higher since the install at ion 

of the new nephelometer in 1985 and have not reached 

the low values expected in winter. The MLO CN record 

shown in Figure 3.1 is typical, giving an annual 

geometric mean concentration of 381 cm-3 (compared 

with 375 cm-3 during 1992); the annual mean of O's p 

(550 nm) is 9.20 x 10-7 m-1 (compared with 8.58 x 10·7 

m·l during 1992). Note that all MLO aerosol data 

presented here are in the form of geometric means 

during 0000-0800 HST (I 000-1800 UT) in order to 

include data for nighttime downslope wind conditions 

only. The MLO data set was presented by Massey et al. 

[1987). A special study concerning aerosol measurements during the MLOPEX experiment is presented in 

section 3.2.2. 

The SMO 1993 CN data are not presented because of 

problems associated with the sampling stack during that 

year. The SMO nephelometer was removed from 

service in March 1991. Future plans for the SMO 

aerosol program include a new humidity-con trolled, 

size-controlled sampling system and a new multiwavelength ncphe lometer. 

The SPO O'sp and CN data are shown in Figure 3.1. 

These data show a strong annual cycle reach ing a 

maximum in the austral summer and a minimum in the 

austral winter, similar to previous years. The crsp data 

show events due to the transport of scasalt particles in 

winter but fairly clean values in the fall. Referring to 

the long-term data set for SPO shown in Figure 3.2, the 

O'sp data generally show intermed iate values in the 

austral summer and fall, and large events, sometimes 

exceeding 10·6 m·l, in late winter. These large aerosol 

events are caused by the transport of seasalt in the 

upper troposphere from stormy regions near the 

Antarctic coast to the interior of the continent. The 
Ae r oso l Da ta f or Bar row Aero so l Da t a f or Ba rr o w 

i~i:l ~~,tiWNI 

:~r:t1m11:~B11ttt1 rntttm!tfl~N 

1~~ttlh~ttfthl JAN FEB lUR APR IUY JUN JUL AUC SEP OCT NOV DEC 1~14#tt+ffi#R+i 78 77 78 7 g 80 8 1 82 83 84 85 88 87 88 89 90 91 g2 g3 

i~~~ttH~~~~l- i~H#~w··1 ll 'f M.MMH 

Hf-1±±t±t+~~vf4:H :~H\il1~N IN IM+M+NJ 

m:tttttttttttJ r1 11fR#fffHHfffm JAN FEB lUR APR IUY JUN JUL AUC SEP OCT NOV DEC 

Ae r osol Da t a f o r Sout h Pol e 

M·+--r--+-++--Wc.+---!-,.+--ll,-~+--'----1.,--1-+---h-ftl~ 

.: 

.. ..... ~~~~hJll.h-~+.+-:--:-i:-lttr-l+-l!lllH-ll 

::; ~~Hh{HHI~~~~~~ 

o~~~....p..!1μ'L~,i,+-J:IH!W-#-..:...i:l4J-ll!...ll+-Ht--l 

, -1--.-.-.1-..-.-+-.-.~...,.;...,....,~~......:-,..i... ............... .-,.--..-J 

JAN FEB lUR APR IUY JUN JUL AUC SEP OCT NOV DEC 

74 7 5 7 8 7 7 7 8 7 g 80 8 1 82 83 84 85 88 87 88 89 9 0 g I 9 2 9 3 

Aeroso l Da t a f or Sou t h P o t e 

fig. 3. I. Daily geometric means of cr,P and CN data at BRW, MLO, Fig. 3.2. Monthly geometric means of cr,P and CN data for the 

and SPO for 1993. Data for MLO a re included only for 0000-0800 entire data record at BRW, MLO, and SPO. Data for MLO arc 

HST. For each station, CN concentration (lower) is shown as a included only for 0000-0800 llST. cr,P data (middle) arc shown for 

solid line and daily mean Pollak counter data arc shown as small 450 (dolled), 550 (solid), and 700 nm (dashed). Angstrom 

squares. cr,P date (middle) a rc shown for 450 (dolled), 550 (solid), exponents (alpha) were calculated from 450 and 550 nm (dolled) 

and 700 nm (dashed). Angstrom exponents (alpha) were calculated and 550 and 700 nm (solid) cr,P data. :\otc that G.E. C~ counter 

from 450 and 550 nm (dolled) and 550 and 700 nm (solid) cr,P data. data are shown as a solid line, TSI CN counter data arc shown as a 

dashed line, and Pollak CN counter data arc shown as small squares. 

32 
TABLE 3.1. Monthly Geometric Means of CN concentration (cm·3) and Osp (m· 1) at 450, 

550, and 700 nm for BRW, MLO, and SPO During 1993 

Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. 

BR\V 

CN 195 256 239 106 127 122 336 583 209 157 116 210 

a,P (450) 1.22-5 9.62-6 1.59-5 9.86-6 5.03-6 7.09-7 2.33-6 2.51-6 3.28-6 5.70-6 3.57-6 t. J0-5 

a,P (550) 1.13-5 8.85-6 1.45-5 8.38-6 4.24-6 7.7 1-7 2.16-6 2.59-6 3.51-6 5.97-6 3.37-6 1.01.5 

a,P (700) 8.74-6 6.81-6 l.10-5 5.73-6 2.82-6 5.90-7 1.44-6 2.25-6 3. 16-6 5.39-6 2.55-6 8.79-6 

MLO 

CN 385 321 364 407 353 347 396 403 473 367 411 363 

a,P (450) 1.08-6 9.88-7 2.21-6 2.26-6 2.11-6 1.38-6 1.62-6 8.20-7 1.16-6 1.09-6 5.35-7 5.75-7 

a,P (550) 8.7 1-7 8.17-7 1.79-6 1.69-6 1.74-6 1.14-6 1.28-6 5.86-7 8.39-7 7.99-7 3.76-7 4.55-7 

a,P (700) 6.97-7 6.21-7 1.43-6 1.22-6 1.39-6 8.84-7 9.58-7 4.03-7 5.59-7 5.51-7 2.84-7 3.38-7 

SPO 

CN 162 281 216 68 37 26 26 33 73 158 233 197 

a ,P (450) 5.01-7 3.26-7 2.03-7 1.06-7 2.03-7 1.85-7 2.31-7 2.88-7 2.67-7 3.03-7 2.32-7 1.87-7 

a,P (550) 3.9 1-7 2.77-7 1.64-7 9.70-8 1.55-7 1.73-7 2. 14-7 2.30-7 2.22-7 2.47-7 1.95-7 1.63-7 

a,P (700) 3.46-7 2.27-7 1.36-7 7.95-8 1.48-7 1.28-7 1.62-7 1.74-7 1.95-7 2.09-7 1.60-7 1.11-7 

A compact exponential format is used for a,P such that 1.22-5 = 1.22 x lO·S. 

SPO 1993 annual means were about 90 cm-3 (69 cm·3 

for 1992) for CN and 2.00 x l0-7 m-1 (4.41 x 10-7 m·l 

for 1992) for o,P (550 nm). The complete SPO data set 

was presented by Bodlzaine and Shanahan [1990]. 

3.1.1.2. REGIONAL OBSERVATIONS 

In order to address questions concerning climate 

forcing by anthropogenic aerosol particles [Charlson et 

al., 1992; Penner et al., 1994), CMDL is establishing a 

network of regional aerosol monitoring stations. Two 

of the stations are located in marine locations and three 

in continental locations; for each category, one site is 

rela tively free of anthropogenic influences and the 

others arc frequently perturbed by anthropogenic 

aerosols. Table 3.2 lists the sites, their charac teristics, 

and their status as of December 1993. Each station 

operates in close collaboration with a local university or 

government agency that provides onsite support for the 

measurements. 

The scientific questions that define the context of the 

measurements at these sites include: 

• What are the sign , mechanism, magnitude, 

uncertainty, and spatial distribution of the c limate 

forcing by anthropogenic aerosol particles? 

• What are the physical and chemical processes, 

including their rates and spatial distributions, leading to 

formation and removal of the particles responsible for 

the forcing, and how do these processes determine the 

33 

size- and chemical-composition dis1ributions of the 

particles? 

• What is the sens111v1ty of the forc in g and its spnti~l 

distribution to changes in these parameters? 

• How has the forc ing changed in the past, and how will 

it change in the future? 

Clearly, ground based measurements at a few sites 

will provide answers to only a few of these questions. 

Recogni z ing this, the strategy of the CMDL regional 

aerosol measurement program is to determine means, 

variability, and possible trends of key op tical, chemical, 

and microphysical properties for a number of impor1an1 

aerosol types. The measuremen ts will provide groundtruth for satellite measurements and global models, as 

well as key aerosol parameters for global-scale models 

(e.g., scattering efficie ncy of sulfate particles, 

hemispheric backscattering frac ti on). An important 

aspect of this s1rategy is th at the chemical 

meas urements are linked to 1he physical mcasuremcn1s 

through simultaneous, size-selective sampling and 

thermal analysis, which allows the observed aerosol 

properties to be connected to the atmospheric cycles of 

specific chemical species. 

When the sites are fully operational, continuous 

measurements will include the total particle number 

concentration (N101), c loud condensation nucleus 

number concentra tion (Nccn), aerosol optical depth (o), 

and components of the aerosol ext inction coefficient at 

one or more wavelengths (total scattering Osp• 
TABLE 3.2. Regional Aerosol Monitoring Sites 

Perturbed Perturbed 

Category Marine Continental 

Location Sable Is., Nova Bondville, Illinois 

Scotia, Canada 

Designator WSA BND 

Latitude +43.933 +40.053 

Longitude +060.007 +088.372 

Elevation (m) 5 230 

Collaborating Atmospheric Univ. of Illinois, 

Institute Environment Illinois State 

Service, Canada Water Survey 

Status Operational Expected to be 

Aug. 1992 operational 

July 1994 

Sample RH RH <40% RH<40% 

Sample size Dp<l μm Dp<l μm 

Fractions l<Dp<IO μm l<Dp<lO μm 

Optical <rsp (3A.), o(4A.) cr,p (IA.) 

measurements 

Microphysical N101 N101 

measurements 

Chemical Major ions Major ions 

measurements 

backwards hemispheric scattering crbsp • and absorption 

cr.p). Size resolved impactor and filter samples 

(submicrometer and supermicrometer size fractions) 

wi II be obtained for gravime tri c and chemical (ion 

chromatographic, organic/elemental carbon) analyses. 

All size-selective sampling, as well as the 

measurements of the components of the aerosol 

extinction coefficient, will be performed at a low, 

controlled relative humidity (40%) to eliminate 

confounding effects because of changes in ambient 

relative humidity. 

A limited sampling program was conducted from 

April 1993 to March 1994 to evaluate the suitability for 

long-term, ground based, aerosol measurements of the 

proposed monitoring site outside of Laramie , Wyoming. 

This site was chosen because vertical profiles of aerosol 

size distribution have regularly been obtained by the 

University of Wyoming for the l ast 20 years at this site. 

However, 12 months of surface measurements of Gsp 

and N10, revealed that the site is very frequently 

contaminated by local sources in the Laramie Valley, 

making it unrepresentative as a clean continental 

monitoring site. Consequently, measurements of Gsp 

and N,01 were initiated in November 1993 to evaluate 

the feasibility of using the University of Colorado's 

facility on Niwot Ridge as a clean continental site. 

Initi al results from this site are promising, although 

transport of polluted air from metropolitan Denver 

occurs regularly during afternoon, upslope flow 

conditions in the summer. 

Perturbed Clean Clean 

Continental Continental Marine 

K'puszta, Keszcemet, Niwot Ridge, Cheeka Peak, 

Hungary Colorado Washington 

KPO NWR CPO 

+46.967 +40.036 +48.30 

-019.550 +105.534 +124.62 

180 3020 480 

Univ. of Veszprem, Univ. of Un iv. of 

Veszprem, Colorado, Washington 

Hungary Boulder 

Expected to be Site feasibility Operational 

operational measurements May 1993 

Sept. 1994 began Nov. 1993 

RH<40% Uncontrolled RH<40% 

Dp<l μm Uncontrolled Dp<l μm 

l<Dp<IO μm 

crap (IA.), <rsp (IA.), cr,p (IA.) cr.o (IA.), <rsp (IA.). 

0(41..) crbso(IA.) 

NlOl NIOI N,Ol 

Major ions None Major ions 

34 

The Cheeka Peak site is operated independently by 

the University of W ashington with major funding from 

the NOAA Climate and Global Change Program. 

Although the sampling protocols are essentially 

identical to those used at the other CMDL si tcs, all da ta 

acquisition and processing is the responsibility of the 

Universi ty of Washington. Eventually, data from this 

site will be included in the CMDL archive and tabulated 

in a future CMDL Summary Report. 

Summary results for Sable Isl and for 1992 and 1993 

are shown in Figure 3 .3 (daily geometric means) and 

Tables 3.3 and 3.4 (monthly geometric means). Table 

3.5 contains statistics on the measured parameters at 

Sable Island (August 1992-June 1994) for three 

categories: al l cases, and those cases when both N, 0 , 

and Gsp (550 nm, D<l μm) are below and above, 

respectively, one standard deviation of their mean val ue 

("clean" and "dirty," respectively). These criteria 

correspond to N10, <398 cm-3 and Gsp <5 .0 Mm-1 (clean) 

and N, 0 , >2089 cm-3 and Gsp >22.9 Mm-I (dirty). The 

Sable Island site was chosen to provide information on 

the properties of pollution aerosols subsequent to longrange transport from the continent, as well as 

information on aerosols in the clean marine boundary 

layer. The initial results reflect the different transport 

patterns influencing the site, with periods of low 

aerosol number concentration and light scattering 

coefficient interspersed wi th periods of high aerosol 

loadings. Trajectory analyses of a limited number of 

cases reveal that transport from the south and southeast 
~ 

'e 

~ a. 

'O"' 

'E 

c 

0 

0 

~ IO 

~ 

o('Q 

(n) 

2000 

o-1-~--.--~.--~~.,-~~~~~....,....~~~~.....::--'----

150 ~~~~~~~~~~~~----,~ ~~~~~ 

100 

.A~1 50 

0 -1-~~----,~-.-~~~~~~~~----,~~~~--"-

3 ~~~~~~~~~~~~ ~~~~~~~ 

~~~~ 2 

0 -1-~--.------,~-.-~~~~~~~--.------,~~~.,-~ 

: :1-t---T-.......---.---.-r--r-ir------r----r ~I~ ~ V ---,---'-l 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

1992 

(hi 

2000 

O-t~.,-----,,---,------,,----r~.--,----,-,-----,,----r .---'-

150 ~----,----,----,~~~~~~~~~~~~~~~~ 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

1993 

Fig. 3.3. Daily mean aerosol p ro perties at Sable Island (a) 1992 and (b) 1993. Values of <Jsp are measured at 550 nm wave le ngth. 

TABLE 3.3. Sable Island Monthly Means for 1992 

Maximum Diameter Wavelength 

Parameter (μm) (nm) Units 

N,o, All cm·3 

<Jso 10 450 Mm-I 

<Jso 10 550 Mm-I 

(Jso 10 700 Mm·I 

(Jso 450 Mm-I 

(Jso 550 Mm·I 

(Jsp 700 Mm·I 

(clean marine) is associated with low aerosol loadings, 

and tha t trajectories from the west and southwest 

(polluted continental) are associated with high aerosol 

loadings. Monthly mean aerosol loadings are 

considerably higher than the levels encountered at the 

CMDL baseline stations because of the proximity of 

Sable Island to continental pollution sources. 

Inclusion of size- and wavelength-dependence of Osp 

in the sampling protocol allows identification of 

systematic shifts in the aerosol size distribution under 

35 

Aug. Sept. Oct. Nov. Dec. 

944 1135 1100 591 183 

29.7 24.3 26.9 NIA NIA 

26.0 21.8 23.8 NIA NIA 

17.8 15.8 17.1 '>I.IA NIA 

18.8 13.5 16.9 NIA NIA 

14.2 10.0 12.6 NIA NIA 

7.7 5.4 7. 1 NIA NIA 

different conditions (Table 3.5). Fine particles 

(diameter <1 μm) are responsible for less than half of 

the aerosol light scattering (550-nm wavelength), and 

this fraction systematically increases from clean to dirty 

cond itions. Similarly, the Angstrom exponent a 

systematically increases from clean to dirty conditions, 

for both fine and total size fraction s. Together, these 

two findings indicate that fine particles arc 

systematically smaller, and more abundant, und er dirty 

cond itions. Linear regression analysis demonstrates 
TABLE 3.4: Sable Island Monthly Means for 1993 

Maximum Diameter Wavelength 

Parameter (μm) (nm) Units Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. 

N101 All cm·3 693 1064 871 64 1 425 1050 1188 1167 1265 842 1441 585 

a sp 10 450 Mm-I NIA NIA 25.9 27.5 25.0 24.8 25.0 33.5 32.3 25.6 34.4 35.4 

a ,P 10 550 Mm·I NIA NIA 2 1.6 24.4 20.7 21.5 20.9 28.3 28.7 23.2 30.9 32.5 

a ,P 10 700 Mm-I NIA NIA 16.3 20.0 15.8 17.5 16.1 21.9 23.9 20.3 26.3 27.6 

o'sp 450 Mm·I NIA NIA 18.6 16.9 17.7 14.3 14.I 22.I 17.I 11.8 16.4 15.3 

asp 550 Mm·I NIA NIA 13.8 12.8 12.9 10.4 9.8 15.4 12.0 8. 1 11.5 11.0 

a 700 Mm·I NIA NIA 8.7 8.2 8.0 6.4 5.7 8.7 6.9 4.7 6.8 6.6 

TABLE 3.5. Mean Observed Values at Sable Island (August 1992-June 1994) 

Parameter Maximum Wavelength Clean All Dirty 

Diameter (μm) (nm) Units Cases Cases Cases 

N,ot All cm·3 245 912 2884 

a,P 10 450 Mm·I 9.8 28.8 93.3 

a ,P 450 Mm·I 4.3 15.I 63.1 

a,P 10 550 Mm·I 8.7 25.I 74.1 

a,P 1 550 Mm·I 3.0 10.7 43.7 

a,P 10 700 Mm·! 7.2 20.0 51.3 

a,P 700 Mm·I 1.8 6.3 24.0 

ll 10 450/550 None 0.49 0.69 1.17 

ll 1 450/550 None 1.76 1.79 1.93 

ll 10 550/700 None 0.74 0.91 1.49 

ll 550/700 None 2.1 2 2. 19 2.47 

a,P fine/total !+IO 450 None 0.48 0.56 0.70 

a,P fine/tola l !+ IO 550 None 0.38 0.46 0.62 

a,P fine/total 1+10 700 None 0.30 0.36 0.5 1 

Notes: (1) The Angstrom exponent is denoted ll to avoid confusion in the future with the mass scattering efficiency CL (2) The entries for "asp 

fine/total" are the fraction of the total aerosol light scattering coefficient attributable to submicrometer particles. (3) Geometric means arc reported for 

N,01 and a sp. while arithmetic means are reported for ll and a,p fine/total. (4) Clean and dirty cases are those hours when both N101 and asp (550 nm, 

D<l μm) are below and above, respectively, one standard deviation of the mean value. 

that 75% of the variance in the Angstrom exponent 

(total size fr actio n) can b e explained by variance in the 

fraction of light scattering caused by fine particl es (550 

nm waveleng th), i.e., the major factor controlling a is 

the r elative abundance of fine and coarse particl es 

(diameter >1 μ m). 

Information and data from the aerosol g roup at CMDL is 

now available on the Internet by FTP and World Wide Web 

(WWW) servers. Recently processed data, file format 

specifications, documents summarizing data processing and 

flow, and cle an processed data presented in hourly 

averaged files for all years of station operation are 

avail able by anonymous FTP to ftp .cmdl.noaa.gov, 

directory "aerosol." In addition to the above, the CMDL 

WWW server at http://www.cmdl.noaa.gov supplies online 

plots of recentl y processed aerosol data and hypertext links 

to various related documents. 

36 

3.1.2. LIDAR OBSERVATIONS OF AERO SOLS 

(See section 1.1.2. for r eport on Mauna Loa Lidar data) 

3.1.3. TOTAL OZONE OBSERVATIONS 

Total o zone observations c ontinued throughout 1993 

at 15 of the 16 stations that comprise the U.S. Dobson 

spec trophotome ter network (Table 3.6). Of the 15 

stations , 5 were operated by CMDL personnel , 5 by 

NWS, 2 are domesti c cooperative stations, and 3 are 

foreign cooperative statio ns. 

Early in 1993, the instrument that was at the Poker 

Flat Resear ch range was installed on the roof of the 

Geophysical Institute, University of Alaska, Fairbanks. 

This station is making both tot al ozone and Umkchr 

effect observations. 
TABLE 3.6. U.S. Dobson Ozone Spectrophotometer Station Network for 1993 

Station 

Bismarck, North Dakota* 

Caribou, Maine* 

Wa llops Is., Virginia* 

SMO* 

Tallahassee, Florida* 

Boulder, Colorado* 

Fairbanks!, Alaska 

Lauder, New Zealand 

MLO* 

Nashville, Tennessee• 

Perth, Australia 

SPO 

Haute Provence, France 

Huancayo, Peru 

BRW 

Fresno, California* 

Period of Record 

Jan. 1, 1963-present 

Jan. 1, 1963-present 

July 1, 1967-present 

Dec. 19, 1975-present 

May 2, 1964-Nov. 30, 1989; 

Nov. I, 1992-present 

Sept. I, 1966-present 

March 6, 1984-present 

Jan. 29, 1987-present 

Jan. 2, 1964-present 

Jan. 2, 1963-present 

July 30, 1984-present 

Nov. 17, 1961 -present 

Sept. 2, 1983-present 

Feb. 14 , 1964-Dec. 31, 1992 

June 6, 1986-present 

June 22, 1983-present 

*Stations for which total ozone data are tentatively reevaluated. 

The Hauncayo, Peru, sta tion ceased ope ration at the 

end of 1992 because of changes in the government 

structure in Peru. This was not reported to CMDL until 

after the end of 1993. The WMO is helping to restart 

the operations at another site in Peru to continue a long 

record of measurements in a region of the world wi thout 

many tot al ozone measurements. 

Encoders and compute rs were added to the Dobson 

instruments at BRW; SMO; Bismarck, North Dakota; 

Caribou, Maine; T allahassee , Florida; Nashville, 

Tennessee; Fresno , California; and W a llops Island. 

This change a llowed for daily reporting of ozone from 

Instrument No. 

33 

34 

38 

42 

58 

61 

63 

72 

76 

79 

81 

82 

85 

87 

91 

94 

Agency 

NOAA 

NOAA 

NOAA; NASA 

NOAA 

NOAA; Florida State University 

NOAA 

NOAA; University of Alaska 

NOAA; DSIR 

NOAA 

NOAA 

NOAA; Australian Bureau Meteorolog) 

NOAA 

NOAA; CNRS 

NOAA; !GP 

NOAA 

NOAA 

these stations to Boulder. The data were relayed to 

Aristotle University, Thessoloniki, Greece, where 

nearly real-time maps of total ozone for much of the 

northern hemispher e wer e prepared on behalf of the 

WMO in support of the Second European Stratospheric 

Arctic and Middle Latitude Experiment. 

Provisional daily 1993 total ozone amounts applicable to 

local apparent noon for the stations listed in Table 3.6 wc1 c 

archived at the World Ozone Data Center (WODC), 4905 

Dufferin Street, Ontario M3H 5T4, Canada, in Ozone Data 

for the World. Table 3.7 lists monthly mean total ozone 

amounts measured at the various stations. 

TABLE 3.7 . Provisional 1993 Monthly Mean Total O zone Amounts (m-atm-cm) 

Station Jan. Feb. March April May June July Aug. Sept. Oct. 

Bismarck, North Dakota 316 329 334 346 331 321 320 302 300 272 

Caribou, Maine 309 351 343 341 336 326 315 306 292 298 

Wallops Is., Virginia 266 302 318 312 316 302 299 298 278 273 

S~10 246 245 237 237 238 251 249 247 249 258 

Tallahassee, Florida 277 291 310 297 301 301 281 267 

Boulder, Colorado 282 296 299 311 303 318 293 286 278 274 

Fairbanks, Alaska* [353) 359 358 347 324 300 292 (275) [329] 

Lauder, New Zealand 287 268 265 284 290 326 308 347 329 353 

MLO 225 234 249 265 275 262 257 257 256 254 

l\ashville, Tennessee 275 298 319 316 314 296 298 297 284 290 

Perth, Australia 275 266 271 261 276 286 281 300 313 319 

SPO 270 266 (278) [269] [255) [271] [270) 109 

Haute Provence, France 282 300 319 330 320 320 320 [300) 297 301 

Huancayo, Peru Station closed 

BRW 359 377 360 321 285 297 268 260 

Fresno, California 284 296 291 308 306 306 294 294 282 274 

Month ly mean ozone values in square brackets are derived from observations made on fewer than 10 days per month. 

*University of Alaska, Fa irbanks 

37 

Nov. Dec. 

299 351 

308 320 

281 292 

252 242 

269 281 

279 313 

330 292 

250 243 

284 307 

308 281 

173 277 

290 284 

263 304 
Reevaluation of NOAA total ozone data, some of 

which date back to the early 1960s, continued in 1993. 

The goal of this effort is to optimize data quality for 

"ground truth" validation of satellite ozone data, as well 

as for ozone trend analyses. The data base is comprised 

of nearly 400 station-years of data. By the end of 1993, 

data reevaluation was essentially completed for 12 of 25 

stations, including those identified by asterisks in Table 

3.6. Data for most of the remaining stations listed in 

the t able will be reevaluated in 1994. 

As illustrated in Figure 3.4, a tendency toward low 

ozone values was observed at Dobson stations over the 

contiguous United States toward the end of 1992 with 

the values becoming unprecedentedly low in 1993 

[Komhyr et al., 1994) (also Figure 3.5). The January 

through August 1993 ozone amounts were more than 2 

standard deviations below normal 72% of the time and 

more than 3 standard deviations below normal 42% of 

the time. (Normal values were taken to be average 

monthly means derived from data obtained at the 

station s prior to 1982.) 

71 10 _!!_ Ill 83 84 86 H H 

79 80 81 82 83 84 15 H V 88 

Ye er 

u 90 II 

89 90 II 

J F M A M J J 

MONTH 

1979-1991 

1992 

1993 

Dobson Touil Ozona 

A S 0 N D 

Fig. 3.4. Combined stati on total ozone monthly means from 

Bisma rck, Caribou, Boulder, Wallops Island , and Nas hvill e for 

1992 and 1993 compared with averaged 1979- 1991 ozone 

monthly mean s at these sites. 

.. 

0 

c., 

., 

60 

.. 

c 0., 5· 

-2 c • 

~'!!! ~ ' Semoe 

~~4----.~.,..-~..--.,..~-.--.~..,.---,r---,-~r---r~-.--.~-,----i 79 10 81 82 13 84 15 H V 88 89 90 11 Ill 13 

Year 

Fig. 3.5. January 1979-September 1993 percent decreases in monthly mean total ozone at six conti guous U.S. stations and in 

Hawaii and Samoa relative to long-term normal monthly means at the sites. Dashed lines are standard deviations of the normal 

monthly means expressed in percent. Dotted lines are the 4th degree polynomial fits to the solid line plots and represent the 

smoothed ozone tre nds at the stations. 

38 
The 1993 monthly mean ozone deviations from 

monthly normals are quantified in Table 3.8 for six U.S. 

mainland stations, MLO, and SMO. Fresno data, where 

observations began in 1983, were referenced to the 

1960-1981 normal period from comparison of Boulder 

and Nashvil le data for the two time intervals. Note 

from the table that January-April 1993 ozone values 

were on average 12.6% below normal, with largest 

ozone deficits of 18% observed at Caribou and Wallops 

Island in January 1993. The record low ozone values 

persisted at four of the six U.S. mainland stations into 

summer. During May-August, ozone at these stations 

was on average 8.5% below normal. Ozone recovery 

toward normal values began in October and proceeded 

into 1994. 

Comparison MLO data in Table 3.8 show a decrease 

with respect to the long-term normals of 5.5% during 

May-August 1993. At SMO lower ozone was observed 

in May-August of 1992 with values, on average, lower 

than long-term normals by 6.2%. 

Figure 3.5 compares 1979-1993 monthly mean ozone 

da ta from the eight Dobson stations with long-term 

normal monthly means measured when atmospheric 

ozone destruction due to anthropogenic chlorofluorocarbons was minimal. Dashed lines in Figure 3.5 

represent standard deviations (±lo) of the normal 

monthly means. The solid lines plot changes in January 

1979-Septem ber 1993 monthly mean total ozone 

amounts rela tive to monthly normals, expressed as a 

percentage. The dotted line in each plot is a smooth 

fourth -degree polynomial fit to the solid line plot and 

represents the smoothed ozone trend for the station and 

the time interval under consideration. 

Three features stand out in the dotted line plots of 

Figure 3.5. First, except for the short Fresno record, 

the remaining seven stations' data exhibit zero or near 

zero ozone trends at times of sunspot maxima (1979-

1980 and 1988-1991) and the sunspot minimum (1985-

1986). (At MLO and SMO the zero ozone trends 

corresponding to the 1985-1986 sunspot minimum are 

displaced toward 1982-1983, the time of the El Chichon 

volcanic eruption as well as the record 1982-1983 El 

Nifio.) Second, all stations show an overall downward 

trend in ozone with time, with the downward trends at 

MLO and SMO being the smallest. Third, all stations 

show a large increase in the downward ozone trend in 

1992-1993. 

Annual and seasonal ozone trends were computed, 

according to the method of Bojkov el al. [ 1990] from 

deseasonalized CMDL ozone data with solar cycle and 

equatorial QBO wind effects removed. Resulting trends 

presumably reflect ozone loss because of: (1) gas-phase 

photochemistry involving chlorine and bromine species; 

(2) heterogeneous chemical processes involving 

chlorofluorocarbons and polar stratospheric cloud and 

volcanic aerosols; (3) residual QBO effects not 

adequately accounted for in the model; and ( 4) d ynamic 

effects induced by ENSO phenomena and stratospheri c 

volcanic aerosols. The trend data for November 1978-

Septembcr 1993 arc compared in Table 3.9. Note 

(Table 3.9) that at five North American stations 

(Caribou , Bismarck, Boulder, Wallops Island, and 

Nashville) having records for the 1978-1993 time 

interval under consideration, ozone decreased most 

quickly during spring months at an average rate of 

-6.0% per decade. The ozone decrease rate was 

smallest at -1.4% per decade during autumn months. 

On an annual basis, the average ozone decrease rate at 

the five stations during November 1978-September 1993 

was -4.0% per decade. With the addition of October 

1993-Decembcr 1993 ozone data (not shown), the 

average annual seasonal downward ozone trends become 

smaller by about 1 % per decade. 

Record low ozone amounts were also observed at S PO 

during October and November of 1993. Mean monthly 

total ozone amounts measured during October 15-3 1 

time intervals of 1962-1993 are plotted in Figure 3.6. 

(Dobson spectrophotometer total ozone observations 

first became possible at SPO in past years in midOctober following the polar night. With considerably 

less ozone at the Pole in Octobers of more recent yea rs, 

fairly reliable data are obtained about a week earlier 

each year.) The October 1993 mean val ue of 11 7 DU 

was the lowest ever recorded at S PO. (The second 

TABLE 3.8. Percent Ozone Decreases at the CMDL Stations in 1993 Relative to 

Long-Term Normal Ozone Monthly Means 

Jan.-April May-Aug. 

Station Jan. Feb. March April 0 3 Decreases May June July Aug. Sept. 0 3 Decreases 

Bismarck, Nonh Dakota -12.5 -13.4 -14.9 -8.9 -12.4 -9.7 -5.3 +0.5 -1.8 -1.7 -4.J 

Caribou, Maine -18.1 -14.7 -16.5 -1 5.9 -16.3 -12.7 -9.4 -7.8 -5.8 -5.2 -8.9 

Boulder, Colorado -11.5 -11.9 -15.1 -1 I. I -12.4 -11.3 -3.2 -2.9 -3.9 -3.0 -5.3 

Wallops Is. , Virginia -18.4 -13.1 -9.7 -12.7 -1 3.4 -9.9 -10.5 -7.7 -6.6 -6.4 -8.7 

Fresno, California• -8.1 -12.4 -16.4 -10.8 -11.9 -13.2 -7.9 -7.6 -5.8 -5.9 -8.6 

Nashville, Tennessee -13.3 - I I.I -6.6 -6.8 -9.5 -8.8 -10.2 -7.7 -4.9 -4.0 -7.9 

MLO -9.0 -7.7 -7.6 -6.9 -7.8 -4.4 -6.4 -6.2 -4.8 -3.8 -5.5 

SMO -2.7 -2.5 -5.1 -4.6 -3.7 -5.9 -1.4 -1.7 -2.9 -2.8 -3.0 

*Values adjusted by-1.9 ± 1.4 (lo) for reference to the mid-1960s to 1981 normal time interval. 

39 
TABLE 3.9. Trends for November 1978-August 1993 

Annual Dec.-Feb. March-Ma}'. June-Aug. SeEt.-Nov. 

Station Latitude Trend Std. Error Trend Std. Error Trend Std. Error Trend Std. Error Trend Std. Error 

Caribou, Maine 46.9°N -4.49 0.86 -5.42 2.11 

Bismarck, North Dakota 46.8°N -3.60 0.70 -3.79 1.63 

Boulder, Colorado 40.0°N -3.50 0.71 -3.33 1.52 

Wallops Is., Virginia 37.9°N -4.73 0.87 -7.03 1.66 

Nashville, Tennessee 36.3°N -3.75 0.80 -5.87 1.50 

Fresno, California* 36.8°N -3.45 2.15 -3.67 2.98 

MLO 19.5°N -.048 0.94 -1.35 1.43 

SMO 14.3°S -1.67 0.80 -0.97 1.16 

Average over first five stations -4.01 -5.09 

*Observations at Fresno began July 1983. 

lowest value of 134 DU was observed there in 1987 .) 

Lo west ever ozone values were observed at SPO early in 

the month. The mean for October 9-14 was 91 DU, and 

the mean for October 15- 18 was 100 DU. 

3.1.4. VALIDATION OF SATELLITE INSTRUMENT OZONE 

DATA 

World primary standard Dobson instrument 83, 

maintained by CMDL, has been operated during summer 

months at MLO since 1979. Data obtained have been 

used to provide "ground truth" for verification of ozone 

measurements made by the NASA TOMS and SBUV 

instruments from aboard the Nimbus 7 satellite. The 

SBUV instrument became inoperable in 1992, followed 

by failure of the TOMS instrument in early 1993. 

However, a new TOMS instrument was launched aboard 

the Russian METEOR satellite in 1992. 

Figure 3.7 compares the Dobson instrument 83 data 

with the original TOMS Version 6 data through 1992 

and with the new TOMS data in 1993, showing 

agreement in results to within about ±0.5%. The Jong-

.. .., mo .... 1990 

SOUTli POLE OCTOBER TOTAL OZONE 

······~···· .•. 

~~~~~~~~~~~~~~~~~~~~~---'-~ 

.. .., 1'70 "'° 1990 

rig. 3.6. SPO mean total ozone amounts for October 15-31 

time intervals of 1962-1993. 

40 

-6.5 1 1.28 -2.69 

-6.56 I. II -2.02 

-7.21 1.43 -1.45 

-5.53 1.60 -3.99 

-4.88 1.59 -3. 18 

-3.96 3.94 -2.35 

-0. 12 1.73 -0.17 

-2.52 0.97 -1.41 

-6.14 -2.67 

g 12 

M 10 co 0 8 ;::,, 

M 

co 6 0 

I -4 

~ 

g 

2 

0 

Trend. 0.008 c:c 0.075 X/yr 

79 81 83 85 

1.00 

1.14 

0.79 

1.14 

1.02 

2.40 

1.22 

1.38 

87 

YEAR 

89 

-2.62 1.57 

-1.11 1.17 

-0.92 1.20 

-1.83 1.40 

-0.54 1.46 

-3.81 2.35 

-0.33 0.90 

-1.77 1.04 

-1.40 

Ak Man - l6 

91 93 95 

Fig. 3.7. Comparison of TOMS and Dobson data at MLO. 

term ozone measurement precision of Dobson 

instrument 83 is estimated to be ±1 % . 

3.1.5. U:\IKEllR OBSERVATIONS 

Umkehr observations with automated Dobson ozone 

spectrophotometers continued during 1993 at Boulder, 

Haute Provence, France; Lauder, New Zealand; MLO; 

Perth, Western Australia; and University of Alaska's 

Geophysical Institute. Umkehr data processing was not 

performed during 1993 for several reason s, inc luding a 

change in the computer used to process this data. The 

change required a rewriting of the suite of computer 

programs used in the processing. 

3.1.6. CALIBRATION OF CMDL DOBSON SPF.:CTROPHOTOMETERS 

Ten Dobson ozone spectrophotometers were 

calibrated during 1993. Table 3.10 lists all of the 

instruments calibrated and the resulting calibration 

difference expressed as a percent difference in ozone. 

This percent difference is between ozone calculated 

from the test instrument and the standard instrument 

measurements with the ADDSGQP observation type at a 

Mu value of 2, and a total ozone va lue of 300 DU, 

before any repair or calibration adjustment is made. 

The table also lists the place of the calibration and the 

standard instrument used. 
TABLE3.10. Dobson Ozone Spectrophotometers Calibrated in 1993 

lnslfllment Calibration 

Station Number Date 

Bologna, Italy 66 May 25 

Aswan, Egypt 69 May25 

Hradee Kralove, Ceska 74 May25 

Irene, S. Africa 89 May25 

St. Petersberg, Russia 102 May 25 

MLO 76 Aug. 18 

SMO 42 June 14 

Tamanrasset, Algeria 11 NIA 

Tehran, Iran 109 NIA 

Bismarck, N. Dakota 33 Sept. 29 

CMDL participated in an in ternational Dobson 

spectrophotometer calibration at Hradec Kralove, Czech 

Republic, May 20-30, 1993, as part of its role as the 

world center for Dobson calibrations. Five instruments 

were calibrated with respect to secondary standard 

Dobson instrument 65. Four of the instruments had the 

optical wedge cali bration performed. 

The SMO Dobson instrument 42 was sent to MLO in 

June and the calibration level checked against world 

standard Dobson spectrophotometer 83. The instrument 

was returned to SPO and an encoder installed for semiautomated operation. 

In 1992 it was noticed that the daily ozone values 

reported for the MLO Dobson instrument 76 were highe r 

than the daily average ozone values calculated from the 

"absolute calibration" of world standard Dobson 

spectrophotometer 83 ope rated at the same station. This 

difference appeared after July 25, 1992. Dobson 

instrument 76 was formally intercompared with standard 

Dobson instrument 83 in the manual mode in June and 

in the automated mode in August. The average 

difference in the August intercomparison was 1.3% 

higher for the Dobson 76 with even higher values c loser 

to noon. A new calibration scale was defined for the 

Dobson 76, based on the August intercomparison, to be 

used from July 25, 1992, onward. There is no known 

explanation for the calibration shift on July 25, 1992. 

The CMDL Dobson instrument 33, operated by the 

Bismarck NWS site, was intercompared with the 

standard Dobson spectrophotometer 83 in late 

September. Dobson instrument 33 had tht. wedge 

calibration performed and the encoder installed for 

semiautomated operation. 

Two Dobson instruments of the WMO GAW program 

were rebuilt and calibrated in Bo ulde r as part of 

CMDL's [unction as the world center for Dobson 

cal ibrations. Dobson instrument 11 operated in 

Toulouse, France, before it was donated to the WMO 

and had been modified with an encoder and special 

electronics. Unfortunately, the original circuit 

diagrams and part of the electronics were missing. The 

instrument was stripped and rebuilt as a normal 

41 

Calibration Standard 

Correction(%) Number Pl ace 

-0.8% 65 Hradec Kralove 

-0.6% 65 Hradcc Kralove 

-0.3% 65 Hradcc Kralove 

-1.0% 65 I lradcc Kralovc 

0.0% 65 llradec Kralovc 

-1.3% 83 MLO 

-0.1% 83 l\U..O 

NIA 65 Boulder 

NIA 83 Boulder 

-0.5% 83 Bismarck 

instrument. Th is instrument was sent to Tamanrassct, 

Algeria, for use at the newly opened WMO Global 

Environmental Fund/Global Atmosphere Watch 

(GEF/GAW) baseline station. A representative or the 

WMO and of the Czech Republic Hydrometcorological 

Inst itute aided in this project. The Tehran, Iran, 

Dobson instrument 109 was optically r ea ligned, and th e 

electronics were replaced with a solid-state version. It 

was returned to its station in 1994. 

3.1.7. TROPOSP HER IC OZONE 

Surface ozone measurements continued at nine 

monitoring sites that include the four CMDL observatories, Niwot Ridge, and four sites in the North 

Atlantic. Many of the signiricant characteristics or the 

ozone distribution at these sites arc dis cussed in 

Oltmans and Levy [ 1994]. 

At SPO the 20-year record of surface observations has 

shown significant ozone concentration decreases 

[Schnell et al., 1991; Oltmans and Levy, 1994]. The 

largest and most significant declines occurred in the 

summer (DEC-JAN-FEB) and autumn (MAR-A PRMAY). In recent yea rs, however, the d ecline h~s 

slowed in the summer but has become more pronounced 

during the rest of the year, particularly the autumn. The 

summer decl ines reported earlier were linked to the 

expected increase in ultraviolet radiation associated 

with the dramatic decline in stratospheri c ozone over 

Antarctica and the consequent enh ancement in 

tropospheri c ozone loss [Schnell et al. , 1991]. Coupled 

with greater photochemical destruction or ozone was an 

increased transport from the coast of Antarctica to the 

interior or the continent bringing air with less ozone to 

the Pole. There are indications that transport pauerns 

may have returned to those seen prior to 1980 [Peterson 

and Rosson, 1993]. Surface ozone val ues have not, 

however, recovered. 

A plot or the smoothed, monthly mixing ratios 

(Figure 3.8) s hows surface ozone beginning to decli ne 

in 1986 and then more dramatically after 1989 

remaining re latively low in recent years . During the 
0 

.,. 

lfl 

n 

lfl 

I 

77 79 81 83 

South Pole 

85 87 89 91 93 

Year 

Fig. 3.8. Monthly means and smoothed monthly departures 

from the long-term monthly mean surface ozone mixing ratios 

at South Pole. The smoothing is a 24-month running mean. 

springs of 1991-1993, the lower stratosphere (below 14 

km) has had particularly low ozone amounts [Hofmann 

et al., 1994a]. This represents a significant downward 

ex tension in altitude of the ozone depletion region as a 

result of the presence of greatly enhanced sulfate 

aerosol from Mt. Hudson (1991) and Mt. Pinatubo (1992 

and 1993) and the resulting heterogeneous destruction 

of ozone. The lowest seasonal minimum values in 

surface ozone were recorded in the late summer 

following each of these years. 

Although differing a bit in detail, the ozonesonde 

record that began in 1986 shows a remarkably similar 

result for measurements obtained near the surface (600 

mb). The ozonesonde data (Figure 3.9) also show that 

the recent (1991-1993) low values at the surface appear 

throughout the troposphere and into the lower 

stratospher e. This suggests that the additional decline 

seen in recent years at SPO is related to the large spring 

and early summer deficit in the lower stratospheric 

reservo ir that feeds ozone into the upper stratosphere by 

cross-tropopause flux processes and thus reduces the 

contribution from the stratosphere to the tropospheric 

burden. Since the ozonesonde record does not 

encompass the period of more gradual decline seen at 

the surface prior to 1987, it is not possible to determine 

whether a portion of that earlier decrease was a result of 

a dimin ishmcnt of the lower stratospheric reservoir. 

There is some evidence that in 1986-1991 the ozone in 

the lowest part of the stratosphere was lower than 

during 1967-1971 when there is a set of ozone vertical 

profile measurements at SPO (Oltmans et al., 1994). 

42 

0 

lfl 

n 

0 

- 0 ;;.. n 

.D 

Q. 

Q. 0 .._, l/) 

"' 

South Pole 

... ... ---..._ ... ·· .... -. . ... ·. ----.. ---······· ····························--·~---···:~,,,.~---··· ·· ··· ··- · 

175mb •-.._,· • ....... 

.... . 

. 

····-.:.;.;;.;.··~~~· ... ............................. . 

600 mb 

87 88 89 90 

Year 

91 92 93 

Fig. 3.9. Smoothed monthly departures from the long-t erm 

monthly mean ozone mixing ratios for the lower troposphere 

(600 mb) and lower stratosphere (175 mb). The data are from 

weekly ozonesonde observations. 

Table 3.11 gives the monthly mean ozone mixing 

ratios for the sites where data is available through 1993. 

3.1.8. 0ZONESONDE OBS ERV A TIO NS 

Ozone vertical profile measurements using 

ozonesondes were continued al SPO, MLO, and Boulder. 

A continuing goal of the measurements was an 

assessment of the effect of the Mt. Pinatubo eruption on 

the ozone distribution in the stratosphere. At SPO the 

continued presence of significantly elevated H2S04 /H20 

aerosol in the lower stratosphere led to unprecedentedly 

low column ozone amounts during austral spring 1993 

[Hofmann et al., 1994a]. During September 25 to 

October 18, there were eight consecutive profile 

measurements with integrated ozone amounts (total 

column ozone) less than· or equal to 100 DU. These 

were the lowest column ozone amounts ever recorded . 

In the region of 17-19 km, essentially all of the ozone 

was destroyed (Figure 3.10). This represented a vertical 

extension of the region of ozone loss. In the lower 

portion of the depiction region (below 16 km) the 

additional depletion is associated with the presence of 

Mt. Pinatubo aerosol and the efficient destruction of 

ozone at temperatures warm enough that polar 

stratospheric clouds (PSCs) do not form, but where the 

sulfate aerosol is an effecti ve · medium for 

heterogeneous chemical processing. Al altitudes above 

20 km, the additional depletion appears to be the result 

of colder temperatures that enhance the formation of 

PSCs [Hofmann et al., 1994a]. 
TABLE 3.1 1. Monthly Mean Surface Ozone Mixing Ratios {ppbv) During 1992 and 1993 

Station Year Jan. Feb. March April 

Westman ls., Ireland 1993 39.7 41.4 45.1 45.4 

Mace Head, Ireland 1993 37.2 33.5 38.8 40.6 

NWR 1993 37.7 40.6 42.7 46.7 

Bermuda 1993 36.4 38.6 38.7 42.8 

Barbados 1992 23.3 23.3 21.5 19.5 

1993 26.3 22.3 24.7 19.7 

In late 1993 and early 1994 Boulder saw the recovery 

of ozone in the lower stratosphere to levels seen prior to 

the eruption of Mt. Pinatubo (Figure 3.11). This was 

consistent with the significant drop in the particl e 

surface area of the stratospheric aerosol in the midlatitudes beginning in the middle of 1993 [Hofmann et 

al., l 994b]. The timing of the ozone recovery with the 

drop-off in particle surface area lends credence to the 

argument that the low ozone anomaly seen following the 

eruption of Mt. Pinatubo was a result of the processing 

of human-produced chlorine on sulfate aerosol in the 

lower stratosphere. 

At MLO ozonesonde measurements began in 

September 1982 but were discontinued in January 1984 

and not resumed until December 1984. Profiles were 

,.......---..,, 

E 

_y_ 

"-..../ 

w 

0 

~ 

I-

-

I-

_J 

<{ 

35 

30 

25 

20 

15 . 

10 

5 

23 AUG 93 276 DU 

12 OCT 93 91 DU 

11 OCT 92 105 DU 

a 

May 

44.3 

39.3 

43.3 

36.6 

16.4 

18.6 

June July Aug. . Sept. Oct. Nov. Dec. 

34.7 27.3 28.8 33.0 37.4 38.0 34.2 

30.4 28.3 29.0 30.3 24.2 28.9 36.5 

44.0 43.6 39.0 37.2 36.6 43.6 41.9 

32.2 25.2 22.5 32.4 32.6 34.6 

16.3 17.1 18.4 21.6 24.4 

21.6 20.4 14.5 17.8 23.5 26.3 

obtained on about a three-per-month schedule since then. 

Figure 3.12 shows the trend for the 12-year period 

beginning in 1982 for levels from the surface to 7 mb. The 

largest changes are decreases in the lowest part of the 

stratosphere and upper troposphere, although these trends 

are not generally significant. Above 30 km at the highest 

levels routinely attained by the ozonesonde, there arc 

significant increases. The trends in the lower stratosphere 

are similar in magnitude to those seen at midlatitudc 

northern hemisphere sites during this period [Logan, 1994). 

It is not clear whether the declines in the upper troposphere 

are related to those in the lower stratosphere. The 

extensive Canadian ozonesonde network also shows 

significant decreases in the troposphere as well as the lower 

stratosphere [Tarasick et al., 1995). 

23 AUG 93 276 DU 

6 OCT 93 93 DU 

12 OCT 93 91 DU 

b 

00 5 10 15 20 0 5 10 15 20 

03 PARTIAL PRESSURE (mPa) 

rig. 3.10. (a) Comparison of the pre-depletion ozone profile at South Pole in 1993 with profiles when total ozone reached a 

minimum in 1992 and 1993. (b) Comparison of the pre-depletion profile with two profiles which showed total ozone destruction in 

the 14- 19-km region. 

43 
40 40 40 

BOULDER BOULDER BOULDER 

DEC-JAN-FEB DEC-JAN-FEB DEC-JAN-FEB 

1985- 1988 1985-1988 1985-1988 

t1 SD •1 SD .1 SD 

• 1991-1992 • 1992-1993 • 1993-1994 

30 30 30 

E 

......., 

~ ·-. 

~20 20 ... 20 

::::> 

.... 

t:= 

...J 

<{ .. 

10 10 10 

0 0 Q'--'--L...-'-'-'-.._.'-'-..._.._..-L... ........ -L....._ ......... _._, 

0 50 1 00 150 200 0 50 1 00 1 50 200 0 50 100 150 200 

OJ PARTIAL PRESSURE (nbor) OJ PARTIAL PRESSURE (nbor) OJ PARTIAL PRESSURE (nbor) 

Fig. 3.11. Winter av erage ozone partial pressure profil es at Boulder, Colorado, after the eruption of Mt. Pinatubo (points connected 

by heavy solid lines). The thin-solid and da she d profil es represent 1he 1985- 1988 seasonal averages plus and minus one standard 

deviation. 

3.1.9. STRATOSPHERIC WATER VAPOR 

In addition to the ongoing monthly water vapor 

profile measurements at Boulder, the program of winter 

soundings at SPO was augmented to give a better 

picture of the strong dehydration that develops in the 

Antarctic str atosphere . 

As temperatures in the stratosphere drop dramat ically 

in May, they become low enough (-80°C) to begin the 

Hilo, Hawaii ; 

/ / 

10 ozonesondes I ( ·" 

f / 

/ 

1982-1993 f I j 

-~ 

i::i.. 

e 

Q.> .. "" -· 

= 100 Vl 

Vl '- Q.> 

I 

j 

1 

s.. - -:..... 

i::i.. ·" / 

1 

., 

' • / 

s 

Trend (percent per year) 

Fig. 3.12. The linear trend (solid line) and 95% confidence 

interval (dashed line) of the ozone monthly departures as a 

function of altitude at Hilo, Hawaii, fo r the period 1982-1993. 

44 

process of Type (nitri c acid trihydratc) polar 

stratospheric cloud (PSC) formation. Temperatures do 

not reach the local water frost point (approx imately 

-90°C), however, until June when Type II PSCs begin to 

form and dehydration proceeds rapidly. PSCs play a 

key rol e by processing chlorine in the winter 

stratosphere and by removing nitrogen in its chemically 

a<.:t ive forms. fi gure 3 .13 s hows two stratospheric 

water vapor profi les obtained at SPO in 1993. In l'vl ay 

30 

South Pole 

25 

20 

..-.. 

e 

.._, 

~ 

~ 15 'O 

= 

-~ 

~ -

10 

~lay 15 Water \'a por :\fixing Ratio 

- Juae 29 Water Vapor Mi xing Ratio 

00000 June 29 Saturalion Mixing Ratio 

0 1000 

0 2 4 8 8 10 

Water Vapor Mixing Ratio (ppmv) 

Fig. 3. 13. Stratospheri c water vapor mixing ratio profile s a1 

SPO on \lay 15, 1993, and June 29, 1993. 
there is no sign of dehydration with stratospheric 

mixing ratios gradually increasing from 3.5 ppmv at 

about 12 km to 5 ppmv at the top of the sounding at 27 

km. In this region, frost-point temperatures are 7-10 

degrees lower than the saturation temperature. By the 

end of June, a broad region from 15-25 km shows 

dehydration, and the entire region has saturated 

conditions. The relative maximum in mixing ratio just 

below 14 km is a result of ice crystal reevaporation 

where the falling crystals encounter somewhat warmer 

conditions. 

Lidar profiles from the University of Rome lidar 

(Figure 3.14) show that by June 29 there is a broad 

region of PSCs that encompasses the dehydrated region 

below 20 km. Above 20 km, ice particles have probably 

already settled to somewhat lower altitudes. Even in 

the region near 16 km, where some crystals have 

evaporated, there are still sufficient numbers to keep 

this region near saturation. 

25 

South Pole 

20 

.-.. 

e 

..._,, 

~ 

QJ 

"O 15 ::s 

.. 

·-.. 

-

< 

10 

June 28, 1993 

5.__....._......_......_......_......_......_.._._......_'-'-.L...L.'-'-.L...L.J 

0 1 2 

Backscatter Coefficient 

Fig. 3.14. Two lidar profiles of the non -Ray leigh backscatter 

observed over SPO during 1993. The inner line is the 

backscaner resuhing primarily from the presence of Mt. 

Pinatubo aerosol and is from a profile in May before PSCs 

formed. The shaded area shows the enhanced signal due to the 

presence of PSCs on June 28, 1993. 

45 

Dat a from McMurdo, on the coast of Antarctica, on 

September 4 show the extent of dehydration achieved by 

the end of the winter with mixing ratios below 2 ppmv 

over an altitude range of nearly 10 km. The McMurdo 

data also show that the dehydration is present 

throughout the area within the pol ar vortex not just in 

the interior of Ant arctica. By summer, though air 

temperatures have warmed dramatically, there is still a 

large dehydrated region giving strong evidence that the 

polar vortex is still intact below 20 km. If air from 

outside the vortex were mixing rapidly into the in terior 

of Antarctica, the stratosphere would be quickly 

rehydrated since water vapor cou ld no longer be 

removed. 

During the winter above 25 km, the stratosphere stays 

rather moist with mixing ratios in the 5-6 ppmv range. 

This probably reflects the descent within the vortex as 

the air continues to cool and sink. 

3.1.10. SURFACE RADIATION 

Solar and Terrestrial Atmospheric Radiation 

The surface radiation budget (SRB) is a basic and 

critically important climate variable that has long been 

inadequately observed because of insufficient global 

coverage and inherent instrumental limitations. 

Surface-based radiation monitoring projects are being 

carried out by CMDL al eight locations: BRW, Eri c and 

Boulder, Colorado (BAO and BLD), Bermuda (BRM), 

MLO, Kwajalein, Marshall Islands (KWJ), SMO, and 

SPO. The long-term continuous measurements at these 

sites include broadband downward solar irradiances and 

several sites, BRW, BAO, BRM, KWJ, and SPO, also 

measure downward thermal infrared irradiances. At 

sites where the measurements were determined to have a 

representative surface (BRW, BAO, and SPO) upward 

solar and infrared irradiance measurement projects are 

also maintained. The more extensive observations are 

made at CMDL sites where the measurements are more 

areally representative especially with respect to land 

surface and cloudiness. Irradianccs observed at the 

more areally representative sites, BRW, BAO, KWJ, 

BRM, and SPO are being incorporated into an 

international data base sponsored by the WMO and 

NASA under the Baseline Surface Radiation Network 

(BSRN). All data from CMDL sites are also maintained 

as part of the long-term CMDL surface radiation record 

that exists for the past 15 years at BRW, MLO, SMO, 

and SPO. Previous CMDL (and GMCC) Summary 

Reports have discussed the wide ranging and useful 

applications of these data to scientific questions. 

Recently completed and ongoing projects utilizing the 

radiation observational results from the CMDL field 

sites include the detection of a long-term decrease in 

Arctic haze [Bodhaine and Dutton, 1993]; comparison 

of satellite and BAO-derived SRB under clear and 

cloudy conditions [Cess et al., 1991, 1993, 1995]; the 

effects of snow surfaces on atmospheric absorption 
[Nemesure et al., 1993); detection of intermediate-term 

trends in cloudiness rel ated to radiation perturbations 

[Dutton et al., 1991; Schnell et al., 1991); a technique 

for monitoring long -term climate variability using 

surface albedo records [Dutton and Endres, 1991; 

Foster et al., 1992]; identification of a strong statistical 

coherence between the QBO and the MLO long-term 

transmission record [Dutton, l 992a]; a surprisingly 

good agreement between modeled and observed thermal 

infrared irradiances over the range of globally extreme 

conditions [Dutton, 1992b]. and a determination of the 

radiative effects of the Mt Pinatubo volcanic eruption 

[Dutton and Christy, 1992; Russell et al., 1993, and 

Dutton et al., 1994]. Dramatically new information on 

cloud absorption is being revealed in an ongoing 

investigation using CMDL surface and satellite top-ofthe-atmosphere solar data, Cess et al. [ 1994). 

Numerous additional requests were made and fulfilled 

for CMDL radiation data for a variety of research 

applications. 

Updated results on the late summer cloudiness and 

irradiance trends at SPO reported by Dutton et al. 

(1991) are shown in Figure 3.15. As suggested by 

Dutton et al. ( 1991). the previously observed trends 

during January and February until 1988, did not project 

into the future. The current SPO irradiance level shows 

an autocorrelated return to previous levels. The 

potential for a >20-year oscillation in these data now 

exists. 

The MLO atmospheric transmission record, updated 

through 1993, is shown in Figure 3.16. The effects of 

the eruptions of Mt. Pinatubo and El Chichon are most 

obvious and are enlarged and compared in the inset of 

the figure. This record is now continuous for the past 

37 years and may provide the best available information 

... JA>< 230 FEB 

If ... v s 

a: 

~ 

ll: 

e ... 

-

-... 

""' 

74 11 71 80 12 M 15 18 to t2 M 

200 

220 

210 

,., 

\IO 

74 78 

~ 71 ea 12 M 8S 81 IO t2 M 

.. ...... , .. v If .. 

~ , .. e .. a: 

~ .. 130 

s .. 1'0 ,. . 

ll: .. 110 

74 11 71 ., 1:2 "" •• 90 t2 ... 74 1't 71 80 12 M 88 88 to t2 M 

... 

~ ... If 

~ 

... ... e ... ~ ... ... ... '"' i '10 ... ... S\O "" 7'7171aol21418eetot2M 7'7'7ll012148&8810t2M 

YEAR YEAR 

Fig. 3. 15. Monthly mean total (direct plus diffuse) solar 

irradiance at the South Pole. The plotted lines are for linear 

least-squares fits for 1976 through 1987. 

46 

.... 0..95 

o.t 0.9 

z 

0 

~~~J iii 

VI .... :i .... VI 

z 

C( 

IC 

I- 0.1 0.1 

'tUAS An1Jt UU'nOfll 

°'7' .. .. 62 &4 66 61 10 n 74 11 71 IQ 12 M ~ M ~ ~ ~ 

YEAR Cl.MQn'~llAILYIFig. 3.16. Monthly mean "apparent" atmospheric transmission 

as determined from broadband direct solar beam observations at 

Mauna Loa. 

on the lack of any significant secular trends in the 

global background atmospheric transmission of solar 

radiation over this time. Two to three more years 

without a major volcanic eruption will be required for 

the record to once again reach its background level. 

Snowmelt date at Barrow, Alaska, was defined as the 

last date each year tha t any significant snow remains on 

the ground (first day each year that <l inch of snow is 

reported in visual observations or the daily average 

surface albedo falls below 30%). Considerable 

differences between the NWS observations within the 

village of Barrow and on the tundra near the CMDL site 

were noted in Fi gure 3.17. When compared with other 

tundra albedo data for the late 1960s and early 1970s 

and the earliest NWS data, the CMDL data [Du11011 and 

Endres, 1991] continue to suggest that there was no 

significant change in the annual date of spring snowmelt 

near Barrow since the 1940s. The NWS data [Foster, 

1989] alone suggest an advancing date of snowmclt that 

can be interpreted erroneously as being due to a general 

warming, but is instead most likely because of 

urbanization of the Barrow village. 

50 >-

0 

~ 

Q) 

<J 40 c 

·;;; 

~ ------------·------- ! 30 i i 

w 

.... 

-<! 20 CMOL CURRENT THRU 199• 

a 199• dote -- 12 June NWS CURRENT THRU 1994 1994 dote -- 4 June 

10.:t-r~~~TT"~~~TT""'~~~,..,.....TT"~TT" .......... ~~ ...... ~-.+ 

19•0 1950 1960 1970 1980 1990 

YEAR 

Fig. 3. 17. Date of annual spring snowmelt as determined by 

va rious researchers at different locations in and around Barrow, 

Alaska. The downward trend indicated by th e Foster (NWS) 

curve is bel ieved to be due to "urbanization" in Barrow. 
The CMDL radiation project accepted the 

responsibil ity of working with the WMO GEF/GAW 

program for the intent of establishing a surface-based 

solar radiation measurement and research program at 

each of four global baseline sites located in developing 

countries. CMDL will acquire the necessary equipment, 

train onsite observers, and assist in the establishment of 

programs in Algeria, China, Argentina, and Indonesia 

over the next 2 years. 

Operations 

There were only a few significant changes in 

observatory operations during the year, which is an 

important attribute of a long-term measurement effort. 

Blowers were added to the upward facing pyranometer 

and pyrgeometer at SPO. The new units are very 

effective in keeping frozen prec1p1tation and 

condensation off the filter domes. Additional blower 

units are being acquired as funds allow for 

implementation at other sites. A critical requirement of 

the radiation project is to make stabl e and accurate 

micro-volt level measurements to ensure that the 

potenti al voltage measurement error is small compared 

with other sources of error. Current data loggers have 

integrating AID converters with auto zeroing and 

achieve 2 microvolt accuracy. Continuous data logging 

at all eight sites now has 3-minute or better resolution 

recorded and permanently stored. Data sampling times 

range from 1 to 2 seconds. 

Incoming data are currently received daily in Boulder 

for all si tes except SMO, are processed within 2 days, 

and revi ewed for quality-control purposes. Data 

editing, processing, and final storage have been moved 

to medium-sized and personal computers all directly 

under the control of CMDL, thereby eliminating the 

dependence of outside computer expertise and 

resources. Final processing is completed about 1 

calendar year after the data are first available for 

processing. Assignment of final calibration information 

is ongoing as updated radiometer calibration data are 

made available. Final data values depend on careful 

review and application of sensor calibration information 

that is provided by the CMDL Solar Radiation Facility. 

Remote Sensing of Aerosol Optical Properties and 

Water Vapor 

Other than clouds, aerosols and water vapor are the 

main contributors to thermal-infrared and solar 

radiation variations and subsequent radiative climate 

forcing. The potential climate variations resulting from 

such variations are exten sive and varied. The observed 

and potential radiative variations may be due to either 

anthropogenic causes such as increased industrial 

production of aerosols and water vapor feedback 

resulting from increasing greenhouse gases or from 

natural causes such as volcanic, biogenic, or surface 

wind-gener ated aerosols and inherently varying water 

vapor. CMDL has a long history of exploratory and 

47 

operational projects relating to the remote sensing of 

aerosols and water vapor as rel ated to climate 

variations. Since 1977 wide-band spectral observations 

of direct solar irradiance using a filte r wheel NIP at 

BRW, MLO, SMO, and SPO were used to infer aerosol 

optical depth and column water vapor amounts. These 

measurements have proven to be durable and stable over 

time thereby excelling in a monitoring effort even 

though their accuracy is less than can be obtained by 

more sophisticated but less robust instrumentation. 

Additional and exceptional effort has been put into 

high-precision narrow spectral band optical depth 

measurements at MLO. At MLO several narrowband 

(0.005 μm) sunphotometers are routinely operated and, 

because of the nearly ideal atmospheric conditions and 

the existence of automated observing platforms, have 

produced reliably consistent long-term data sets. 

Results from the MLO aerosol optical depth 

measurement project are reported by Dutton et al. 

[1994) and Russell et al. [1993) and in previous CMDL 

Summary Reports. One year of narrowband 

sunphotometer data were collected from Sable Island, 

Nova Scotia, as part of a comprehensive surface-based 

aerosol sampling project described in section 3.1.1.2. 

3.1.11. SOLAR RADIATION FACILITY (SRF) 

Support for the CMDL solar radiation measurement 

programs at seven field sites continued during 1993. 

Sensor procurement, maintenance, and repairs were pan 

of the ongoing activities of the SRF in addition to 

providing calibrations and characterization information. 

The seven sites include the four CMDL baseli ne 

observatories plus KWJ, BRM, and BAO. Also, a suite 

of continuous broadband measurements was maintained 

at the SRF facility in Boulder as part of a historical 

record dating back to 1977. Instrument characterization 

methodologies were investigated as part of the ongoing 

activity of the SRF. 

The SRF supported. and participated in an 

intercomparison of automated cav ity radiometer systems 

held at the National Renewable Energy Laboratory 

(NREL) September 27-0ctober 4, 1993. Four c avit y 

radiometers and other CMDL equipment contributed to 

the success of the comparison. Post-comparison data 

analyses and data entry tasks were also performed by 

CMDL personnel in support of the event. An on going 

collaboration with NREL invol ving cavity comparisons 

is part of the SRF means of maintaining the integrity of 

the calibrations used by CMDL monitoring activities at 

its sites. 

A project was started during 1993 by the SRF as a 

result of a proposal to the WMO for impl ementing 

broadband solar radiation measurements at GEF/GA W 

sites. Each site will be equipped with pyranometers, 

pyrheliometers, automated solar trackers, shadowband 

systems for diffuse-sky radiation measurements, and an 

automated absolute cavity system for use as a primary 
calibration standard. Data acquisition systems identical 

to those used at the CMDL baseline observatories will 

be constructed and used at the GEF/GA W sites as well. 

The instruments, data acqms1t1on components, 

computers, and cavity radiometer systems destined for 

each GEF/GA W site will be assembled and put into 

operation at the SRF in Boulder. Each country will 

send its representative to Boulder for training in the 

collection of solar data and calibration techniques using 

the equipment that will ultimately be shipped to each 

respective country. The procurement of equipment 

began in late 1993, and the first trainee is expected 

during the second quarter of 1994. 

3.2. SPECIAL PROJECTS 

3.2.1. AN ANALYSIS OF 10-DAY ISENTROPIC FLOW 

PATTERNS FOR BARROW, ALASKA: 1985-1992 

Atmospheric transport patterns to B RW were 

investigated using a newly developed isentropic model 

described in CMDL Summary Report No. 21 [Peterson 

and Rosson, 1993). The new mode l features a layeraveraged mode that is activated whenever an air parcel 

traveling isentropically approaches the earth's surface 

and a dynamic preprocessing program that ensures 

trajectories always arrive at a constant, predetermined 

altitude. Some highli ghts of this study [Harris and 

Kahl, 1994) are described below. 

Ten-day back trajectories arriving above BRW at 500 

m, 1500 m, and 3000 m as! were calculated for the 8-

year study period. Cluster analysis was used to 

summarize trajectories for the entire 8 years, for each 

year individually, and for each month (e.g., eight 

January's, eight February's, etc.) The focus of this 

report is only on some of these results, particularly 

those relating to transport of Arctic haze to BRW. 

Figure 3.18 shows the means of each of the six 

transport clusters determined for the middle arrival 

elevation (1500 m as!) where flow is near and usually 

above the inversion level. Two cluster means in Figure 

3.18 indicate transport from south of BRW. Both of 

these, clusters 1 and 3, have cyclonic curvature, 

consistent with tran sport from the area of the Aleutian 

Low. On average, southerly transport occurs one third 

of the time. . Approximately one quarter (26%) of 

trajectories to BRW fall into cluster 4, which depicts 

very light northerly and northwesterly flow, with 10-day 

origins south of 80°N in the East Siberian Sea. The 

flow pattern with the next highest frequency (15 %) is 

represented by the mean for cluster 6. It shows 

moderate northwesterly flow and an ongin for 

trajectories in the central polar basin. Cluster 2, 

representing 14% of flow to Barrow, has a stronger 

westerly component than that for cluster 6 and a I 0-day 

origin over north-central Russia near the Taymyr 

Peninsula. Finally, the mean for cluster 5 indicates 

northeasterly flow from the Canadian Archipelago with 

48 

160° w 

Fig. 3.18. Atmospheric flow patterns for the period 1985-1992 

depicted by cluster-mean back trajectories arriving at Barrow at 

1500 m asl. Plus signs indi cate I-day upwind intervals. The 

numbers I 0-days upwind of Barrow show (top) the percelllage 

of trajectories occurring in that cluster and (bottom) the cluster 

number (1 -6) used for identification. 

a frequency of 12%. Notably absent at this level arc 

any cluster means showing transport within 10 days 

from either Europe or the contiguous United States. 

To more precisel y quantify transport from three source 

regions of particular interest, trajectories were counted that 

intersected the source boxes shown in Figure 3.19. 

Although no cluster means originate over Europe for the 

1500-m arrival elevation, this region was investigated 

because it is often cited as a significant source of Arctic 

haze. Trajectories were counted over the Taymyr region 

because the cluster means indicated this as a consistent 

source at all three levels. The north Pacific region is of 

interest as the most direct source of heat transported to 

Barrow. Table 3.12 presents the results tabulated 

according to arrival elevation. The percent frequency of 

transport from each region is shown, followed in 

parentheses by the average transport time in days. 

March and April trajectories were analyzed in th is 

way (not shown) because recent studies have found 

decreasing trends in aerosol concentration [Bodhainc 

and Du11on, 1993) and sea-ice extent, and an increasing 

trend in surface temperature [Chapman and \Va/sh, 

1993) during spring. The source region ana lysis 

presented no evidence of a significant change in 

transport that may have been linked to these trends. It 

is quite likely that our 8-year study period is too short 

to reveal a true climate change. It could also be that the 

spring warming seen by Chapman and Walsh (1 993) is 

primarily a radiative effect, without an identifiable 

transport component. Bodhaine and Dull on [ 1993) 

hypothesize that the decreasing aerosol trend they saw 

resulted from decreased anthropogenic emissions. 
..... ········ 

.... ·· 

) 

···· ..... ·· .. , 

100° w 

160° w 

Fig. 3.19. Three potential source regions in which trajectories 

were tabu lated: Europe, north-centra l Russia near the Taymyr 

Peninsula, and the north Pacific. 

Figure 3.20 shows contour elevation plots of the average 

modeled transport surfaces for January 1992 for the (a) 

500-m as! arrival elevation; (b) 1500-m as! arrival 

elevation; and (c) 3000-m asl arrival devation. The 

surfaces shown in Figure 3.20 are intended to convey a 

sense of the vertical motion that an air parcel may 

experience on its journey to Barrow. The contour levels 

are not intended to imply preferred transport from any 

particular area. Rather, they are intended to answer the 

question: If an air parcel transported isentropically to the 

specified arrival elevation at Barrow were to pass over a 

certain area, at what altitude would the transport likely take 

place? Aside from the prominent topography of the 

Tibetan Plateau, the Rocky Mountains, and the Greenland 

Ice sheet, the isentropic features of the extratropical 

northern hemisphere are evident. Isentropic surfaces on 

individual days during the haze season will vary at times 

from the January means shown here. Inspection of other 

winter-spring months proved the surfaces in Figure 3.20 to 

be representative of the season. 

TABLE 3.12. Percent Frequency of Origin and (Average 

Transport Time in Days) According to Arrival Elevation 

Arrival 

Elevation (m asl) Europe Taymyr Nonh Pacific 

500 1.3 (8.0) 21.l (6.3) 19.8 (4.2) 

1500 4.4 (1.6) 24.1 (5.9) 36.3 (4.1) 

3000 11.0 (1.0) 23.6 (5.2) 50. l (3.6) 

49 

The lowest transport level, shown in Figure 3.20a, is 

quite flat, indicating travel mostly in the near-surface 

layer. The higher isentropic surfaces (Figures 3.20b 

and 3.20c) arc more peaked over the polar basin. In 

addition, the higher surfaces extend downward from 

Barrow to the south, whereas the lowest surface is 

limited in downward extent from Barrow. The result is 

that upper-level trajectories will encounter more 

vertical motion than lower ones. 

The shape of the isentropic surfaces may have 

relevance to pollution transport to Barrow, if pollution 

is assumed to be confined to the lower levels at its 

source. Table 3.12 shows that transport occurs from the 

Taymyr reg ion at a frequency greater than 20% at all 

three levels. However, the pollution assumption implies 

that d irect transport from the Taymyr region must be 

close to the ground, following a surface similar to that 

shown in Figure 3.20a. Europe is only an occasional 

origin for 10-day back trajectories at the lower levels, 

but trajectories arriving at 3000-m as! originate from 

Europe 11 % of the time. Cluster means (not shown) 

and the average transport surface (Figure 3.20c) favor 

Scandinavia as opposed to midlatitude eastern European 

sources at this level. 

Because of the shape of the iscntropic surfaces, 

trajectories generally ascend from the south and 

descend from the polar region to BRW. The effect of 

the isentropic vertical parameterization , is not 

significant for near-surface trajectories, but higher level 

trajectories could be markedly different than their 

isobaric counterparts, depending on the degree of wind 

shear and temperature differences encountered during 

transport. It appears that isentropic transport to BRW 

can be slower than horizontal transport because wind 

speeds are often less along the lower periphery of the 

isentropic surfaces compared with those on isobaric 

surfaces. 

3.2.2. AEROSO L MEASUREi\tE:'\TS AT MLO DUR ~G 

M L OPEX 

Introduction 

The routine aerosol monitoring program was initiated 

at MLO in 1974 with the installation of instrument ation 

for the continuous measurements of CN concentration 

and aerosol scattering extinction coefficient (o,p), 

although apparently the earliest aerosol measurements 

were made by Nakaya et al. [1957). A brief history of 

MLO aerosol measurements was given by Bodlzaine 

[ 1983). 

The Mauna Loa Observatory Photochemistry 

Experimen t (MLOPEX) was a multi-agency cooperati ve 

experiment designed to study the chemistry of the free 

troposphere near 3.4-km altitude. The experiment 

consisted of four intensives that were designed to obtain 

data repres entative of four different seasons at MLO. 

The periods chosen were September 16-0ctober 
(a) 

Fig. 3 .20. Contour elevation p lo ts (m asl) of the average transport surfaces for Ja nuary 1992 at the (a) 500 m as! arrival elevation, 

(b) 1500-m asl a rrival elevation, an d (c) 3000 mas! a rriva l elevation. The contou r interval is 500 m. 

23, 1991; J anuary 15-February 15, 1992; April 12-May 

15, 1992; and July 15-August 14 , 1992. An important 

part of this experiment was to investigate the diurnal 

cycles of the parameters measured, both the effects of 

the upslope-downslope win dflow, and the diurnal 

photochemical cycles in free tropospheric air. All d ates 

and times are presented here as Julian day-of-year 

(DOY) and Hawaii Standard Time (HST). For 

comparison with Universal Time (UT), UT= HST + 10 

hours at MLO. 

Instrumentation 

CN measurements were initiated in 1974 using a G.E. 

automatic CN counter (1974- 1989) and a TSI 3760 CN 

counter (1989-present). A Pollak CN counter [Metnieks 

and Pollak, 1959] has been operated daily since 1974 to 

so 

provide comparison points for the automatic CN 

counters. Aerosol scattering extinction coefficient 

(05p) measurements were initiated in 1974 using a fourwavelength nephelometer similar to the design of 

Ahlquist and Charlson [ 1969]. Aerosol absorption 

(Oap) has been measured at MLO since 1990 using an 

aethalometer [Hansen el al., 1982]. The instrument and 

data for 1990-1991 were. described by Bodhaine et al. 

[ 1992]. The S02 data shown here were provided by 

Gerd Hiibler (personal communication, 1994). 

Dat a Analysis 

Diurnal cycles. Data from intensives 3 and 4 were 

used to study the character of the diurnal cycle at MLO. 

Figure 3.21 shows means by hour of the day for the 

entire periods of intensives 3 and 4. The primary data 
set used to form these means was the hourly data 

produced by the MLO data acquisition system. An 

hourly data point was deemed acceptable for inclusion 

in the mean if the 450-, 550-, and 700-nm nephelometer 

data were all present and if no local pollution was 

detected during that hour. Next, the Angstrom exponent 

(a) was calculated from the <Tsp data. Finally, if CN, 

wind direction (WD), or wind speed (WS) data were 

present for that hour, they were included in their means 

for that hour of the day. Thus the tallies of <Tsp• CN, 

WD, and WS, could all be different for a given hour. 

However, this procedure was necessary to avoid 

problems caused by missing data when several data sets 

are merged. 

Referring to Figure 3.2la, the average diurnal range 

in CN concentration was about 300-1000 cm-3 between 

night and day, with the beginning of background 

sampling cond itions at about 2100 HST and the onset of 

the upslope wind at about 1000 HST. The <Tsp data show 

somewhat narrower background sampling conditions 

between about 0200 and 0800. Historically, 0000-0800 

was the time interval chosen to sample background 

values of <Tsp at MLO [Bodhaine, 1978]. The WD data 

in Figure 3.2la show clearly that WD changes from 

northerly to southerly at about 1800, and back to 

northerly at about 0900. Clearly, a time lag exists 

between when WD changes and when stable sampling 

conditions exist at the site. WS averaged about 5 m s-1 

during both night and day. 

The a data in Figure 3.2la show that the particle size 

tended to be larger during downslope conditions than 

during upslope conditions during this intensive. 

Particle sizes are generally l arger at this time of year 

because of Asian dust transport. The interpretation of a 

data has been discussed by Bodhaine and DeLuisi 

[1985); however, qualitatively speaking, larger a 's 

imply smaller particles and v ice versa. 

Fi gure 3.2lb shows a similar presentation of the 

average MLO diurnal cycle during intensive 4. Aerosol 

scattering extinction coefficient values are about a 

factor of five lower than in intensive 3. A diurnal cycle 

of <Tsp is apparent with background conditions occurring 

during about 2200-0 800. WD shows an upslopedown slope effect with a change to southerlies at 1800 

and the onset of the upslope at 0800. In the summer 

(Figure 3.2lb) the winds had an easterly component 

whereas in the spring (Figure 3.2la) the winds had a 

westerly component. Also, note that the winds were 

weaker during the upslope-downslope transition periods. 

A classic example of an upslope-downslope event 

with c lean background conditions during downslope 

fl ow, is shown in Figure 3.22 for DOY 118-119 (April 

27-28) 1992. Here the CN concentration shows clean 

conditions from 1700 on DOY 118 to 1000 on DOY 119, 

and WD is clearly in the southerly band during that 

time. The <Tsp data are interesting because they 

apparently settle to background values by about 2000 on 

DOY 11 8, but assume a new, lower value during about 

51 

z 

(.) 

d 

MLOPEXApr 12- May 15, 1992 

·: t, ' ' ' ' '.~o~ ~~- 3~) , , , ' , ' ' ' , f 360 270 ~ - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - -~ -=_ --~ -=_ -=_ --~ ~ 180 - - - - - - - - - - - - - - - - - - -

90 ------------------

0 I I I I I I I I I i I I I I I I I I I I I I 

___________ , 1

1.5 .0 ~ f 0.5 I I I I I I I I I I I I I I I I I I I I I I I 

:. "' i :; :·' ' ' ' ' -: . :~ ;·'.:~. :H .~~:.:~: ~ ;:; ' 0 

·.,, 

12 

Hour (HST) 

18 

MLOPEX Jul 15 - Aug 14. 1992 

24 

' ' (~ . -227), ' ' ' ' ' ' ' ' f 

0 ~ ;~ 180 ~ - - - - - - - - - - - - -

= = = = = = = = = = = = = - -

- - - - -- = = = ~ s:: 90 --------- -- - ----- -

::'. f · · · .. .. · .. .. .. .. · r z 

(.) 

~ f 1.5 

1.0 I I I I I I I I I I I I I I I I I I I I I I t 

:. ,,. i ··; ; ; -~ ' ... :: ; .-.=-.~. ~ :~~~:. . ~ 0 6 12 

Hour (HST) 

18 24 

Fig. 3.21. Data for MLOPEX (a) inlcnsivc 3 and (b) intensive 

4. Mean s by h our arc shown for wind sp eed (\VS); wind 

dircclion (\VD); CN conccn lration ; o:; and crsp for 450 (doncd), 

550 (solid), and 700 nm (dashed). o: values were calcu lated 

suing equalion (1). The shaded areas on the WO graphs denolc 

winds with a southerly (downslope) component. Hour of the 

day is shown as HST. 

0800-1100 on DOY 119 before the upslope event 

app ears. This behavior may be explained by a decrease 

in aerosol concentration at about 0800 on DOY 119 
(possibly by a few large dust particles), which gave an 

obvious decrease in crsp and an increase in a, but a 

negligible effect on the CN concentration. Note the 

fairly high WS on these two d ays. The S02 data 

superimposed here in Figure 3.22 follow the CN data 

quite c losely, indicating an island source for S02. 

These local sources of S02 c ould be either 

anthropogenic (e.g., fuel combustion) or natural (e.g., 

fuming from Kilauea caldera). The black carbon (BC) 

data in Figure 3.22 show a diurnal cycle that follows the 

CN and S02 data quite closely, suggesting similar 

sources. Since BC can be produced local ly by both 

natural and anthropogenic sources, it can be a good 

indicator of a local pollution event. 

Asia11 desert dust event. Examples of Asian dust 

events are shown in Figure 3.23. Episodes of closelyspaced three-waveleng th cr5 p data (low values of a) 

strongly suggest a relatively larger aerosol size, most 

likely Asian dust [BodJzaine et al., 1981). The crsp data 

"111 

z 

(.) 

a. 

t:> ~ 

. --~-.-~~--

50 l 

1 --.....,-·~/·.,,--Ir--..\._ 

0 

'. 

---------

2 -

0 ---- ~:--------------------:-- ---

10·5 = 

=~ · 10-6 

0 12 

118 

, 

18 0 6 

DOY/Hour (HST) 

12 

119 

-- \ 

18 0 

Fig. 3 .22. Hourly values of wind speed (\VS); wind direction 

(WO); S02 concentration; BC concentration; CN concentration; 

a; and cr,P for 450 (dotted), 550 (solid), and 700 nm (dashed), 

on DOY 118-119, 1992. a va lues were calculated using 

equation (1). The shaded area on the WD graph denotes winds 

with a southe rly (downslope) component. Hour of the day is 

shown as HST. 

52 

in Figure 3.23, at the beginning of DOY 126, show the 

end of a downslope event dominated by large particles 

at about 0800 and smaller upslope particles at about 

1200. The large particle peak was about 2 x 10-5 m-1 

with an a near 0. By about 0000 on DOY 127 the data 

show a small-partic le downslope regime, illustrating the 

patchy nature of the Asian dust. Large particles 

dominated the upslope-downslope cycle th at began at 

about 0800 on DOY 127 and continued through about 

1000 on DOY 128 . Similar effects occurred over the 

next several days and the Asian dust was gone by about 

DOY 134. 

At about 1000 on DOY 128, 129, and 130 three 

obvious small-particle upslope events broke through the 

Asian dust cloud. Note the clean downslope event on 

DOY 135 that gave crsp values of about 5 x 10-7 and CN 

concentrations of about 300 cm-3, even though WO did 

not indicate strong downslope conditions. The multiwavelength crsp data clearly identify the presence of 

z 

(.) 102 -----------

' :ti~{\,/\_, fl_,~~j\J'!'-j 

-;~ 10·

5 it'\ rv''Vv'"V-,; ~··.-.... ·\ _.- ;··, ~- .s : { \!\ft'"\ ~: 

a. 10-6 -.! I - ~ ; r ~., 5 ~ ''V F 

i~rri ~- --r 

126 127 128 129 130 131 132 133 134 135 136 

Day of Year 1992 (HST) 

Fig. 3.23. Hourly values of wind speed (WS); wind direction 

(WO); S02 concentration; BC concentration; C N concentration; 

a; and cr,P for 450 (dotted), 550 (solid), and 7 00 nm (dashed}, 

on DOY 126-135, 1992, during which an Asian desert dust 

event occurred. a values were ca lculated using equation(! ). A 

3-hour running mean was applied to the BC data. The shaded 

area on the WO graph denotes winds with a southerly 

(downslope) component. Hour o f the day is shown as HST. 
large Asian dust particles as opposed to smaller 

background-tropospheric or locally-produced particles. 

Note that Asian dust can dominate the aerosol 

measurements during upslope as well as downslope flow. 

The S02 data for this period appear to correlate best 

with the CN data, and the a data show that S02 events 

tend Lo be correlated with small-particle events. Of 

particular interest is the fact that S02 events occur 

during the Asian dust events, raising the possibility that 

S02 may be transported from Asia. The BC data shown 

in Figure 3.23 tend to follow the CJ5p data during the 

beginning of the record and the CN and S02 data during 

the latter part of the record. This suggests that the BC 

may have been transported over long distances when it 

is associated with the desert dust as determined from 

the CJ 5p data [Bodhaine et al., 1992]. 

Mixed regime. Data for DOY 219-228 are presented 

in Figure 3. 24. This 10-day period was chosen to 

illustrate the difficulty of just classifying MLO data as 

10 ... 

. ·--.....___-............. "' 

__ ..... ·-- _·.·-... ---.---

102 -------._ - ---.......-----~ --- ---- __;_ 

2 - ., --- l --.. _,---............. .. , . 

1 AJ V·" ,-v\1 ~· ..-· .. · ,'.'·'.·.' .· 'v'" t 0 -----. --.-- ---------

10·5 1 i\ i ·: r. -. ~ --,..,".";\ ':---:- ~ ·§. 10-6 ~ ' · 1 , : --- v - _ r<- ~ ifv -/'\-:d - - -~.~ --:~,--=~-:. ~ ·: ' ~ t> 1o·7 - . -----,-.--.-

219 220 221 222 223 224 225 226 227 228 229 

Day of Year 1992 (HST) 

Fig. 3.24. Hourly values of wind speed (WS); wind direction 

(\VD); S02 concentration; BC concentration; CN concentration; 

et.; and cr,P fot 450 (dolled), 550 (solid), and 700 nm (dashed), 

on DOY 219-228, 1992, during which rather uncerta in 

conditions existed. Ct. values were calcu lated using equation 

( 1 ). A 3-hour running mean was applied lo the BC data. The 

shaded area on the WD graph denotes winds with a southerly 

(downslope) component. Hour of the day is shown as HST. 

53 

upslope or downslope. This was a period of generally 

light and somewhat uncertain winds (with the exception 

of DOY 220). The particle size distribution, as 

suggested by the CJ5p and a data, was dominated by 

small particles during both upslope and downslope 

conditions throughout the entire period. The a data 

here tend to be somewhat noisier than those during the 

Asian dust period because the CJsp data are much lower. 

The cleanest background conditions exhibit CJsp values 

of about 2 x 10-7 m·l and CN concentrations of about 

300 cm·3 on DOY 222 and during the clean period of 

226-227. 

The upslope event at about 1200 on DOY 219 is quite 

obvious in the CJsp• a, CN, and S02 data. However, it is 

not so easy to predict based on WD and WS data. The 

next upslope event at about 1200 on DOY 220 again 

shows up clearly in all data records and does have a 

northerly WD. The secondary peak at about 2300 on 

DOY 220 appears during southerly winds but seems to 

be associated with a minimum in WS. Then a strong 

downslope at 0200 on DOY 221 gave clean conditions 

before the next upslope event in CJsp at about 1200 on 

DOY 221. 

The downslope event at about 1800 on DOY 221 

produced very clean background conditions in both CJ5 p 

and CN data, followed by classic upslope wind flow at 

about 0800 on DOY 222. The secondary event in CJsp 

(but not in CN) at about 0000 on DOY 223 is 

unexpected and not easily explained on the basis of 

these data alone. Likewise, the obvious upslope events 

at about 1200 on DOY's 223 and 224 arc expected, but 

the polluted values during 0000-1200 on DOY 224 or 

the peak beginning at about 0200 on DOY 225 are not 

expected. A clean period begins at about 0000 on DOY 

226 and continues until the upslope event begins at 

about 0800 on DOY 228. Note, however, the slight 

upslope event at about 0800 on DOY 226 and the 

spurious event at about 2000 on DOY 227 , apparently 

associated with light winds. 

Referring to the S02 data in Figure 3.24, it is possible 

to explain the unexpected features discussed previously. 

These data show peaks of about 2 ppbv that coincide 

with the upslope events at about 1200 on DOY 219 and 

220. However, a peak during downslope conditions at 

about 2300 on DOY 220 coincides with those in CN and 

CJsp· S02 events at 0000 on DOY 223, 0000 on DOY 

224, 1800 on DOY 224, and 0200 on DOY 225 all occur 

during downslope conditions and are most likely caused 

by venting from the Mauna Loa caldera. 

The BC data shown in Figure 3 .24 tend to follow 

upslope events, although not always. The three largest 

events in the BC data coinc ide with upslope events; 

however, the volcanic events discussed previously show 

low BC concentrations. Note the extremely low BC 

concentrations during DOY 226-227, probably 

representative of clean background tropospheric 

conditions. 

Data screening. Clearly it would be difficult LO 
design a computer algorithm for routinely screening 

data that could cope with the data shown in Figures 3.23 

and 3.24. Historically, MLO aerosol data were screened 

on the basis of time of day and WD. The time window 

1000-1800 UT for accepting background Osp data was 

used by Bodhaine [ 1978), based on 3 years of 

nephelometer data. This time window allows for the 

slow time response of the nephelometer. Wind criteria 

for accepting MLO aerosol data require WD with a 

southerly component (90° < WD < 270°) and WS > 0.5 

m s-1 [Bodhaine et a l., 1980]. Currently, routine MLO 

aerosol data editing also includes the manual 

identification of suspicious hours that may have been 

influenced by some unknown short-term local activity. 

These hours are l abeled with "P" flags [Massey et al., 

1987]. It is apparent from the previous examples that 

MLO data should be edited on a d ay-by-day basis, using 

as many different data sets as possible, including S02 

and BC concentration. Continuous S02 measurements 

at MLO would be extremely desirabl e. 

3.2.3. WATER VAPOR AND OZONE PROFILES OVER THE 

TROPICAL PACIFIC DURING CEPEX 

Introduction 

The Central Equatorial Pacific Experiment (CEPEX) 

took place during March 1993. The broad objective of 

this experiment was to obtain the measurements 

necessary to establish the roles of cirrus radiative 

effects and surface evaporation in limiting maximum 

surface temperature in the equatorial Pacific. In 

addition to playing a key role in climate in the western 

and central Pacific region because of the strong 

convection, it is also the major area where material 

from the troposphere can be injected into the 

stratosphere. Because of the cold tropopause 

temperatures seen in this region during the boreal 

winter and spring, air passing through the tropopause is 

dried as it enters the stratosphere . Understanding of the 

mechanism for this drying is an active area of research 

and a major focus of this effort. In addition, the 

horizontal circulation induced by the convection 

(Walker circ ulation) was also investigated. 

Measurements 

Water vapor and ozone profiles were obtained from 

the research vessel John Vickers as it sai led northeast 

from Honiara, Guadacanal (9.5 °S, 160°E), to Nauru 

(0.3°S, 166.5°), then east to Christmas Island (2°N, 

157.5°W). Soundings were made from Christmas Island 

(Kirimati) for a week (March 20-26) at the end of the 

ship cruise (March 7-1 8). During the experiment there 

were at least 13 partially successful water vapor 

soundings and 26 ozone soundings. On 12 of the 

flights, the ozone and water vapor were measured 

simultaneously . The water vapor profiles were obtained 

using a balloonborne frost-point hygrometer. For many 

years such instruments were used to make stratospheri c 

54 

water vapor measurements in Boulder. The uncertainty 

in the mixing ratio is about ±10%. Ozone was measured 

with a digital version of the ECC ozone sensor th at also 

has a long history of ozone profile measurements. The 

estimated uncertainty in the ozone partial pressure is 

±5% in the stratosphere and ±7- 10% in the troposphere. 

Both the wa ter vapor and ozone profiles could be 

classified into three groups with rather distinct fea tures 

based on the longitude (and time) of the observations. 

In the most westerly group of soundings (west of 

174°W) done between March 7 -13, there was a very low 

minimum water vapor mixing ratio (<1.5 ppmv) th at 

corresponded in altitude to the local tropopause (Fi gure 

3.25a). Ozone was ve ry low ( <30 ppbv) throughout the 

troposphere with a sharp increase in the mixing r atio at 

the tropopause . Although the only successful water 

vapor sounding when active convection was nearby was 

on the first day, the sate llite imagery showed strong 

convection in this region throughout the period of 

observations. The very low water vapor mixing rat ios 

at the tropopause indicate air is being dried as it passes 

through this cold trap . The observations of water vapor 

at the tropopause never showed saturation, but minimum 

temperature measured during the four-times daily 

radiosonde ascents were very close to the measured 

frost-point temperature. Minimum radiosonde 

tropopause temper atures in this region usually occurred 

at night or early morning , while the water vapor 

soundings were done later in the morning. It also may 

be that the saturation at the tropopause occurs only 

during the deep convective events when no successful 

balloon ascents were made. 

In the second group of soundings th at were done 

between 173°W and Christmas Island close to the 

equator, mixing ratios increase a bit at the tropopause 

but are still low (l-2 ppmv). Above the tropopause 

amounts are higher by about l ppmv. The shape of the 

profiles in these two groups is also generally the same. 

In this region convection was not intense and the 

tropopause was further from saturation even though 

frost-point temperatures were warmer. The main 

charac teristics of the upper troposphere and stratosphere 

in this region appear to reflect the processes taking 

pl ace further to the west. 

For the fin al group of soundings done at Christmas 

Island at the tropopausc (Figure 3.25b), the minimum 

water vapor mixing ratio was between 2.5 and 3.5 

ppmv. There is an absence of a sharp step in ozone at 

the tropopause, and ozone values were much higher in 

the upper troposphere. Convection, although present 

over Christmas Island, was not deep and hence neither 

the ozone nor water vapor profiles show characteristics 

seen in the more convective region. 

Discussion and Conclusion 

The water vapor and ozone profiles obtained during 

CEPEX show that deep convection in the western 

Pacific dries air passing through the tropopause to very 
0 

20 

18 

14 

5 10 15 

., . • • •••• 

a) 

0 

2.o•s. 178.o•w, 13 March 1993 

+ + + Waler Vapour Mixing Ratio 

o o o Saturation Mixing Ratio 

• • • Ozone Mixing Ratio 

-t\.t+ * + 

12..._,._._....._,_._......_.. .................. ~~~~~~~ .................. ~~~~~~~~ 

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.60 0.90 1.00 

Ozone Mixing Ratio (ppmv J 

0 

20 

18 

14 

5 10 

b) 

og o o o ; 0 0 

Tropopeuse 

~. 

oio 8 

o o}\ o 

Christmas Is. (157.2"Wl.5°N), 

24 March 199~ 

+ + + Water Vapour Mixing Ratio 

o o o Saturation Mixing Ratio 

• • • Ozone Mixing Ratio 

15 

12~.._._.~~...._.. .................. ~~~~~~'-'-'-'-'-'-'~~~~~~-'-'-'-' 

0.00 0.10 0.20 0.30 0 40 0.50 0.60 0.70 0 80 0.90 1.00 

Ozone Mixing Ralio (ppmv) 

f-ig. 3.25. Water vapor and ozone mixing ratio profiles from the upper troposphere and lower stratosphere du ring CEPEX. In (a) 

the profiles were obtained near the equator al the dateline and show the affects of deep convection. In (b) the profiles done on 

Ch ristmas Island do not show convection penetrating to such high altitudes. 

low values (-1 ppmv), which is the primary factor in 

establishing the dryness of the stratosphere. This 

drying takes place over a broad region as evidenced by 

the large horizontal extent over which dehydration was 

observed. The single, sharp minimum in temperature at 

the tropopause supports a mechanism for dehydration 

associated with deep convection in tropical disturbances 

[Danielsen, 1993). 

The changes in the stratospheric water vapor profiles 

seen at Christmas Isl and not only represent conditions 

further to the east out of the deep convective region but 

they also reflect a change in flow pattern in the lower 

stratosphere. The relatively high ozone values seen in 

the upper troposphere indicate transport from the 

stratosphere into the troposphere consistent with 

downward motion in the eastern branch of the Walker 

circulation. 

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Chapman, W.L. and J.E. Walsh, Recent variations of sea ice and air 

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Cha rlson, R.J., S.E. Schwartz, J.M. Hales, R.D. Cess, J.A. Coakley, 

Jr., J.E. Hansen, and D.J. Hofmann, Climate forcing by 

anthropogenic aerosols, Science, 255, 423-430, 1992. 

Danielsen, E.F., In situ evidence of rapid, vertical, irreversible 

transport of lower tropospheric air into the lower tropical 

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upwelling in tropical cyclones, J. Geophys. Res., 98 , 8,665-8,68 1, 

1993. 

Dutton, E.G., A cohe rence between the QBO and the amplitude of 

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C/im., 12, 383-396, 1992a. 

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Dutton, E.G., and J.R. Christy, Solar radiative forc ing at selected 

locations and ev idence fo r global lower tropospheric cooling 

following the eruptions of El Chichon and Pinatubo, Geophys. 

Res. Lett., 19, 2313-23 16, 1992. 

Duuon, E.G., and D.J. Endres, Date of snowmeh a Barrow, Alaska, 

U.S.A., Arc.Alp. Res., 23, 11 5- 11 9, 199 1. 

Duuon, E.G., P. Reddy, S. Ryan, and J. DeLuisi, Aerosol optical 

depth at l\1auna Loa, 1982- 1992, J. Geophys. Res., 99, 8295-

8396, 1994. 

Duuon, E.G. , R.S. Stone, D.W. Nelson, and B.G. Mendonca, 

Recent inierannual varia tions in solar rad iation cloudiness, 

and surface 1empra1ure at th e South Pole, J . Climate, 4(8), 

84 8-858, 1991. 

Elkins, J.W., and R.M. Rosson (Eds.), Geophysical Monitoring for 

Clima tic Change, No. 17: Summary Report 1988, 142 pp., NOAA 

Environmental Research Laboratories, Boulder, CO, 1989. 

Fosler, J.L., The sign ificance of the date of snow disappearance on 

the Arctic tundra as a possible indicator of climate change , Arc. 

Alp. Res., 21 , 60-70, 1989. 

r:oste r, J.L., J.W. Winchester, and E.G. Duuon, The date of 

snow disappearance on the Arctic tundra as determined from 

satellite, meteorologica l station a nd radiometric in -situ 

observations, IEEE Trans. Geosci. Remot. Sens., 30, 793-

798 , 1992. 

Hansen, A.D.A., I!. Rosen, and T. Novakov, Real-time measurement 

of the absorption coefficien t of aerosol particles, Appl. Opt., 21, 

3060-3062, 1982. 

Harris, J.M., and J.D.W. Kahl, An analysis of 10-day isentropic flow 

pauerns for Barrow, Alaska: 1985- 1992, J. Geophys. Res., 

99(Dl2). 25,845-25,854 , 1994. 

Hofmann, D.J., S.J. Ohmans, J.A. Lathrop, J.M. Harris, and II. 

Vomel, Record low ozone at the South Pole in the spring of 1993, 

Geophys. Res. Lttt., 21, 421-424, 1994a. 

56 

Hofmann, D.J., S.J. Oltmans, J.1'!. Ilarris, J.A. Lathrop, G.L. 

Koenig, W.D. Komhyr, R.D. Evans, D.'.\1. Quincy, T. Deshler. 

and B.J. Johnson, Recovery of stratospheric ozone over the 

United States in the winte r of 1993-1994, Geophys. Res. Le11., 21, 

1,779-1,782, 1994b. 

Komhyr, W.D., R.D. Grass, R.D. Evans, R.K. Leonard, D.'.\!. 

Quincy, D.J. Hofmann and G.L. Koenig, Unprecedented 1993 

ozone decrease over the United Stales from Dobson 

spectrophotometer observations, Geophys. Res. Lett., 21 (3 ), 201. 

204, 1994. 

Logan, J.A., Trends in the vertical distribution of ozone: An 

analysis of ozonesonde data, J. Geophys. Res., 99, 25,553-

25,585, 1994. 

Massey, D.M., T.K. Quake nbush, and B.A. Bodhaine, 

Conden sation nuclei and aerosol scallering extinction 

measurements al Mauna Loa Observatory: 1974-1985, NOAA 

Data Rep. ERL ARL·14, Air Resources Labo rat ory , Silver 

Spring, MD, 1987. 

l\letnieks, A.L., and L.W. Pollak, Instruction for use of photoelectric condensation nucleus counte rs, Geophys. flu//., 16, 1-1 8, 

1959. 

Nakaya, U., J. Sugaya, and '.\1. Shoda, Report of the l\!auna Loa 

expedition in the winter of 1956.57, J. Faculty Sci., 5, 1·36, 

Hokkaido Univ., Japan, 1957. 

Nemesure, S., R.D. Cess, E.G. Dunon, J.J. DeLuisi, Z. Li, and 11.G. 

Leighton, Impact of clouds on the shortwave radiation budget of 

the surface-atmosphere system for snow-covered surfaces, J. 

Clim., 7, 58 1-585, 1993. 

Ohmans, S.J., and H. Levy 11, Surface ozone measurements from a 

global network, Atmos. Environ., 28, 9-24 , 1994. 

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Ozone vertical profile changes over South Pole, in Ozone in the 

Troposphere and Stratosphere, Part 2, NASA Conf. Pub. 3266, 

edited by R.D. Iludson, pp. 578-581, l\ationa! Aeronau tics and 

Space Administration, Greenbelt, l\!D, 199.\. 

Penner, J.E., R.J. Charlson, J.'.\1. Hales,:\. Lau!ainen, R. Leifer, T. 

~ovakov , J. Ogren, LE Radke, S.E. Schwartz, and L. Travis, 

Quantifying and minimizing uncertainty of climate forcing b}' 

anthropogenic aerosols, Bull. Amer. Meteor. Soc. 75, 375.400, 

1994. 

Peterson, J.P., and R.'.\1. Rosson (Eds.), Climate Monitoring and 

Diagnostic Laboratory, No. 21, S11mmary Report 1992, 131 pp., 

l\OAA Environmental Research Laboratories, Iloulder, CO, 

1993. 

Quakenbush, T.K., and B.A. Bodha ine, Surface aerosols at the 

Barrow GMCC Observatory: Data from 1976 through 1985, 

NOAA Data Rep. ERL ARL-10, Air Resources Laboratory, Silver 

Spring, MD, 1986. 

Russell, P.B., E.G. Dutton , RF Pueschel, J.M. Livingston, T. 

DeFoor, D. Allen, P. Pilewsk ie, M.A. Box, J.A. Reagan, B.~I. 

llcrman, S.A. Kinne, and D.J. llofmann, Pinatubo and prePinatubo optica l depth spectra: ~launa Loa measurements, 

comparison, inferred particle size distributions, radiative effects, 

and relationship to lidar, J. Geopyhs. Res., 98, 22,969-22,985, 

1993. 

Schnell, R.C., S.C. Liu, S.J. Oltmans, R.S. Stone, D.J. Ilofmann, 

E.G. Duuon, T. Deshler, W.T. Sturges, J.\V. llHder, S.D. Sewell, 

M. Trainer, and J.M. Harris, Decrease of summer tropospheric 

ozone concentra ti ons in Antarctica, Science, 351, 726-729, 1991. 

Tarasick, D.W., D.I. Ward le, J.B. Kerr, J.J. 13ellefleur, and J. 

Davies, Tropospheric ozone trends over Canada: 1980-1993, 

Geophys. Res. Lett., in press, 1995. 
4. Acquisition and Data Management Division 

G. HERBERT (EDITOR), M. BIEl\IULIS, T. MEFFORD, AND K. THAUT 

4.1. CONTINUI NG PROGRAMS 

4.1.1. STATION CLIMATOLOGY 

The climatology of surface weather observations at the 

CMDL observatories is based on hourly-average 

measurements of the wind direction and speed, atmospheric 

pressure, air and dewpoint temperatures, and the 

prec1p11ation amount. The 17-ycar station climatologies 

arc an important record for the interpretation of measured 

values of aerosols, trace gases, and for long-term changes 

in the records themselves. Such measurements also serve 

to delineate periods of local contamination. The sensors 

currently in use were selected not only for high accuracy, 

but also for ruggedness, Lo minimize failure in the extreme 

conditions of the polar region. Since I-minute average 

values are also recorded to determine the variability within 

the hourly-average values, the sensors must also have a 

minimum response time of less than I minute. To the 

extent that it is practical, WMO siting standards [WMO, 

1969] are followed; i.e., winds arc measured at 10 m and 

temperatures al l.25 lo 2 m heights (Table 4.1 ). 

Thermometers are also positioned at the top of the local 

sampling tower to measure lhe lempcraturc gradient lo 

determine the stability of the surface boundary layer. 

On DOY 302 the first of a new set of sensors was 

installed at MLO and the sensors described in Table 4 . 1 

were decommissioned, with the sole exception of the 

Aerovane model 120 on the 8.3-m mast. (The Acrovanc 

was retained because it ties the changes in the nearsurface wind flow, due to continued building at MLO, to 

the climatology for the past 25-30 years.) A detailed 

discussion of the new meteorolog ical sensors follows 

the observatory climatologies. If Table 4.1 is compared 

with the previous CMDL Summary Reports [e.g. 

Pe1erso11 a11d Rosso11, 1993). small changes in the 

heights of sensors wi ll be noted. The values in Table 

4.1 reflect the results of a detailed audit of all sensors 

conducted at the time the older sensors were 

decommissioned for BRW (April 1994), SMO (June 

1994), and SPO (January 1994). There were no changes 

in the instrumentation at BRW, S~IO, or SPO in 1993. 

Barrow 

Descriptions of the BRW sta1ion and its climate arc 

given in previous CMDL Summary Reports [e.g., Deluisi, 

1981]. Wind roses of hourly average resultant wind 

directions and speed arc presented in 16 direction c lasses 

and 4 speed classes (Figure 4.1). Winds from the "clcanair" sector, north-northeast to southeast occurred 57.0% of 

the time as compared with 62.3% for the 16-ycar 

climatology. Wind speeds greater than 10 ms· I occurred 

18.8% of the time as compan.:d with l l.7 % of the 16-ycar 

climatology. The average speed of 6.9 ms·! (Table 4 .2) for 

the year is the highest average in the 17 years at this 

location. For September and December the maximum arc 

new records as well. 

TABLE4.l. CMDL CAMS Meteorological Sensor Deployment December 31, 1993* 

BRW ~11..0 

Serial Elevation, Serial Eleva1ion, 

Sensor No. m t\o. m 

Primary anemometert 576 16.5 1829 8.3 

Secondary anemometert 782 40.5 

Pressure transduceq 2366 9.5 225 3398.4 

Mercurial barometer 641 9.5 278 3398.4 

Air temperature A§ 8801 2.5 8805 1.7 

Air temperature B§ 8802 14.7 8809 37.8 

Airtempcrature C** GOOS 3.2 G046 2.0 

Dewpoint GOOS 3.2 G046 2.0 

Rain gauge -4 0.8 

See Table 4.6 for upgraded specifications. 

*Except at MLO where the values refer to conditions as of October 29 , 1993. 

t Aerovane, model no. 120, Bendix, Inc., Baltimore, :--laryland. 

S~10 SPO 

Serial Elevation, Serial Elevation, 

No. m No. m 

070 14.3 826 10.9 

752 78.5 28 2838 

961 78.5 215 2838 

8803 9.1 293 1.8 

8806 2.3 291 20.7 

G050 10.7 GOO! 2.4 

G050 10.7 GOO! 2.4 

-4 

tPrcssure transducer, model no. 1201 Fib, Rosemount, Inc., \1inneapolis, \linnesota. Heights of all pressure sensors arc given with respect to \lSL. 

§Linearized thermistors, Yellow Springs Inst. Co., model no. 44212, Yellow Springs, Ohio, except at SPO where platinum resistor thennometers, Ycllo\\ 

Springs Inst. Co., model no. RTD-358, Yellow Springs, Ohio, are used. 

'Thermometer, positioned at the top of the local sampling tower to facilitate an estimation of boundary layer stabiluy. 

••Hygrothennome1er, Technical Services Laboratory model no. 1063, Fon Walton Beach, Florida. 

57 
BARROW .-·· 1977 - 92 / .... · 

.•. ······· ···.}: ... _ ....... -··· 

.· . ... ;,.:···· . ········1.·····-· ./ ·· .. ____ .... · ·---.... .. -x ..... _ .. -·· ... ----· .. -----··i·········---...... . 

! / / .-.: / _ .... ··: ... ········ ..... , ........ . 

....... . .. ·· 

... -········ ___ ... ······ 

I 

____ .. --

:> ~ 

--········ 

frJ. ······-... ·---.... _ 

·----... __ 

--.. 

····· ·-.. 

---.... 

··--.. --.. .>·-. ·---... ">:" ····--.•. 

'•>:::-·· ··--... __ _ 

·. 

f .· 

. .w ... .. : ... ···: ·---~- -- i }-+-~!ml$H~=t··· · ····• .... ~;... 

\ -. .... \ \ 

\ \ . .-·· · .•. · · .. __ 

·-.... 

·-.. ··-... __ 

·· ... _ ···-.. 

.. · •. ·----... ·-..... . 

··· .... 

··--- ... L ... --···· 

·····t······· 

.... -........ 

_ ... ··· 

... -·· 

.··· .... -·· 

.1$-···· 

/ 

~ .. 

' 

' 

/ 

... ··.,·· 

/ 

/ 

1-W~l~ND~SPc"E-=,ED~(M._.,=s)., · .• ._ ·.. .. ··· .•• 

·-.. _ ·· -· ·- ~ ..... L .................. ---····· --.5 s WS < 5 

t2'lll2'll12'J5 'WS < 10 

c:::::::J WS • I 0 

··--... )~( ..... · .-··· ·-..... ·· ... -s· ···· ··· ···-··· ... 

... -·· 

. .. ·· WIND FREQ 

BARROW 

1993 

--.5 ' WS < 5 

rl12ZlZ!ll.a5 'WS < 10 

c:::::::J WS • I 0 

Fig. 4.1. Wind rose of su rface w inds for BRW for 1993 (left) and 1977- 1992 (righl). The distribution of resultant wind direction 

and speed are given in units of percent occurrence for the 16-year period. Wind speed is displayed as a fun ction o f direction in 

three speed classes. 

Prevailing wind 

direction 

Average wind 

speed (m s"

1) 

Ylax.imum wind 

speed* (m s·

1) 

Direction of max. 

wind* (deg.) 

Average station 

pressure (hPa) 

Maximum pressure* 

(hl'a) 

Ylin imum pressure* 

(hPa) 

Average air 

1empera1ure ('C) 

Maximum temperature* 

("C) 

Minimwn temperature* 

("C) 

Average dewpoint 

1empera1ure ("C) 

Ylaximum dewpoint 

1empera1ure ('C) 

Minimum dewpoint 

temperature ('C) 

Precipitation (nun) 

TABLE4.2. BRW 1993 Monthly Climate Summary 

Jan. Feb. March April May June July Aug. Sept. Oct. 

WSW NE ENE NE ENE E E w WNW ENE 

7 .3 6.9 5.8 6.3 7.0 5.0 5.9 6.0 8.6 8.9 

18 18 13 14 14 14 2 1 14 19 22 

105 57 69 54 104 54 253 228 333 270 

1006.3 1018.6 1015.3 1019.0 1020.8 1015.2 101 5.6 10 12.3 1008. 1 1007.8 

1024 1044 1045 1028 1033 1028 1027 1026 102 1 1023 

98 1 993 990 1009 1009 998 992 997 991 99 1 

-26.1 -24.9 -24 .9 -15.0 -5.7 0.9 5.3 1.6 -0.1 -5.0 

-3 -3 -16 -6 2 17 21 8 9 2 

-47 -48 -37 -27 -20 -5 -1 -2 -7 -22 

-28.4 -27.3 -27.5 - 17.0 -7.4 -0.9 2.3 0.1 -2.5 -7.I 

-4 - 3 -17 -8 5 13 8 6 0 

-51 -53 -40 -29 -22 -6 -4 -5 -1 3 -25 

0 0 0 0 0 0 9 22 19 5 

Nov. Dec. 1993 

SSW ENE ENE 

5.8 8.7 6.9 

17 2 1 22 

203 87 270 

1007.9 101 2.7 10 13.3 

1021 1035 1045 

981 983 981 

- 14.6 -22.3 -10.8 

-2 -1 2 2 1 

-36 -34 -48 

-16.8 -24 .8 -13.I 

-3 -14 13 

-39 -37 -53 

0 0 54 

Instrument heights: wind, 16.5 m; pressure, 9.5 m (MSL); air temperature, 2.5 m; dewpoint temperature, 3.2 m. Wind and temperature instruments arc 

on a tower 25 m northeast of !he main building . 

*:Vlaximum and minimwn values arc hourly averages. 

58 
The annual-average temperature of -10.8°C (Table 

4.2) is the second highest on record. Monthly-average 

temperatures for July, October, and November were also 

the second highest for the 16-year record. The annualaverage pressure was not significantly different from 

the long-term mean, but a new record low monthly 

pressure occurred for January. The summertime 

precipitation total for the year measured 54 mm, which 

is below the 16-year average of 66 mm. 

Mauna Loa 

The climatological summary of MLO is better 

understood when it is considered m two distinct 

regimes, the night (downslope) period (1700-0600 HST) 

and the day (upslope) period (0700-1800 HST). The 16-

year night and day wind roses illustrate the two distinct 

wind palterns (Figures 4.2 and 4.3). 

Night Regime. The 16-year wind rose (Figure 4.2), 

shows that 91.3% of all winds observed had a southerly 

component. In 1993, the percent occurrence of nocturnal 

winds was 90.3%. Pressure gradient controlled winds 

(WS~lO ms·I), from predominately westerly and southeasterly directions, occurred 8.4% of the time in 1993, 

while the 16-year record shows a 7 .0% occurrence. The 

annual-average wind speed is not significantly different 

from the long-term mean (Table 4.3). The monthly average 

wind speed for January set a new maximum record while 

the value for November is a new minimum value. The 

upslope or northerly component winds (north-northwest 

through east-northeast) 4.7% of the time are primarily the 

result of daytime, upslope flow extending into the early 

MAUNA LOA 

1977-92 

,,,' 1··-.. _ 

.. _ ...... --

/ .. --··· 

_l I ,, 

.t I ,.-··· .. -·,,. ! ; I ./ .. ,. 

I ! _l 

w T 

\ 

\ ,.· ... · ...... 

WIND SPEED (11/S) ,, 

--.5 I WS < 5 

rzl)'12'l'Oia5 1 WS < 10 

c::::::::JWS • 10 

--~. 

.. N .. ___ ---... 

---- ·-.. ··· ... ····..• .._ 

... .,.·~ ..... 

....... . \, '·. ····., 

----~ ·····--... 

......__ ./·, ' \ ' 

;:,: ~,:._·:··' .... \ \ '\\ __ .... \ \ .. \ \ \ 

1 ···-·--. 

-·-.. r-·-

·. i I 

, .. ~.J .... + .. + .. + .. ·r--

! ! 

; I 

/ I 

' / 

// / 

/ 

/ 

.. 'b ........ , .. ---··· 

' . .. ..... ·····$•"' WIND fREQ 

evening hours. 

Day Regime. The 1993 daytime wind rose (Figure 

4.3) indicates that winds from the west-northwest 

through east-northeast occurred 56.9% of the time 

compared with the expected occurrence of 58.8% based 

on the 16-year record. Pressure gradient controlled 

winds (WS~lO ms·I) occurred 8.5% of the time in 1993, 

while the 16-year record shows an expected occurrence 

of 5.5%. While the percentage of occurrence of 

pressure-gradient determined winds, generally 

associated with storms, · is the same for both timeregimes for 1993, the expected value is less in the 

daytime case. The day wind rose is more uniformly 

distributed in the light wind classes than the night wind 

rose. This is due to the occurrence of variable wind 

directions during the transition periods at dawn and 

dusk, most of which are included in this regime. 

The average air temperature for 1993 (Table 4.3), 

combining both day and night records, was 7.1°C, 0.1 °C 

above the long-term average while the average pressure, 

680.5 mb, equals the 16-year average .. Monthly mean 

wind speeds for January set a new maximum for that 

month, and November set a new minimum for that 

month. The monthly mean pressure for January and 

October set new record minimum values for those 

months. The monthly mean temperature for June set a 

new maximum and September set a new minimum. The 

precipitation total for the year measured 299 mm which 

is significantly below the 16-year average of 520 mm. 

This is the second lowest precipitation amount reported 

in the past 7 years . 

MAUNA LOA 

1977-92 

. ...... ~: ...... N .. . ~:.·. ~ 

__ .. -· 

_ ... "<. __ ...--··· / '/ 

/ / / I I ./ 

I / ,• ,; / I ... 1 

//////// I ! I 

f 1 

--W .... ·-·t·...!.... t-T' . \ 

\ \ 

\ 

\ 

--.5 • WS <S 

rllZl2'1ZlZ!5 • WS < 10 

c::::::::Jl!S • 10 

, .. ·· 

-·~ ·· ........... . I 

-· t·-···· ... ···-.... 

.-·····. 

~ ...... -... 

·....... .... ., . ' ·-......... ····· ... ' /'-. ...... '· 

'-._/: ... _ ", \\ \, . /' \ \ \ 

' '\\_........ \. \, \\ \ \ \ 

.. L.\ ··B-· 

..... 3 ......... · .. :=:.~.-· WIND f'REQ 

Fig. 4.2. Wind roses of the surface winds for MLO for 1977-1992 night (left) and day(right). The distribution of resultant wind 

direction and speed are given in units of percent occurrence for the 16-year period. Wind speed is displayed as a function of 

direction in three speed classes. 

59 
MAUNA ·-- ···~ ··· · LOA _..- 1993 / .. ·· ··· ... 

.... -·· .-···· ··· .... 

_,,(· _ ... ··· ,.··· ··,-,( ..... 

. -·· -· .. · 1 ··... - ······ ... _ .. -·· ·-..... . ............ r .. -· .... :a:: ............. -··· . .-·· .. ----· ··-.. ___ .. >< ----···:-·-·· __ .:.:. ___ _ 

. 

/ .>"·- ·-.... _ ">::· 

/ 

_.:· ... 

...... -~>··... . ... -----·· ./ 

····· ... 

·····-... 

.··'·· :-. 

·· .. 

I . ···---..... ·· / \(' .. -· -··· ··1 ··- .. .-··· .. ..... 

.; ..... ~ ····t 

\ 

\ 

--

/ ··:.:-·< ... -··-:-· ... ">:. 

>< 

\ ·· .... -· ·-.. 

..... · 

\ 

... · .. 

,! I" ·B 

' 

··----.:··········-... __ 

·----... -·· ··---.... _ ····-.. ··-... ....... j···---· -·· ·:-:· 

. .. --·· ____ ...... ·-··--··~:: .·· 

WIND SPEED (M/ S) 

--.5 'WS < 5 

rll22'l.ll1'l35 • WS < 10 

c:::::J WS • I 0 

·-... 

·-... _ 

..... -····· ·······--i--········ 

-······· 

.. --··· .-·· .•. "/;"° .. -·· .-·· 

.... ·· WIND FREQ 

c::::::::::JWS • 10 

Fig. 4.3. Wind ro ses of the surface winds for MLO for 1993 night (left) and day (right). The distribution of resultant wind direction 

and speed are given in units of percent occurrence for th e year. Wind speed is displayed as a fu n ction of direction in 1hree speed 

classes. 

Samoa 

A comparison of SMO's 1993 wind rose (Figure 4.4) 

with that of the 16-year period shows a higher 

percentage (68.8%) of "clean air" sector winds (northnorthwest through southeast) in 1993 than in the 16-

year record (59 .3%). Yet the 1993 value is less than the 

75 .8% observed in 1992. The occurrence of winds in 

the 10 ms·! or greater class is 7 .0% in 1993 while the 

expected occurrence based on the 16-year r ecord is 

4.8%. The average wind speed for the year, 5.3 ms· l 

(Table 4.4) is near normal. Monthly average wind 

speed for May was a new record high, while the 

monthly average wind speeds for January and February 

were new min imum values. 

Average station pressur es for the months of January 

and February were also in the lowest 10% compared 

with the 16-year record (Table 4.4). The average 

station pressure for the year was 1000.6 mb, a large 1.3 

mb above the long-term average at Cape Matatula. The 

average air temperature, 27.6°C, is 0.5 °C above the 16-

year average. The precipitation total for the year 

measured 1934 mm which is below the 16-year average 

of 2095 mm. 

South Pole 

The distribution of the surface wind direction in 1993 

(Figure 4.5) shows a lower percentage of winds (92.6%) 

from the "clean air" sector (grid north-northwest 

through east-southeast) than the 16-year average 

(93.9%). A higher percentage of winds in the >10 ms·l 

60 

cl ass (3. 2%) was observed in 1993 than th e long -term 

average (4.0 %). While the average wind speed of 5.4 

ms-I is equal to the long-term average, the average 

value for March is a new max imum for that month. 

The 1993 annual-average station pressure was 677.0 

mb, 2.1 mb below the 16-ycar average (Table 4.5). The 

1993 value is the third lowest annual-average pressure 

recorded in the 17-year history. The annual-average 

temperature was -49.3°C, 0.3°C below the long-term 

annual average. Whil e the monthly -average temperatures for August and December we re in the lowest 10 

percentile of the record, no other month ly means were 

records. The minimum temperature of the year was 

observed to be -76°C in August. 

Meteoro logical Measurement System Upgrade 

The last major upgrade in the meteorological sensors 

at the CMDL stati ons occurred 6 years ago when th e 

Technical Service Laboratory (TSL) mode l number 1063 

hygrothcrmometer was selected as the preferred 

instrument for measuring humidity . This is the same 

instrument used by the National Weather Service to 

measure temperature and humidity at airport locations. 

While individual instruments have been replaced, the 

basic complement of instruments has not changed in the 

past 20 years. Recentl y it has become increasingly 

difficult to purchase replacement instruments and 

reliable parts. For the same reasons it has been more 

difficult to keep the Control and Monitorin g System 

(CAMS ) operational as we ll. Thus it was decided to 
TABLE 4.3. MLO 1993 Monthly Climate Summary 

Prevailing wind 

direction 

Average wind 

speed (m s·1) 

>!aximum wind 

speed• (m s"1) 

Direction of max. 

wind* (deg.) 

Average station 

pressure (hPa) 

>!aximum pressure• 

(hPa) 

> linimum pressure• 

(hPa) 

Average air 

temperature ("C) 

>1aximum temperature• 

("C) 

>1inimum temperature• 

("C) 

Average dewpoint 

temperature ("C) 

Maximum dewpoint 

temperature ("C) 

Minimum dewpoint 

temperature ("C) 

Precipitation (mm) 

Prevailing wind 

direction 

Average wind 

speed (m s·1) 

>faximum wind 

speed• (m s"1) 

Direction of max. 

wind• (deg.) 

Average stalion 

pressure (hPa) 

>1aximum pressure• 

(hPa) 

Minimum pressure• 

(hPa) 

Average air 

temperature ("C) 

>laximum 1empera1ure• 

("C) 

>linimum temperature• 

("C) 

Average dewpoint 

tempcratu re ("C) 

>laximum dewpoint 

temperature ("C) 

>linimum dewpoint 

temperature ("C) 

Precipitation (mm) 

Jan. Feb. March 

SW WSW SSE 

7.7 6.0 5.2 

20 15 15 

263 269 227 

676.8 678.5 679.7 

682 682 686 

666 674 669 

2.4 3.3 3.0 

10 9 10 

-4 -3 -3 

-16.4 -20.9 -15.9 

4 0 7 

-35 -35 -37 

77 0 0 

WSW W N 

7.8 6.1 5.2 

19 17 16 

244 245 235 

676.7 678.5 679.7 

682 682 686 

666 674 670 

6.0 7.8 7.8 

13 14 16 

-3 -2 -3 

-11.0 -15.0 -8.7 

6 5 11 

-36 -32 -37 

64 0 0 

April May June July Aug. Sept. Oct. Nov. Dec. 1993 

Night 

SSE SSE SSE SSE SE SSE SSE SE SE SSE 

4.6 5. 1 5.2 3.7 3.5 3.2 4.4 4.0 5.4 4.9 

12 14 14 12 9 10 15 11 15 20 

161 161 151 149 141 159 226 154 123 263 

680.9 680.1 68 1.1 680.8 681.5 68 1.0 679.7 679.2 679.6 679.9 

684 684 684 684 685 684 683 682 683 686 

678 676 679 678 679 677 675 677 676 666 

5.5 5.0 8.3 6.5 5.2 5.2 5.2 4.7 4.7 4.9 

13 10 15 13 10 10 10 9 10 15 

5 3 3 2 2 0 -4 

-19.4 -18.3 -20.l -9.9 -6.2 -3.6 -10.0 -22.3 -18.1 -15.7 

7 4 7 7 6 8 8 2 3 8 

-36 -34 -33 -26 -20 -20 -27 -35 -35 -37 

0 0 14 0 3 4 0 0 98 

Day 

N NW NE SE NE N WNW NNW ESE NNW 

4.4 5.0 5. 1 3.9 3.5 3.5 4.6 3.2 4.9 4.8 

IO 13 15 13 9 8 17 11 16 19 

161 15 1 150 137 89 156 181 164 130 244 

681.0 680.2 681.3 681.0 681.6 681. 1 679.7 679.2 679.6 680.0 

684 684 684 684 684 684 684 682 683 686 

678 676 679 679 679 678 674 676 675 666 

10.9 10.3 13.4 10.5 9.9 9.5 9.2 9.2 8.4 9.3 

17 16 19 18 15 16 15 14 15 19 

2 6 4 3 

-1 1.6 -9.6 -10.3 -1.5 0.9 

11 6 9 10 8 

-35 -32 -32 -26 -19 

0 0 0 41 0 

3 

0.3 

9 

-23 

39 

2 

-3.7 

8 

-25 

39 

2 -3 

-13.5 -14.4 -8.9 

7 6 11 

-33 -33 -37 

4 13 201 

Instrument heights: wind, 8.3 m; pressure, 3398.4 m (MSL); air temperature, 1.7 m; dewpoint temperature, 2.0 m. Wind and temperature 

instruments are on a tower 15 m southwest of the main building. 

•Maximum and minimum values are hourly averages. 

61 
SAMOA 

1993 

--.5 'WS < 5 

C?IJ2"}'l'll'15' WS < 10 

115 • JO 

··· .... 

llJND FREQ 

SAMOA 

1977- 92 / .. ·· 

llJND SPEED ( 11/S) 

--.6' WS < 5 

r?J2Zll.llld5 • WS < 10 

c::::::J 115 • I 0 

Fig. 4.4. Wind roses of the surface winds for SMO for 1993 (left) and 1977- 1992 (right). The distribution of resultant wind direction and speed 

are given in units of percent occurrence for the year and 16-year period, respectively. Wind speed is displayed as a function of direction in three 

speed classes. 

Prevailing wind 

direction 

Average wind 

speed (m s'1

) 

Maximum wind 

speed• (m s·1) 

Di rcction of max. 

wind• (deg.) 

Average station 

pressure (hPa) 

Maximum pressure• 

(hPa) 

Minimum pressure• 

(hPa) 

Average air 

temperature ("C) 

Maximum temperature• 

('C) 

Minimum temperature• 

('C) 

Average dewpoint 

temperature ("C) 

Maximum dewpoint 

temperature ("C) 

Minimum dewpoint 

temperature ("C) 

Precipitation (mm) 

Jan. 

SE 

2.5 

14 

306 

997.9 

1004 

998 

28.7 

37 

22 

23.3 

26 

19 

202 

Feb. 

NW 

2.3 

10 

305 

997.7 

1003 

989 

28.8 

36 

23 

22.9 

25 

20 

144 

TABLE 4.4. SMO 1993 Monthly Climate Summary 

March April May June July Aug. Sept. 

NW SE SE SE SE ESE SE 

4.0 3.9 8.0 6.6 7.4 5.2 6.3 

12 13 15 14 13 10 13 

3 18 3 10 139 99 139 124 137 

1000.4 999.7 1001.8 1001.9 1001.8 1002.6 1002.7 

1004 1003 1006 1006 1006 1006 1007 

996 996 997 998 998 998 998 

28.0 28.4 27.5 26.9 25.9 27.0 27.0 

35 35 32 32 33 33 35 

23 24 24 22 21 22 23 

23.5 24.0 22.7 22.1 21.1 22.1 21.9 

25 25 25 24 24 25 24 

19 22 19 19 18 17 19 

290 179 86 63 94 86 198 

Oct. ~ov. Dec. 1993 

SE SE SE SE 

6.1 6.1 4.4 5.3 

12 14 15 15 

149 123 33 139 

1001.7 1000.5 998.7 1000.6 

1006 1005 1002 1007 

998 997 994 988 

27.0 27.8 28.6 27.6 

35 36 35 37 

22 24 23 21 

21.5 22.7 23.8 22.6 

24 25 26 26 

18 20 22 17 

277 112 202 1934 

lns!Tument heights: wind, 14.3 m; pressure, 78.5 m (MSL); air temperature, 9 m. Wind and temperature instruments arc on Lauagae Ridge, 11 0 m 

northeast oflhe main building. Pressure sensors are in the main building. 

•Maximum and minimum values are hourly averages. 

62 
........... 

SOUTH POLE _ ........ - 1993 ... .. ·· 

·· ····· .....• ::·:::· ... ....... 

··-.... ··-····· ~····· ·····-...... .. ·· ........ 

' 

' 

...... 

·······-· .. 

-··········· 

····--... · ... 

·· ... .. >t" ······ ... _ ·· .•. ··•. .... .. 

.. ·· 

....... ··""· ... ~.,,: ... ·· 

·· ... 

l 

..·· .. •.·····• ..······ 

.... 

/ 

............ ····· .... 

..• : ..... 

······ ... -~--~:·<..... \ .... · ... \ .. \ 

\ 

1-+-+-~!m!!l!!I· ··l-·····i ....... g .. 

' 

f--!-+-+-....._lmmll: ··r···B· ··~---,···-:, __ 

· ,.t\\_\··r·· W·······l·····r·t ;,··\ ·i .. Ht 

' j 

....... /< ..... _ ... /···i·. . ....... . ... .....,..···· ··... . .. ·.i , ..~--. ·:< / 

\ ..... v ..... ··... - ·- do .. ~>< .. ,. .... ~ \:: ... .-~···· ··. ~ " ......... · · .... ,. .. ·· .. _ .... ·,.: .... . ... ·.. ··... .... ··· ........ _ ________ ... _l . ......... ··· 

.... ···., ••• ••• ••••• ,1; •• ..-··· ..... ••• ••• 

. ··.. . ... ·O ... -··'····· ..•.. -··/ / ....... .... .. ... ;.·:···· ····........ ··- .. i . . . . 

· ............ ·.·_ .. ><.·.···.......... . ... ··· ... ··· . . - ···-··!,_· ····· -~ ... :·= .•• ···.... ...·· _ .. ·· ··--::· ..... 

1-W~~ND~SP,..,E ~(11'"'1"'s)~ '··· ·-·-·j· .... --.5• WS< 5 

tl1llll1'lla5 I WS < 10 

c:::JYS • 10 

·······-... 

.. -.:/ 

_ ... ~( .... .... ···· .. ·· . ... -···· WINO FREQ 

.. ······ 

::<. 

\. \ ... \ ..... ,_)·::: ............ ····. 

··.. ·· ........ ·..... ···-..... . .. r·. .. ... ::-::·······....... ··... . .... J······ ·· WIND SPEED (11/S) 

--.5 • l!S< 5 

rzomzzz35 I W'S ( 10 

c:::JWS • 10 

·· ...... ·· .. ·· .... 

················1--·············· 

........... , ............... ·· 

........ ··$·--· .. 

">( 

. .. -1'·· .. >< ..... / : 

)./ ........ / 

.

·""···· ·.,_.· 

.··· ·····:'.::··· ./ __ ... ···· .. ·· ·-...... .... ·· -~-.. -·· 

_ .. ·· 

WIND f'REQ 

.. ····· 

Fig. 4.5. Wind roses of the surface w inds for SPO fo r 1993 (left) and 1977-1992 (right). The distribution of resultant wind 

direction and speed are g iven in units of percent occurren ce fo r th e year. W ind speed is displayed as a funct ion of direction in three 

speed classes. 

Prevailing wind 

direction 

A vcrage wind 

speed (m s·1) 

Max.imum wind 

speed• (m s·1

) 

Direction of max. 

wind• (deg.) 

Average station 

pressure (hPa) 

Maximum pressure• 

(hPa) 

Minimum pressure• 

(hPa) 

Average air 

temperature (°C) 

Max.imum temperature• 

('C) 

Minimum temperature• 

(°C) 

Average dewpoint 

temperature ("C) 

'vlaximum dewpoint 

tempera tu re ("C) 

'vlinimum dewpoint 

temperature ("C) 

Precipitation (mm) 

TABLE 4.5. SPO 1993 Monthly Climate Swnmary 

Jan. Feb. March April May June July Aug. Sept. 

ENE N NE NNE NNE ENE N E NNE 

4.7 5. 1 6.6 5.4 6.0 5.4 4.3 5.3 5.8 

10 10 13 11 14 12 12 11 13 

2 347 19 9 6 7 353 348 9 

693.0 680.1 680.2 677.5 673.8 673.7 670.9 667.4 672. l 

706 693 696 690 690 694 690 687 687 

683 665 670 667 661 660 656 650 655 

-27.4 -41.5 -52.4 -57.6 -56.4 -60.4 -56.4 -63.8 -59.0 

-18 -26 -35 -46 -34 -30 -40 -47 -44 

-36 -55 -62 -68 -71 -74 -73 -76 -74 

-28.4 -41.7 -52.0 -58.1 -56.6 -60.4 -57. 1 -63.0 -57.8 

-19 -27 -36 -47 -35 -3 1 -41 -46 -43 

-37 -56 -63 -68 -69 -10 -71 -72 -7 1 

0 0 0 0 0 0 0 0 0 

Oct. Nov. J)ec. 1993 

NNE NNE N NNE 

6.6 4.9 4.6 5.4 

15 II 12 15 

351 24 357 351 

672. 1 682.6 681. I 677.0 

685 694 690 706 

660 674 674 650 

-50.4 -38.4 -28.8 -49.3 

-33 -29 -20 -18 

-61 -48 -37 -76 

-50.I -39.2 -30.1 -49.5 

-33 -29 -23 -1 9 

-61 -49 -40 -72 

0 0 0 0 

Instrument heights: wind, 10.9 m; pressu re, 2938 (MSL); air temperature, 1.8 m. The anemometer and thermometer arc on a tower 

I 00 m grid east-southeast of CAF. Pressure measurements are made inside CAF. 

•Maximum and minimum values are hourly averages. 

63 
reconsider the specific instruments used to me asure the 

station pressure , temperature gradient and wind speed 

and directi on, along with a dedicated data acquisition 

system, in designing a replacement weather measuring 

system. 

Due to the recent, mostly favorable, experience with 

the TSL 1063 hygrothermometer (Technical Services 

Laboratory, 630 Lovejoy Road, Fort Walton Beach, 

Florida 32549) it was decided to continue to use this 

instrument for dry air and dewpoint temperature 

measurements at ground level at the observatories. A 

good reason could not be found for changing to another 

precipitation gauge so the tipping bucket rain gauge 

used from the 1976-1977 period (Belford Instrument 

Company, 1600 South Clinton St. Baltimore, Maryland 

21224) was incorporated into the design of the 

repl acement system. 

After limited testing and review, a variablecapacitance ceramic sensor, similar to the old 

Rosemount transducer (Rosemount Inc ., 12001 W. 78 th 

St., Eden Prairi e , Minnesota 55344) was selected. The 

new sensor is a Setra model 270 barometer (Setra 

Systems, 45 Nagog Park, Acton, Massachus etts 01 727). 

When the fi ve pressure transducers purchased for the 

stations and Boulder were compared with the mercury 

barometer in Boulder, the average daily difference was 

less than 0.1 mb with a standard deviation of 0.2 mb. 

These values are consistent with the specified accuracy 

of the sensor (Table 4. 6). 

To elimin ate the need for semi-annual calibration of 

the thermometers used to measure the temperature 

gradien t, standard RTD (Resistor Temperature Device ) 

sensors were selected for which matching electronics 

could be purchased. The sensor is a Logan 4150 series 

plat inum resistance probe in a steel sleeve that was 

machined to reduce the thermal mass and inherent 

thermal tran sfer in a ventilated flow (Logan Enterprises, 

8844 US North West, Liberty, Ohio 43357). For the 

range of air temperatures at the CMDL stations, an 

accuracy of 0.1 °C can be realized (Table 4.6). 

Linearized thermisters, YSI part number 442 12 (Yell ow 

Springs Instrument Co., Yellow Springs, Ohio 45387) 

were previously us ed to measure the air temperature. 

(Radiation shielding was accomplished using the Gill 

aspirated temperature-dewpoint radiation shield model 

number 43406 (R.M. Young Company, 28 01 Aero-Park 

Drive, Traverse City, Michigan 49684). Due to smal l 

non-linearity in the calibration, a "warm" and "cold" 

season calibration had to be used to guarantee 0 . 1°C 

accuracy over the specified range of -50° 10 +50°C. 

Since 1976, platinum resistance probes have been used 

at SPO to obtain accurate temperatures below -50°C. 

Cambridge System Inc., model number 137-MI-TC 

(Cambridge System Inc., Newton, Massachuset1s) 

temperature-dewpoint measuring system aspirated 

radiation shields were used to shie ld the thermometers. 

Measurements indicate that the thermometer is aspirated 

at an average rate of about l ms- I . 

After a careful review of the anemometers used at 

SPO, it was decided that the R.M. Young (RMY) model 

number 05105 (R.M. Young Company) propeller 

anemome ter would withstand the severe ant arctic 

conditions. (RMY model number 05305 , a high 

performance anemometer desi gned for air quality 

measurements, was used at MLO where there is a higher 

percentage of li ght winds during the upslope-downslope 

transitions.) Unlike the Bendi x Friez aerovane mod el 

number 120 (Bendi x Corp., Baltimore, Maryland 

2 1204) , which was used for wind speed and direc tion 

measurements since the initial installat ions in 1973-

1975 and that uses a magneto and is subject to magnet 

strength changes and line loss errors, the RMY sensor 

produces a pulse for unit run -of-wind. Wind tunnel 

testing indicated th at the aerovane h ad a threshold wind 

speed of 1-1.3 ms·t, while similar tests showed the 

RMY sensors to reach threshold speeds at about 0. 4-0.7 

ms· 1. 

The design of the revised electronics for the 

meteorological sensors has focused on distributing the 

signal acquisition electronics so that only seri al digital 

signals are transmitted over long distances and thus 

elimin ate the need for on-site calibrations whenever 

TABLE 4. 6. CMDL Upgraded Meteorological Sensor Specifications* 

Th reshold 

Sensor Range Resolution Accuracy Sensitivity 

RMY wind speed 0 to 60 ms·l 0 .01 ms·l 1 ms·1 

RMY wind direction 0 to 355 d eg rees 0. 1 degree 1 ms·l 

Sc1ra station pressure 600 lo 1100 mb 0.005% ±0.03% FS 

RTD temperatures -20 0 to +600°C 0.1 c ±0.3 CFS 

±0. l C (-85 to +50 C) 

TSL hyg rothermometcr -60 to +60 C 0. 1 c 0.5% RMS , I % MAX (>0 C) 

2 % MAX (<O C) 

RMY, R.M. Young Company, Traverse City, Michigan; RTD, resistor temperature device; TSL, Technical Services Laboratory, fort 

Walton Beach , Florida. 

•Values refer to conditions a t MLO as of October 30, 1993. 

64 
possible. Indiv idual analog-to-digi ta! converter 

modules MetraByte (MB) module numbers 1000/2000 

(Kiethley MetraByte Co., 440 Myles Standish Blvd., 

Taunton, Massachusetts 02780) interface the sensors to 

the computer interface by a RS-485 interface. Nonvolatile memory is used to store sen sor identification 

and calibration information. I t is also possible to 

invoke digital filtering of the signals. The 

measurements from each sensor-module pair are, 

therefore, filtered and calibrated to give values scaled 

in physical units. A computer requests data from the 

individual sensors at intervals determined by the 

filtering that is employed. 

A rack mounted computer is used to acquire and store 

all of the d ata. The primary data file is initialized daily 

after the system does a survey of the active sensors. 

One-minute average values from each sensor are stored 

in the data fil e . To the maximum extent possible, these 

values are fully calibrated. The system also provides 

features to allow the operator to enter supplementary 

observations and calibration information such as 

weather and mercury barometer observations. The 

system also provides a simple text editor for metadata 

entries. In all cases these observations and entries are 

stored with the data files since they pertain to the data 

and determine , in part, its quality. Multitasking of the 

data acquisition program and data display-input 

program is accomplished under the Microsoft Windows 

environment. 

4.1.2. DATA MANAGEMENT 

During 1993, the CAMS operated 98 .15% of t he time. 

CAMS gathers data from sensors that oper ate 

continuously at each of the four CMDL observatories. 

The CAMS performance was monitored by comparin g 

the number of d ata files recorded against those expected 

for the year. In CAMS, there are data files regularly 

recorded 12 or 24 times a d ay. In Tables 4.7a and 4.7b, 

the hourly solar rad ia tion file was used to monitor the 

ASR CAMS. The hourly C02 data files were used for 

the C02 CAMS. The hourly-aver age meteorological 

data file was used for the M03 CAMS. 

Due to the remoteness of the observatories, power 

outages are common and arc the main reason for data 

loss. Hardware failure is another reason for data loss. 

During 1993, BRW had two boards fail plus the C02 an alyzer went down, MLO had three boards and two 

power supplies fai l, SMO had two boards fail, and SPO 

had one board and one power supply fail. 

4.2. SPECIAL PROJECT: BOUNDARY WIND AND 

TEMPERATURE STUDY AT MLO, 1992- 1993 

Introduction 

Perched on the north fl ank of the Hawaiian Mauna 

Loa volcano at an elevation of 3.4 km, MLO has been 

an important source of background atmospheric-aerosol 

and chemistry measurements for more than 35 years. 

The Mauna Loa volcano rises to an elevation of 4. 17 km 

and stands as a major obstacle to the midPacific. 

subtropical flow creating widely varying local wind 

regimes. At this latitude (19°N) the dominant 

climatological feature is the midNorth Pacific 

subtropical anticyclone centered to the southcas! of 

Hawaii in winter and to the northeast in the summer 

months [Blumenstock and Price, 1974]. In the winter 

and spring period the synoptic scale wind field is 

predominately westerly at this latitude. During the 

summer months the flow is easterly on the southern side 

of the anticyclone. Superimposed on the large-scale 

synoptic flow is the diurnal up-down slope wind 

produced by diurnal heating and cooling of Mauna Loa. 

In the transition months the synopti c scale winds arc 

significantly less important, and the local winds at MLO 

are determined in l arge measure by the regional scale 

thermal "breathing" of Mauna Loa. The resulting 

circul ation, pressure, temperature, and moisture 

distributions are described in a series of studies and 

reports [Pri ce and Pales, 1963; Chin et al. , 1971; 

Mendonca, 1969]. 

In 1984 an eruption and subsequent lava flow from 

fiss ures along the Mauna Loa east rift zone produced a 

lava flow to a point 2 km east of the observatory. This 

put a sense of urgency in efforts to construct a reccntl yapproved lava barrier to the south of MLO to deflect 

TABLE4.7a. CMDL CAMS Operations Summary, 1993 

Expected No. of 

Individual CAMS Blocks 1993 

ASR 8760* 

C02 8396 

M03 4380t 

Total 21536:j: 

*The expected number of ASR blocks from SPO is 7680. 

tThc expected number of M03 blocks from MLO is 3672. 

Percent Data CaEture and [Blocks Missing] 

BRW MLO SMO 

99.49% [45] 98.04% (1 72] 99.94% [5] 

87.49% (1050] 99.83% (14) 99.65% (29) 

99.45% [24] 98.56% [53) 99.38% [27] 

94.80% (1119] 98.85% (239] 99.72% [61] 

tThe expected total number of blocks from MLO is 20828; the expected total number of blocks from SPO is 20456. 

65 

SPO 

99.40% (46] 

98.75% [105] 

99.75% [I I] 

99.21% [162] 
TABLE4.7b. Number of Blocks of CAMS Data Expected and Blocks Recorded in 1993 

Block BRW MLO SMO SPO 

Type Description Expected Recorded Expected Recorded Expected Recorded Expected Recorded 

A Hourly aerosol data 2190 2181 2190 2148 2190 2187 2190 1907 

B Secondary aerosol data• Variable 0 Variable 1344 Variable 2189 Variable 0 

c Hourly C02 datat 8396 7346 8396 8382 8396 8367 8396 8291 

D Daily C02 data 365 325 365 365 365 370 365 369 

E Hourly C02 calibration data 364 374 364 361 364 366 364 386 

F C02 calibration report 52 53 52 52 52 53 52 58 

H Daily aerosol data 365 366 365 361 365 364 365 345 

I Meteorological calibration 365 360 305 303 365 364 365 365 

M Hourly meteorological data 4380 4356 3672 3619 4380 4353 4380 4369 

N Surface ozone calibration 52 56 45 34 52 5 0 0 

0 Daily surface oz.one data 365 365 305 300 365 365 365 368 

s Hourly solar radiation data 8760 8715 8760 8588 8760 8755 7680 7634 

T Daily solar radiation data 365 363 365 358 365 365 320 317 

w Daily meteorological data 365 364 305 301 365 365 365 368 

*Nominal block count equal to total hours in year less 52 7-hour calibration periods. 

tNominal block count equal to 52 7-hour calibration periods. 

any future flows that may originate above the 

observatory. From a micro-meteorol ogical perspective , 

the concern at the time was that the l ava barrier would 

selectively d eflect the downslope winds or possibly 

create a separation of the low-level winds isolating 

MLO from the prevailing winds aloft. A stairaccessible tower was proposed to fac ilitate sampling 

above the influence of the lava barrier. 

The lava barrier was constructed in January 1986, and 

in December the 40-m tower was er ected. For the first 

time it was possible to install and maintain 

instrumen tation well above the influence of the cluster 

of buildings that make up the observatory. I ts 

predecessor, a 27 -m tall antenna mast, was j udged by 

most to be unsafe to climb due to its telescoping-type 

construction and age. In February 1987 an anemometer 

was installed on top of the 40-m tower. This was the 

second of two anemometers at the observatory, the first 

being at a height of 8.5 m, from which the station 's 

wind climatology was derived (for the latest update, see 

Peterson and Rosson, 1993). Some months later when 

the measuremen ts from both anemometers were 

compared, it was dis covered that during periods of 

southerly winds, a distinct flow separation occurred in 

which the wind direction at the top of the tower was 

significantly different than that at the 8.5-m level. In 

some cases the difference was in excess of 90°. At such 

times the depth of the downslope flow is very shallow, 

less than 40-m deep. Using a captive balloon to obtain 

wind p rofiles in the lowest 0.5 km, Mendonca [1969) 

found the top of the nocturnal downslope flow to be at 

about 50 m in three soundings in September-November 

1966. I t is, therefore, reasonable to expect that a layer 

depth of less than 40 m could occur at other times of the 

year. Other than Mendonca's balloon study , there are 

66 

few relevant observations of the temporal changes of 

the MLO boundary layer as a function of hei ght. 

The Bendix aerovane model no. 120 was used at MLO 

for the past 2 decades because of its durability, but at 

the price of a relatively high starting speed of 1-2 ms-1 

and a long distance constant (63% recovery) of about 5 

m [Mazzarella, 1972). Starting thresholds in excess o f 

1 ms-I and longer distance constants limited the 

response of the anemometer such that it was not a 

reliable sensor of wind fluctuations at heights less than 

10 m where wind speeds were more often less than 3 

ms-I. A more sensitive anemometer was needed to 

depict changes that occur during the light wind 

characteristic of upslope-downslope transitions. 

The objective of this report is to define the 

instruments, the installation process, and the procedure 

used to obtain a data set describing the first 40 m of the 

MLO boundary layer as a function of hei ght and time. 

In addition, the wind and temperature profiles for the 

MLO Photochemical Experiment II (MLOPEX II) 

intensives from January 15, 1992 , to February 15, 1992, 

April. 15, 1992, to May 15, 1992, and from July 15, 

1992 to August. 15, 1992, are ava ilable from Internet by 

anonymous FTP@ftp.cmdl.noaa.gov. MLOPEX II is a 

continuation to an earlier field study and modeling of 

the photochemistry of the remote troposphere conducted 

at MLO in 1988 [Ridley and Robinson, 1993). 

Instrumentation 

During 1991 a large number of meteorological 

sen sors were obtained from government surplus. 

Among these were sensitive cup anemometers (Climate 

model 011 -4), wind vanes (Climate model 012-1 ), and 

aspirated air and dewpoint temperature sensors 

(Cambridge System model 137-MI-TC). The c up 
anemometers and air and dewpoint-temperature sensors 

needed modification before they could be used in the 

field. The anemometers were of a 1960s design in 

which the light from a small lamp was interrupted by a 

rotating chopper producing one pulse per revolution. A 

16-slot chopper was installed yielding an event for 

approximately every 10 cm of wind as compared with an 

event for every 148 cm of wind with the single chopper 

setup. A frequency measurement with a resolution of 1 

Hz yields a wind speed measurement to a resolution of 

about 0.25 ms·l . The circuitry was removed from the 

air and dewpoint-temperature sensor, and the aspirated 

sun shield was used for a thermome ter housing. 

Precision RTD platinum resistance thermometers 

(Logan model 4150) were used. 

The anemometers were calibrated in the NCAR wind 

tunnel. The standard deviation of the calculated wind 

speed at 5 ms·l was 0.18 ms·l for the six anemometers. 

The accuracy of the wind tunnel was about 0.2 ms·l. 

The wind vanes were mechanic ally aligned to an 

accuracy of ±1°. Additional uncertainty on the order of 

±2-3° was added when the vanes were installed on the 

tower. All six thermometers were compared against a 

stand ard instrument and found to agree to within 

±0. l °C. 

Anemometers and thermometers were installed on the 

40-m tower at approximately 3, 6, 10, 20, 29, and 38 m 

heights. A 1.2-m long arm was used to extend the 

anemometer and wind vane from the south side of the 

tower. \Vind directions f~om 20 to 320° were rel atively 

unaffected by the tower structure. The thermometers 

were also attached to this arm approximately 0.3 m 

from the tower. At each level, e lectronic modules were 

used to translate the signals from the sensors to a 

computer-compatible serial protocol (RS-485). A 

frequency-to-serial converter (MetraByte mode l M2602) 

was used to measure wind speed, and a bridge module 

(Metr aByte model M25 32) was us ed to measure the 

resistance changes that indicated wind direction. A 

RTD type 392 module (MetraByte model M1422) was 

used to interface the temperature probes. All modules 

were interrogated once a minute by a personal 

computer. Individual values were displayed on the 

computer monitor for quality assessment purposes. The 

observations were also stored on disk and sent Lo 

Boulder for further analysis. During the first 9 months 

that included MLOPEX II, J anuary, April, and August 

intensifies, a telephone linkup between Boulder and 

MLO was u sed to transfer data on a daily schedule. 

Discussion of Jl,feasurements 

Case study April 23-29, 1992. Figure 4.6. displays 

the hourly-average wind profile in the first 40 m for the 

7-day period April 23-29, 1992. The height is shown in 

meters on a logarithmic scale; Lime is in Hawaiian 

Standard Time (HST). This was a period of unusually 

steady winds from the west during which the MLOPEX 

observers noted considerable haze. Such windy periods 

67 

are usually associated \vith mi gra ting cyclones from 

higher latitudes and can represent periods of long-range 

transport from as far as the Asian continent. The largescale pressure gradient will tend to overpower the local, 

thermally-driven upslope flow during such times. On 

April 23, a well-defined northerly upslope developed, 

but as the westerlies increased in intensity on 

subsequent days, the upslope consisted of a very slight 

veering of the wind during the daytime hours. As the 

strength of the westerly winds decreased on April 28-

29 , the winds shifted to a more northerly direction 

during the daytime hours. 

The temperature profiles in Figures 4.7 and 4.8 show 

the temperature change as a function of he ight for April 

23 and 25, respectively. The temperatures are hourly 

averages. On April 23 during the downslope flow 

(0000-0700 HST), the west-southwesterly winds were 

less than 10 ms·l (Figure 4.6) and the temperature 

profiles showed very small changes in temperature until 

0700 HST. Such temperature profi les are typical of the 

stable, nocturnal boundary l ayer. Note that the 

transition from westerly Lo northerly winds takes less 

than an hour (0900- 1000 HST), and the temperature 

decreases by 3°C or more at all levels. This is due to 

the arrival of the cool, moist air from the Saddle region 

below MLO. With the return Lo a westerly flow at 1400 

HST the sounding warms by about 2°C. After sunset 

the temperatures cool below 10 m and warm above that 

level to become nearly isothermal for the remainder of 

the day. 

The situation is con sid erably different on April 25, 

when the effect of the thermally-driven upslope is 

masked by the dominant westerly flow from the west 

with no significant decrease in wind speed observed. 

The temperature profile (Figure 4.8) reflects the effect 

of a well-mixed boundary layer, as one would expect 

with winds greater th an l 0 ms· I . The nocturnal 

sounding (0000-0600 HST) is isothermal with liul e 

change. Due to the mixing, all levels warm and cool 

adiabatically during the daytime, returning to a steady 

isothermal temperature between 8-9°C after sunset. 

(The 0.2-0.3 °C warming at 30 m on all sound ings 

indicates that this thermometer is biased to that degree.) 

In the steady nocturnal wind cond itions of 0400 HST, 

April 25 (Figure 4.6) the Ri chardson number (Ri = (g/8) 

(d8/dz)/dU/dz)2, g = 9.8 ms·2) is calculated to be 

0.0004. Thus with a logarithmic wind profile, u *(lO m) 

= 0.83 ms· l (u* = kzdu/dz, k = 0.4), and the z 0 (u(z) = 

u*ln(z/zo)/k) is about 1 cm [Ka imal and Finnigan, 

1994). At 1200 HST the Richardson number is -0.003, 

z0 = 0.02 cm, and u* = 0.56 ms·l. 

Climatology. The distribution of wind speed in four 

classes as a function of wind direction in 16 classes for 

the 10 and 38-m levels is shown in Figure 4.9. The 

wind roses include all of the hourly observations for the 

2-year period in two classes, daytime and nighttime, 

since the diurnal forcing of the flow at MLO dominates 

the seasonal forcin g. The times used to separate the 
April 23, 1992 

• PLANETARY BOUNDARY LAYER WINO PROfLER • 

: ~~~- \ l f~-;~:::~ 2 '(A~~~.......,....-f.- I\ l\'.11._~ 

f [f\'.ci_~ 

J 11 11 1, JT lt Zl 21 

TIME (hr) HST 

April 2.S, 1992 

• PLANET ARY BOUNDARY LA YER WIND PROfLER • 

t U 11 15 1'7 lt Zl 1 1 

TIME (hr) HST 

Apr il 27, 1992 

• PLANETARY BOUNOARY LAYER WINO PROFL ER • 

i~~~~.........,....._...,._.._!1<-11.._~ 

2 tuil>-t.1-'lll-<ll~l>-"'" ......... ~!LL."'-."'-."'-.~ 

2~~~~-'i>-11.1..W-'~!4...."'-."'-."'-.t;._~ 

April 24, 1992 

i ~ ........ ~1»-"_.,_~1>-'4>.-'1>-~-1!......u._ Ii..... ".i. Ill llo !!, !11 !lo II 

2 l.-<l.-<L..\1.-'l»-"__.,_~l.A.-llL-"'-!4.... 14__ II._"-~!. Ill u. u. "· 11. u.... 

2 ,._..__,,_-11.-'._.....-"-~"-11>-"'-'"'-l,4.._ il...._11._ li....., ~!. II, U, U, 11 IL u.,_. 

t 11 1 J 1 ~ 1 '7 1' :11 lJ 

TIME (hr) HST 

ApriJ 26, 1992 

t 11 u n u n u 11 

TIME (hr) HST 

Apr il 28, 1992 

• PLANETARY BOUNDARY L AYER WINO PROfLER • 

i ~.,,....._,,.~..,~lt._1/.....11._ll._11._t..._~ 

2 ~~~v~ci_tz...11.....11.....11._r....._i..._~ 

'¥¥<>/'~u._l/.....'Z..11.....li.....1..._"-...4.....~ 

I 

,_ ~ MH'.>-~"""--'11>-11......_ ......... ~!l<-"'-.~~v' :I: 

I 0 ,_ . v...r...r..,1~!t.....li.....lt.....li....."--.."-...4.....~ 

~~~ AJ',/~L...'Z..li......'.'-'-''~ 

VVv~l......4.....'.'.4.....4.....'.'--.~ 

Q J: 

~ 1_1<_'Z..l/.....li.....ci_1<_~ 

(!) 

w 

J: 

Hl---\\.-'6..~A>--"_.._.~!t-li.....li....."--.f......Cl__~..; 

J 11 1S U JT 1t 31 2J 

TIME (hr) HST 

t 11 11 u .., lt Zl ,, 

TIM£ (hr) HST 

Apr il 29, 1992 

I 0 ,_ . 

6 

w 

:I: 

• PLANETARY BOUNDARY LAYER WIND PROFLER • 

.0 L lo ~~'<..__\\\'-'---'"""~.....__....__ 

""" ~"-\\\\\\'''''---~'-----

"" '· ~"-~\\\\\,\\\'~~ 

' 

. ~"-\\\\\\~\\'~/// 

~ ~<..__~\\\\\\\\\\.......___/// 

' l '- ~<..__\\\\\\\\\~"'------Ill 

' t J1 U J5 n J t 11 ZJ 

TIME (hr) HST 

Fig. 4.6 . Profiles of hourly average wind s at MLO fo r April 23 through April 29, 1992. Individu a l wind ba rbs equal 10 knots. 

68 
Apnl lJ. 1991 0000 · 1100 HST 

Uot111 (llST) 

'° 

JS 

JO 

~. 

lS 

lO 

ll 

10 

.\. . "-.., 

II IJ l l " Tcmptnl\ln: (dc&C) 

Apnlll, 1991 1200· 2!00 HST 

'° 

__ JS ,, 

lO 

IS 

! 

~ lO 

__ ,, ~ __ ll ,, 

--11 10 

II ll ll 17 

T at1pcnNn: (de& C) 

Fig . 4.7. Profil es of hourl y average temperatures at ~LO for 

April 23, 1992. 

daytime-nighttime regimes (0900 to 2000 HST, and 

2100 to 0800 HST) were based on the most common 

time of transition from upslope to downslope. The 

northerly, upslope flow is clearly the dominan t feature 

during the daytime at both levels while southerly, 

downslope winds are most predominant at night. 

During the dayt ime, the secondary maximum of stronger 

winds from the southeast and west directions are 

associated with periods when the large-scale pressure 

gradient domina tes the upslope-downslope regime. The 

pressure grad ient wind signature is also evident in the 

nighttime wind roses. The small percentage of 

northerly winds in the nighttime roses is due, in most 

part, to periods when the upslope flow persists for more 

than 12 hours, which usually occurs during the summer 

months. It is noteworthy that while there is clearly a 

higher percentage of stronger winds at the 38-m level 

than at 10 m as would be expected, there is also a 

higher percentage of calm winds (WS<0 .5 ms-t) at the 

top of the lower as well. 

As in Figure 4.9, the frequency of occurrence of wind 

speeds as a function of direction was calculated at the 

69 

Apnl ll. 1991 0000 • 1100 HST 

Hoi.1n (HST) 

'° 

IS 

--· JO 

~, 

ll 

__ lO , 

ll 

--· 10 l 

.\. 

II ll ll " Tcmpm.rurc (dcsC> 

AprJ 25. 1992 1100 · 2300 HST 

'° 

__ JS ,, 

JO 

~ .. lJ 

! t lO 

--__ .. l l ,. 

- •-u 10 

Fig. 4.8. Profiles of hourly average temperatures at YlLO for 

April 25 , 1992. 

intervening four levels, and the results for all directions 

for both daytime and nighttime periods arc shown in 

Table 4.8. The daytime flow is predominately upslope 

driven by the thermal heating of the mountain. Due to a 

well-mixed boundary l ayer, changes of the distribution 

of winds with height are small above the 3-m level. 

While there is a decrease in the percentage frequency in 

the three higher speed classes in the lowest 10 m, the 

changes are small above that level. The changes in the 

percent occurrence of winds Jess than 0.5 ms-I (calm) 

decreases with height, except for a small increase at 38 m. 

Reflecting the increase in stability in the boundary 

layer at night, the distribution of the wind speed with 

height takes on a different character from the daytime 

si tuation. While the percen tage frequency of occurrence of calm conditions and of winds greater than 5 

ms-I increase with height, the most common wind (0.5 

lo 5 ms- I range) percentage o f occurrence decreases 

with height. Considering winds from the southsouthwest to west directions at speeds greater than 5 

ms-I, indication of the large-scale sign ificant winds, 

there is a general increase in the percentage of 
fig. 4.9. Wind roses of the 10 m and 40 m level winds at MLO for night (left) and day (right) reg imes. The distribution of resultant 

wind directions and speed are given in units of percent occurrence for the period January 1992 throu gh Janua ry 1994. Wind speed 

is displayed as a fun ction of direction in three classes. 

70 
TABLE4.8. Percent Frequency of OccU1Tence 

of Wind Speed at Six Height Levels 

Winds Wind Height 

Speed (m s·l) 3m 6m !Om 20m 29 m 38 m 

Day/ ime conditions (0900 to 2000 HST) 

Calm 4.8 3.9 3.3 3.1 3.1 4. 1 

.5 10 5 73.8 67. 1 60.8 54.6 53.5 53.6 

5 to 10 19.4 24.8 30.l 33.5 33.5 32.1 

10 2.0 4.1 5.8 8.8 9.9 10.3 

Nighllime conditions (2100 to 0800 HST) 

Calm 4.1 3.1 3.4 4.8 7.5 10.6 

.5 10 5 70.5 62.8 54.9 47.9 44.3 42.I 

5 to 10 23.2 29.8 35.2 36.4 34.2 32.1 

10 2.2 4.3 6.5 10.8 14.0 15.2 

5* 5.2 7.9 9.0 13.0 13.9 13.5 

*Direction limited to west through west southwest. 

occurrence with height. Interestingly, above 10 m the 

percentage occurrence at all wind speeds is rel atively 

constant with height. 

Summary 

Based on this ana lysis, the measured gradients of 

temperature and wind arc generally uniform above 10 

m . Thus measurements al 10 m and near the top of the 

tower will describe the temperature and wind structure 

of the boundary layer over this range of heig hts. The 

10-m level was selected as the reference level to remain 

con sistent with \VMO observational recommendations. 

A thermometer and anemometer are positioned al 38 m 

to characterize the flow on the upper h alf of the tower. 

Due to terrain irregularities it would be difficult to 

71 

characterize the flow in any useful way w ith wind 

measurements below 3-5 m. However, temperature 

measurements at 2 m are important to depict the 

stability of the surface layer (Figure 4.8). 

4.3. REFERENCES 

Blumenstock, D.L., and S. Price, The climate of Hawaii, in 

Climates of the States, vol. 2., pp. 6 14-639, NOAA, USDC, 

Water Informacion Center, Inc., Port Washington, NY, 1974. 

Chin, J.F.S., H.T. Ellis, B.G. Mendonca, R.P. Puesche l, and ll.J. 

Simpson, Geophysical monito ring at Mauna Loa 

Observatory, NOAA TM ERL APCL-13, 36 pp., 1971. 

DeLuisi, J. (ed.), Geophysical Monitoring for Climatic Change 

No. 9 Summary Report 1980 , 163 pp., NOAA Environmental 

Research Labo ratories, Boulder, CO, 1981. 

Kaimal., J.C., and J.J. Finni gan, Atmospheric Boundary Layer 

Flows, Their Structure and Measurement, 289 pp., Oxford 

Univ. Press, NY, 1994. 

Mazzarella, D.A., An inventory of specifications for wind 

measuring in struments, Bull. Amer. Mete or. Soc. 53, 860-

871, 1972. 

Mendonca, B., Local wind circulation on the slopes of Y!auna 

Loa, J . Appl. Meteorol., 8, 533-541, 1969. 

Peterson, J.T., and R.M. Rosson (eds.), Climate Monitoring and 

Diagnostics Laboratory No. 21 Summary Report 1992, 132 

pp., NOAA Environmental Re search Laboratories, 13oulcler, 

CO, 1993. 

Price, S., and C.J. Pales, Mauna Loa Obse rvatory: The first five 

years, Mon . \Veather Rev., 91, 665-680, 1963. 

Ridley, B.A., and E. Robin son, The Mauna Loa Observatory 

photochemistry experiment, J. Geophys. /?es. 97 , 10,285-

10,290, 1992. 

World Meteorologica l Organization (WMO), Guide to 

Mete orolog ical Instrumentation and Observing Practices, 

No. 8, Tech. Pap er 3, 347 pp., World Meteorological 

Organization, Geneva, 1969. 
5. Nitrous Oxide and Halocarbon Division 

T .M. THOMPSON (EDITOR), J.W. ELKINS, J.H. B UTLER, S.A. MONTZKA, R.C. MYEI~S. 

T.J. BARING, S.0. C UMMINGS, G.S. D UTTON, J .M. GILLIGAN, A. H . H A YDEl\, 

J. M . LOBERT, T.H. SWANSON, D.F. H URST, AND C.M. VOLK 

5.1. CONTINUING PROGRAMS 

5. 1.1. FLASK SAMPLES 

Air samples were collected in p airs and analyzed as in 

the past with one change. In mid-June , flasks started 

being humidified by filling them with air flowing 

through a bubbler prior to their being returned to the 

field sites. This cond itioning step is an attempt to 

passivate the fl ask walls and minimize surface 

chemistry for compounds l ike carbon tetrachloride 

(CC14 ) . Filling instructions were r evised and, the refore, 

flasks are purged 50% longer. The effi cacy of these 

changes is currently being assessed. 

Other minor program c h an ges also in stituted in June 

included: (l) using flow meters with the larger flasks 

during filling so that flushing rates are equal, (2) 

conducting field site pump performance tests 

periodically, and (3) checking flask pressures a fter 

filling and before analysis on each instrument. More 

0.85 and 2.5 L flasks were added; therefore, instrumen ts 

such as the gas chromatograph-mass spectrometer 

(GC-MS) were guaranteed s uffic ient a ir for an alyses. 

A maintenance trip was made to Alert, Northwest 

Territories, Canada, in May to install an air sampling 

in let system [Montzka et al., 1992). The air inlets are 

a t 10 m and 5 m on the north to wer. Flasks are 

c urrently filled only from the highest inl et. SPO is the 

other field site where fl asks are filled through this type 

o f inlet system. 

A year of analyzing the fl ask air samples on the 

o riginal electron capture -gas chromatograph (EC-GC) 

and the Autofl ask system is complete . The Autoflask 

system is patterned a fter the Radiatively Important 

Trace Species (RITS) GC in situ system [Montzka et al., 

1992]. This comparison showed some weaknesses in 

the Autofl ask flask inlet plumbing and system control 

soft ware. Necessary changes were made, and an 

additional period of overlapping analyses will be done 

before the old GC is ret ired from serv ice. 

Chlorofluorocarbon (CFC) -11 and -12 concentration 

growth rates continue to decrease as their expected 

usage dimin ished [Elkins et al. , 1993) . In 1993 the 

CFC-11 growth rate was about 1 ppt yr·l with CFC-12 

being 10 ppt yr·l ( Figure 5 .1). 

The g rowth rate of nitrous oxide (N20) h as decreased 

since 1991 from about 1 ppb yr· l to 0.5 ppb yr-1. The 

yea rl y global means of measurements from flasks 

collected at seven sites s how that mixing ratios of N20 

appear to have leveled off in 1993 (Figure 5.2). The 

72 

cau se o f this decrease in the growth rate is unknown and 

may be the result of many m it igat ing factors. 

Worldwide use of fertilizer has decreased by over 10% 

whic h will lessen its source of N20. Sin ce the eruption 

of Mt. Pinatubo in June 1991, northern hemispheric 

temperatures have decreased by 0.5 °C; this could reduce 

the N20 amount produced by bacteria that arc strongly 

influenced by temperature change. Since the summer of 

1990 through the end .of 1993, the SOI was consistently 

negat ive. A large negative anomaly (<-1) indicates a 

warming event in the trop ica l ocean that usually means 

less equatorial upwellin g and less flux of deep water 

N20 into the atmosphere. Two such events were 

recorded in the summer of 1991 and summer of 1992 

through the spring of 1993. 

280 

--

Q. 240 

Q. 

,.... 

,.... 200 I 

u 

LL 

u 

160 

500 

--450 Q. 

Q. 

-

N 400 ,.... I 

u 350 

LL 

u 

300 

25 0 

a 

x Alert 

0 Pt. Barrow 

0 Niwot Ridge 

6 Mauna Loa 

0 Am. Samoa 

M Cape Grim 

x Soulh Pole 

78 80 8 2 84 86 88 90 92 94 

Year since 1900 

Fig. 5.1. Monthly means of atmospheric mixing ratios measured from 

flasks collected at the seven 1\0AII fla sk network sites for (a) CFC-I I 

and (b) CFC- 12. Values are reported as dry mole fractions [Elkins et al., 

1993) in parts-per-1rillion (ppt). A color figure is available from the 

authors. 
:a 

Q. 

-9: 

0 N 

z 

312 

310 

3 08 

306 

304 

3 0 2 

300 

298 

78 80 82 84 86 88 90 92 94 

Year since 1900 

Fig. 5.2. Yearly global means of atmospheric N20 mixing ratios 

collected al the seven NOAH flask network sites. Values are reported as 

dry mole fractions in parts-per-billion (ppb). 

5.1.2. RITS CONTINUOUS GAS C HROMATOGRAPH SYSTEMS 

During scheduled maintenance trips to the fi eld sites, 

calibration tank regulator heaters and automatic shut-off 

solenoid valves were installed. The regulator he aters 

operate at 60°C and reduce contamination buildup. The 

solenoid valves are in-line between the two calibration 

tank rcgulatms and the stream select valve. If a power 

outage occurs, the solenoid valves close preventing the 

possible loss of valuable calibration gases. 

Electron capture detectors (ECDs) at BRW, NWR, 

and SMO had to be replaced during 1993. In all cases 

the channel that measures CFC-II , CFC- 113, CH3CC13, 

and CC14 was the one that had basel ine frequency 

gradually increase from a nominal 100 Hz to well over 

1000 Hz. The method of cleaning a detector by flow ing 

H2 through it at normal operating temperature for 24 

hours or more did not improve the background 

frequency . 

Calibration cyl inder gases at the field si tes typically 

l ast about 1.5 years. The ratios of the chromatogram 

areas for all components in the two cal ibration tanks arc 

monitored for possible drift. When a cal ibration 

cylinder's pressure falls below 1.3 MPa it is replaced. 

The new tank componen ts' mixing ratios were 

determined with a pr ecision better than 0.5%. For a 

c hemical like N20, whose grow th rate in the atmosphere 

is smal l being similar to the calibration precision, step 

jumps can occur in the data when calibration gases are 

c hanged. A techn ique to counteract th is problem and 

also attempt to detect drift in the working standards was 

instituted in 1993. Two well-cal ibrated gas standards 

(round robins), one at ambien t and the other at - 10% 

below amb ient mixing Tatios, were taken to the field 

si tes over a period of a month and analyzed in place of 

outside air for 2 days. This intercalibration documented 

working standard mixing ratios over a span of a few 

73 

weeks at all of the sites except SPO. GC linearity and 

precision were also determined. By continuing this 

procedure quarterly, problems associated with 

standards' drift and instrument vagaries should be 

minimized. Some adjustments in the data base wil l 

probably be r equired as this method becomes routine 

and attempts are made to back correct the data based on 

better defined instrument cali bration curves. 

Monthly mean data for CFC-11 arc pictured in Figure 

5.3. The marked decrease in growth rate is obvious and 

comparable to that determined from the longer flask 

record. Likewise, CFC-12 data arc shown in Fi gure 5.4 

and correlate well with the flask mix ing ratios. The 

data for N10 (Figure 5.5 ) were adjusted because of the 

round robin intercalibrations. These data arc 

preliminary and may require further adjustment as the 

290 

280 

- 270 -a. 

a. 

-,... 260 ,... I 

u . BRW 

LL 250 . NWR u 0 MLO 

240 . SMO 0 SPO 

230 

87 88 89 90 91 92 93 94 

Year 

Fig. 5.3. Monthly average CFC- I I mixing ratios in ppt from the in situ 

GCs. 

540 

520 

- 500 -a. 

a. 

-

N 480 ,... 

I 

u . BRW 

LL 460 . NWR u 0 MLO 

440 . SMO 

0 SPO 

420 

87 88 89 90 91 92 93 94 

Year 

Fig. 5.4. Monthly average CFC-12 mixing ratios in ppt from the in situ 

GCs. 
313 

311 

:0 

a. 309 

~ 

0 ... z 307 . BRW . NWR 

Q MLO 

305 . SMO 0 SPO 

303 

87 88 89 90 91 92 93 94 

Year 

Fig. S.S. Monthly average N20 mixing ratios in ppb from the in situ 

GCs. New calibration and water vapor corrections were applied. 

intercalibrations continue. NWR da ta were corrected 

for the period when the Nafion drier was not installed . 

This removed or reduced the annual cycle seen in 

previously published results. 

5.1.3. Low ELECTRON ATTACHMENT P OTENTIAL 

S PECI ES (LEAPS) 

Measurements of halons H- 1301 and H-1211, 

CrC-113, Cil3Dr, and CII3Cl continued with the new 

LEAPS GC system throughout 1993. Except for 

H-1301, these compounds were also measured by 

GC-MS throughout the year. Halon data from the 

EC-GC installed in April 1992 arc extremely precise 

(w ithin 0.0 1-0.03 ppt on average), although the 

response for H- 12 11 is still non-linear on the new 

system. By mid-1992, the data suggested a substantial 

slowdown in the growth of the two halons in the 

atmosphere [Butler et al., 1992). However, the recen t 

values, which are more frequent and more precise and 

that ex tend the data set from 5 to 7 years, indicate that 

the slowdown may not be as substantial as previously 

reported. During 1993, atmospheric H-1211 increased 

at 0.1-0.2 ppt yr-I (3-7% yr-1), and H-1301 increased at 

about 0.2 ppt yr-1 (10% yr-1). At the end of 1993, the 

latitudinally weighted, mean mole fractions of H-1301 

and H-1211are2.1and3.1 ppt, representing 25-35% of 

organic bromine in the remote atmosphere (Figure 5.6). 

Because of a numerical error in the calculation 

routines, previously reported values for H-1211 should 

be adjusted upward by 15%. Reanalyses of cylinder 

SRL-K-009288, an Aculife-treated steel cylinder that 

has served as the principal secondary standard for all 

reported halon values, have agreed within ±0.2 ppt for 

each of the halons over 3-5 years. Earlier calibrations, 

however, were not as precise as those done since early 

1992, therefore it is difficult at this time to determine 

74 

--

Q, 

Q, 

-

c 

0 

·-

-(.) 

~ LL. 

C1) 

-

0 

:E 

~ 

c 

2.5 

2.0 

1.5 

1.0 

3.5 

3.0 

2.5 

2.0 

1.5 

. . . . ... . ~ ..... ·, ....... · . -... ; .. . . . 

.... : .. . ... : ... ~---~--~- ; ~ : .oo 

: ;i::I 0 :o oOJ .......... . t.f ' ··-. v .... . JP; 

: : • . 0 l:B"¢> . 

~ . -- -~: .; ... .,. . ; ; . : ...... : .... . 

( .j ..... r .... '.o ___ ; ..... L ..... :···b)·· o t 0 ' ' ' I 

. . . . 

87 88 89 90 91 92 93 94 95 

Year 

Fig. S.6. Composite plots of all CMDL halon data (a) 11-1301 (b) 

H-1211. Circles represent analyses with the old EC-GC, triangles 

represent analyses with the new EC-GC, squares arc for data obta ined by 

GC-MS(ll-12 11 only). 

drift within th is range. Data from the GC-MS and 

EC-GC systems agree within ±0.1 ppt overall. 

One indicator of potential sampling error or storage 

effects is a comparison of agreement for flask pairs 

versus that for individual measurements of the same 

flask . From purely statistical considerations, one would 

expect flask -pair agreement to be better than the 

precision for indiv idual measurements if there is no 

flask or sampli ng effect. This is because the value 

obtained for each flask is a mean and, consequently, a 

closer estimate of the true mean than is an individual 

measurement. From EC-GC measurements, it is clear 

tha t agreement for H-1301 within pairs of 

simultaneously collected flasks is similar to the 

analytical precision for repeat measurement of 

individual flasks (Figure 5.7a). Because surface effects 

in all flasks are not expected to be identical, this 

indicates that there is little chance of storage having 

affected H-1 301. The median standard deviations for 

replicate analyses and for flask-pair agreement arc both 

around ±0.01 ppt (±0.5%). However, for H-1 211, 

agreement between flasks is somewhat poorer than for 

replica te analyses ( Figure 5.7b). The median standard 

dev iation for replicate analyses is ±0.02 ppt (±0.7%), 

but for flask pairs is ±0.04 ppt (±1.3%). This is not a 

large effect and it may be symptomatic of some problem 

occurring within a flask after it has been sampled. 
-

0 ~ 

->a 

CJ 

c 

C1> 

:::I 

C" 

C1> 

... 

LL 

C1> 

> ;: 

ca 

:::I 

E 

:::I 

0 

75 

50 

25 

75 

50 

25 

75 

50 

25 

··- ··:············ ·· ··········:· ·········-

............ \. a). 

.... 

. . 'b) . . . . . . . . . --.... -- ~ ...... -..... : ........... -~- . . . . . . .. . 

... ... ········· ····· · .. . :::· ..... : ....... --.. ·:· .. ... .... . . . . . . 

...... r··········t············:·c·> ....• • ;r ~ • • • • ~· • • • • • • • • • • •: • • • • • • • • • • • ·:· • • • . . 

. . 

0.00 0.05 0.10 0.15 0.20 

Standard Deviation (ppt) 

f-ig . 5.7. Cumulative error plots for repeat ana lysis of 

individual fla sks (dotted line) and analysis of flask pairs (solid 

line): (a) 11 - 1301 by EC-GC, (b) H-1211 by EC-GC, (c) H- 1211 

by GC-MS. 

Whether this effect involves H- 1211 directly or some 

other compound affecting the analysis is uncertain al 

this time. It does not appear related to sampling site, 

sampling dates, or time between sampling and analysis. 

The possibility that it may be something other than 

H- 1211 is underscored by a similar evaluation for 

GC-MS data. In this case, the agreement for H-121 1 

between flasks is actually slightly better than that for 

replicate analyses, as one would expect from purely 

statistical considerations (Figure 5.7c). Because the 

GC-MS is specific for the m/z = +85 ion from H-1211 

and the ECD is less specifi c, it is more probable that the 

la rger differences between flask pairs, as observed by 

EC-GC, may be some matrix e ffect, such as that caused 

by a co-eluting compound. It is also possible, however, 

that the effect is just beyond the detection ability of the 

GC-MS. 

5.1.4 . ALTERN ATIVE HALOCARBON MEASUREMENTS 

Hydrochlorofluorocarbons (HCFCs) are important 

substitutes for CFCs in industrial applications. Their 

75 

use will significantly shorten the time required for 

complete elimination of CFCs in industry [UNEP, 

1991). Although HCFCs contain chlorine, models 

indicate that they have a much reduced potential to 

deplete stratospheric ozone compared with CFCs. 

Ozone destruction capacity for HCFCs, a s predic ted by 

semi-empirical steady state ozone depletion potentials, 

ranges between 1and12% that of CFC- 11 [WMO, 1991; 

Solomon et al., 1992). However, the ozone depiction 

potential for HCFCs over short periods, such as the next 

5-1 0 years when chlorine is expected to reach a 

maxtmum in the stratosphere, is more accurately 

estimated with time-dependent ozone depiction 

potentials [Solomon and Albritton, 1992). Because 

HCFCs have shorter atmospheric lifetimes than CFC- I I, 

time-dependent depletion potentials can be as much as 

five times higher than steady-state ozone depiction 

potentials. For these reasons, and because of 

uncertainties concerning the chemistry and dynamics of 

the atmosphere, there is increasing concern over 

ex tensive use of HCFCs as replacements for CFCs. 

Some nations have accelerated the timetable for 

eliminating HCFCs earlier than recommended by the 

Copenhagen Amendments to the Montreal Protocol 

[UNEP, 1993). Monitoring the global spati al and 

temporal variability of HCFCs is necessary for 

maintaining an accurate atmospheric chlorine inventory 

as replacements gain acceptance in the marketplace and 

for validating model predictions concern ing the fate of 

these compounds in the atmosphere [Prather and 

Spivakovsky, 1990). 

Paired sample flask s filled at the four CMDL stations 

and three cooperative flask sampling locations during 

1993 were analyzed in the Bould er laboratory using gas 

chromatography with mass spectrometric de tection for 

HCFC-22, HCFC-142b, and HCFC- 141 b [Montzka et 

al., 1993; 1994a, b]. Results for both HCFC-22 and 

HCFC-142b represent a continu ation of measurements 

made in previous years. Before 1993, however, only 

preliminary mixing ratios were reported for HCFC-142b 

[Swanson et al., 1993]. In addition to fin ali zing 

standardization for HCFC-142b, a consistent set of 

cal ibration standards was also prepared for HCFC- 141 b 

in 1993. 

Chlorodifluoromethane (HCFC-22) 

Measurements of the most abundant atmospheric 

HCFC continued in 1993 (Figure 5.8; Table 5.1). The 

latitudinally-weighted global mean mixing ratio for 

HCFC-22 in mid-1993 was 106 ppt (Table 5 .2). This is 

an increase of 4 ppt over the global mean de termined 

for mid-1992 [M ontzka et al., 1993]. The growth rate 

for HCFC-22 from November 1991 through Deccm her 

1993 is estimated at 4. 9 (± 1.0) ppl yr-1. The average 

difference between the northern and southern 

hemisphere during 1993 was 13 ± 1 ppt. 
13 

12 

a 

.£; 110 

C\J 

C\J 

0 10 

LL 

u 

I 90 

• •••• • ... • 

1992 1993 1994 

Fig. 5.8. Mixing ratios determined for HCFC-22 from air collected in 

flasks from seven different remote sampling locations: Alert,(•); BRW, 

(.6); Ni wot Ridge, ( +); MLO, (•); SMO, (6); CGO, (0); and SPO, (0). 

l -chloro-1,1-dif l uoroet ha ne ( H CFC-142 b) 

Hydrochlorofluorocarbon-142b is u sed predominantly 

as a substitute for CFC-12 in the fabrication of closc<lcell foam [AFEAS, 1994). It was also used lo a lesser 

extent as an aerosol propellant and in r efrigeration 

applications. The shift to H CFC-142b and away from 

CFC- 12 for blowing foam began in 1988, and industry 

predicted that complete conversion would occur before 

the end of 1993 [UNEP, 1991). 

The l atitudinally-weighted global m ean mixing ratio 

for HCFC- 142b in mid - 1993 was 4. 3 (±0.1) ppt (Figure 

5.9; Table 5.1 and 5.2). Th is is an increase of 1.0 ppt 

over the global mean determined for mid-1992 . The 

growth rate for HCFC- 142b over the entire sampling 

period ( D ecember 1991 through December 1993) is 

estimated at 1.1 ppt yr·l . 

M ixing ratios determined for H CFC-142b during early 

1992 in the northern hemisphere (Figure 5. 9) are tn 

reasonable agreement with those reported b y Schauffler 

et al. (1993) from a ir collected in the upper troposphere 

TABLE 5.1. CMDL Measurements of HCFCs from Flasks (1991-1993) 

Station 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

BRW 

BRW 

BRW 

BR\V 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

Date 

1991.871 

1992.052 

1992.128 

1992.328 

1992.385 

1992.620 

1992.7 13 

1992.907 

1993.038 

1993.112 

1993.362 

1993.438 

1993.595 

1993.688 

1993.880 

1993.975 

1993.995 

1991.951 

1992.022 

1992. 120 

1992.268 

1992.372 

1992.459 

1992.538 

1992.6 18 

1992.866 

1992.940 

1992.959 

1993.016 

1993.186 

1993.214 

1993.381 

1993.556 

1993.627 

1993.688 

HCFC-22 

(ppt) 

110.2 

110.0 

109.5 

110.5 

113.4 

11 1.5 

112.1 

114.7 

11 3.6 

113.7 

115.2 

117.2 

122.9 

117.2 

119.5 

119.0 

121.0 

109.2 

112.2 

109.1 

110.7 

111.2 

110.0 

110.4 

111.4 

114.5 

116.3 

114.3* 

113.2 

114.9 

114.6 

114.0 

116.2 

114.9 

114.5 

HCFC-142b HCFC-14lb 

(ppt) (ppt) 

3.6 

3.8 

4.3 

4.1 

4.1 

4.1 

5.0 

5.0 

5.4 

5.5 

5.7 

5.6 

6.4 

6.8 

7.6 

3.3 

3.8 

3.3 

4.1 

3.5 

4.2 

4.8 

5.3 

4.9 

5. 1 

5.5 

4.5 

5.1 

5.0 

5.7 

5.3 

0.55 

0.65 

0.70 

0.93 

0.87 

1.05 

1.51 

1.64 

1.99 

1.87 

0.55 

0.58 

0.69 

0.91 

0.85 

1.04 

1.24 

1.34 

Station 

BRW 

BRW 

BRW 

BRW 

76 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

Date 

1993.767 

1993.78 1 

1993.882 

1993.943 

199 1.885 

1991.910 

1992.036 

1992. 11 5 

1992.1 53 

1992.306 

1992.363 

1992.402 

1992.555 

1992.587 

1992.669 

1992.705 

1992.746 

1992.798 

1992.95 1 

1992.970 

1993.008 

1993.014 

1993.126 

1993.145 

1993. 186 

1993.266 

1993.334 

1993.356 

1993.471 

1993.537 

1993.564 

1993.608 

1993.669 

1993.688 

1993.718 

HCFC-22 

(ppt) 

117.4 

115.8 

119.8 

122.6 

93.0 

91.9 

90.3 

90.6 

92.4 

94.2 

95.l 

94 .8 

94.5 

96.2 

96.3 

96.6 

96.2 

96.0 

96.4• 

97.4• 

95.8 

94.8 

97.4 

95.6 

96.3 

97.3 

98.2 

98.6 

99.2 

98.2 

100.3 

99.9 

100.2 

100.2 

99.8 

llCFC-142b llCFC-14lb 

(ppt) (ppt) 

5.8 

6.0 

5.9 

6.4 

2.3 

2.4 

2.6 

2.2 

2.7 

2.6 

2.7 

2.2 

2.4 

3.0 

2.9 

3.3 

2.7 

3.0 

3.7 

2.9 

3.6 

3.1 

3.3 

3.6 

3.4 

3.7 

3.6 

4.0 

3.7 

3.3 

3.5 

3.8 

1.29 

1.48 

1.86 

1.97 

0.23 

0. 19 

0.24 

0.20 

0.20 

0.14 

0.26 

0.35 

0.33 

0.35 

0.34 

0.34 

0.43 

0.46 

0.45 

0.45 

0.42 
TABLES.I. CMDLMeasurements ofHCFCs from Flasks (1991-1993)-Continued 

HCFC-22 HCFC-142b HCFC-141b HCFC-22 HCFC-142b HCFC-14lb 

Station Date (ppt) (ppt) (ppt) Station Date (ppt) (ppt) (ppt) 

CGO 1993.756 100.6 3.5 0.53 NWR 1993.606 114.1 5.2 1.35 

CGO 1993.841 102.0 4.2 0.45 NWR 1993.701 11 5.4 5.5 1.63 

CGO 1993.890 102.7 3.9 0.52 NWR 1993.740 11 2.6 5.3 1.29 

CGO 1993.953 101.9 4.1 0.59 NWR 1993.855 115.5 5.9 1.69 

NWR 1993.932 121.1 6.1 1.98 

YILO 1991.995 102.9 NWR 1993.951 117.8 5.9 1.88 

MLO 1992.033 104.4 2.9 

MLO 1992.109 101.8 3.1 SMO 1991.901 96.2 

MLO 1992.262 103.6 2.9 SMO 1991.995 94.2 

MLO 1992.281 103.6 3.2 SMO 1992.046 93.6 2.4 

YILO 1992.473 105.7 3.5 SMO 1992.112 90.4 2.4 

MLO 1992.530 106.I 3.6 SMO 1992.262 95.2 2.5 

YILO 1992.596 108.5 3.3 SMO 1992.301 95.7 2.9 

MLO 1992.607 104.3 3.0 SMO 1992.456 95.5 2.8 

MLO 1992.691 103.0 3.3 SMO 1992.530 95.0 2.7 

MLO 1992.740 109.1 5.0 SMO 1992.607 96.3 3.3 

MLO 1992.779 106.3 3.9 SMO 1992.686 98.2 2.9 

MLO 1992.893 108.4 4.0 SMO 1992.784 98.3 3.8 

MLO 1992.913 105.0 3.6 SMO 1992.921 97.5 

MLO 1992.970 111.6 4.6 SMO 1993.036 98.6 2.6 0.25 

MLO 1992.989 109.7• 4.6 0.41 SMO 1993.069 98.8 2.9 0.28 

MLO 1993.027 107.5 3.8 0.41 SMO 1993.093 100.2 3.3 0.40 

MLO 1993.162 106.3 3.9 0.53 SMO 1993. 107 98.6 3.6 0.29 

MLO 1993.280 107.4 4.2 0.66 SMO 1993.299 99.6 3.4 0.39 

MLO 1993.334 108.2 4.8 0.71 SMO 1993.321 98.l 3.7 0.32 

MLO 1993.353 108.4 4.2 0.70 SMO 1993.359 96.7 3.3 0.33 

MLO 1993.469 113.3 4.9 0.91 SMO 1993.455 99.6 3.6 0.46 

MLO 1993.5 15 109.1 4.5 0.87 SMO 1993.532 99.2 3.4 0.36 

MLO 1993.526 110.4 4.8 0.71 SMO 1993.603 101.3 3.9 0.50 

MLO 1993.603 110.9 5.6 1.02 SMO 1993.704 102.0 4.0 0.61 

YILO 1993.660 110.6 4.9 1.17 SMO 1993.729 103.5 3.7 0.61 

MLO 1993.699 109.8 4.7 1.1 3 SMO 1993.855 101.7 3.8 0.63 

MLO 1993.718 111.0 4.8 1.20 SMO 1993.953 104.7 4.4 

MLO 1993.737 11 3.6 5.1 1.10 

MLO 1993.871 111.3 4.7 1.43 SPO 1991.948 92 2. 1 

MLO 1993.890 11 5.2 5.3 1.39 SPO 1992.063 92.1 2.1 

MLO 1993.929 11 3.2 5. 1 1.39 SPO 1992.079 90.3 2.1 

SPO 1992.434 93.8 3.1 

NWR 1991.978 103.3 SPO 1992.506 96.9 2.7 

NWR 1992.131 107.3 3.5 SPO 1992.590 96.2 2.8 

NWR 1992.265 108.4 3.4 SPO 1992.694 96.4 2.8 

NWR 1992.322 112.7 3.5 SPO 1992.781 96.8 2.7 

NWR 1992.552 111.5 4.0 SPO 1992.817 96.2 2.5 

NWR 1992.571 109.7 3.9 SPO 1992.853 97.l 3.0 

NWR 1992.609 111.7 3.6 SPO 1993.022 95.7 3.0 0.24 

NWR 1992.727 111.8 4.0 SPO 1993.044 97.6 3. 1 0.25 

NWR 1992.877 108.7 3.6 SPO 1993.066 94.9 2.9 0.28 

NWR 1992.954 115.1 4.5 0.57 SPO 1993.104 95.7 3.6 0.20 

NWR 1993.049 108.3 5.8 0.47 SPO 1993.181 95.4 2.9 

NWR 1993.104 110.9 4.4 0.69 SPO 1993.274 94.7 2.7 

NWR 1993.244 117.2 6.0 1.00 SPO 1993.353 96.6 3.3 0.36 

l\'WR 1993.280 113.1 4.6 0.84 SPO 1993.458 98.9 3.2 0.30 

NWR 1993.356 112.1 4.9 0.89 SPO 1993.545 98.4 3.5 0.38 

NWR 1993.452 117.2 5.3 1.08 SPO 1993.603 99.7 3.0 0.37 

NWR 1993.515 116.3 5.3 1.33 SPO 1993.701 99.6 3.6 0.3 1 

NWR 1993.529 120.3 5.7 

•Revised from that reported in Swanson el al. [1993) 

77 
TABLE 5.2. Estimates for Mid-Year Global Mean Mixing 

Ratios and Globally-Averaged Growth Rates 

1992 Mixing 1993 Mixing All Data Growth 

Ratios (ppt) Ratios(ppt) Rates 

HCFC-22 102 106 4.9 ppt yrl 

HCFC-142b 3.3 4.3 I. I ppt yrl 

HCFC-141b 0.7 >100%yrl 

of the northern hemisphere (2.9-3.9 ppt, CMDL versus 

2.1-3.4 ppt, NCAR) [Montzka et al., 1994a]. Informal 

comparisons of gas standards prepared independently at 

these two laboratories were performed at CMDL and 

indicate that the standards agree to within 5%. 

When compared with levels calculated from emission 

estimates [AFEAS, 1994) and a finite-increment model, 

the results from both laboratori es are 1.5-1.8 times (or 

1.3-1.5 ppt) greater than expected [Montzka et al., 

l 994a). Although the reasons for this discrepancy are 

unclear at present, it is not likely that this difference 

results from inaccurate estimates of atmospheric 

lifetime for HCFC- 142b. HCFC-142b has been emitted 

into the atmosphere for only a short period of time 

relative to its predicted atmospheric lifetime and, 

therefore, model calculations performed with a much 

longer lifetime than 20 years (100-1000 years) do not 

remove the discrepancy between observations and model 

results based on available emission estimates. 

1,1-dichloro-l-fluoroethane ( HCFC-141 b) 

HCFC-14lb is currently used as a CFC-11 substitute 

for blowing closed-cell foams and as a substitute for 

CFC- 113 as a solvent and cleansing agent. Unlike 

HCFC-142b, HCFC- 141 b was not commercially 

avai lable until the beginning of 1993 when toxicological 

7 

6 

• • • 

.t 

0 9t,rf 

1992 1993 1994 

Fig. 5.9. Mixing ratios determined for HCFC-142b from air collected in 

flasks from seven different remote sampling locations: Alert, (•); BRW, 

(~); Ni wot Ridge, ( + ); MLO, (•); SMO, (.1); CGO, (O); and SPO, (0). 

78 

studies were scheduled lo be completed [UNEP, 1991 ). 

Before 1993, many companies in the foam sector stal ed 

their intention to eliminate CFC-11 for this use during 

that year [UNEP, 1993; EPA, 1993). While substitution 

of CFC-113 with HCFC-14lb is also likely to occur 

rapidly, industry experts estimate that only -5% of past 

demand for CFC-113 will be satisfied with HCFCs 

owing to the many alternative processes and approaches 

that were developed by industry to reduce the amount of 

CFC-113 needed in these applications [UNEP, 1991). 

The latitudinally-weighted global mean mixing ratio 

for HCFC-14lb in mid-1993 was 0.7 (±0.1) ppt (Figure 

5.10; Table 5.1 and 5.2) [Montzka et al., 1994a]. The 

global mean mixing ratio increased exponentially during 

1993, at greater than 100% yr· I. The rapid increase in 

ambient mixing ratio during 1993 is likely the result of 

a dramatic shift towards use of HCFC-14lb in industrial 

appl ications after toxicological studies were completed. 

Recently, Schauffler et al. [1995] reported mixing 

ratios for HCFC-141 b from samples collected during a 

number of cruises in the Pac ific, Southern, and Arctic 

Oceans over the past 2 yea rs. A comparison of mixing 

ratios determined from samples collected at similar 

times and at similar latitudes, reveals that results from 

the two independent laboratories agree to within 0.1 ppt 

[Schauffler et al., 1995). 

Stability of HCFCs in Flasks 

Because measurements arc based on the analysis of 

air contained within flasks that were filled at an earlier 

date, it is necessary to ensure that these compounds arc 

stable within these containers over time before reliable 

and accurate mixing ratios can be reported. The 

potential for production and/or loss o f HCFC-22, -142b, 

and -14lb within sample flasks is investigated here by: 

(1) reanalyzing air with in a flask after a period of time 

2 

.0 

T"" 

"Q' 1 T"" 

I 

() 

LL 

() 

I 

• # ... 

• t. ... • •• • 6 

'brr?"' !i 0 0 

1993.0 

• 

.. '· . .. 

• 

• ... 

• • ••• ... . ••• • ..... ••• 

• 

6 0 ~ 0 ~ 0 

6A 

0 

CDo 

0 

,. 

... . 

•• 

... 

6 0 0 0 

1994.0 

Fig. 5.10. Mixing ra1ios determined for HCFC-141b from air collected in 

flasks from seven different remote sampling locations: Alert,(•); BRW, 

(.1); Niwot Ridge,(+); MLO, (•); SMO, (.1); CGO, (D); and SPO, (0). 
has elapsed to see if consistent results are obt ained; (2) 

determining if relationships between the amount of time 

the air is stored in a flask and reported mixing ratios are 

apparent; (3) determining if differences attributable to 

humidity levels within a fl ask are apparent in results 

from SPO and COO; and (4) de termining if disagreements in HCFC mixing ratios within simultaneously 

filled fl asks are significant relative to the precision of 

the analysis. 

After they were received in Boulder, selected flasks 

were analyzed two or more times to study the e ffects of 

storage time on different compounds within flasks 

(Figure 5.11). Results from the two analyses arc 

compared with the variability observed for duplicate 

injections of air from flasks that were collected in 1992 

and 1993. For more than 90% of the flasks that were 

reanalyzed, the results obtained for all three HCFCs 

were within the 95% confidence interval for variability 

observed for duplicate injections of air from flasks. 

The larger differences observed for HCFC- 141 b and 

-142b upon rean alysis are associated with the initi al 

stages of the measurement program when mixing ratios 

and signal-to-noise ratios were exceptionally low. 

Although the second analysis was usually performed 

under identical instrumental conditions, a more polar, 

chromatographic column was sometimes used (Figure 

5.1 1). In the chromatographic analysis of complex 

environmental samples, it is useful to compare results 

obta ined under different instrumental conditions to 

ensure that these results are independent of the 

conditions chosen. Analysis of air samples with 

capill ary columns having different polarity allows for 

an estimate of the importance of coeluting compounds 

on the results obt ained for atmospheric HCFCs using 

this chromatographic instrument. For all three HCFCs, 

results obtained during reanalysis with the more polar 

column were not significantl y different from the initial 

analysis. Because it is unlikely that a compound would 

interfere consistently under different instrumental 

conditions, these results suggest that measurements of 

these HCFCs are free of these types of interferences. 

Flask samples sent from the stations in 1991, 1992, 

and 1993 (excluding SPO) were analyzed at the CMDL 

Boulder laboratories anywhere from 2 to 76 days after 

they were collected (mean = 24 days; median = 22 

days). These delays result from shipping and 

instrument availability. Longer delays are associated 

with samples c ollected at SPO because no shi pments 

leave this site during the southern hemisphere winter. 

To ascertain if these delays adversely affect HCFC 

measurements, residuals from loess fits to the data 

obtained at each station are compared with the time 

elapsed between sampl ing and analysis of each fla sk 

( Figure 5.12). A loess smoothing fraction of 0.3 was 

used to generate the residuals plotted in this figure to 

remove variability associated with seasonality and nonlinear growth rates but retain short-term variability. No 

79 

...... 

c 

Cl) 

::::J 

0-

CL> 

(/) 

..0 

::I 

(/) 

-.::: 

::::J 

(/) 

CL> 

\... 

I • DB-5 both analyses I + DB-5 and DB-1301 

a) HCFC-22 

1.1 

1.0 ~t ::: :: 1~ :::::: :::::tt::::::: :: ::::~ ': ::~ :::: ::: ::::.~ + 

0 .9 

0.8 +----t--- ---+-- --+--- -+------i 

0 10 20 30 40 50 

b) HCFC-142b 

1.5 -.:----------------------, 

1.4 ~ - - - - - - -

1.3 - - - - - - -

1.2 

0.8 

0 .7 

0.6 

-. • 0.5 +-----<r----+- ---+-----+-- ---1 

0 10 20 30 40 50 

c) HCFC-141b 

1.5 ..---- -------------~ 

1.1 

1.0 

0 .9 

0 .8 

0.7 

- - - - - - - - - - - - - - - - - - - - -

0.6 .. .. ... - - - - - - - - - - - - - - - - - -

0.5 of----t------+- ---+----+------i 

0 10 20 30 40 

Time Elapsed between initial 

and subsequent analysis (days) 

50 

f-ig . 5.11. Res ults o bta ine d when a ir w ithin samples fla sks wa s 

re-anal yzed afte r a pe ri o d o f time h ad e la psed for (a ) l!Cf-C-22, 

(b) HCFC- l 42b, and (c) HCf-C- 14 1 b . Squa res re presen t re -

anal yses that were pe rforme d u nde r identica l instrumen tal 

conditions. Plu s symbo ls(+) represent resu lts from re.an al yses 

that were pe rformed with a more po lar an a ly tic al co lumn 

(Dll-1 301 versus Dll-5 ). The shade d a rea re presents 2 times 

95% of th e range of variabi lit y o bse rv e d for d u plica te 

injection s o f air from all flasks coll ecte d in 19 9 2 and 1993. 
6 .

0 a) HCFC-22 

a 4.o 

0.. '-" 2.0 

ro 

~ 0.0 

(/) 

~ -2.0 

-4.0 

2.0 

- 1.5 

~ - 1.0 

0.5 cu 

:::J 32 0.0 

CJ) 

Q) -0.5 "-

-1 .0 

10 

b) HCFC-142b 

• 

100 1000 

-1.5 ~----+--~--1--------1 

0.5 

0.4 

_o.3 

a. 0.2 

~0.1 

~ 0.0 

'U -0.1 'fil -0.2 

"- -0.3 

1 10 100 1000 

c)HCFC-141b .l 

• 

• . • • \ 

• 

-~. • =!Ri·~"' .l• 

• t ... .. ~~·. 

:I <li 0 ·-~ . ,.. . . • • ... -0.4+---~~-+-~-~~--+---~--...... 

1 10 100 1000 

Storage time (day) 

r:ig. 5.12. Residuals from loess fits to flask data obtained over 

time are ploned against elapsed time between flask collection 

and analysis for (a) JICFC-22, (b) l!Cr:C-142b, and (c) 

IICr:C-141 b. Symbols represent the different sampling stations 

(see Figure 5.8). The loess fits are performed for each 

compound at each sampling station with a smoothing fraction 

of 0.3. 

significant relationship between storage time and 

residual is observed, and scatter in the residual does not 

increase at longer storage times. Although the scatter 

observed in Figure 5.12 represents an upper limit for 

the magnitude of problems associated with sample 

storage in these flasks under a wide range of sample 

humidities, it also encompasses variability associated 

with the atmosphere and instrumental analysis. 

80 

The effect of humidity on mixing ratios for HCFCs 

within "flasks can be investigated by comparing data 

from SPO with the results obtained at CGO. For 

compounds emitted predominantly in the northern 

hemisphere, and for which atmospheric growth and loss 

rates are ·small when compared with intrahcmisphcric 

mixing rates, similar mixing ratios are observed at SPO 

and CGO [Steele el al., 1987; Elkins el al., 1993]. 

Ambient conditions at these two locations, however, arc 

significantly different; while air collected at SPO can 

be extremely dry, air is sampled from within the marine 

boundary layer at CGO and ambient temperatures arc. 

on average, -60°C higher. Losses of certain compounds 

such as CCl4 within electropolished stainless-steel 

flasks are known to be dependent upon the amount of 

water in a flask [Schauffler el al., 1993; Momzka et al .. 

1994b]. Despite large losses of CC14 within a number 

of flasks filled at SPO, ambient mixing ratios for 

HCFC-22 and HCFC- 142b are very similar at both of 

these stations (Figure 5.13). These results suggest that 

within the range of humidities encountered at these two 

stations, mixing ratios determined for these HCFCs are 

independent of the amount of water present within these 

flasks [Montzka et al., 1994b] . 

Based on the majority of measurements made for 

HCFC-141b in flasks collected at SPO. a similar 

conc lusion can be drawn for this HCFC. However, in 

three flasks it appears as if mixing ratios from SPO arc 

low relative to the measurements made concurrently at 

CGO. While this suggests that HCFC-14lb may 

undergo losses within ex tremely dry flasks, rather large 

uncertainties are associated with these measurements 

owing to the extremely low mixing ratios of this 

compound in the southern hemisphere during early 

1993. Furthermore, observed di ffcrcnccs bet ween 

mixing ratios determined for HCFC- 141 b within flasks 

collected at SPO and CGO arc not corre lated with 

carbon tetrachloride losses in these flasks, suggesting 

that the characteristics of a flask that cause losses of 

carbon tetrachloride do not affect mixing ratios 

determined for HCFC-141 b. 

Results from the flask measurement program arc 

based on flask pairs collected simultaneously and in a 

parallel flow arrangement. During analysis, each flask 

is treated independently, and the results obtained arc 

averaged to arrive at a best est imate for ambient air 

mixing ratios at the time the flask was filled. Results 

obtained for compounds within simultaneously filled 

flasks should agree to within the analytical precision of 

the instrument. Disagreements between mixing ratios 

determined within flasks that are filled in parallel can 

indicate problems associated with filling flasks, flask 

cleanliness, and compound integrity within flasks. 

For all three HCFCs, the median d ifference observed 

between simultaneously filled flasks is similar to the 

median uncertainty associated with repetitive injections 

of air from a single flask (Figure 5.14). Furthermore, 

the entire distribution of flask-pair differences arc 
104 

102 

100 

98 

a. 96 

a. 94 

....... 

92 

90 

88 

0.7 

0.6 

0.5 

0.4 

§: 0.3 

0.2 

0.1 

0 

a) HCFC-22 

..... . ,~ ·~· 0 "• ~ ~ 

ooo.,i : •• • B Q ••'.t1 ~ •• D • • 0 tJ .. .- ·r. t.J • • • 0 

.. . o o•• 

1992 

D • 

c) HCFC-141b 

1993 1994 

. .. . .. : . . . 

0 

1993 

~ 

. .. 

0 0 

D • ["] . 

1994 

7.0 

6.0 

5.0 

....... 4.0 

a. 

0.3.0 

2.0 

1.0 

b) HCFC-142b 

.. .. • D : r•• • • • •• • : n. ;' • • .-o ~ • • e • 0 • tr' 4 0 • ooB .. :::i • ..n •o • o • •. ~ •.a + D o.o .: • • . .. ; 

0.0 +-~~~+-~~~t--~~--i~~~--+~~~---i 

120 

100 

80 

0..60 

a. 

40 

20 

1992 1993 

d) Carbon Tetrachloride 

D 

••• 

D 

0 

D 

oD 

D 

D 

0 

0 

D 

1994 

D 

D 0 

D 

..--~~~..--~~--~u-~~~c9+--~~-nut-'~~->--~---< 

1992 1993 1994 

Fig. 5.13. :vlixing ratios observed within individua l flasks for different HCFCs at both CGO (+ )and SPO (0) for (a) l!CFC-22, (b) 

l!CFC-142b, (c) l-ICFC-14 1b, and (d) CCl4 • 

similar to, if not lower than, observed analysis standard 

deviations for all three HCFCs, and this suggests that no 

measurable differences are observed in flasks filled 

simultaneously at 1he sampling staiions. For HCFC-22, 

however, !here are instances where values obta ined 

from simultaneously filled flasks disagree signifi canily 

(::;5% occurrence for disagreemenls greater than 3 ppt). 

Sample pairs with such large differences are not used 

when calculating atmospheric growth rates or global 

background mixing ratios [Montzka et a l., 1993). In the 

discussion above, it was concluded that HCFC-22 is 

stable within flask canisters for extended periods under 

widely differing ambient water mixing ratios and, 

therefore, it is difficult to explain these larger 

differences based on the instability of HCFC-22 within 

flasks. A more likely cause for these larger differences 

rests with problems associated with fil ling flasks or 

flask cleanliness. Separate analyses have shown that 

levels of HCFC-22 arc typically 100-1000 times higher 

in laboratory air than in ambient air at remote sampling 

locations (S. Montzka, unpubl ished data). Occasional 

problems wi th small leaks or insufficient purging of 

flasks either during fi lling or analysis could generate 

the type of result observed. 

81 

M easurem ent of Additional Chlorin ated Compo unds 

with GC-M S In strumentation 

The versatility of the GC-MS technique allows for the 

detection of many different compounds within a single 

chromatogram. In addition to the compounds already 

quantified with GC-MS during a single analysis of air from 

flasks (HCFCs, CFCs, halons, methyl halides, methyl 

chloroform, and carbon tetrachloride), monitoring of 

several more chlorinated compounds began in 1993. 

Mixing ratios for methyl chloride (CH3Cl), dichloromethane (CH2Cl2). chloroform (CHCl3), and lctrachloroethylene (C2Cl4) were determined for air contained wi1hin 

flasks. Measurements of these additional compounds arc 

performed by monitoring ions unique to these chlorinated 

hydrocarbons at predetermined elution times. No 

additional changes to the experimental technique arc 

required. Preliminary results for these compounds are 

presented in Figure 5.15. 

5.1.5. G RAVIM ETRIC S TA:S DARDS 

New Blending Manifo ld 

An ultraclean gas blend ing manifold was designed 

and built for the preparation of gravimetric standards. 
'ii 1 

-

z- 0.8 

:.0 

cu 0.6 .0 

0 

....... 

Q. 0.4 Q) 

> 

·.p 

cu 0.2 

:J 

E 

:J 0 (.) 

0 

- 1 

"#. 

-

.~0 8 

:.0 

cu 0.6 .0 

0 

....... 

Q. 0.4 

Q) 

> 

+;::; 

cu 

:J 

E 

:J 0 

(.) 0 

- 1 

~ 

-~ 0.8 

:.0 

cu 0.6 .0 

0 

....... 

Q. 0.4 

Q) 

> 

+;::; 

cu 0.2 

:J 

E 0 ::J 

(.) 0 

··•·· ... ........... ............................ . 

• Flask Pair 

s.d. 0 Analysis 

s.d. 

2 4 6 8 

std. dev. (ppt HCFC22) 

10 

...... 1 ................................................. ~ 

0.1 0.2 0.3 0.4 

s. d. (ppt HCFC-141b) 

: : ....... } .............. , ........ ..... , 

·······=· ··············:············· ....................... . 

·············:--······-

0.5 1 1.5 2 2.5 3 

s. d. (ppt HCFC-142b) 

Fig. 5. 14. Standard deviations obtained for duplicate injections of air 

from individual flasks (analysis s.d.) plotted on a cumulative probability 

scale. Also shown arc !he differences measured in simultaneously filled 

flasks (pair standard deviations). The data presented are for all samples 

collected and analyzed lhrough !he end of 1993. 

The main manifold system (Figure S.16) was made 

using electropolished stainless steel tubing (6.35 mm 

o.d.) that was connected toge ther using an automatic 

tube welder provid ing relatively smooth weld joints on 

82 

20 a) CHCl

3 

15 .... M. 

#• • ~ 

10 

5 

4 4 ..... 

• 

•• • 

• • • .... 4 -

. . ~ 

• •• • • •• ~. ..,. . 0 0 • 

o~og~~ w~ R '¢".6. ~ c:zlJ B 

o+-.-.--.--,--t---.---.---.---.--+--.--.----.---,--1 

1992.5 1993 1993.5 1994 

1000 b) C~CI 

800 

600 

400 

200 

0-1-~~~~--+-~~~~--<f--~~~...,.----, 

1992.5 1993 1993.5 1994 

60 c) CH,p!2 

50 

40 .1· 

• 

30 • • • 20 

10 0 0 0 0 oo 0 Cl'.J tj 0 

0 

0 

1992.5 1993 1993.5 1994 

12 d) C2

Cl

4 

10 • 4 

8 •• 

6 • • 

4 •• 

2 0 0 

oO 0 Cl'.J fl oo 0 0 

1992.5 1993 1993.5 1994 

Fig. 5. 15. Mixing ratios determined fo r different chlorinated compounds 

from air collected in flasks at seven different remote sampling stations. 

Symbols are identical to !hose in Figure 5.8. Mixing ratios for 

c6mpounds other than CH3Cl are reported re lative to a preliminary 

calibration scale. 
MANIFOLD BLENDING SECTION 

LOW RELIEF 

···«< VA .. VE fit'1 W·:· 

k~~=--

FLOW METER 

FORELINE 

TRAP 

= = c::::===:; 

VACUUM 

PUMP 

Fig. 5.16. Main section of gas blending manifold. 

the interior surface of the tubing . Welded, metal-gasket 

face-seal fittings were also used to connect the 

subsections of the manifold together and at the cylinder 

connection ports. Packless all-metal diaphragm valves 

with welded, metal-gasket face-seal fittings were used 

at all valve locations. Three strain gauges were 

installed on the manifold system for pressure 

measurements. A 0-20.7 MPa gauge is used for 

measuring pressure in the main part of the manifold. 

Two additional gauges measure pressures from vacuum 

to 103.4 kPa and from vacuum to 1.33 kPa. These low 

pressure gauges arc isolated from the main part of the 

manifold by a valve in the vacuum segment of the 

manifold. The low pressure gauges arc protected from 

high pressures by using a high-vacuum solenoid valve 

wired to a pressure-readout meter. Vacuum is achieved 

using a high flow rate vacuum pump. A foreline trap 

containing molecular sieve prevents oil vapors from 

entering the manifold. The manifold can be evacuated 

to approximately 4 Pa. A gas purification section of the 

manifold (Figure 5.17) is used for further purification 

of diluent gases such as air or N1 suppl ied by 

commercial gas suppliers. Two traps contammg 

Ambcrsorb and Molecular Sieve l 3X can be heated to 

250°C while they are purged with high-purity N2. The 

traps are then cooled to room temperature prior to use. 

The N2 used to purge the traps can also be used to purge 

the manifold of residual gases. 

Sta11dards 

A suite of calibration standards contammg N10 and 

C02 in air were prepared this year for the CSIRO 

Division of Atmospheric Research. The standards were 

gravimetrically prepared at nominal m1xmg ratios 

ranging from 265 ppb to 345 ppb of N10. Carbon 

83 

PURIFICATION AND PURGE SECTION 

DILUENT 

GA.S 

. ~'.~ w~= LOW HIGH 

RELIEF RELIEF 

VALVE VALVE 

FLOW r . . 

VALVES 

METER ::: ::: I 

AMBERSORB I ::: :> I MOLECULAR 

[ _ _ SIEVE 

PURIFIER OVEN 

N2 

PURGE GA.S 

Fig. 5.17. Purification scc1ion of gas blending manifold. 

dioxide was added to the parent N20 mixture that was 

used to prepare the ppb level N20 mixtures at nominal 

mixing ratios ranging from 330 ppm to 430 ppm. 

Standards containing methyl bromide (CH3Br) and 

me thyl chloride (CH3Cl) in air were prepared this year. Jn 

the past, both methyl halides were used as refrigerants, 

solvents, and in organic synthesis [Braker a11d Mossman, 

1980). Methyl bromide is mostly used as a pesticide. 

Small aliquots of each compound were added to individual 

Aculife-treated aluminum compressed-gas cylinders 

providing ppb level mixtures. The Aculifc treatment 

provides an internally inert surface that prevents both 

methyl halides from reacting with the aluminum. The 

mixtures were then blended together into one cylinder. 

Gravimetric standards containing from 5 to 25 ppt of 

CH3Br and 400 to 1000 ppt of CH3CJ were then prepared. 

The response factors (GC-MS response per mole injected) 

for both ppb and ppt level CH3Br and CH3CI standards 

were consistent to within 5%. 

Standards containing HCFC-14 1b and HCFC-142b were 

also prepared using the same gravimetric techniques used 

to prepare the methyl halide standards. Single component 

standards containing each HCFC were prepared at ppb 

levels. The standards at ppb levels were combined 

together, and the mixture containing both compounds was 

used to prepare standards at 5, 25, 50, and 500 ppl with a 

ratio of approximately 1:1 for HCFC-141b and HCFC-142b. 

Response factors determined by GC-MS analysis of each 

HCFC within the suite of standards (ppt to ppb levels) were 

consistent to within 5%. 

5.2. SPECIAL PROJECTS 

5.2.1. AIRCRAFT PROJECT: STHATOSPllF.RIC 

PllOTOCIIEMISTRY, AEROSOLS, AND DYNAMICS EXPEDITION 

(SPADE) 

Compact correlations between long-lived tracer 

molecules (e.g., CFCs, N10. CH4, and H20) in the 
stratosphere are used to calculate the average age of air 

samples [Pollock et al., 1992]. the chlorine budget of 

the atmosphere [Kawa et al., 1992; Woodbridg e et al., 

1995), the ozone deple tion potentials of substitute CFCs 

[Po llock et al., 1992). and lifetimes of long-lived trace 

gases [Plumb and Ko, 1992). The results of tracer 

correlations of CFC-11, CFC-113, CH4, and N10 in the 

midlatitudes during SPADE in November 1992 and 

through April and May 1993, are compared to an earlier 

mission, the Airborne Arctic Stratospheric Expedition 

(AASE-II), from August 1991 through March 1992. 

Trace gases whose local lifetime are longer than quasihorizontal transport time are in climatological slope 

equilibrium. A scatter plot of the mixing ratio of one 

versus the other collapses to a compact curve because 

they share surfaces of constant mixing ratio [Plumb and 

Ko, 1992). In general, the long-lived tracers such as 

N20, CH4 , CFC-11, and CFC-113 reach slope 

equilibrium throughout the stratosphere, hence define a 

compact correlation when plotted against each other. 

Exceptions to this general rule can occur when mixing 

across exchange surfaces is faster than diffusion along 

mixing ratio isople ths. One such exception occurred in 

Stratospheric Photochemistry Dynamics and Aerosols 

Expedi tion (SPADE) during the flight of May 7, 1993. 

Using the tracer correlations during slope equilibrium 

al lows the calculation of lifetimes of the tracers in the 

stratosphere, and in some cases in the absence of 

tropospheric sinks, the total atmospheric lifetime of the 

specie. 

For the first time, CH4 measurements from an in situ 

GC are compared agai nst an in situ tunable diode laser 

(TDL) spectrometer and three different water vapor 

techniques conducted during SPADE. 

Experimental Mel hods 

The Airborne Chromatograph for Atmospheric Trace 

Species (ACATS), was a cooperative development 

between CMDL and the NOAA Aeronomy Laboratory 

(AL). The first ACATS instrument was a singlechannel GC capable of measuring CFC-11 and CFC-113 

once every 120 seconds aboard the NASA ER-2 aircraft 

during AASE-II. The instrument remained unchanged 

in the November 1992 deployment of SPADE. A second 

GC channel was added for CH4 measurements during 

the second deployment of SPADE in April and May 

1993. Because of longer times required for separation 

of CH4 and CO from the air peak, both channels 

sampled every 180 seconds. ACATS occupies a 

rectangular space (45.7 cm wide x 86.4 cm long x 20.3 

cm tall) inside the AL reactive nitrogen package and 

mounted together inside the equipment bay (Q-bay) of 

the ER-2 aircraft. The two in struments shared gases on 

a common cylinder rack, pump motor, and data 

acquisi tion system to reduce space and weight. The 

GC's sample air inlet, fo rward facing, L-shaped, 

stain less steel tubing, 6.4 mm diameter was located on 

the lower Q-bay hatch extending 20 cm away from the 

84 

fuselage in order to sample outside the aircraft (Figure 

5.18). 

Typical ER-2 flight speeds of 200 m s·t (0 .8 mach) 

required faster sampling rates than commercial GCs 

provide to gain adequate data spacial resolution. The 

sampling rates are made possible by a 12-port, 

2-position gas sample valve from Valeo Instruments, 

Inc. (Houston, Te xas). The gas sample valve diverts or 

heart-cuts the large oxygen peak away from the ECO to 

improve the resolution of the smaller trace species. In 

addition to the gas sample valve, each channel contains 

two gas chromatographic separation columns, a precolumn and a main column, and an ECO from Shimadzu 

Corp. (Tokyo, Japan). Upon injection of the sample 

into the GC, the gas sample valve position is switched 

and the carrier gas sweeps the sample 5 cm3 for CFC 

channel and 15 cm3 for CH4 channel into the 

pre-column and subsequently through the main 

analytical separation column. Both channels share a 

clean supply of ultra-high purity N1 carrier gas 

GC.: Muduk: AC:ATS 

V·h•) 

l:)llndu 

k><k 

Sz C:arrtc:r 

c;1u 

E 

0 

~ 

Fig. 5. 18. Schematic of the ACA TS. The instrument contained 

two separate GC channels that were used to measure Cf-C-11, 

CFC-11 3 , and CH4 with 180-seconds resolution. The n itrogen 

carrie r gas was scrubbed in series through a hot zirconium 

(labe led Z) column (9.5 cc al 350°C) 10 remove Cf-Cs, a 

Ilopcalite (H) trap (manganese dioxide and copper oxide 

mixture, 40 cc at ambient temperature) 10 oxidize po ssible CO 

contamination of C02 , and finally a molecular sieve (M) l 3X 

trap (40 cc at ambient temperature). The crimped (C) tubing 

located after the regulator (R) of the pure (N20 tank that 

delivers 20 ppm of N20 into the ECD o f channe l 2. A 

proportional-integral-d iffe rential (PID , MKS Instruments, 

Massachusells) controller (P) maintain the pressure lo about 

93.0 ± 0. 1 kPa on the ECD of channe l I, while two p ressure 

re lief valves (T. Tavco, Ca lifornia) maintain sepa rately the 

ECD p ressure of channel 2 and the pressure of the sample loop 

to about 93.0 ± 0.1 kPa. 
(99.999%, General Air, Colorado) and a stream 

selection array of solenoids that can supply either 

sample air or calibration gas wh ile maintaining 

continuous flow throughout- the flight. 

The measurement technique for CH4 was adapted from 

the work of Golda11 el. al. [1982]. The advantage of this 

technique is that a flame, a problem for some high-altitude 

applications, is not required as in the flame ionization 

detector for detection of CH4 . An ECD can be "sensitized" 

to CH4 and CO by doping the carrier gas into the detector 

with mixing ratios about 15-50 ppm of nitrous oxide. Pure 

N20 was delivered to the CH4 ECD through a small piece 

of crimped tubing into the ECD make-up flow of -10-3 cm3 

min·l, yielding a mixing ratio of approximately 20 ppm of 

N20 in N2 inside the ECD. 

The halocarbon channel used a l m pre- column and a 

2 m analytical c olumn of 10% OV- 101 (Analabs, 

Massachusetts) preconditioned at l 70°C and temperature 

controll ed at 55°C. During the course of the SPADE 

mission, two different column packing combinations 

were us ed on the CH4 channel. In the first, a precolumn with a 3.2-mm o.d. and 3-m long was packed 

with Porapak Q (a porous polymer) was used. It was 

pre-conditioned at 230°C with 20-30 cm3 min·! N2 flow 

for about 8 hours. The main column of 3.2-mm o.d. by 

3-m was packed with molecular sieve, conditioned 

always to 350°C. Unfortunately , Porapak Q produced 

CO at temperatures above 50°C. At l00°C, mixing 

ratios in excess of 500 ppb of CO were found. In the 

second combination, a pre -column (3.2-mm o.d. by 3-m 

long) packed with silica gel and was preconditioned at 

350°C with 20-30 cm3 min·! N2 flow did not produce 

any detectable CO (>26 ppb). This pre-column was 

temperature controll ed at 50°C with a backflush flow of 

100 cm3 min·t maintained by a differential pressure 

flow controller (Model VCD-1000, Porter Instruments, 

Pennsylvania). The main column was increased to 4 .8 

mm o.d., with a flow controlled at 60 cm3 min-I by a 

mass flow controller (Model FC-260, Tylan Corp., 

California), and a constant temperature of l 05°C. To 

maintain constant de tec tor sensitivity, the ECD housing 

was purged with a 3 cm3 min-I flow rate of pure N2, 

operated at a constant current of 1 nA, and were 

pressure controlled at 93 kPa. The temperatures of the 

ECDs on the halocarbon and CH4 /CO channels were 

c ontrolled with an Omega (Stamford, Connecticut) 

temperature controller (Model. CN9000A) at 350°C and 

360°C, respectively. 

Every fifth sample injection was a multi-component 

stand ard with 600 ppb of CH4 , 57 ppt of CFC-113, and 

130 ppt of CFC-11. This yielded a single-point 

calibration every 15 minutes during a flight. Using 

calibrated secondary standards from the Carbon Cycle 

Division of CMDL in ground based checks 

[Dlugoke11cky el al., 1994]. showed that the calibration 

curve was linear for CH4 but had a large positive 

intercept of -400 ppb as a result of interference from 

the oxygen peak of the sample. Thus the single-point 

85 

calibration standard of 600 ppb was not sufficient to 

establish the calibration curve for CH4 . Val ues of CH4 

measured by ACATS in the troposphere were calibrated 

by using a correlation of CH4 versus CFC- 11 

measurements [Elkins el al., 1993; Dlugoke11cky et al., 

1994] from the CMDL cooperative fla sk station al 

Niwol Ridge, Colorado (40.05°N, 105.59°\V, alti1ude 

3472 m). The station resides in the midtroposphcrc at 

nearly the same l atitude as Moffett Field, California 

(37°N, altitude 30 m). The calibration scales for 

CFC-11 and CFC-113 were established by compari ng 

the instrumental response Lo the gravimetric standards 

prepared by simil ar techniques described in Novelli el 

al., [1991]. The stab ility of the CFC-11 scale 1s 

described in Elkins el al., (1993]. 

The other measurements used here are described in 

the following: from the ATLAS tunable diode laser 

(TDL) spectrome ter [Lowenstein et al., 1990, 1993] 

from the ALIAS TDL spectrometer [We bster et al., 

1994]; from the Harvard Lyman a /OH fluorcscncc 

instrument [Hi11sta et al., 1994]; from balloon borne 

frost-point hygrometers [ Oltma11s, 1985]; and H20 from 

the AL Lyman a /OH fluoroescenc instrument [Kelly et 

al., 1989]. The sampling of these instruments is 

typically 1 Hz. For use here, the data were averaged ror 

20 seconds before each ACA TS sample, except for 

ATLAS N20 that was averaged for 10 seconds. As a 

comparison , the AASE-II measurements CFC-11 and 

-113 from ACATS are included here. The AASE-II 

measurements and their correl at ion arc discussed in 

Woodbridge el al., [1995]. Measurements of CH4 

collected from flask samples using the Whole Air 

Sampler during AASE-II are also included [Schauffler 

et al., 1993]. 

Results 

During SPADE, ACATS provided measurements of 

CFC-11 on ten fli ghts (November 9 and 12 , 1992; April 

30, May 1, 3, 6, 7, 12, 14, and 18, 1993, 1215 data 

points) of CFC-1 13 on nine fl ights (November 12, 1992; 

April 30, May 1, 3, 6, 7, 12, 14, and 18, 1993, 1117 

points), and CH4 on eight fli ghts (April 30, May 1, 3, 6, 

7, 12, 14, and 18, 1993, 970 points). 

Perhaps the most interesting individual flight during 

the SPADE campaign was that of May 7, 1993 (sec 

Figure 5.19). The ER-2 ascended to a cruising altitude 

of about 20 km (7 .5 kPa) and operated in racetrack 

patterns such that the plane sampled the same locations 

several times. Three distinct levels of mixing ra tios can 

be seen in the ACATS data. Ambient tropospheric 

levels of CH4 and CFC-11 arc observed during the 

ascent and descent. During the ascent the h igh CH4 

measurements (CH4 > 1.80 ppm) were auributed to 

polluted air above the San Francisco Bay area . 

Midl atitude and polar stratospheric vortex m ixing ratios 

were measured during the main portion of the rlight. 

The higher mixing ratios (CH4 -1.40 ppm and CFC-11 

- 140 ppt), immediately following the ascent and 
2.0 I"+ 

1.8 ~C ~ 250 ,-.. ("} + CFC-11 e 200 ~ 

Q, 1.6 ("} 

Q, I 

.._, 1.4 150 .... ~ .... ::t: ,-.. 

u 1.2 100 "O 

"O 

1.0 50 

.._, 

- 2 \OO J 

E I 000 .............. --.....--.....--.....--.....--.....~ 80000 90000 I 00000 

GMT (Seconds) 

Fig. 5. 19. ACAT:-S CH4 and crC-11 mixing ratios measured 

during the flight of May 7, 1993, with accompanying pressure 

profile. Tropospheric measurements were observed on the 

ascent and descent. Two distinct air pace ls with constant 

mixing between the air parcels were encountered in the lower 

stratosphere (20 km, about 7.5 kPa) as the plane repeatedly 

circled through the same location. 

throughout the constant altitude portion of the fligh t, 

are typical of midlatitude lower stratospheric air. 

Similar mixing ratios were measured throughout the 

SPADE campaign (see Figure S.20 for complete ACATS 

SPADE data) and AASE-II. The low mixing ratios (CH4 

< 1.00 ppm and CFC- 11 < SO ppt) are levels consistent 

with polar vortex air measurements made during 

AASE-II. The polar air parcel was located near the 

Paci fie coast (north of 37°N and west of 123. 7 S

0

W) and 

was encountered eight separate times. 

Comparison of the ACATS tracers measured during 

AASE-II and SPADE shows that the May 7 flight does 

not obey the same correlations as the remaining d ata , 

especially the CFC-11 data (Figure S.20). This flight 

exhibits a breakdown in slope e quilibrium where mixing 

between the two air parcels has not had enough lime to 

mix along global mixing ratio isopleths. Since there is 

mixing between two distinctl y different air parcels, a 

linear fit intersects the original correlation at two 

points, namely the initial midlatitude and polar air 

mixing ratios. 

Figure 5 .20 shows the various SPADE correlations 

between the lon g-lived tracers and the May 7 flight 

displayed with a plus(+) symbol. The thick, solid lines 

arc least-square fits to the combined data sets from 

AASE II and SPADE: the fit spans only the range of 

measured mixing ratios. The two missions can be 

usefully combined since there was only a short time 

span between the missions, growth rates of the species 

in the stratosphere have not changed significantly, and 

the missions were conducted at comparable l atitudes. 

Drawing a linear fit through this flight (excluding the 

86 

tropospheric values), the initial polar vortex CFC-11 

mixing ratio can be inferred as 11 ± S ppl, CFC-11 3 as 8 ± 

8 ppt, CH4 as 870 ± 50 ppb, and NiO as 90 ± 10 ppb. 

These mixing ratios are indicative of higher stratospheric 

air that has gone through vertical descent over the polar 

region, typical of values seen during AASE-II. 

The correlations of CFC-11 versus NiO and CH4 arc 

the most affected and may be related to the relative 

lifetimes of the tracers. The linear portion of the 

correlation plots in Figure S.20, exclud ing data from 

May 7, can be used to calculate the stratospheric 

lifetime of the species, if slope equil ibrium is obeyed 

and the ratio of the gradients of the species arc nearl y 

constant (a necessary condition for linearity) [Plumb 

and Ko , 1992). Potential temperature (0) values below 

430 K were excluded to filler troposphe ric values from 

the data. Using the arguments of Plumb and Ko [ 1992) 

for calculating steady~state life ti mes the linear 

relationship between two tracers can be expressed as: 

(I) 

where -r1 and -r2 are the stratospheric lifet imes as 

defined as the mass of the compound in the total 

atmosphere divided by the stratospheric loss, cr1 and cr2 

are mixing ratios of specie 1 and 2, and dcr2/dcr1 is the 

the slope of the linear correlation between the species. 

Since the growth rates of CFC-11 [Elkins et al., 1993) 

and CH4 [Dlugokenaky el al., 1994) have decreased lo 

near zero, and the growth rate of N10 is small 

(0.2-0.3% yr-1), steady state can be assumed. 

The fit through the CH4 and CFC-11 correlat ion 

(containing 1013 points) is crcH4 (ppm) =(0.0029 ± 

O.OOOl)*crcFc-1 1(ppt) + ( 1.02 ± 0.01), where crc 114 and 

crcFC-l l are the mixing ratios of each tracer. CFC- 11 

has no significant tropospheric sink. The stratospheric 

lifetime is equivalent to the atmospheric lifetime 

estimated to be SS ± 8 years [Elkins et. al., 1993). The 

CFC-1 1 lifetime is the best known of all tracers 

measured during SPADE, because the ind ustrial 

emissions are known to better than ±S% and because an 

extensive set of worldwide measurements exists for 

CFC-11. The calculated stratospheric CH4 lifc1imc is 

then 129 ± 20 years and compares well with the lifetime 

of 147 years estimated by WMO [1991) . The large 

uncertainty in the calculations is proportionally divided 

between the uncertainty in the CFC-11 lifetime, mass of 

the atmosphere , the uncerta inty in the mi xing ratios, 

and a small contribution from the error in the slope. 

Nitrous oxide was used as a stratospheric tracer 

because of its long life time and relatively small growth 

rate. The most reliable and consistent N10 data from 

the AASE-II and SPADE campaigns was provided by 

the ATLAS instrument [Loewenstein et al., 1993]. 

Using CFC-11 as a lifetime standard in eq. I and the 

asymptotic linear slope near the tropopause, [crN2o (ppb) 

= 0.662 ± 0.006) crcFC-ll + ( 143.7 ± 0.7) 2100 points] a 

stratospheric lifetime of 106 ± 16 years was calculated. 
300 + 

80 b •• • -I;+ 

a .. ; .. " 250 + 

--

Q. 200 --Q. 60 

Q. Q. 

"-" "-" 

~ ~ 

~ 150 ~ 

I ~ 40 u I 

u ~ 100 ~ u u 

20 

50 

0 0 

50 100 150 200 250 300 100 150 200 250 300 

N20 (ppb) N20 (ppb) 

2.0 2.0 +· .. ': :+· .. 

d . -

·. •• . :i.!t:: ·~ #.... . . .. .·.a. ·· .. ,. ·.~~~ ~,,,· . . s 

1.5 1.5 , .. ~-a· 

~ ·. ' -s -s 

Q. Q. 

c. Q. 

"-" 1.0 "-" 1.0 

= "" = "" 

u u I= 

0.5 0.5 

0.0 0.0 

100 150 200 250 300 0 50 100 150 200 250 300 

N20 (ppb) CFC-11 (ppt) 

Fig. 5.20. Correlations between ACATS spec ies for (a) CFC-1 1, (b) CFC- 113, (c) CH4 versus ATLAS N20, and (d) ACATS Cll4 

versus ACATS CFC-I I. The squares (CJ) are data for all of the ACATS SPADE flights excluding May 7, 1993, whi ch arc sho wn as 

the pluses (+). The solid lines are least sq uares fits through the same spec ies by combining data from the AASE-II and SPADE 

missions. Both Figures 5.20a and d show considerable dev iation, with respect to the flight on May 7 , from the combined mission fit. 

This is probably the result of rap id mixing between two distinct air parcels originati ng from the mid latitudes and the polar regions. 

Since there are no significant tropospheric sinks for N20, 

this value is also equal to the atmospheric lifetime. In 

contrast, higher estimates are reported yielding 132 years 

and 170 years by WMO (1991) and by Prinn el al., (1990) 

respectively, where the latter use inverse method 

calculations and global tropospheric data from N20. Based 

on new absorption cross sections for 0 2 in the SchumannRunge band, Ko et al., (1991) calculate an atmospheric 

lifetime of 110 years using vertical profiles of NiO from 

satellites and Minschwaner el al., (1993) calculate a 

lifetime of 123 ± 20 years from balloon measure-ments. 

87 

These results arc in support of the more recent, shorter 

lifetime estimates. 

During the SPADE campaign, both ACATS and the 

TDL spectrometer, ALIAS [\Vebster et al., 1994), were 

measuring CH4 . A comparison betwee n the two 

measurements for 0>430 K, gives a fit ALIAS CJc11, 

(ppm) = (0.86 ± 0.04) * ACATS crcu. + (0.03 ± 

0.03)(ppm) (r2 = 0.8516), where the average residual 

standard deviation of the fit is 0.1 ppm. This 

discrepancy is not within the stated experimental e rror 

limits of the ALIAS (5-10%) and ACATS (7%) 
instruments, and is surpnsmg since a comparison of 

laboratory standards is within the errors [Webster et al. , 

1994]. The comparison between ACA TS CH4 and CFC-11 

shows tropospheric mixing ratios of the two species agree 

with those from the CMDL network (crcH4 = 1.75 ppm and 

crcFc-1 1 = 270 ppt). The ALIAS data would give a 

considerably lower value of 1.52 ppm for tropospheric 

CH4. Since ALIAS relies on spectroscopic parameters for 

calibration and not in-flight calibration, an error in either 

the line strength or air-broadening coefficients could be 

responsible for this difference . Therefore, the ACATS 

values were used for CH4 for this work. 

The dominant sink for stratospheric CH4 is from 

oxidation by the hydroxyl radi cal (OH) [see Le Texier et 

al., [1 988)). As CH4 is oxidized, both H20 and H2 are 

produced. Molecular hydrogen is subsequently oxidized 

to H20. The rate and efficiency at which CH4 oxidizes 

and the rate the remaining H2 is oxidized lends to the 

production efficiency of H20 from CH4. In the 

midlatitude lower stJ"atosphere, H2 is produced more 

rapidly than H20 and the rate at which H2 oxidizes is 

slower than the CH4 rate. Thus, the H2 oxidation is not 

concurrent with CH4 oxidation, lead ing to a local H20 

production expressed as dH201dCH4 of less than 2.0. 

Mix ing with dehydrated air (occurs more often in the 

southern hemisphere) and mixing with low water vapor 

air parcels can also yield a lower production. Fi gure 

5.21 shows three different H20 measurements: Harvard 

H20 measurements on the ER-2 aircraft, AL 

measurements on the ER-2 aircraft, and CMDL 

measurements on balloons at a nearby l ocation , Crow's 

Landing, California, p lotted against ACATS CH4 

conducted durin g SPADE. The slope of each line gives 

the production that ranges from -0.8 ± 0 .4 for the 

CMDL H20 measurements, -1.34 ± 0.04 for AL H20 

measurements, and -1.77 ± 0.04 for the Harvard H20 

measurements. The difference between the production 

of H20 cannot be the resul t of the CH4 measurements 

since ACATS agrees well with previous CH4 

measurements of Whole Air Sampler [Schauffler et al., 

1993) versus AL H20 during AASE-II (Figure 5.21). 

Correlation of ALIAS CH4 with Harvard H20 yields a 

slight increase in the production of H20 (-2.28 ± 0.04) 

that is higher than the theoreti cal value at this altitude 

[Le Texier et al. , 1988]. Whil e arguments were made 

by Dess/er et al. [ 1994] that the production should be 

near 2, the absolute value of Harvard H20 is also higher 

than the two other H20 measurements. 

Conclusions 

Slope equilibrium is generally obeyed in the polar 

region s and midlatitudes at the altitudes (0-21 km) 

covered by the ER-2 aircraft. An exception occurs after 

the breakup of the polar vortex and its subsequent 

mixing with the midlatitudes when quasi-horizontal 

mixing is not fast enough to e stablish the original slope 

equilibrium. If the lifetime o f one tracer is much less 

than the lifetime of the second tracer, a new slope on 

88 

the cross-pl ot is established that is maintained by 

conservative mi xing between the two air parcels. If the 

application of CFC-11 as a stratospheri c lifet ime 

standard is valid and slope equilibrium is obeyed, then 

based on the measurements presented here, the 

calculated lifetime of N20 is shorter ( 106 ± 16 years) 

than previously estimated (150-170 years) by examining 

tropospheric N20 budgets. Unless an unknown 

tropospheric sink exists, there could be large missing 

sources as high as 50% of the total N20 source that 

remain unaccounted for in the inventory of sources. 

S.2.2. AUTOMATED FOUR-CIIANNEL FIELD GAS 

CIIROMATOGRAPIIS 

The NOAH Division continued to build and test the 

newest generation .of four-chann el GCs. These 

instrumen ts are designed to make frequent, automated 

measurements of radiatively import ant and halogenated 

trace gases. The deployment of four-channel GCs at 

existing CMDL observatories (B RW, MLO, SMO, and 

SPO), the NWR cooperative site, and new field sites al 

WITN tower (North Carolina), Harvard Forest 

(Massachusetts), and Alert, Canada, will expand both 

the geographical coverage of trace gas monitoring and 

the number of species measured. 

Features 

Much of the technology found in the new generation 

of fi el d GCs has evolved through the development of 

compact, lightweight, automated GCs for in situ trace 

gas analysis aboard the ER-2 aircraft. Thus, the field 

GCs are very compact and modular with each channel 

having its own 12-port gas sampling valve, 

chromatographic column pair, ECO, and e lectromctcr. 

If a component requires maintenance or repair, it can 

effectively be removed and replaced wi thout disrupting 

measurements on the other channels. 

The control and acqms1t1on software for the 

instrument runs on a conventional IB M-compatible 

personal computer with a 80486 CPU. The control and 

data acquisition hardware within the GC consists of a 

96-channel analog-to-d igital (AID) board, a digital 110 

board, and a dedicated four-channel AID board for 

logging ECO signal data. The run program includes 

on-screen display of chromatograms and pertinent 

eng ineering data such as component and zone 

temperatures, sample loop flow rate and pressure, 

carrier gas flow rates, carrier gas and calibration gas 

tank pressures, and the relative humid ity of the sample 

stream. A new and extremely useful feature of the run 

program is the real-time integration of peaks, which 

permits a "quick look" at data and aids in 

troubleshooting. 

Using an e ight-port stream selection valve, several 

ambient air streams and calibration gas flows can be 

sampled and analyzed in a user-defined sequence. 

Ambient air streams are dried through Nafion mbing to 
7 

6 

,-._ 5 

e 

Qc 

Qc 4 ..._,, 

0 

N 

= 3 

2 

1 

+ AASE-II 

SPADE 

••• Harvard H20 

- NOAA \AL H20 

- • • NOAA \CMDL H20 

+ 

+ + + • 

+ 

+ 

+ 

+ 

.. 

0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 

CH4 (ppm) 

Fig. 5.21. ~ethane and water vapor correlations can be used lo estimate the production efficiency al whi ch Cll 4 is oxidized 10 11 20. 

The solid line is a linear fit (y = - l .24•x + 6.08) th rough the combined AASE-!!(+) and the SPADE(-) m1ss1ons ov e r 1hc range CllJ 

< 1.7 ppm. The absolute value of the slope is the production efficiency. The lop dashed line is a similar fit (y = -!.77•x + 7 .45) 

using the SPADE Harvard H20. The bouom dashed line is y = -0.Sx + 4.7 for ACATS CH4 versus C~DL 11 20. 

a dewpoint of -25°C before analysis. The four sample 

loops are pressure-controlled using a pressure sensor 

and valve feedback system. 

Each column pair, ECO, mass flow controller and sample 

loop is isothermally maintained by proportional, integral, 

derivative algorithm temperature controllers. Temperature 

data are logged to disk by an RS-485 loop between the 

temperature controllers and the computer, and controller 

setpoints can be changed from the keyboard. Column pairs 

and ECDs are encapsulated in well-insulated, cylindrical 

ovens 13 cm in diameter and 18 cm high that provide 

excellent temperature stability (I s.d., ± 0.1°C). 

There arc currentl y five possible channels for 

implementation in these four-channel automated gas 

chromatograph s. The more pertinent chromatography 

89 

parameters for each channel are listed in Table 5.3. 

These include column dimensions (o.d. x length) and 

packing materials, sample loop sizes, specia l detection 

methods employed (if any), species measured, and the 

precision of measurement of each specie at its mixing 

ratio in high-pressure tanks of Niwot Ridge air. 

Work will begin in 1994 to utilize the sample loop 

pressure control for "pressure-calibrations, " the 

injection of different pressures of a calibration gas to 

generate calibration curves. Pressure-ca libration curves 

show little nonlinearity over a pressure ran ge o f 15% 

(90 % to 105% of a given s ctpoint). If sa ti sf tor ) 

resu lts can be obtained through this me thod, the need 

for having several calibration tanks at a given site will 

be eliminated. 
TABLE 5.3. Pertinent Chromatography Parameters for Each 

Channel of New Automated Field GC, Species 

Measured, and Precision of Measurements 

Parameter 

Precolumn 

Main column 

Sample size 

Detector 

Species measured: 

l-12 

Cl-1

4 

co 

Precolumn 

Main column 

Sample size 

Detecror 

Species measured: 

CFC-12 

CFC-II 

Cl-:C-113 

Precolumn 

Main Column 

Sample size 

Detector 

Species measured: 

Cl-:C-1 1 

crc-113 

Chloroform 

Methyl chloroform 

Carbon tetrachloride 

Trichlorocthylene 

Perchloroethylene 

Precolumn 

Main Column 

Sample size 

Detector 

Species measured: 

N20 

SF6 

Trap no. I 

Trap no. 2 

Precolumn 

Main column 

Sample size 

Detector 

Species measured: 

l-ICFC-22 

Description 

Channel 1 

3.175 mm x 2.0 m unibeads IS 

3.175 mm x 4.0 m molecular sieve SA 

5 cm3 

N20 -doped ECD 

Precision: 

0.6% 

0.4% 

1.0% 

Channel 2 

3.175 mm x 1.5 m unibeads 2S 

3.175 mm x 2.5 m uni beads 2S 

2.5 cm3 

ECD 

Precision: 

0.2% 

0.2% 

2.8% 

Channel 3 

3. 175mm x2.0 m OV-IOI (20%) 

3. 175 mm x 5.0 m OV- 101 (20%) 

5.0 cm3 

ECD 

Precision: 

0.2% 

0.5% 

5% 

0.5% 

0.5% 

Unknown 

1.5% 

Channel4 

4.7625 mm x 2.0 m Porapak Q 

4.7625 mm x 3.0 m Porapak Q 

15.0cm3 

ECD 

Precision: 

0.2% 

1.2% 

Channel 5* 

3. 175 mm x 0.040 m uni beads IS 

3. 175 mm x 0.024 m Porapak Q 

3. 175 mm x 0.5 m unibeads 2S 

3. 175 mm x 1.0 m unibeads 2S 

40.0cm3 

OrdopcdECD 

Precision: 

2.8% 

*Samples are first pre-concentrated on trap no. I cooled to 

-50°C. Species of in terest are desorbed from this trap by 

heating to 11 o·c, then a re focused on trap no. 2 cooled to 

-50°C. Trap no . 2 is rapidly heated to 11 o·c just prior to 

injection. 

90 

5.3. REFERENCES 

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Study), Historic production, sales and atmospheric release of 

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Butler, J.1-1. , J.W. Elkins, B.D. Hall, S.O. Cummings, and S.A. 

Montzka, A decrease in the growth rates of atmospheric halon 

concentrations, Nature, 359,403-405, 1992. 

Collins, J.E., Jr., G.W. Sachse, B.E. Anderson, A.J. Weinheimer, 

J.G. Walega, and B.A. Ridley , AASE-II in situ tracer correlations 

of methane, nitrous oxide, and ozone as observed aboard the 

DC-8, Geophys. Res. Lei/., 20(22), 2543-2546, 1993. 

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Webster, R.D. May, J.W. Elkins, and G.S. Duuon, An 

examin ation of the total hydrogen budget of the lower 

stratosphere, Geophys. Res. Lei/., 21 (23) 2563-2566, 1994. 

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and E.G. Nisbet, A dramatic decrease in the growth rate of 

atmospheric methane in the northern hemisphere during 1992, 

Geophys. Res. Lell., 21(1), 45-48, 1994. 

Elkins, J.W., T.M. Thompson, T.H. Swanson, J.ll. Butler, B.D. llall, 

S.O. Cummings, D.A. Fisher, and A.G. Raffo, Decrease in the 

growth rates of atmospheric chlorofluoroca rbon s 11 and 12, 

Nature,364, 780-783 , 1993. 

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ozone, Federal Register, 58, 15,014-15,048, 1993. 

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monoxide at ambient levels with an N20 -sensitizcd 

electron-capture detector, J . Chromatogr., 239, 115-126, 1982. 

1-lintsa, E. J., E.M. Weinstock, A.E. Desslcr, and J.G. Anderson, 

SPADE 1-120 measurements and the seasonal cycle of 

stratospheric water vapor, Geophys. Res. Lei/., 21 (23 ), 2559-

2562, 1994. 

Kawa, S.R., D.W. Fahey, L.E. Heidt, W.J-1. Pollock, S. Solomon, 

D.E. Anderson, M. Loewenstein , M.ll. Proffill, J.J. Margitan, and 

K.R. Chan, Photochemical partitioning of the reactive nitrogen 

and chlorine reservoirs in the hi gh-latitude stratosphere, J. 

Geophys. Res., 97(08), 7905-7923, 1992. 

Kelly, K.K., A.F. Tuck, D.M. Mu rphy, M.1-1. Proffiu , D.W. Fahey, 

R.L. Jones, D.S. McKenna, M. Loewenstein, J.R. Podolske, S.E. 

Strahan , G.V. Ferry, K.R. Chan, J.F. Vedder, G.L. Gregory, W.D. 

Hypes, M.P. McCormick , E.V. 13rowcll, and L.E. llcid1, 

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winter and early spring, 1987, J . Geophys. Res., 94, 

11,317-11,357, 1989. 

Ko, M.K.W., N.D. Sze, and D.K. Weisenstein, Use of satellite data 

to constrain the mode l-calculated atmospheric lifetime for N20: 

Implications for other trace gases, J. Geophys. Res., 96(D4), 

7547-7552, 1991. 

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hydrogen and methane oxidation in the water vapo r budget of the 

stratosphere, QJ.R. Meteorol. Soc., 114, 28 1-295, 1988. 

Loewenstein, M., J.R. Podolskc, and S.E. Strahan, ATLAS 

instrument characterization: Accu racy of the AASE and AAOE 

nitrous oxide data sets, Geophys. Res. Lei/., 17, 481-484, 1990. 

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P. Tin, A. Weaver, P.A. Newman, S.E. Strahan, S.R. Kawa, 

M.R. Schoebcrl, and L.R. La il, New obse rvation s of the 

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lifetimes of N20, CFC13 , and CF2Cl2 , J. Geophys. Res., 

98(D6), 10,543-10,561, 1993. 

Montzka, S.A., J.W. Elkins, J.H. Butler, T.M. Thompson, W.T. 

Sturges, T.H. Swanson, R.C. Myers, T.M. Gilpin, T.J. Baring, 

S.O. Cummings, G.A. Holcomb, J.M. Lober!, and B.D. Hall, 

in Climate Monitoring and Diagnostics Laboratory No. 20: 

Summary report 1991, pp. 60-8 1, edited by E.E. Ferguson 

and R.M. Rosson, NOAA Environmental Research 

Laboratories, Boulder, CO, 1992. 

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Cummings, Global tropospheric distribution and calibration 

sca le of IICFC-22, Geophys. Res. Lett., 20, 703-706, 1993 . 

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trends in the g lobal tropospheric abundance of 

hydrochlorofluorocarbon-14 1 b and - I 42b, Geophy. Res. 

Lett., 21(23), 2483-2486, 1994a. 

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Cummings, Atmospheric measurements of HCFC-22 at the 

South Pole, Ant. J. U.S., 28(5), 267-269, 1994b. 

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and evaluation of a gravimetric reference scale for 

measurements of atmospheric carbon monoxide, J . Geophys. 

Res., 96(D7} , 13,109-13,121, 1991. 

Ohmans, S.J., Measurements of water vapor in the stratosphere with 

a frostpoint hygrometer, Proceedings of 1985 International 

Symposium on Moisture and Humidity, pp. 251-258, Instrument 

Society of America, Washington, DC, 1985. 

Plumb, R.A., and M.K.W. Ko, Interrelationships between 

mixing ratios of long-lived stratospheric constituents, J. 

Geophys. Res., 97, 10,145-10,156 , 1992. 

Pollock, W.11., L.E. Heidt, R.A. Lueb, J.F. Vedder, M.J. Mills, 

and S. Solomon, On the age of stratospheric air and ozone 

depiction potentials in polar regions, J. Geophys. Res., 

97(Dl2}, 12,993-12,999, 1992. 

Prather M., and C.M. Spivakovsky, Tropospheric OH and the 

lifetimes of hydrochlorofluorocarbons, J. Geophys. Res., 

95(Dll}, 18,723-18,729, 1990. 

Prinn, R., D. Cunnold, R. Rasmussen, P. Simmonds, F. Alyea, 

A. Crawford, P. Fraser, and R. Rosen, Atmospheric emissions 

and trends of nitrous oxide deduced from I 0 years of 

ALE-GAGE data, J. Geophys. Res., 95(Dll}, 18,369-18,385, 

1990. 

Schaufflcr, S.M., L.E. Heidt, W.11. Pollock, T.M. Gilpin, J.F. 

Vedder, S. Solomon, R.A. Lueb, and E.L. Atlas, 

91 

Measurements of halogenated organic compounds near the 

tropical tropopause, Geophys. Res. Le/I., 20(22), 2567-2570, 

1993. 

Schauffler, S.M., W.H. Pollock, E. L. Atlas, L.E. Heidt, and J.S. 

Daniel, Atmospheric distributions of IICfC-141 b, Geophys. 

Res. Lett., in press, 1995. 

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potentials for short- and long-term forecasts, Nature, 357, 

33-37, 1992. 

Solomon, S. , M. Mills, L.E. Heidt, W.H. Pollock, and A.f. 

Tuck, On the evaluation of ozone depletion potentials, J. 

Geophys. Res. 97(Dl}, 825-842, 1992. 

Steele, L.P., P.J. Fraser, R.A. Rasmussen, M.A .K. Khalil, T.J. 

Conway, A.J. Crawford, R.H. Gammon, K.A. Masaric, and 

K.W. Thoning, The global distribution of methane in the 

troposphere, J. Atmos. Chem., 5, 125-171, 1987. 

Swanson, T.H., J.W. Elkins, J.H. Butler, S.A. Montzka, R.C. 

Mye rs, T.M. Thompson, T.J. Baring, S.0. Cummings, G.S. 

Dutton, A.H. Hayden, J.M. Lobcrt, G.A. Holcomb, W.T. 

Sturges, and T.M. Gilpin, in Climate Monitoring and 

Diagnostics Laboratory No. 2 I: Summary report I 992, 

59-75, edited by J.T. Peterson and R.M. Rosson, l\OAA 

Environmental Research L"aboratories, Boulder, CO, 1993 . 

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Kendall, Aircraft laser infrared absorption spectrometer 

(ALIAS) for in situ stratospheric measurements of IICI, N20, 

CH4 , N02 , and HN03 , Appl. Opt., 33(3), 454-472, 1994. 

Woodbridge, E.L., J.W. Elkins, D.W. Fahey, L.E. Heidt, S. 

Solomon, T.J. Baring, T.M. Gilpin, W.H. Pollock, S.M. 

Schauffler, E.L. Atlas, M. Loewenstein , J.R. Podo lske, C.R. 

Webster, R.D. May, J.M. Gilligan, S.A. Montzka, K.A. 

Boering, and R.J. Salawitch, Estimates of total organic and 

inorganic chlorine in the lower stratosphere from in situ and 

flask measurements during AASE II, J. Geophys. Res., in 

press, 1995. 

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Research and Monitoring Project, Geneva, Switzerland, 

1991. 
6. Cooperative Programs 

Evaluation of Arctic Meteorological Buoys 

GERALD F. APPELL 

NOAA National Ocean Service, Ocean Systems Development Group, Silver Spring, Maryland 20910 

INTRODUCTION 

The United States Interagency Arctic Buoy 

Program (USIABP) was formed in 1991 to establish 

and maintain a network of drifting meteorological 

buoys in the Arctic. The USIABP is a collaborative 

program fund ed by nine government agencies/ 

programs and managed by the National Ice Center in 

Suitland, Maryland. The USIABP supports the 

International Arctic Buoy Program (IABP) which 

consists of numerous countries participating in the 

collection of meteorological data from Arctic drifting 

buoys. 

The buoys are located to define surface synoptic 

scale atmospheric pressure, air temperature, and seaice drift fields. The data are available in real time, 

via ARGOS satellite transmissions, to operational 

weather fore-casting centers as well as research into 

climate change . At the inception of the program, 25 

buoys gathered temperature and press ure data in the 

Arctic with 72% reported on the Global Telecommunications System (GTS). In early 1994, 47 

buoys were in operation with 96% reported on the 

GTS. 

There are many different buoys used by the IABP 

with different sensors, configurations and sampling 

schemes. Many of the temperature measurements 

reported by the buoys were suspect when compared to 

atmospheric model predictions. In 1993 it was 

decided by the USIABP to halt deployment of new 

buoys until the sources of temperature measurement 

errors were investigated. A program was established 

to evaluate the available "off-the-shelf" Arctic buoy 

systems being used by the I ABP. As part of this 

evaluation, a long -term test site was established at 

the CMDL fac ility in Barrow, Alaska. 

THE FIELD TEST SITE 

In August 1993, a Coastal Climate buoy and a DSl -

TAD buoy were placed at the Barrow facility. A data 

acquisition system was placed at the site consistin g 

of a Telonics ARGOS uplink receiver and a Compaq 

notebook computer. Buoy transmissions are received 

and logged on the computer. Weekly interrogations 

of the computer are performed from Silver Spring, 

Maryland, and data files are downloaded. In 

December 1993, a Canadian MetOcean CALIB buoy 

92 

was added to the array, and in March 1994 a 

Norwegian ICEX buoy was placed at the site. 

DATA ACQUIS ITION AND ANALYS IS 

All buoys in the test program undergo temperature 

sensor calibration at the National Weather Service 

Test Facility in Sterling, Virginia, prior to shipment 

to Barrow. 

Each buoy has its own measurement scheme, 

sampling interval, data format, and data transmission 

interval. Data collected in Silver Spring arc 

processed and reduced into a standard 1-hr averaged 

data format. CMDL meteorological data arc sent 

monthly for comparison with buoy data. Solar 

radiation data from CMDL is collected weekl y via a 

recently established link to Internet. 

Measurements are analyzed and compared to 

CMDL standards. Temperature differences between 

sensors and/or st andards arc analyzed to determine 

the effects of sensor he ight differences, solar 

radiation, and wind . Prelimin ary results indicate 

sign ificant differences attributed to the measurement 

height of the sensors above the surface and to solar 

radiation effects. 

CMDL measurements at BRW are on a tower 

located approximately 20 m from the buoy array. 

The CMDL temperature sensors arc 2.5 m (B RW 2.5 

m) and 15 m (BRW 15 m) above the g round. They 

are aspirated and kept clean of ice and snow by the 

staff at CMDL. Figure 1 shows temperature data 

from three buoys compared to the CMDL temperature 

standards during February 16- 18, 1994. This period 

had winds below 5 m s-1 and insigniricant solnr 

radiation. The Coastal Climate buoy measures 

temperature at approximately the same height above 

the ground as the BRW 2 .5-m sensor. The OSI-TAD 

buoy has an internal temperature sensor in a 

spherical hull approximately 1 m in diameter that sits 

on the surface. The CALIB buoy is a cylindrical 

buoy with an external temperature sensor that is 

measuring at a he ight of 1 m off the surface . The 

Coast al Climate buoy general ly tracks the BRW 2.5 

m sensor to within 1 'C. The OSI-TAD buoy shows a 

strong time lag to the falling temperatures because of 

its internal sensor. The CALIB sensor shows lower 

temperatures at times when there is a vertical 

temperature gradient indicated by the BRW 2.5 m and 
-36-t-- ~--~--~----i--~---..--~~--+ 

940.7 94048 

Julian Date 

• Coastal Climate o OS~ TAD 

7 BRW2 5m · • BRW 15m 

+ CAUB 

-Wind 

94049 

f<ig . l. Hourly-averaged temperature measurements for 

three buoys and the BRW standards. The BRW sensors are 

identified by their height, BRW 2.5 m is the sensor at 2.5 m 

above th e ground, BRW 15 mis 15 m above the ground 

BRW 15 m sensors, showing the gradient continues to 

ground level. 

Figure 2 shows a 24-hr period on April 17, 1994. This 

period shows a typical day of strong solar radiation with 

low temperatures and light winds. The aspirated BRW 

sensors show no vertical temperature gradients. The 

additional ICEX buoy is a spherical type buoy that sits 

on the surface and has an external temperature sensor at 

approximately 1 m above the ground. All sensors have 

some form of radiation shielding. The ICEX and the 

CALIB buoys show strong effects from solar heating 

while the Coastal Climate buoy does not due to a larger 

radiation shield. The DSI-TAD shows moderate effects 

with long response times. 

93 

-10 

~ -15 ;;; 

Qi 

u r20 

c;, 

~ -25 

-35+--~--~--~--t--~--~--.----t-200 

94106.5 94107 94107.5 

Julian Date 

• Coastal Climate '" OS~ TAD 

w BRW 2.5m .. BRW 15m 

+ CAllB 

- Solar NIP 

z ICEX 

Fig. 2. Hourly -averaged temperature readings for four 

buoys and the BRW standa rd s. Direct solar radiation is 

shown by measurements from the No rmal Incidence 

Pyrgeometer (NIP). The effects of solar heating arc 

depicted. 

FUTURE PLANS 

It is planned to introduce one more buoy to the site 

in August 1994. We will a lso place a 3-m Rohn 

tower with aspirated temperature sensors at the 1-m 

and 2.5-m level, a solar radiation sensor, and an 

anemometer. These sensors wil l complement 

information on the vertical and horizontal spatial 

effects of the temperature field when compared to the 

CMDL Barrow standards. The tower wil l be located 

in the buoy array area. The site will remain until 

sufficien t long-term data has been acquired to assess 

the performance of each buoy. 
Global Precipitation Chemistry Program Measurements 

at Mauna Loa Observatory 

R.S. ARTZ 

NOAA Air Resources Laboratory, Silver Spring, Maryland 20910 

W.C. KEENE AND J.N. GALLOWAY 

University of Virginia, Charlottesville, Virginia 22903 

INTRODUCTION 

The Global Precipitation Chemistry Program (GPCP) 

was initiated in 1979 to address questions regarding the 

composition of precipitation chemistry prior to the 

advent of fossil-fuel combustion and to study the 

influence of sulfur and nitrogen species transported 

over long distances on the remote troposphere. This 

program was funded by the NOAA Air Resources 

Laboratory and was conducted in collaboration with the 

University of Virginia Department of Environmental 

Sciences and Cary Arboretum, New York . Published 

reports summarize progress to date [e.g., Galloway et 

al., 1984,1992, 1994; Keene et al., 1986. 

METHODS 

The GPCP has analyzed samples of precipitation 

collected at 14 land-based sites and during 12 oceanic 

cruises. Samples of precipitation were collected by 

event in scrupulously washed polyethylene containers. 

Immediately after collection, pH was measured, samples 

were treated with CHC13 to prevent biological activity, 

and aliquots were subsequently sent to the University of 

Virginia for analyses for all major organic and 

inorganic chemical constituents. 

One of the stations of the GPCP was located at the 

Mauna Loa Observatory (MLO). Beginning in August 

of 1983, 305 event precipitation chemistry samples were 

collected through a cooperative venture involving 

CMDL MLO. The MLO data set was collected to 

prov ide complete event chemistry suitable for processoriented studies on Hawaii. All samples were collected 

on an event basis using a wet-only sampling device and 

were discarded if they remained in the collector more 

than 24 hours following the cessation of precipitation. 

No attempt was made to collect small volume events or 

samples over weekends and holidays. 

DISCUSSION 

The high data quality coupled with complete major 

ion analysis and short measurement periods will allow 

94 

us to address a number of quest ions regarding the 

chemical climatology of MLO. In particular, we will 

investigate sources for nitrogen at MLO through 

rigorous trajectory studies using the daily chemistry 

data and the ARL HY-SPLIT [Draxler, 1992] model. 

The effect of the volcano on so;2 can be addressed with 

this data set. We will also assess volcanic contributions 

to H2S04 acidity in precipitation at the site. This 

analysis will contribute substantially to the 

understanding of nitrogen and sulfur cycling in the 

remote marine troposphere. 

The data set is currently being analyzed in 

conjunction with transport models and we ant1c1pate 

publishing the results in a peer-reviewed journal article. 

Unfortunately, due to reductions in Air Resources 

Laboratory funding, collection and analysis of 

precipitation at MLO ceased in February 1994. 

REFEREl'iCES 

Draxl e r, R.R., Hybrid Single-Particle Lagrangian Integrated 

Trajectories (HY-SPLIT): Version 3.0-User's Guide and 

Model Description, NOAA Tech. Memo., ERL ARL-195, Air 

Resources Laboralory, Si lver Spring, MD, 1992. 

Galloway, J.N., G.E. Likens, and M.E. Hawley, Acid 

precipilation: natural versu s anthropogen ic components, 

Science, 236, 829-830, 1984. 

Ga lloway , J.N., H.Levy II, and P.S. Kasibhatla, Year 2020: 

Consequences of population growlh and deve lopment on 

deposition of oxidized nitrogen, Ambio, 23(2), 1994. 

Galloway, J.N., J.E. Penner, C.S. Ath erton, J.M. Prospe ro, II. 

Rodhe, R.S. Artz, Y.J. Balkanski, 11.G. Bingemer, R.A. Brost, 

S. Burgermeister, G.R. Carmichael, J.S. Chang, R.J. 

Charlson, S. Cobe r, W.G. Ellis, C.J. Fischer, J.M. Hales, D.R. 

Ha stie, T. Iversen, D.J. Jacob, K. John, J.E. Johnson, 1'.S. 

Kasibhatla, J. Langne r, J. Lelievcld, II. Levy, 11, F. 

Lipschultz, J.T. Merrill, A.F. '.\1ichaels, J.l'vl. '.\1illcr, J.:--1. 

Moody, J. Pinto, A.A. Pszenny , P.A. Spi ro, L. Tarrason, S.'.\I. 

Turner, and D.M. Whelpdale, Sulfur and nitrogen levels in 

the No rth Atlanti c Ocean's Atmosphere: A systhesis of field 

and modeling results, Global Biogeochem. Cycles, 6, 77 -1 00, 

1992. 

Keene, W.C., A.A. P. Pszenny, J.N. Galloway, and :--1.E. 

Hawley, Sea-sail corrections and interpretation of 

constitutent ratios in marine p recipitation, J. Geophys. Res .. 

91, 6647-6658, 1986. 
Global Atmospheric 02/N2 Measurements from Isotope Ratio Mass 

Spectrometer Analysis 

MICHAEL L. BENDER, JOHN T. ELLIS, AND MARK 0. BATTLE 

Graduate School of Oceanography, Vnivusity of Rhode Island, Narragansett, Rhode Island 02882 

INTRODUCTION 

Measurement of atmospheric oxygen can provide 

important constraints on the global carbon cycle. When 

02 is monitored with sufficient accuracy, the 

monitoring is complemented with measurements of 

C02, and the observations are augmented with an 

atmospheric circulation model, it is possible to gain 

understanding about new production of organic matter 

in ocean surface water, the distribution of terrestrial 

sources and sinks of carbon, and the oceanic storage of 

anthropogenic C02 [Keeling et al., 1993; Keeling and 

Shertz, 1992). 

To this end , air sample collection began at BRW in 

December of 1992. Working in conjunction with SIO, 

we have also started collecting samples in SMO and 

from the top of the light tower at Cape Kumukahi, 

Hawaii (via the MLO station). Sampling at these two 

stations began in June of 1993. The samples collected 

at these CMDL stations supplement our ongoing 

acquisitions at Cape Grim, Tasmania; Baring Head, New 

Zealand; Sable Island, Canada; and Syowa, the Japanese 

coastal Antarctic station. The CMDL Carbon Cycle 

Division in Boulder, Colorado, performs the 

complementary measurements of carbon dioxide for all 

of these samples. 

SAMPLING AND ANALYTIC TECHNIQUE 

Samples are collected in 2-L glass flasks equipped 

with a p air of shaft-seal valves fitted with Viton orings. A small pump draws ambient air through a cold 

trap, drying the sample. The flask is flushed with at 

least 40 liters of dry air before being filled to a pressure 

of one atmosphere. Duplicate pairs of these flasks are 

collected biweekly al each site . 

The 0 2/N2 ratio of air is measured using a 

conventional isotope ratio mass spectrometer. As with 

all such devices, the 0 2/N2 ratio is measured rel ative to 

some arbitrary reference. In our case, we use air 

coll ected by the CMDL Carbon Cycle Division al Niwot 

Ridge, Colorado, and stored in hi gh-pressure aluminum 

cyli nders. For use on the mass spectrometer, these 

cylinders are used to fi ll 70-L glass flasks that we refer 

to as working standards. 

95 

For analysis, gas from samples and standards is 

admitted into evacuated glass inle t lines. Each inle t is 

connected to the mass spectrometer by a 1-m length of 

fused silica tubing with an inside diameter of 25 

microns. The volume of each inlet is adjustable with a 

manually controlled piston, allowing us to equalize the 

flow rates from the inlets by compensating for variation 

in collection pressure of the samples or depletion of the 

standard. The analysis of a fl ask consists of at least 

four expansions of each sampl e-stand ard comparison. 

Two of the expansions arc carried out with one inletsample/inlet-standard pairing. The relationship is then 

reversed for the two remaining expansions. The 

spectrometer is configured to simultaneously measure 

masses 29 (15N14N) and 32 (1602). This coincident 

measurement of the two species, along with repeated 

switching between the sample and working standard , 

and long integration times, provides a high level of 

analytic precision. 

We have chosen to express the re lative changes in the 

0 2/N2 in units of "per meg. " This is simil ar to a 

percent change and is mathematicall y defined as 

In these units, 4 .8 per meg (J/0.2095) is equivalent to l 

ppm V since 0 2 is 20.95% of air by volume. The 

procedure outlined above gives an analyti c prec ision of 

approximately 4 per meg. 

RESULTS 

To date , we have collected rough ly l year of data at 

BRW. The values of the 0 2/N2 measurements arc 

presented in Figure 1, where the seasonal cycle is 

clearly visible with an amplitud e of -170 per mcg. 

Preliminary results from Cape Kumukahi and SJ\10 

show seasonal cycles of smaller amplitude, but with less 

than a full year of data availabl e, the size is hard to 

quantify. Our more extended records from Tasmania 

and New Zealand show a seasonal ampli tude of -90 per 

meg. Since the seasonal cycle comes from the 

combined effects of the ocean biosphere, thermal 
N 

z 

N 

-

0 

C-0 

92.5 

calendar year 

93.5 94.5 

0 -+-~+-~1----t...._-+-~..f'.~.1----11---+~~ 

i1i9· 

-50 ,,, 'll 

.,. 

-100 

-150 _...._...,._~.__ ....... _ e· .......... -tm-~·-io-..-0"' 

_r.f; "" 

Barrow -+--+--f--'"t~·.,.~ 

-200 ..._____._..........___.'---'---''---'--.____, 

l'ig. l. The 0 2/N2 ratio as measured at the BRW station from 

late 1992 until mid 1994. The ratio is given as a difference (in 

units of per meg) from some arbitrary standard. At each point 

in time, two flasks are filled. The analysis of each fl ask's 

contents is shown on the plot, giving some indicati on o f the 

overa ll reproducibility of the procedure. The seasonal cycle 

hJs an amplitud e of- 170 per meg. The interannual decrease of 

0 2 also seems to be v isible, but is not yet quantifiable. 

96 

e ffects at t h e a ir-sea boundary, and the terrestrial 

biosphere, different cycles in the n orthern and southern 

hemispheres are to be expected. 

With longer records at all of the collection sites, we 

will be better able to constrain short-term interannual 

variation and the long -term consumption of 0 2 due to 

human act ivities, as well as the distribution of carbon 

sources and sinks, terrestrial and oceanic. \Ve look 

forward to the extension of th is record in the coming 

years . 

Acknowledgment. We wish to thank Dan Endres al BRW, '.\·lark 

\Viney at SMO, John Chin at MLO, and Duane Kitzis of the 

Boulder Carbon Cycle Division for the collection of th e 

samples and standards used in this investigation . 

REFERENCES 

Keeling, R.F. and S.R. Shertz, Seasonal and interannual 

variations in atmospheric oxygen and implications for the 

global carbon cycle, Nature, 358, 723-727, 1992. 

Keeling, R.F., R.P. Najjar, M.L. Dender, and P.P. Tans, What 

atmospheric oxygen· measurements can tell us about the 

global carbon cycle, Global Biogeochem. Cycles, 7(1), 37-

67, 1993 . 
Latitudinal Profiles of Selected Trace Gases 

DONALD R. BLAKE AND F. SHERWOOD ROWLAND 

Department of Chemistry, University of California, Irvine California, 92717 

I NTRODUCTION 

Atmospheric trace gas concentrations are important as 

both signals and agents for change during the coming 

decades. These changes include perturbation of the 

stratospheric ozone layer by chlorine atoms released in the 

upper atmosphere from the destruction of organochlorine 

compounds; exacerbation of the greenhouse effect long 

altributed to increasing concentrations of C02, and now 

known to involve important contributions from additional 

trace gases; and variations in the oxidative capacity of the 

global atmosphere through HO radical perturbations. 

The source strengths of CFC gases such as CCl3F (CFC11), CCl2F2 (CFC- 12) and CCl2FCClF2 (CFC-113) are 

known well enough to establish that the atmospheric 

lifetime of each exceeds 50 years, and that tropospheric 

losses other than diffusion to the stratosphere are of 

negligible importance. With negligible loss to tropospheric 

sinks, both CCl3F and CCl2F2 serve as essentially inert 

tracers and have been used as calibration gases for 

atmospheric transport on a global scale in models ranging 

in sophistication from very simple one-box models to fullscale 3-D transpon models. 

Tropospheric HO is produced by the reaction of H20 

with 0(1 D) atoms released by solar ultraviolet photolysis of 

ozone . Atmospheric chemistry models clearly show that 

HO removal of hydrocarbons and hydro-halocarbons is 

much faster in the tropics than in polar regions. It is also 

more rapid during summer than winter in temperate zones. 

METHOD 

This research group has been monitoring the tropospheric 

concentrations of several halocarbons since November 1977 

[Tyler, 1983; Gilpin, 1990; Wang, 1993] and of methane 

beginning early in 1978 [Blake and Rowland, 1988]. Since 

the mid 1980s measurements of carbon monoxide and 

numerous nonmethane hydrocarbons (NMHCs) have been 

added to our routine analysis [Blake and Rowland, 1986; 

Hurst, 1990]. Quarterly collections centered around the 

beginning of each se ason occur at approximately 40 remote 

land sites distributed throughout the Pacific region in the 

latitude range between 7 1°N and 47°S. The CMDL stations 

at Barrow, Alaska, and American Samoa are part of the 

97 

sampling network. Gas chromatography utilizing either 

flame ionization or electron capture detection are the 

methods used for all sample analysis. Samples exhibiting 

numerous large, unidentified peaks may undergo further 

analysis using GC-MS detection. 

RESULTS 

Our CFC measurements have been useful in providing 

data to follow the temporal changes in the global mixing 

ratios and interhemispheric gradients of these importani 

gases during periods when their production and emissions 

are changing [Wang, 1993]. Other halocarbons routinely 

assayed provide data critical for estimating their source and 

sink strengths. 

To date, rel atively little information has been obtained 

from actual atmospheric measurements of tropospheric 

trace gases to show the seasonal and latitudinal variations 

in their source and sink strengths. However, our 

measurements of the seasonal variations in tropospheric 

C2H6 concentrations do demonstrate a decrease by a factor 

of 3 from winter to summer in the northern hemisphere and 

by a factor of 2 in the suuthc::rn hemisphere, together with a 

strong preference for emission in the northern hemisphere 

[Blake and Rowland, 1986]. These results are in reasonable 

agreement with various measurements and 3-D atmospheric 

models [Rudolph et. al., 1989; Kanakidou et al. , 1991; 

Penkett et. al., 1993]. 

R EFERENCES 

Blake , D.R. and F. S. Rowland, Continu ing world-wide increase in 

tropospheric methane, 1978-1987, Science, 239, 1129-1131, 

1988. 

Blake 0. R. and F. S. Rowland, Global atmospheric concentrations 

and source strength of ethane, Nature, 321, 231 -233, 1986. 

Gilpin, T.M., Global concentrations of three chlorofluorocarbons, 

1984- 1988, Ph.D. dissertation , 355 pp., University of California, 

Irvine, 1990. 

Hurst, D.F., Seasonal variations in the latitudinal distribution of 

tropospheric carbon monoxide, 1986- 1988, 267 pp., Ph.D. 

dissertation, Un ivrsity of Californ ia, Irvine 1990. 

Tyler, S.C., Chlorinated hydrocarbons in the troposphere, Ph.D. 

dissertation , Univeristy of California, Irvine, 1983. 

Wang, C.J.-L., Global concentrations of selected halocarbons, 2988-

1992, Ph.D. dissertation, Un iersity of California, !vine, 1993. 
Antarctic UV Spectroradiometer Monitoring Program: Contrasts in 

UV Irradiance at the South Pole and Barrow, Alaska 

C.R. BOOTH, T. B. LUCAS, J. R. TUSSON IV, J. H. MORROW, AND T. MESTECHKINA 

Biospherica/ Instruments Inc ., San Diego, California 92110-2621 

INTRODUCTION 

The Antarctic ultraviole t spectroradiometer 

monitoring network was established by the U.S. 

National Science Foundation (NSF) in 1988 in response 

to predictions of increased UV radiation in the polar 

regions. The network consists of several automated, 

high-resolution spectroradiometers; five are placed in 

strategic locations in Antarctica and the Arctic (Table 

1), and one is established in San Diego to collect data 

and serve as a training and testing facility. The network 

makes essential measurements of UV spectral irradiance 

and provides a variety of biological dosage calculations 

of UV exposure. Biospherical Instruments Inc., under 

contract to Antarctica Support Associates (ASA), 

directed by NSF, is responsible for operating and 

maintaining the network and distributing data to the 

scientific community. 

The spectroradiometers used in the system are 

Biospherical Instruments, Inc. model SUV- 100. Each 

instrument contains an irradiance diffuser, a doubleholographic grating monochromator, a photomultiplier 

tube, and calibr ation lamps. A vacuum-formed Teflon 

diffuser serves as an a11-weather irradiance collector, 

and it is heated by the system to deter ice and snow 

accumulation. Tungsten-halogen and mercury-vapor 

calibration lamps are used for automatic internal 

calibrations of both responsivity and wavelength that 

occur two to four times daily. All instrument functions, 

calibration activities, and data acqu1s1t1ons are 

controlled by an MS DOS-compatible computer. 

Further details on the spectroradiometers can be found 

in Booth et al. [1994). 

UV RADI ATION CLIMATE AT THE AMUNDSENSCOTT SOUTH POLE STATION, AND BARROW, 

ALASKA 

The South Pole and Barrow, Alaska, insta11ations of 

the network are in locations that also have CMDL 

installations. Therefore, the balance of this report will 

focus on these two sites. The South Pole site is 

uniquely suited to examinations of radiative transfer 

including the effects of ozone on UV radiation. This 

site is located away from the influence of mountains in 

a region of almost constant albedo. Cloud cover is 

relatively infrequent and it is generally thin when it 

does occur. The very small hourly change in the solar 

zenith angle at the South Pole supports examination of 

changes in total column ozone (as estimated by UV 

irradiance) at hourly resolution. 

Barrow can be contrasted with the South Pole in that 

it is located where a sign ificant change in surface 

albedo occurs because of both the springtime snowmclt 

[Dutton and Endres, 1991] and changes in sea-ice 

coverage. Also, Barrow experiences significant changes 

in incident irradiance because of Arctic storms. The 

contrast in irradiances between Barrow and the South 

Pole can be seen in Figure lb, whi ch depicts the 

integrated noontime irradiances over the UV-A 

spectrum (320-400 nm) from January 1992 through 

December 1993. 

The large changes in total-column ozone encountered 

at the South Pole make it an ideal site to examine the 

relationship between ozone depletion and enhanced UV 

irradiance. For example, in Figure la, a substantial 

decrease is seen in the 300 nm irradiance around 

TABLE 1. Installation Sites 

Site Latitude Longitude Established 

South Pole 90.oo·s o· February 1988 

McMurdo 11.s1 ·s 166.40°E March 1988 

Palmer 64.46°S 64.03°W May 1988 

Ushuaia, Argentina 54.49"S 68.19·w November 1988 

Barrow, Alaska 7 1.1 8°N 1s6.47°W December 1990 

San Diego, California 32.45°N 11 7.11 ·w October 1992 

*CADIC: Centro Austral de lnvestigaciones Cientificas, Argentina. 

**Ukpeagvik Inupiat Corporation-National Arctic Research Laboratory 

98 

Location 

Clear Air Building 

Arrival Heigh ts 

Clean Air Building 

CADIC* 

UIC-NARL** 

Biospherical Instruments Inc. 
South Pole - Barrow, Alaska --

(a) 

N 

E 

{ 

1-Jan-92 24-Jun-92 I 6-Dec-92 9-Jun-93 1-Dec-93 

4500 l 

4000 

3500 

3000 ~ 

2500 

2000 .,_ 

(b) 

~ I 

5~ ----"__,,.....,_...,____,__ _ ___,____,.._ 

1-Jan-92 24-Jun-92 16-Dec-92 9-Jun-93 l-Dec-93 

Fig. I. Noontime irradiance at Barrow, Alaska, and the South Pole from January 1992 through December 1993. Panel a (left) shows 

the irradiance at 300 nm and is contrasted with panel b (right) that illustrates the integrated UV-A (320-400 nm) irradiance. The hi gher 

irradiance values at Barrow are due to the higher sun elevation. Note that the irradiances a l Barrow peak in June, while the irradiances 

at the South Pole normally peak in December. 

December 6, 1992. Meanwhile , Total Ozone Mapping 

Spectrometer (TOMS Nimbus-7) d ata report that the 

ozone column over the South Pole increased from 193 

DU on December 5 to 292 DU on December 7, 1992. 

Similarly, a substantial increase in the 300 nm 

irradiance occurred between November 15 and 

November 20, 1993. As shown in Figure 2, this rise 

corresponded with a decrease of approximately 70 DU 

in the TOMS data. 

By comparing the strongl y depleted, springtime ozone 

levels over the Pole with the higher ozone levels 

observed at summer solstice, observations can be made 

regarding the impact of ch anges in ozone on UV 

irradiance - most o ther conditions (i.e. , cloud cover, 

albedo, and solar zenith angle) being equal. Figure 2 

contrasts integrated UV measurements with data from 

the TOMS satellite and corresponding solar zenith 

angles for September through December of 1993. As 

expected, ozone concentration and UV appear to be 

inversely correlated. Notice that as the season 

progressed toward summer solstice in December, the 

100 -, - ----------

1sl 

-<>-Integrated (298. 3Q3)nm 

~ ~ - - - Solar Zenrth Angle 

JI 50 - il 

:;i 

e --TOMS (Meteor 3) 

25 -

---

r - 500 

- 400 

100 

mmmJDJS@ :.......... __ L------------ 0 

9/10/93 10/1/93 10122193 11112193 1213/93 12124193 

Fig. 2. Daily flux in mill iJoules cm·2 integrated over the spectral 

region of 298 to 303 nm at the South Pole during the spring of 

1993. Also shown is the Nimbus-7 TOMS reported total column 

ozone values in DU. TOMS data courtesy of Rich McPeters of 

GSFC, NASA. 

99 

increase m solar angle (i.e. , decrease in solar zen ith 

angle) and small decreases in ozone r esulted in a 

dramatic increase in UV (i.e., "radiation amplification"). Evaluation and calculation of the exact 

amplification factor of ozone on UV are described in 

Madronich [1993) and in Booth and Madro11ich (1994]. 

SUMMARY 

High spectral r esolution scanning UV spectroradiometers were established at six sites and are 

successfully providing multi-year data sets. Resulting 

data were used to test radiative transfer models [Lubin 

and Frederick, 1990, 199 1, 1992; Lubin et al., 1989, 

1992; and Smith et al., 1991 , 1992a, b, c]. derive ozone 

concentrations [S tamnes et al., 1990, 1991, 1992], and 

examine the biological impact of enhanced UV [Lubin 

et al., 1992; Cullen et al., 1992; and Smith et a l., 1991, 

1992b, c; Set/ow, 1974). 

The data discussed here and all other data recorded by 

the NSF UV monitoring network are available to all 

qual ified researchers. The data arc div ided into three 

classes. Level 1 data arc in their original, uncorrected 

binary form and level 2 data were refere nced to 

beginning-of-season calibration constants. These two 

cl asses are available only to NSF-sponsored researchers 

upon special request. Level 3 data are referenced to 

both beginning- and end-of-season calibration 

constants. These data are distributed on CD-ROM and 

are available to any researcher. For more information, 

please contact: C.R. Booth at Biospherical Instruments 

Inc., 5340 Riley St., San Diego, CA 92110 (Fax: (619) 

686-1887, or Internet: booth@biosphcri cal.com). 

Acknowledgments. This research and monitoring 

activity was funded by contract A1T-Ml743 from 

Antarctic Support Associates under the direction of 

Polly Penhale at the National Science Foundation, 

Office of Polar Programs. B. Mendonca of Cl\IDL 
assisted in providing operators and support for the 

install ations at Barrow. R. McPeters of NASA/GSFC 

provided TOMS Total Ozone data for comparison 

purposes. TOMS Update CD-ROM is available from the 

National Space Science Data Center (NSS DC), Goddard 

Space Flight Center. Barrow operators include D. 

Norton (Arctic Sivumnun Ilisagvik College), D. Endres 

and B. Halter (CMDL). The Ukpeagvik lnupiat 

Corporation of Barrow provided assistance in the 

installation. Operators at Palmer and McMurdo were 

prov ided by ASA. Special thanks go to John Gress of 

ASA who has been invaluable in the operation of the 

network. 

R EFERENCES 

Booth, C.R., T.B. Lucas, T. Mestechkina, J.R. Tusson IV, D.A. 

Ncuschuler, and J.H. Morrow, NSF Polar Programs UV 

Spectroradiometer Network 1991-1993 Operations Report, 218 

pp., Biospherical Instruments Inc., San Diego, CA, 1994. 

13ooth, C.R., and S. Madronich , Radiation amplification factorsimprovcd formulation accounts for large increases in ultraviolet 

radiation associated with Antarctic ozone depletion, in 

Ultraviolet Radiation in Antarctica: Measurements and 

Biological Effects, Antarctic Res. Series, Vol. 62., Am. Geophys. 

Union , pp. 39-42, 1994. 

Cullen , J.C., P.J. Neale, and M.P. Lesser, Biological weighting 

function for the inhibition of phytoplankton photosynthesis by 

ultrav iolet radiation, Science, 258, 646-650, 1992. 

Dutton, E.G., and D.J. Endres, Date of snowmelt at Barrow, Alaska, 

U.S.A., Arctic Alpine Res., 23(1), 115- 119, 1991. 

Lubin, D. and J.E. Frederick, Column ozone measurements at 

Palmer Station, Antarctica: variations during the austral springs 

of 1988 and 1989,J. Geophys. Res., 95, 13,883-13,889, 1990. 

Lubin. D. and J.E. Frederick , The ultraviolet radiation environment 

of the Antarctic Peninsula: the roles of ozone and cloud cover, J. 

Appl. Met., 30, 478-493, 1991. 

Lubin, D., and J.E. Frederick, Observations of ozone and c loud 

properties from NSF ultrav iolet monitor measurements at Palmer 

Station, Antarctica, Ant. J. U.S., 25(5), 241-242, 1992. 

Lubin, D., J.E. Frederick, C.R. Booth, T.B. Lucas, and D.A. 

Neuschuler, Measurements of enhanced springtime ultraviolet 

radia tion at Palmer Station, Antarctica, Geophys. Res. Leu., 

16(8), 783-785, 1989. 

Lubin, D., Mitchell, B.G., J.E. Frederick, A.D. Alberts, C.R. Booth, 

T.B. Lucas, and D.A. Neuschuler, A contri bution toward 

understanding the biospherica l significance of Antarctic ozone 

depletion,J. Geophys. Res., 97, 78 17-7828, 1992. 

Madronich, S. UV Radiation in the natu ral and perturbed 

atmosphere, in UV-B Radiation and Ozone Depletion, edited by 

M. Tevini, pp. 17-19, Lewis Pub., Boca Raton, FL, 1993. 

Setlow, R.B., The wavelengths in sunlight effective in producing 

skin cancer: a theoretical analysis, Proceedings of the Nat. 

Academy of Science, USA, 7 1(9), 3363-3366, 1974. 

Smith, R.C., K.S. Baker, D. Menzies, and K. Waters, Biooptical 

measurements from the IceColors 90 cruise 5 October-2 1 

November 1990, S/O 91-13, 12 1 pp., Scripps Institution of 

Oceanography, La Jolla, CA, 199 1. 

Smith, R.C., B.B. Prezelin, R.R. Bidigarc, D. Ka rcntz, and S. 

Macintyre, JccColors'90: Ultraviolet radiation and phytoplankton biology in Antarctic waters, Science, 255, 952-959, 

1992a. 

100 

Smith, R.C., B.B. Prezelin, K.S. Baker, R.R. Bidigarc, N.P. 13oucher, 

T. Coley, D. Karent z, S. Macintyre, H.A. Matlick, D. Menzies, M. 

Ondrusek, Z. Wan, and K.J. Waters, Ozone depiction: Ultraviolet 

radiation and phytoplankton biology in Antarctic waters, Science, 

256,952-959, 1992b. 

Smith, R.C., Z. Wan, and K.S. Baker, Ozone depiction in Antarctica: 

Modeling its effect under clear-sky cond itions, J. Geophys. Res., 

97, 7383-7397, 1992c. 

Stamnes, K., J. Slusser, and M. Boden, Derivation of total ozone 

abundance and cloud effects from spectral irradiance 

measurements, Appl. Opt., 30, 44 18-4426, 1991. 

Stamnes, K., z. Jin, J. Slusser, C.R. Booth and T.B. Lucas, Severalfold enhancement of biologically effectiv e ultrav iolet radiation 

levels at McMurdo Station , Antarctica, during the 1990 ozone 

hole, Geophys.Res. lett., 19, 1013-1017. 1992. 

Stamnes, K., J. Slusser, M. Bowen, C.R. Booth, and T.B. Lucas, 

Biologically effective ultraviole t radi ation, total ozone 

abundance, and cloud optical depth at McMurdo Station, 

Antarctica, September 15, 1988, through April 15, 1989, 

Geophys. Res. lett., 17, 2 181-2 184, 1990. 
Examination of the Mauna Loa Robertson-Berger Meter Data 

for Calibration Inconsistencies 

1. DELUIS I 

NOAA Air Resources Laboratory, Boulder, Colorado 80303 

This investigation was concerned with the stability of 

the calibrations done by Temple University on the 

Robertson-Berger (R-B) meter [Berger, 1976] instrumentation at MLO. 

A demonstration of the R-B meter stability and a 

demonstrat ion of a drift in the calibration can be seen in 

the data obtained at MLO that is operated by CM DL. 

Clear skies were determined by con tinuous direct-sun 

radiometer measurements made routinely at the 

observatory. A Dobson instrument operated at the 

station supplied the total ozone data [Komhyr et al., 

1989]. Figure I is the calculated rat io of the calibrated 

MLO R-B meter data to the model calculated irradiance 

(scaled to a convenient magnitude) and Figure 2 is the 

ratio using the uncalibrated R-B meter data. The large 

variations seen in the clustered groups of points reflect 

calibration and instrumental problems requiring sever al 

replacements in the early part of the record, therefore , 

rendering the data unfit for the Scotto et al. (1988] 

analysis. Attention is called to the record after 1979; 

the period when the calibrated data ratio showed a 

downward trend of roughly 10% between 1979 and 

1988 . It is o ur understanding that Scotto et al. [ 1988] 

used a linear interpolation method to remove the 

discontinuities between calibration periods and this is 

why calibration jumps do not appear in the calibrated 

data prev ious to 1988. Apparently, this was not done in 

1987 when an upward jump appeared. The uncalibrated 

data ratio showed v irtually no trend, remaining 

>-

(!) 

a: 

uJ 

z 

uJ 

;:::: 

z 

::::> 

0 

(_) 

co 

a: 

0.5 

0.4 

0.3 

0.2 

0.1 

0.0 L....L--'-~-'--L-----L--'---'---'.__._,_ _ _._____, 

74 76 78 80 82 84 86 08 90 92 94 

YEAR 

Fig. I. Ratio o f ca librated MLO R-B meter data to mode l 

calculated iradiance. The R- B m eter data is the half-hour va lue 

sum 11 :00-11 :30 a .m. fo r clea r days between 1974 a nd 1992. 

101 

>-

(!) 

a: 

uJ 

z 

uJ 

;:::: 

z 

::::> 

0 

(_) 

co 

a: 

0.5 

0.4 

0.3 

0.2 

0.1 

N!!fl.~·~ 4'\ ~ 

~ 

0.0 L-L~__.._ _ _,_ _ _..__..___, _ _,_~_._~_.._ _ _,____, 

74 76 78 00 02 04 86 88 ·so 92 94 

YEAR 

Fig. 2 . Ratio of un ca li brated Mauna Loa R-B meter data to 

model calculated irradi ance as in Figure I. 

remarkably uniform, and thereby demonstrating the 

stability of a meter and the sound ness of our approach. 

During this period, the instrument operated wit hout an 

inc ident tha t would require replacement. Considering 

the exceptional quality of the MLO site for view in g the 

sky radiation, there is no reasonable explanation for the 

downward trend seen in the calibrated ratio data other 

than a calibration error. 

The eruption of El Chichon occurred in the spring of 

1982 and a short data gap exists near this time in the RB meter record. Nevertheless, the r atio hardly varies 

after 1981 indicating little sensitivity to the 

stratospheric aerosol that was still significant after the 

data gap . The aerosol optical depth ranged between 0.1 

and 0.2 or roughly 10 times greater than background 

(see DeLuisi et al., 1989]. A m ax imum stratospheric 

aerosol optical depth of slightly more than 0.1 from El 

Chichon occurred over the U.S . in January 1983 [e .g., 

DeLuisi et al., 1989]. Strong forward scattering and 

minimal absorption of UV rad iation by the stratospheric 

aerosols are believed to be responsible for the UY 

irradiance. On the basis of this result, it seems unlikely 

that a significant effect would be seen over the U.S. 

The experience with the Mauna Loa data led us to 

proceed with a similar analysis of the data used by 

Scotto et al. (1988] in search of a pattern that might he 

attributed to possible calibration inconsistencies. A 

paper is being prepared summari?ing the results of 

examining the calibrations of instrumen_ts operating in 

the U.S. network. 
REFERENCES 

Berger, D., The sunburning ultraviolet meter: design and 

performance, Photochem. Photobiol. 24, 187-192, 1976. 

DeLtiisi, J.J., D.U. Longenecker, C.L. Mateer, and D.U. 

Wuebbles, An analysis of northern middle-latitude Umkehr 

measurements corrected for stratospehric aerosols for 1979-

1986, J. Geophys. Res .. 94(D7), 9837-9846, 1989. 

Komhyr, W.D., R.D. Grass, R.K. Leonard, Calibration of primary 

standard Dobson spectrophotometer No. 83 and total ozone 

trends at Mauna Loa Observatory, Hawaii, and American 

Samoa, South Pacific, in Ozone in the Atmosphere, edited by 

R.D. Bojkov and P. Fabian, 85-87, A. Deepak, Hampton, 

Virginia, 1989. 

Scotto, J., G. Cotton, F. Urbach, D. Berger, and T. Fears, Biologically 

effective ultraviolet radiation: surface measurements in the United 

States, 1974-1985, Science, 293, 762-764, 1988. 

102 
Comparison of Mauna Loa Observatory And Hilo Radiosonde 

Meteorological Measurements 

ELEANOR FOLTZ* 

Kwajalin High School, Kwaja lin A toll, P.O. Box 929, APO AP 96555 

I NTRO DUCT ION 

This report compares meteorol ogical measurements 

taken automat ically a t Mauna Loa Observatory (MLO) 

with twice daily concurrent Hilo radiosonde 

measurements. Hilo is 25 km upwind of MLO. It is 

well known that MLO nighttime downslope winds and 

dayt ime upslope winds do not relate wel l to free 

tropospheric wind flow in the region of the Mauna Loa 

massive. The regular downslope winds bring noc turnal 

upper level air to the observatory site that allows MLO 

to make background atmospheric composttton 

measurements most days of the year. Less well known 

is the fact that other surface meteorological 

measurements (such as temperature and dewpoint) may 

also differ considerably from free atmosphere 

(rad iosonde) measurements at or near to the same 

altitude. For this study, it is assumed that both the 

rad iosonde and MLO meteorological instruments are 

accurate and thus the data from each fully comparable. 

The M LO and Hi lo radiosonde data for 1992 were 

al:quin:<l from the MLO data base maintained in Ilil o. 

MLO had an average station pressure of 680 mb 

durin g 1992. For case of comparison, radiosonde data 

for the 700 mb level for 0 and 12 GMT (0200 LST and 

1400 LST) soundings were compared to the MLO hourly 

average data for the same hours grouped by month. 

According to the Smithsonian Meteorological Tables, 

the 20 mb offset between MLO and the radiosonde data 

would produce a maximum temperature error of I .5°C 

in dry air (i.e., cooler at MLO) and a lesser difference 

in wet air. One would expect little difference in 

humidity between MLO and the radiosondes at the same 

altitude and no difference in wind speed and direction 

due solely to the 20 mb height differential. But, the 

mass of the mountain and its dark color considerably 

distorts the MLO surface meteorological readings as 

shown below. This report should be considered as an 

early step towards quantifying and understanding some 

of these effects. 

WIND DIRECTION 

The effect of the mountain on wind direction was as 

previously known: air flow at MLO was northerly 

during the day and southerly at night, fairly independent 

of the free tropospheric air flow patterns (Figures 1 and 

2). These results arc considered a reality check and 

suggest that the MLO surface data was processed in a 

103 

WIND DIRECTION, DAY 

N SW W NW 

0 Sonde, 1400 LST I 

Fig. 1. Monthly average frequency of 700 mb winds measured 

at 1400 LST by the Hilo radiosonde in the free troposphere and 

the corresponding winds at MLO measured at 2 m above ground 

and 680 mb. 

35 

30 

~25 !?..... 

{)'20 

c 

~ 15 

O" 

it 10 

WIND DIRECTION, NIGHT 

l·· ······· ..... ........ . 

t 

t .. .. ..... .. 

0 +-'-4-'-'+-.Lif-..u+~ .......... r--'+""'~'-'+"~----i~r--"T-'"'-t-"-4-"-'1 

N NE E SE S SW W NW 

I• MLO, 0200 LST 0 Sonde, 0200 LST I 

Fig. 2. Monthly average frequency o f 700 mb winds mearnred 

al 0200 LST by the llilo radiosonde in the free tropo sphere and 

the corresponding winds al MLO measured at 2 m above gro und 

and 680 mb. 

correct manner. From the radiosonde data alone it ma~ 

be observed that winds were most often flowi ng from an 

easterly direction night and day, but that there arc 

diurnal effects in the 700 mb free atmosphere winds. 
Again this is nothing new and serves more as a 

confirmation that the radiosonde data was acquired and 

processed in a reasonable manner rather than a 

presenta tion of new science. 

The daytime upslope winds at MLO presented in 

Figure 1 (hourly average winds at 1400 LST) are mainly 

from the northeast through northwest that slip under the 

free troposphere. It is worthy of note that the free 

troposphere winds over Mauna Loa are not exclusively 

easterly in direction. 

At night (Figure 2) the downslope southeast through 

southwest winds d ominate in a narrow 90° arc with 

negl igible winds recorded in the northeast through 

northwest directions at 0200 LST. Like the upslope 

flows, these downslope winds slip under the free 

tropospheric flow and rush down the mountainside 

passing the observatory on a regular and highly 

predictable pattern. 

AIR TEMPERATURES 

The monthly average air temperatures at 0200 and 

1400 LST recorded at 2 m above the surface at MLO 

compared to the concurrent radiosonde measurements 

are presented in Figure 3 . From Figure 3 it may be 

observed that the MLO monthly average temperatures 

were 2-4°C warmer at 1400 LST and 2-5 °C cooler at 

0200 than the temperatures of the corresponding free 

atmosphere. There is a small diurnal cycle in the 

radiosonde data with slightly higher temperatures 

during the day and slightly cooler temperatures at night. 

The higher daytime temperatures at MLO are explained 

by the fa c t that the dark lava heats up during the 

generally c loud-free days that occur above the 

temperature inversion some 1200 m below the level of 

MLO. This warming drives the daily upslope fl ows that 

mu st be warmer than the free tropospheric air or they 

14 

~ 12 

~ 

Q) 10 '-

::l 

~ 8 Q) 

~ 6 Q) 

t- 4 

AIR TEMPERATURES 

2 -'----!---+-~+--+~+--+~+--+ +--+ -+--+~ 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

-.. MLO, 1400 LST ..... Sonde, 1400 LST 

-e- Sonde, 0200 LST -<:>-- MLO, 0200 LST 

fig. 3. ~lonthly average air temperatures at 0200 and 1400 LST 

measured by the Hilo radiosonde al 700 mb in the free troposphere 

and at 680 mb and 2 m above ground level at MLO. 

104 

would not be rushing up the mountain each day. Both 

the surface heat ing effects and the warm air movements 

combine to produce the warmer daytime temperatures at 

MLO. 

At night, the dark lava radiates heat to the clear sky 

and cools the air above it. This cooling drives the 

nightly downslope winds as the cool, dense air flows 

down the mountain slope. As observed in Figure 2, 

these downslope winds are pervasive, thus indicating 

that the air is always cooler at night at the surface at 

MLO than in the corresponding free atmosphere. 

DEWPOINT TEMPERATURES 

The dewpoint temperatures at MLO (Figure 4) exhibit a 

pattern of higher dewpoints in the day (i .c., more moisture 

in the air) than at night when the dry downslope air 

dominates. The relatively moist (and adiabatically cooling) 

upslope flow indicates that air influenced by the marine 

boundary layer is reaching the observatory during the day. 

It may also be observed in Fi gure 2 that the daytime 

radiosonde dcwpoint temperatures arc also generally 

slightly higher than the nighttime values. This is to be 

expected as the dewpoint temperature tendencies fol low 

temperature in conservative, non-precipitating meteorological situations. 

CONCLUSIONS 

Monthly average measurements of 1400 and 0200 

LST wind directions, air temperatures and dcwpoints at 

MLO are unrepresentative of the true state of the free 

atmosphere at the altitude of MLO. Thus, one should be 

cautious in using MLO surface meteorological data for 

c limato logical purposes. Follow-u p studies should 

correct each data point for the 20 mb difference 

between the true air pressure at MLO and the standard 

10 

5 

8 

Q) 0 '-

::l 

~ -5 Q) 

o._ 

E -10 Q) 

t-

-15 

DEWPOINT TEMPERATURES 

-20 .J......+-+---l--+--l-+---+--+--f--+--+---+-' 

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

-.. MLO, 1400 LST ..... Sonde, 1400 LST 

-e- Sonde, 0200 LST _.,... MLO, 0200 LST 

Fig. 4. Monthly average dewpoint temperatures at 0200 and 14 00 

LST measured by the l!ilo radiosonde at 700 mb in the free 

troposphere and at 680 mb and 2 m above ground level at ~!LO. 
700 mb level radiosonde data. For the purposes of the 

current study, this 20 mb offset did not unduly obscure 

nor accentuate the much larger effects on meteorology 

produced by the mountain's topography and physiography. 

105 

•Eleanor was a stud ent in the 1994 Hawa ii Student Science 

Training Program held each year al the University of Hawaii, 

Hilo. She conducted her 10-day off campus research project al 

MLO under the supervision of Drs. John Barnes and Russ 

Schnell. Eleanor had completed grade 11 al 1he 1ime of 1hc 

srndy and plans on entering engineering school at ;>.!IT in the 

fall of 1995. 
Intercomparison of Stable Isotope Measurements of C02 

R.J. FRANCEY, C.E. ALLISON, L.P. STEELE, R.L. LANGENFELDS, AND E.D. WELCH 

CS/RO Division of Atmospheric Research, Aspendale, Victoria, Australia 

J .W.C. WHITE AND M. TROLIER 

University of Colorado, Institute of Arctic and Alpine Research, Boulder, Colorado 80309 

P.P. TANS AND K.A. MASARIE 

NOAA, Climate Monitoring and Diagnostics Laboratory, Boulder, Colorado 80303 

I NTRODUCTION 

Over the last decade the two most extensive, highprccision measurement programs measuring the 813C of 

C02 [Keeling et al, 1989; Whorf et al. , 1993; Francey et 

al., 1990] have resulted in data that have very different 

implications for the global carbon budget over the period 

[Francey et al., 1995a]. The 1)13C data are primarily used 

to partition the uptake of fossil carbon emissions between 

ocean and terrestrial plant reservoirs. The requirement for 

high precision in these measurements was emphasized by 

Ellling et al. [1993, 1994] and Tans et al. (1993) and the 

requirement for extensive spatial coverage by Ciais et al. 

[ 1994]. The recent advent of isotopic measurements on the 

extensive CMDL flask network has added stimulus for a 

number of improvements in the intercalibration of isotope 

measurement programs. This report gives preliminary 

results from one such program where a subset of CMDL 

flasks filled at Cape Grim, Tasmania, were analyzed with 

both CSIRO and INSTAAR mass spectrometer facilities. 

The results were compared to the long running CSIRO in 

situ C02 extraction program at Cape Grim [Francey et al., 

1995b]. 

The normal mass spectrometric measurement of 813C in 

atmospheric C02 requires the simultaneous measurement of 

ion currents because of three mass-to-charge ratios (m/e) at 

44, 45, and 46. The m/e 46 is primarily measured so that 

any 170 contribution to the m/c 45 can be calculated and 

removed in order to obtain the actual 13C contribution. 

With some precautions, a bonus is a record of the 1)180 in 

atmospheric C02. a useful tracer in its own right. An 

explanation that described the global distribution of this 

species was first presented by Tans et al. (1986] and 

Francey and Tans [ 1987), and subsequently further 

expounded by Farquhar et al. [1993]. An intercomparison 

of the measurements of 1)18Q in C02 shows considerable 

systematic influence, but the preliminary data arc included 

for completeness. 

METHODS 

The isotopic analysis of air collected in CMDL flasks 

filled at Cape Grim commenced in December 1991 and still 

continues; data are presented for samples collected to the 

106 

end of 1993. The 2.5-L glass flasks arc flushed for 5 

minutes at 8 L min- 1, then pressuri zed to around 0.4 bar 

above ambient. The air is scaled using Teflon 0-ring 

valves. For details of the sample collection procedure for 

flasks in the CMDL-INSTAAR network sec Conway ct al. 

(1994) and associated references. 

A subset of the flasks (Table 1) is routed through the 

CSIRO/DAR Global Atmospheric Sampling Laboratory 

(GASLAB) in Aspendale, where about 150 bar-mL of air is 

used for the duplicate determinations of C02 , CH4 , CO, H2, 

and N10 by gas chromatography. Comparisons of results 

from Aspendale and Boulder for these species will be the 

subject of a separate report (Steele et al., in preparation, 

1994). An additional 30-50 bar-mL of the flask air 

provides 1)13C02 and 1)18C02 using a Finnigan MAT 252 

mass spectrometer with MT Box-C accessory for the 

extraction of C02 from the air. 

Flasks are then returned to Boulder, Colorado, for 

analysis by CMDL and INSTAAR. The CMDL Carbon 

Cycle Division analyzes the air for the mixing ratio of C02 

using a non-dispersive infrared analyzer and for mixing 

ratios of CH4 , CO, and H1 by gas chromatography [Conway 

et al., 1994, Steele ct al., 1987, Novelli ct al., 1992]. The 

Stable Isotope Laboratory at INSTAAR uses -700 bar-mL 

of the sample to determine the 813C and ol 8Q of the C02 

using a Vacuum Generators SIRA Series II mass 

spectrometer that is equipped with a "triple-trap" assembly 

to cryogenically separate C02 from the air sample (/11. 

Trolier et al., Monitoring the stable isotopic composition 

of atmospheric C02: measurements from the CMDL global 

network, in preparation, 1995). 

TABLE 1. Annual Average and Standard Deviation of 

813C for the Cape Grim In Situ Method and for 

Corrected GASLAB and INSTAAR Measurements 

1992 

(n = 2) 

1993 

(n = 4 4) 

In situ 

-7.756 

(0.031) 

-7.759 

(0.030) 

G/\SL/\ 13 

-7.759 

(0.028) 

-7.758 

(0.029) 

li'\ST/\/\R 

-7.752 

(0.038) 

-7.765 

(0.044) 
Calibration strategies for the mass spectrometer raw data 

and correction strategies for the isotopic determinations are 

critical considerations. This reflects the fact that the 

scientific requirement is for an inter-laboratory precision in 

average 813C values close to, or better than, the instrument 

internal precision on an individual analysis. In this 

intercomparison it was found necessary to consider the 

following factors: (a) the assumed isotopic composition of 

the primary international reference materials, (b) the 

methodology used to determine the isotopic composition of 

secondary or working standards, (c) the algorithms 

employed to calculate the 13C and 170 contributions to the 

m/e 45 ion beam intensity (the 170 correction), (d) the 

constants and trace gas concentration calibration scales 

used in the estimation of the N20 contribution to the m/e 

44 ion beam current, (e) modification of the isotopic 

composition of the working standard C02. (f) isotopic 

fractionation in the extraction of C02 from whole air 

samples, and (g) mixing of sample and working standard 

C02 in the mass spectrometer ion-source region. 

Points (a), (b), and (c) have recently been addressed 

in detail [A llison et al. l 994a,b, Allison and Francey, 

1994]. Summarizing, both the CSIRO and INSTAAR 

mass spectrometer values were corrected using the same 

recommended values for the isotopic composition in the 

hypothetical V-PDB international isotope standard, and 

both l aboratories have re lated the measured 1)45, and 1)46 

of samples to the primary stand ard by the measured 1)45, 

and 1)46 of intermediate standards to avoid propagation 

of e rrors associated with the ion corrections. The same 

assumption about the relationship between 170 and 180 

[Craig, 1957] is then applied in the conversion of the 

fina l rat ios to 813C, 1)180. 

Point (d) uses a correction involving the ratio of 

N20/C02 in the sample and a relative ionization 

e ffi c iency of the two gases in the mass spectrometer 

source [Mook e t al., 1983]. At DAR a rel ative 

ionizat ion efficiency of 0.72 ± 0 .0 1 has been measured 

(C.E. All ison, private communication, 1994). The C02 

concentrations used to determine the N10/C02 ratio in 

the sample are the GASLAB measured values for the 

flask , calibrated against a suite of standards, linked in 

1993 to the CMDL scale to better than 0.1 ppmv. For 

N20 a nominal 310 ppbv was employed; the annual 

average value at Cape Grim in 1992 is estimated at 310 

ppbv [Montzka et al., 1993). At INSTAAR, the relative 

ion ization efficiency of N20/C02 has been measured at 

0.754 ± 0.010 on the SIRA Seri es II instrument 

[ Gemery, 1993). The C02 mixing ratios used in the 

N20 correction for each flask are the values measured 

by CMDL on the same flasks. The NiO mixing ratios 

are approximated from global mean values determined 

at CMDL, taking the global mean for January 1, 1993, 

lo be 310 ppbv, with a linear growth rate of about 0.66 

ppbv yr- 1 [Mon1zka el al., 1992). 

A 1ypical N20 correction to 1)13C is -0.2%0, and an 

error of 1 % in N20 or C02 concentration results in a 

1)13C error of <0.003%0, considered negligible in the 

present case. There are p otential differences because of 

errors in the determination of the relative N20/C02 

ionization efficiency, but they are relatively small. For 

example, a +5% error translates into changes of 

-0.006%0 and -0.009%0 for 1)13C and 1)180, respectively . 

Point (e), the modification of standard C02 during 

analysis, refers to a fractionation of the C02 gas in the 

standard reservoir during bleed through the capillaries 

or waste line. At GASLAB a fractionation of about 

0.0028%0 per hour in l)l3C of C02 in the standard 

reservoir is measured; the effect is twice as large for 

1)1 80. This is documented by Allison el al. [ 1994a] for 

the MAT252 and a correction automatical ly applied to 

the data; in practice the standard reservoir 1s 

automatically refilled every four to six samples. For 

the MAT252 analysis of the CMDL flask data set, the 

average "bleed" correction amoun ted to 0.011 ± 0.009%0 

in l)l3C and 0.023 ± 0.01 8%0 in 1)180, correspond ing to a 

mean bleed time of 3.9 hours. The correction is made 

implicitly at INSTAAR by measuring a working 

standard (whol e air) at the beginning and end of every 

analysis run, and linearly interpolating to account for 

all instrument drifts. The observed drifts are variable 

but are typically less than 0.05%0 for 1)13C (over 8 

hours); they are probably dominated by instabilities in 

the VG SIRA mass spectrometer. 

Point (f) addresses potentially signifi cant differences 

arising from the different C02 extraction methods. The 

GASLAB MAT252 MT Box-C was supplied with a 

capillary to drop the sample pressure for cryogenic 

drying and C02 extraction in cold traps. In a typical 

flask analysis, about 30 bar-mL of air is bled through 

the capillary and two -180"C cold traps in series. Th e 

trap pressure rises from 0 to around 200 mb during this 

process in which the HiO. C02. and NiO are retained in 

the traps and the remaining air components arc pumped 

away. In a succession of distillations, HiO is then 

retained at -IOO"C and the mobile C02 and N20 finally 

collected in a third cold trap at - 180"C; maximum 

pressure in these tran sactions (the yie ld) is a few mb 

and about 0.5 μmo! of C02 is collected. From here the 

sample C02 (and N20) is fed to the mass spectrometer 

changeover valve for analysis. The cryogenic 

separation scheme at INSTAAR is rather d ifferent. 

Because of the larger volume of air required for 

analysis, and the consequent drop in backing pressure 

within the sample fl ask, a mass flow controll er is used 

instead of a capillary to limit the flow through the 

extraction system. The air is drawn through a high 

capacity glass trap held at -90"C to remove wa ter 

(common to all samples), then through a stainless-steel 

trap at -196"C to remove C02 (N20). A flow rate of 60 

bar-ml min-1 is used; the pressure in the traps during 

this process is typically a few mb. The yield of C02. 

about 12 μmo!, is released to the mass spectrometer by 

expansion after warming the C02 trap. 

107 

On April 28 , 1993, the GASLAB MT Box -C was 

modified to permit the analysis of very small (ice core) 
samples and operating parameters optimized for the 

small sample analyses. The influence of the 

modifications on the routine measurements of flask 

samples is discussed below. The results from both the 

INSTAAR and GASLAB trapping boxes are compared to 

an independent manual system operated at Cape Grim as 

part of the long running in situ program [Francey et al., 

1995). This system uses an air flow of 300 mL per 

minute over 2 hours, with trapping at a maximum 

pressure of 20 mb. The collected C02 is stored in 50 

mL glass bulbs with a Teflon 0-ring tap for analysis at 

Aspendale on the MAT252 mass spectrometer through 

the normal inlet variable volume. 

Finally, point (g) brings up the potential for 

systematic errors arising from the mixing of sample and 

standard gases in the source region of the mass 

spectrometer. Similar effects were discussed by Mook 

and Groot es [ 1973) and were documented in the 

MAT252 (C. Flehoc et al., Systematic influences in the 

high prec1s1on stable isotope measurements of 

atmospheric trace gases, in preparation, 1995). They 

arc emphasized by having a standard C02 with isotopic 

ratio very different from the sample C02 or by 

insufficient evacuation of the source region during 

normal sample-standard switching. The effect can be 

manifested as a sample size dependence in o, but more 

importantly, a sample value biased towards the working 

standard isotopic ratio. 

CALIBRATION STRATEGIES 

Different calibration strategies are employed by the 

two groups. At GASLAB all isotopic values are 

routinely expressed relative to the one working-standard 

(high-pressure cylinder "HC453" C02) used in the 

reference reservoir of the MAT252. The working 

standard isotopic value is monitored each measurement 

session by prior calibration against an independent subsample of the working gas. The small difference of 

around l %0 in o13C between ambient air and standard, 

minimizes possible sample-standard mixing effects. 

The calibration is also monitored by analysis of a highpressure cylinder containing "standard" Cape Grim air, 

before, in the middle, and at the end of automatic 

sequences of sample analyses (typically 10 samples and 

l to 2 additional low pressure air standards). Generally, 

the air standard data has not been used to modify 

sample results, an exception being the so-called "APC 

correction" discussed below. 

INSTAAR uses a different routine calibration 

strategy. INSTAAR's working standard is C02 in whole 

air, just as the samples are. The C02 gas in the mass 

spectrometer's standard reservoir is used only to relate 

samples to the working standard within the same 

analysis run, not as an isotopic reference material as is 

the routine at GASLAB. Several aliquots of the 

working standard are used at the beginning and end of 

each analysis run (typically 10-20 samples). The 

isotopic composition of the working 

monitored monthly by intercalibration with 

in-air and pure C02 secondary standards. 

standard is 

other C02-

RESULTS 

The results of the intercomparison are shown in 

Figure l (a) and (b) for o13C and ol8Q, respectively. 

The main features of the o13C intercomparison are: 

(a l ) The flask record defines the seasonality of the tn 

situ record faithful ly in 1993 but not so well in 

1992. This appears to be due to increased scatter 

in the early flask data. 

(a2) The agreement between the annual mean levels of 

all three records is surprisingly good, particularly 

108 

-7 .7 

-7Jj 

-7 3 +-'~._._-'-t_._ ......... '-t-~~~+""~ ........ -'-t-'-........ ~'-t-~~~ 

91.5 92 92.5 93 93.5 94 94.5 

0 

, . . ,\h . . ~ . Ji\ • 'I-./ 'It: ' ,. \ 

('-t! · · · "·" ·'-,~ \.Jff)V;,.i < i,,q, -~-- ' t---.. ."I. • . :· .. • \ •JJ~fjt +•+ + " I \ L . * r.. • .++ • ' ·. ~ T .~ , . ·+ x: •• • . • l( • ' . x. JC /' ' ..• ', . , ¥ .. X:-;r 

. •J 1. ¥ ¥ 

,; 

• 

• 

91.S 92.5 93 93.5 94.S 

Fig . I . (a) The o13C o f Cape Grim C02 measured in C:"-IDL 

fla sks by GASLAB (+: un corrected, o: with "Al'C" correction) 

and INSTAAR (filled squares). The line connects 

measurements at GASLAB on C0 2 extracted in situ at Cape 

Grim. (b) The ot3Q o f Cape Grim C02 mea sured in ~IDL 

fla sks. Symbols are as for ol3C, except th at 1:0.:STAAR values 

are given separately for unflagged data (fill ed squa res) and 

flagged data (stars). In this case th e "APC/id le time" 

adjustment is not independently corrected, rather maintains the 

1992 relationship with the in situ data (s ee text). 
in view of the independent calibration of standards 

between the two laboratories. The annual averages 

and standard deviations for each year are 

summarized in Table 1. There is excellent 

agreement between the in situ and CMDL mean 

values. All values agree within one standard 

deviation (which include the seasonality). Taking 

only flasks analyzed on both GASLAB and INSTAAR 

instruments, the mean difference is negligible though 

this may be somewhat fortuitous as the scatter 

remains comparable to that in the annual averages. 

t.813C(GASLAB-INSTAAR) = -0.004 ± 0.034%0 

(a3) The very good agreement in 818C is only achieved 

after all GASLAB analyses after April 28 , 1993, are 

corrected by -0.081 %0. At this time, the MT Box-C 

extraction line on the GASLAB MAT252 was 

modified to permit analysis of very small (ice core) 

air samples and operating parameters optimized. The 

capillary connecting the flask manifold to the 

cryogenic traps was by-passed (connected in parallel) 

with an "Automatic Pressure Flow Controller" (APC). 

Recent removal of the APC resulted in no change in 

calibration, and the step change in April 1993 is 

attributed to a change in mass spectrometer "idle 

time" which was increased from 12 to 20 seconds at 

that time (C. Flehoc et al., Systematic influences in 

the high precision stable isotope measurements of 

atmospheric trace gases, in preparation, 1995). The 

correction of -0.08 1 ± 0.010%o was obtained from 

least squares regressions to the data obtained from the 

most frequently analyzed of our air standards 

(AL VZ86 l) before and after the APC installation and 

idle time change, though slightly larger uncertainty is 

obtained by averaging the results from several other 

air standards in use around this time (C.E. Allison, 

private communication, 1993). The comparison here 

supports the magnitude of the standard-derived 

correction, and highlights the potential for significant 

differences in 813C to arise from apparently minor 

changes to routine. 

For 8180, the situation is less satisfactory. This reflects 

the fact that the CMDL flasks are filled without drying of 

the sample air and so are susceptible to oxygen exchange 

between C02 and trace water inside the flask. Isotopic 

composition of the trace water (i.e., past flask history) is 

likely to be an important influence [Gemery, 1993]. It also 

reflects the fact that the GASLAB APC correction is not 

yet well defined by independent analyses of GASLAB air 

standards. For 8t 8C, most air standards are relatively 

stable and extrapolation of results from several standards 

gives a consistent correction. This is not the case for 8180 

where drifts are a common feature in the GASLAB tanks, 

and in particular in the tank in most use around the time of 

the APC installation. The small sample size employed in 

GASLAB almost certainly emphasizes the difficulty. 

In Figure lb an "APC adjustment" was applied to the 

GASLAB measurements that maintains the relationship 

between the flask and in situ measurements and between 

the GASLAB and INSTAAR measurements on the flasks. 

This determines an effective 8180 APC correction for use 

in further study of the effect at GASLAB. The main 

features of Figure lb are: 

(b l) Despite several outliers, the flask data record features 

of the in situ 8180 record (in which the opportunity 

for oxygen exchange in flasks 1s considered 

negligible). 

(b2) The INSTAAR values arc, on average, significantly 

lower than the GASLAB numbers. Excluding 

INSTAAR values, and using only prc-APC GASLAB 

data, only 5 points arc available, for which: 

t.818Q(GASLAB-INSTAAR) = -0.443 ± 181 %0. 

Allison et al. [1994a] have postul ated that a slowly (1-

2 year) converging difference in 8180 between the 

new MAT252 and previous VG602D at GASLAB, was 

a readjustment of the isotopic content of trace water 

in the MAT252 instrument from closer to northern 

continental (depleted) to closer to southern ocean 

ambient water values. The present results are 

qualitatively in this sense, as is the sense of the 

outliers. The mean 8180 of precipitation at INSTAAR 

is about -89'00, very similar to the valu.:s fur Germany 

and UK, from where the various mass spectrometers 

originate. At Cape Grim latitudes around -4%o is 

observed [Yurtsever and Cat, 1981). and the 

assumption is that the VG602D, purchased in 1976, 

had equilibrated towards this value because of 

exposure to room air during maintenance, power 

failures, etc. The outliers, when appearing in the 

results from both laboratories, presumably reflect 

oxygen isotope exchange between C02 and trace 

water condensed within individual flasks [Gemery, 

1993]. Outliers in INSTAAR data alone could reflect 

exchange occurring during shipment of the flasks to 

Boulder. (b3) There is reasonable agreement in the 

temporal behavior between the majority of GASLAB 

flask samples and the in situ samples, and similarly 

between the GASLAB and INSTAAR measurements 

on individual flasks. This suggests that many of the 

CMDL flasks, despite the potential for contamination 

by water, are reflecting atmospheric values at Cape 

Grim. 

109 

CONCLUSIONS 

Considering the very preliminary state of 

intercalibration between the two laboratories, and the 

potential for systematic error in both the C02 ex traction 

and mass spectrometric isotope ratio determination, 

there is excellent agreem·ent in 8!3C measured on Cape 
Grim samples. The merging of data sets used by Ciais 

et al. (1994) for inversion studies is strongly supported 

by the data presented here. 

The confirmation of the large shift in the GASLAB 

flask ol3C compared to the in situ record and the CMDL 

flask results, accompanying relatively minor plumbing 

modification of the trapping box inlet, emphasizes the 

potential for serious interlaboratory discrepancies. The 

importance of calibrations using whole air standards, 

and redundancy in measurement and calibration 

strategies is obvious. 

It is also clear that much more work is required to 

achieve similar consistency and compatibility in the 

measurements of 01 so in C02, though there are quite 

encouraging sections of the intercomparison record. 

Acknowledgments. The staff of the Austral ia n Bureau of 

Meteorology/CSIRO Cape Grim Baseline Air Pollution Station 

are thanked for the conscientious sample collection. Pamela 

Gemery and Cyndi Brock are acknowledged at INSTAAR for 

their dedicated efforts in analyzing the CMDL fl asks, and 

Marco Lucarell i al GASLAB for engineering support. 

REFERENCES 

Allison, C.E., and R.J. Francey, High precmon stable isotope 

measurements of atmospheric trace gases, in Report to IA.EA . 

Consultant's Meeting on Stable Isotope Standards and 

lntercalibration, Vienna, Austria, December 1-3, 1993, International 

Atomic Energy Agency, Vienna, in press, 1994. 

Allison, C.E, R.J. Francey, R.L. Langenfelds, and E.D. Welch, 

Comparison of high precision Cape Grim CD2, stable isotope 

measurements using two mass spectrometers, in Baseline Atmospheric 

Program (Australia) 1991, edited by C. Dick and J.L. Gras, pp. 10-19, 

Bureau of Meteorology and CSIRO, Division of Atmospheric 

Research, Melbourne, Australia, 1994a. 

Allison, C.E., R.J. Francey, and H.A.J. Meijer, Recommendations for the 

reponing of stable isotope measurements of carbon and oxygen in 

C02 gas, in Report of I A .EA. Consultants' Meeting on Stable Isotope 

Standards and lntercalibration, Vienna, Austria, December 1-3, 1993, 

International Atomic Energy Agency, Vienna, in press, 1994b. 

Ciais, P., P. Tans, J.W. White, R. Francey, M .. Trolier, 1. Berry, D. 

Randall, P. Sellers, J. Collatz, and D. Schimmel, The global carbon 

budget inferred from a new worldwide data set of l)l3C measurements 

in atmospheric C02, J. Geophys. Res .. in press, 1995. 

Conway, T.J., P.P. Tans, L.S. Waterman, K. W. Thoning, D.R. Ki1iis, 

K.A. Masarie, and N. Zhang, Evidence for interannual variabili1y of 

the carbon cycle from the NOAA/CMDL global air sampling network, 

J. Geophys. Res., 99, 22,831-22,855, 1994. 

Craig, H., Isotopic standards for carbon and oxygen and correction 

factors for mass-spectrometric analysis of carbon dioxide, Geochim. 

Cosmochim. Acta., 12, 133-149, 1957. 

Enting, I.G., C.M. Trudinger, and R.J. Francey, A synthesis inversion of 

the concentration and 1)13C of atmospheric C02, Tellus, in press, 1994. 

Enting, l.G., C.M. Trudinger, R.J. Francey, and H.Granek, Synthesis 

inversion of atmospheric C02 using the GISS tracer transpon model, 

Div. Atmos. Res. Tech. Paper No. 29, 45 pp., CSIRO Melbourne, 

Australia, 1993. 

Farqhuar, G.D., J. Lloyd, J.A. Taylor, L.B. Flanagan, J.P. Syvensen, K.T. 

Hubick, S.Chin Wong and J.R. Ehleringer, Vegetation effects on the 

110 

isotope composition of oxygen in atmospheric C02, Nature, 363, 439-

443, 1993. 

Francey, R.J., and P.P.Tans, The latitudinal variation in oxygcn-18 of 

atmospheric C02, Natuu, 327, 495-497, 1987. 

Francey, R.J., F.J. Robbins, C.E.Allison, and N.G. Richards, The CSIRO 

global C02 isotope survey, in llaseline Atmospheric Program 

(Australia) 1988, edited by S.R. Wilson and G.P. Ayers, pp. 16-27, 

Bureau of Meteorology and CSIRO, Division of Atmospheric 

Research, Melbourne, Australia, 1990. 

Francey, R.J., P.P. Tans, C.E. Allison, l.G. Enting, J. White, and M. 

Trolier, Changes in the oceanic and terrestrial carbon uptake since 

1982, Nature, in press, 1995a. 

Francey, R.J., C. E. Allison, and E. D. Welch, The I I-year high precision 

in situ CD2, stable isotope reco~d from Cape Grim, 1982-1992, in 

Baseline Atmospheric Program (Australia) 1992, editc<l by C. Dick 

and P.J. Fraser, Bureau of Meteorology and CSIRO, Division of 

Atmospheric Research, Melbourne, Australia, in press, 1995b. 

Gemery, P.A., Investigation of the source of deviation in oxygen isotope 

measurements made on atmospheric carbon dioxide, Ph. D. thesis, 

University of Colorado, Boulder, 1993. 

Keeling, C.D., R.B. Bacastow, A.F. Caner, S.C. Piper, T.P. Whorf, ~!.. 

Heimann, W.G. Mook, and H. Roeloffzen, A three-dimensional model 

of atmospheric C02 transpon based on observed winds: I. Analysis 

of observational data, in Geophys. Monograph 55, Aspects of Climate 

Variability in the Pacific and the Western Americas, edited by David 

II. Peterson, pp. 165-236, American Geophysical Union, Washington, 

DC, 1989. 

Montzka, S.i\., J.W. Elkins, J.H. Butler, T.M. Thompson, W.T. S1urgcs, 

T.11. Swanson, R.C. Myers, T.:vt. Gilpin, T.J. Baring, S.0. Cummings, 

G.J\. Holcomb, J.M. Lobcrt, and 13.D. Hall, in Climate Monitoring and 

Diagnostics Laboratory Swnmary Report 1992, cdi1cd hy J.T. 

Peterson and R.M. Rosson, pp. 60-67, NOAA Environmcma l 

Research Laboratories, 13oulder, CO, 1993. 

Mook, W.G., and P.M. Grootes, The measuring procedure and 

corrections for the high-precision mass-spectrometric analysis of 

isotopic abundance ratios, especially referring 10 carbon, oxygen and 

ni1rogen, Int. J. Mass Spectrom. Ion Phys., 12, 273-298, 1973. 

Mook, W.M., and S. Van dcr Hoek, The N20 correction in the carbon 

and oxygen isotopic analysis of atmospheric C02, Isotope Geosci., I, 

237-242, 1983. 

Novelli, P.C., L.P. Steele, and P.P. Tans, Mixing ratios of carbon 

monoxide in the troposphere, J. Geophys. Res., 97, 20,731-20750, 

1992. 

Steele, L.P., P.J. Fraser, R.A. Rasmussen, M.A.K. Khalil, T.J. Conway, 

J\.J. Crawford, R.H. Gammon, K.A. Masaric, and K.W. 'llloning, "lhc 

global distribution of methane in the troposphere, J. Atmos. Chem., 5, 

125-171, 1987. 

Tans, P.P, R.J. Francey, and G.I. Pearman, Large Scale varia1ions in 1)180 

of Tropospheric C02, in llaseline Atmospheric Program (A 11stralin) 

1983-84, edited by R.J. Francey and 13.W. Forgan, pp. 10-14, l3urcau 

of Meteorology and CSIRO, Division of Atmospheric Research, 

Me lbourne, Australia, 1986. 

Tans, P.P., J.A Berry, and R.F. Keeling, Oceanic 13Cf12C observations: 

A new window on ocean C02 uptake, Global lliogeochem. Cycles, 7, 

353-368, 1993. 

Whorf, T.P., C.D. Keeling, and D.M. Wahlen, in Climate Monitoring and 

Diagnostics Laboratory Summary Report 1992, edited by J.T. 

Peterson and R.M. Rosson, pp. 119-122, NOAA Environmental 

Research Laboratories, Boulder, CO, 1993. 

Yurtsever, Y., and J.R. Gat, Atmospheric Waters, in Stable Isotope 

Hydrology: Deuteriwn and Oxygen in /he \Valer Cycle, /!\EA Tech. 

Rpt. Ser. No. 210, edited by J.R. Gal and R.Gonfian1ini, pp. 103-142, 

International Atomic Energy Agency, Vienna, 1981. 
Barrow, the Westernmost Magnetometer Site in the STEP Polar Network 

K. HAYASHI 

Department of Earth and Planetary Physics, The University of Tokyo, Tokyo 113, Japan 

Within a global network system, we conducted an 

international program, the Solar Terrestrial Energy Program (STEP) with two types of magnetometer, fluxgates 

and search-coil types, distributed through the polar 

region of the northern hemisphere . 

Both types of magnetometer detect variations in DC 

120° 60° 

180° 

240° 

and AC magnetic fields caused mostly by fluctu ation in 

the ionospheric currents and also by c hanges of 

magnetic fields in the magnetosphere. We placed both 

the fluxgate and search-coil magnetometers at 22 sites 

while eight sites had onl y search-coil magnetometers 

(Figure 1). 

August 1993 

00 

300° 

• Flu xgate and induction 

magnetiometers 

in operation 1993 

• Fluxgate and induction 

magnetometer, temporal 

Corrected Geomagnetic Coordinate, epoch 1990- 01 

6J Induction magnetometer (digital) 

GJ Induction magnetometer (analog) 

Fig. I. Magnetometers in the STEP polar network. 

The major objective of our network is to research 

magnetospheric disturbances in two-dimensional, dynamic 

nature mapped onto the ionosphere, especially in high-lime 

resolution . 

One search-coil magnetometer site operated courtesy of 

CMDL at Barrow, is situated at the key location of the 

westernmost location of our network station distribution. 

111 

The data acquisition at BRW started about 10 years ago and 

was intermittently activated . We plan to start a new data 

acquisition period at Barrow linked with the STEP program 

by the end of August 1994. A new datalogger capable of 

recording search-coil data of 10 Hz sampling rates 

continuously during a month will be shipped and installed 

before then. 
Total Nitrate Variation at Mauna Loa 

B.J. H UEBERT AND J.A. HEATH 

Department of Oceanography, University of Hawaii, Honolulu, Hawaii 96822 

INTRODUCTION 

Much of the NO and N02 emitted into the atmosphere 

is converted to nitric acid vapor or aerosol nitrate 

before being removed by dry or wet deposition. This 

conversion to nitrate is largely complete within a few 

days of the odd-nitrogen's emission; therefore in remote 

areas such as at the Mauna Loa Observatory, the total 

nitrate concentration (vapor plus aerosol) represents a 

fair estimate of the total odd-nitrogen concentration 

[Atlas el al., 1992]. 

With support from NSF, we have measured nitrate 

concentrations al MLO for several years to help identify 

the important sources of odd-nitrogen compounds in 

remote parts of the globe. We now measure total nitrate 

every night from the walkup tower in collaboration with 

the MLO staff. 

MATERIAL AND METHODS 

A Teflon/nylon filler pack method is used for collecting 

atmospheric nitrate. Since August 1988, one filter has been 

exposed each night, from 2000 LST to 0800 LST. Filters 

arc returned to the University of Hawaii for extraction and 

analy~ s by ion chromatography. 

The data from August 1991 to July 1992 was, 

unfortunately, treated somewhat differently from the 

remainder. These samples were all analyzed as a batch 

during a brief period between the return of our 

analytical laboratory from a field deployment in the 

Azores and its shipment to its new home at the 

University of Hawaii. Once it became apparent that this 

data looked very different from previous years, it was 

no longer possible lo replicate the analytical conditions 

or the standards to resolve questions of its validity. 

RESULTS AND DISCUSSION 

Lee el al., 1993 published a description of gradient 

measurements of nitric acid and aerosol nitrate at MLO. 

This work showed that surface-active species like nitric 

acid often have large gradients near the surface at MLO, 

raising the potential for underestimating free 

tropospheric concentrations due to depletion of material 

upstream of samplers. The deposition velocity of nitric 

acid to the lava surface varied from 0.3 to 4 cm s-1. 

During our intermittent MLO sampling prior to 

September of 1988, we observed a sharp maximum in 

nitric acid and aerosol nitrate concentrations in the 

summer. The search for an explanation for this 

maximum continues to stimulate our science. The daily 

total nitrate values for 1993 are plotted in Figure 1. 

The lowest sustained concentrations are still ev ident in 

the winter, with a mix of high-concentration events and 

cleaner periods in the spring and late summer. 

Figure 2 shows monthly averages of 2000 LST to 

0800 LST total nitrate concentrations from September 

of 1988 to May of 1994. The questionable data from 

1991 and 1992 (represented by smaller dots) is included 

for completeness, although we have serious questions 

abou t its validity. The 1993 data represent the lowest 

(defendable) concentrations we have observed during 

our sampling at MLO. They may represent a minimum, 

however, since early 1994 concentrations have returned 

to levels not seen since 1990. 

The concentration of total ni tra te al MLO is to a large 

extent controlled by precipitation scavenging of soluble 

material during transport from the continents [Lee el al., 

1994] so this interannual variability may be an indicator of 

changes in large-scale precipitation pauerns. The 

112 

250 ----------------------

200 

Fig. 1. Nightly concentrations of total nitrate in 1993. 

I.fauna Loa Ob~rva ory 300 ~---------~------, 

250 ~ 

~ 200 z 

Iii 150 

~ z 100 0. 

0. 50 

I t . 

I • 

T • • ~ • 

I • • I ~ • • • J'. • • ,. • 

. . • 

... 

I . 

• . .. .. ... .. . . / ....... L--~-----~"---~----

1988 1989 1990 1991 1992 1993 1994 1995 

Fig. 2. Monthl y average total (aerosol plus vapor) n itrate 

versus time . 
apparently-monotonic decrease in summertime total nitrate 

from 1988 through 1991 suggests that a cyclic process, 

such as the southern oscillation, may be reflected in this 

record. It is certainly reasonable that the transport of 

continental materials like mineral aerosol and fixed 

nitrogen (which can be limiting nutrients in certain parts of 

the Pacific) should be sensitive to changes in large-scale 

atmospheric circulation patterns. Clearly we need to 

identify the climatological differences that cause this 

dramatic change in the annual cycle of nitrate from one 

year to the next since they may have impacts on phenomena 

as diverse as marine biological productivity and the earth's 

radiation budget. 

ONGOING RESEARCH 

We are continuing our inclusive nightly sampling from 

the tower with the help of the MLO staff. Although 

equipment failures and analytical problems have 

occasionally caused lapses in the data, a very interesting 

record is emerging. We intend to continue this total nitrate 

data record in the hopes of identifying those factors that 

control the form and the range of its annual cycle. 

REFERENCES 

Atlas, E.L., B.A. Ridley, G. Huble r, M.A. Carroll, D.D. Montzka, 13. 

Huebert, R.B. Norton, J. Walega, F. Grahek, and S. Schaufflc r, 

Partitioning and budget of NOy species during MLOPEX, J. 

Geophys. Res., 97, 10,449-10,462, 1992. 

113 

Lee, G., L. Zhuang, B.J. Huebert, and T.P. Meyers, Concentration 

gradients and dry deposition of nitric acid vapor at Mauna Loa 

Observatory, Hawaii,]. Geophys. Res., 98, 12,661-12,671, 1993 . 

Lee, G., J.T. Merrill, and B.J. Huebert, Variation of free 

tropospheric total nitrate at Mauna Loa Observatory, Hawaii, J. 

Geophys. Res., 99, 12,821-12,831, 1994. 
Trends of CO at Hawaii: Seasonal Cycles and Decreasing Concentrations 

M.A.K. KHALIL AND R.A. RASMUSSEN 

Global Change Research Center and Department of Environmental Science and Engineering 

Oregon Gradua/e Institute, Portland, Oregon 97291 

INTRODUCTION 

The importance of carbon monoxide in global change 

science comes from its role in affecting, or perhaps 

controlling, the concentrations of tropospheric OH 

radicals. Tropospheric OH is the main oxidant in the 

vast non-urban atmosphere. Increases of CO, for 

instance, may trigger a decrease in the oxidizing 

capacity of the earth's atmosphere that could indirectly 

lead to global warming and stratospheric ozone 

depletion. That this would happen was indeed the 

current thinking since the concentrations of CO were 

observed to be increasing [Khalil and Rasmussen, 1985; 

Levine et al., 1985; see also Thompson and Cicerone, 

1986). Recent data, however, show that CO 

concentrations have now begun to decline, eliminating 

this potentially significant reinforcement of climatic 

change. 

This paper will discuss the data taken in Hawaii at 

two sites: Cape Kumukahi and Mauna Loa Observatory 

(21.08 ' N, 157.l'W) and, specifically, to evaluate the 

trends and seasonal cycles of CO at these sites. Both 

sites are located on the island of Hawaii. Mauna Loa is 

at an altitude of 3.4 km and Cape Kumukahi is nearby at 

sea level. The existence of two sites, so close to each 

other, provides a unique data set on the cycles and 

trends of trace gases in and above the boundary layer in 

the northern hemisphere tropics [see Khalil and 

Rasmussen, 1981). 

SAMPLING AND ANALYSIS 

Samples were collected in tripl icate using a pump, in 

0.8-L stainless-steel cans that are especially designed 

for the analysis of clean background air. The cans are 

internally passivated by a combination of processes that 

include eltropolishing. Each can is tested and certified 

before it is used in the field. Concentrations are stable 

for more than a year in these sampling containers [see 

Rasmussen and Khalil, 1980). 

The samples were analyzed by a Carle 211 MS 

GC/FID and Trace Analytical HgO GCJRGD. 

Measurements before 1984 were by GC/FID and 

afterward s by both instruments. The detection limits 

are 5 ppbv (RGD) and 20 ppbv (FID). Triplicates 

usually agree within 1-2%. If one is more than about 

20% different from the other two, it is eliminated (very 

few were discarded). The stability of the calibration 

standards is determined by periodic measurements. The 

11 4 

records show no significant drifts [Khalil and 

Rasmussen, 1994). 

CONCENTRATIONS, 

TRENDS 

SEASONAL CYCLES AND 

Concentrations: Table contains the seasonally 

averaged CO concentrations at the two sites (also shown 

in Figure 1). The most prominent feature of the record 

is the seasonal cycle (about 50-110 ppbv). This cycle is 

caused by three processes which , in the order of their 

importance, are the seasonal c hanges in the removal of 

CO by reaction with OH, seasonal changes in the 

emissions, and variations in transport. 

Seasonal Cycles. The seasonal cycle is the largest 

source of the variability of CO during the year. During 

the course of the experiment the av~age monthly 

conce.!!_lration of CO is calculated as: Ci = L. Ci/N. 

Here Ci is the average concentration in month i (1...12) 

and Cij is the average concentration in month i and year 

j (l, .. .,N). SincP the trends are much smaller than the 

cycles, this ca!...:ulation is an accurate representation of 

TABLE 1. The Seasonal Average Concentrations of CO, 

and Their Variabilities at Mauna Loa Observatory 

and Cape Kumukahi, Hawaii 

CO Concentrations (ppbv) Variability (ppbv) 

Month Cape MLO Cape MLO 

Kumukahi Kumukahi 

Jan. 98.2 ± 5.8 84 .0 ± 3.4 13.5 10. l 

Feb. 98.4 ± 6.0 96.5 ± 4.7 18.7 16.9 

March 105.7 ± 5.3 102.0 ± 2.7 10.6 17.2 

April 107.4 ± 5.3 104.7 ± 1.9 10.7 12.2 

May 94.2 ± 4.9 86.0 ± 3.5 10.6 12.1 

June 78.7 ± 5.2 69.0 ± 1.3 8.4 8.0 

July 60.0 ± 3.6 56.8 ± 2.0 6.3 7.3 

Aug. 53.6 ± 6.0 48.8 ± 1. 8 5.0 3.9 

Sept. 61.2±4.6 57.6 ± 1.6 6.2 7.0 

Oct. 68.0 ± 6.1 60.5 ± 1.5 6.3 8.1 

Nov. 73.6 ± 4.9 67.6 ± 19 8.0 14.3 

Dec. 86.0 ± 5.4 76.2 ± 3.2 14.8 10.5 

The ± values are 90% confidence limits of the mean 

concentrations. The last two columns show the variability in each 

month. It is defined as the average (over 12 years of data) of the 

monthly standard deviations. 
- 100 .. 

p 

~ "' 1 0 

0 

u 60 

40 ~-'-~~~~""'-~~~~~__,__~~-'-~~-'-~~-' 

lUO 1'12 1914 1916 UU 1990 1992 1994 

Time C..uoal) 

O C.X11m111tahl • Ma1111a Loa 0 

Fig. I. Seasonally-averaged concentration of CO (ppbv) at Mauna 

Loa and Cape Kumukahi over a 12-year period. Concentrations at 

Cape Kumukahi are higher than at Mauna Loa at an average 

difference of 5 ppbv. The most significant variability is the seasonal 

cycle that is similar at the two sites. 

the season al cycle (Table 2 and Fig ure 2a). In addition 

to the average cycle, the seasonal cycl e of the 

variab ility can also be calculated as: Sd1 = .E S;/N. 

where S;j is the standard devi a tion of the measurements 

in month i and year j. The results are shown in Figure 

2b. The cycle of variability is hig hly correl ated with 

the cycle of the con centration . In the w inter, the 

concentrations of CO are the highest and so is the 

TABLE 2. Seasonally-Averaged Concentations of 

CO (ppbv) at MLO and Cape Kumukahi From 1980- 1993 

Cape Cape 

Time Kumukahi MLO Time Kumukahi MLO 

1980 Fall 76 1987 Winter 100 84 

1981 Winter 86 87 Spring 107 100 

Spring 106 97 Summer 68 66 

Summer 67 50 Fall 71 67 

Fall 63 64 1988 Winter 93 93 

1982 Winter 106 99 Spring 108 100 

Spring 110 102 Summer 60 59 

Summer 56 Fall 68 66 

Fall 54 1989 Winter 87 86 

1983 Winter 92 Spring 96 93 

Spring I ll Summer 62 58 

Summer 60 Fall 66 62 

Fall 57 1990 Winter 98 82 

1984 Winter 83 Spring 86 88 

Spring 91 Summer 57 57 

Summer 59 Fall 67 62 

Fall 7 1 62 1991 Winter 84 74 

1985 Winter 95 86 Spring 98 88 

Spring 107 107 Summer 55 54 

Summer 70 62 Fall 48 52 

Fall 80 71 1992 Winter 95 89 

1986 Winter 93 84 Spring 104 96 

Spri ng 102 99 Summer 62 53 

Summer 69 66 Fall 58 59 

Fall 72 66 1993 Winter 99 78 

115 

120 

---- C.Kumukahi 

.-.. 

> Mauna Loa ~ 

Clo 100 ----- Clo ...., 

0 

;:; 

;... 

u 80 

Oi , 

, 

c , 0 Ii "' , 

"' , 4) 60 ... Cl.) ••• 

0 . , 

, . , u •• 

(a) 

40 

J F M A M J J A s 0 N D 

Time 

20 

--- C.Kumukahi 

. .-.. 1 6 . Mauna Loa • ----- > . ~ . Clo 

~ 

. . ~ ...., . ' . ' . 12 >- ' ... ' ' ' 

:0 ' ' 

"' ' 

-.: 

"' 

8 

::> 

0 

CJ 4 

(b) 

0 

J F M A M J J A s 0 N D 

Time 

Fig. 2 (a). The average seasonal concentration of CO at Cape 

Kumukahi and Mauna Loa. The concentration at Cape Kumukahi 

(in the boundary layer) is higher than at Mauna Loa (above the 

boundary layer). The difference is about the same throughout the 

year. This feature is also observed for other trace gases. (b). The 

seasonal cycle of the variability of CO. The variability is defined as 

the average standard deviation of the monthly concentrations over 

the 12-year period of the record. The variability follows a pattern 

similar to the concentration. When the concentration is low the 

variability is low. 

monthly variability. In the summer, the average 

concentrations and variability are the lowest. 

Trends: In Figure 3, the 3-year running averages of 

the monthly concentrations of CO are plotted. By 

filterin g the data over th is period, most of the effect of 

the seasonal variations of CO (Figure 1) and other 

random variability are eliminated. The running 
90 .. 

<> 

.. 

'" .. 

<> 86 C.Kumukahi > 

'" 

.. 

c 

c 82 c 

::> 

.. 

.. 

;.. 

I 78 .... 

....... 

> Maun a Loa .D 

Q, 74 Q, ....,, 

0 

u 

70 ~~~~~~~~~~~~~~~~~~~~~~ 

19 80 19 82 1 984 1986 1988 1990 

Ti mo 

Fig. 3. Three-year running averages of CO concentrations (ppbv) 

based on monthly average concentrations. These calculations show 

the long term trends in which the effects of seasonal cycles are 

eliminated. The graph s show that CO may have been increasing in 

the beginning of the record and has been declining during the last 6 

years or so al fairly rapid rates. 

averages are plotted in the middle of the time over 

which the average is taken. This figure suggests that 

CO was increasing between 1980-1985 and has 

decreased since then. Similar trends were observed at 

other sites around the world. The earlier global 

increases in CO and the recent decreases are reported by 

Khalil and Rasmussen [1984, 1988, 1994] and by 

Novelli et al. [1994]. 

By looking at the seasonal minima in Figure 1, it is 

apparent that the concentration of CO increased in the 

early part of the record and has been decreasing in 

recent times. The trends are estimated quantitatively as 

follows: First, annual averages of the seasonally 

averaged data were taken. The annual averages are not 

affected by the seasonal variation (on the average). 

Then, the trends were calcul ated as: 

Trend (i+o /2)=([C(i+8 )-C(i)] /[C(i)O ])xt00% 

where Trend (i) is the rate of change of concentration at 

time i + 0/2, C(i + o) is the annual average concentration at 

time i + 8, C(i) is the annual concentration at time i, c (i) 

is the average concentration for the years between i and i + 

8. 8 is taken to be 5 years for the calculation discussed 

here. These calculations are shown in Figure 4. The 

results show that CO was increasing at about 1 % yr-I in the 

early 1980s and has been decreasing in recent years at rates 

of -3% yr-1 or so. Similar declining trends are observed at 

other si tes around the world [Khalil and Rasmussen, 1994; 

Novelli et al., 1994]. 

2 

~ 

"' 

~ t•-- 0 

.. "' 

... 0 

"' - 1 

.. 

... 

~ -2 

; 

0 

() -3 

"' 

-· 1913 

Mauna Loa 

-.. __ 

191<4 t9 1S 

--· 

t 986 

T lmo 

1917 

-· 

19 81 1919 

Fig. 4. The trends of CO. The trends are ba sed on the annual 

averages of CO concentrations (see text). CO increased in the early 

part of the record and has declined in the recent 5 years. Both sites 

give the same results (note the trend at 1983 for Cape Kumukahi -

for 1984- 1986 there arc no data to calculate the trends at this site). 

116 

CONCLUSIONS 

Measurements of CO showed that between the 1950s 

and middle 1980s, the · concentrations of CO were 

increasing. This increase may have gone on for longer 

times [Khalil and Rasmussen, 1988 ; Rinsland et al., 

1985]. Since then, however, the conc entrations appear 

to be declining. Both of these observations arc in 

accord with our understanding of the sources and sinks 

of CO. Anthropogenic emissions have been increasing 

over the last 50 years. Major anthropogen ic sources 

include urban areas (with many sources such as 

automobiles) and biomass burning [see Logan et al., 

1981; WMO, 1986, 199 1; USEPA, 1990]. Emissions of 

other hydrocarbon s (including methane) may also have 

contributed to increasing trends. In recent years, 

however, the urban sources of CO in the United States 

and in Europe, have decreased rapidly because of air 

quality regulations. The decrease of CO in the southern 

hemisphere is most easily explained by a hypothesized 

decrease or a stabilization in tropical biomass burning. 

Whether biomass burning is decreasing awaits direct 

observational and statistical verifi cation. In addition to 

the decreasing emissions, there are various possibilities 

that may have caused an increase of OH at some 

latitudes that would also lead to a decrease in CO [sec 

M adronich and Granier, 1992]. All of these processes 

would lead to declining global concentrations of CO 

since it has a relatively short lifetime and responds 

quickly to changes in emissions or sinks. Yet at this 

time, it is impossible to say whether these declining 

trends will continue. It is c lear, however, that the 

current declining trend shows an improvement in global 

air quality. 
Acknowledgments. Samples were collected by CMDL 

staff at Mauna Loa Observatory and for some of the 

time at Cape Kumukahi. Samples were analyzed in the 

laboratory by Don Stearns and others. Sporadic 

financial support was provided by NSF and DOE 

(DEFG06-85ER60313) for measurements of sampling of 

specific gases. Additional funding was provided by the 

resources of the B iospherics Research Corporation and 

the Andarz Co. 

REFERENCES 

Khalil, M.A.K., and R.A. Rasmussen, Differences in the 

concentrations of trace gases in and above the tropical boundary 

layer, Pure Appl. Geophys., 119, 990-997, 1981. 

Khalil, M.A.K .. and R.A. Rasmussen, Carbon monoxide in the 

Earth's atmosphere: Increasing trend, Science, 224, 54-56, 1984. 

Khalil, M.A.K., and R.A. Rasmussen, Causes of increasing 

atmospheric methane: Depletion of hydroxyl radicals and the rise 

of emissions, Atmos. Environ. 19, 397-407, 1985. 

Khalil, M.A.K., and R.A. Rasmussen, Carbon monoxide in the 

earth's atmosphere: Indications of a global increase, Nature, 332, 

242-245, l 988. 

Khalil, M.A.K., and R.A. Rasmussen, Global decrease of 

atmospheric carbon monoxide, Nature, 370, 639-641, 1994. 

Levine, J.S., C.P.Rinsland and G.M.Tenille, The photochemistry of 

methane and carbon monoxide in the troposphere 1950 and 1985, 

Nature, 318, 254-257, 1985. 

Logan, J.A., M.J. Prather, S.C., Wofsy, and Yl.13.McElroy, 

Tropospheric chemistry: A global perspective, J. Gcophys. Res. 

86,7210-7254, 1981. 

Madronich, S., and C. Granier, Impact of recent total ozone changes 

on tropospheric ozone photodissociation, hydroxyl radicals and 

methane trends, Geophys. Res. Lei/. 19, 465-467, 1992. 

Novelli, P.C., K.A. Masarie, P.P. Tans, and P.M. Lang, Recent 

changes in atmospheric carbon monoxide, Science, 263, 1587-

1590, 1994. 

Pinto, J.P., and M.A.K. Khalil, The stability of tropospheric OH 

during ice ages, inter-glacial epochs and modern times, Tel/us, 

438, 347-352, 1991. 

Rasmussen, R.A., and M.A.K. Khalil, Atmospheric methane (Cl l4) : 

Trends and seasonal cycles, J. Geophys. Res .. 86, 9826-9832, 1981, 

Rasmussen, R. A., and M.A.K. Khalil, Atmospheric methane 

(CH4): Trends and seasonal cycles, Proceedings, NATO 

Advanced Study Institute on Atmospheric Ozone, edited by 

A.E. Aikin, Dept. Trans., Washington, DC., 1980. 

Rinsland, C.P. and J.S.Levine, Free tropospheric carbon monoxide 

in· 1950 and 1951 deduced from infrared total column amount 

measurements, Nature, 318, 250-254, 19 85 . 

Thompson, A.M. and R.J.Ciceronc, Possible perturbations of CO, 

CH4 and OH, J.Geophys. Res. 91, 10,853-10,864, 1986. 

USEPA (U.S. Environmental Protection Agency) Air Quality Criteria for 

Carbon Monoxide, EPA, 551 pp., Washington, D.C., 1990. 

117 

WMO (World Meteorological Organization), Scientific Assessment 

of Ozone Depletion:l991, 211 pp., WMO, Geneva, 1991. 

WMO (World Meteorological_ Organization), Almospheric Ozone 

1985, 1094 pp., WMO, Geneva, 1986). 
Radioactivity in the Surface Air at BRW, MLO, SMO, and SPO During 1993 

RICHARD J. LARSEN AND COLIN G. SANDERSON 

Environmental Measurements laboratory, U.S. Department of Energy, New York JOO 14-3621 

INTRODUCTION 

High-volume air filter samples arc routinely collected by 

CMDL pcrsormcl at BRW, MLO, SMO, and SPO for EML's 

Surface Air Sampling Program (SASP). The primary objective 

of this program is to identify and study the temporal and spatial 

distribution of specific anthropogenic and natural radionuclidcs 

in the lower troposphere. The naturally occurring radionuclidcs 7Be and 210Pb arc of particular interest since they 

serve as excellent tracers for air masses of upper and lower 

tropospheric origin. Beryllium-7 (f1ri = 53.2 d) is produced by 

cosmic-ray interactions in the upper troposphere and the 

stratosphere, and 210Pb (f 1ri = 22.3 years) is a decay product of 

222Rn, a noble gas that diffuses from soils. 

MATERIAL AND METHODS 

Weekly air filter samples are continuously collected using 

Dynawcb filter material. The air samplers move -1700 m3 of 

air per day tl1rough a 20.3-cm diameter filter. The weekly 

filter samples collected at BRW and MLO are analyzed by 

gamma-ray spectrometry using a high-purity germanium 

(HPGc) detector with a 1.5-cm diameter well. The individual 

weekly samples from SMO and SPO are not routinely 

analyzed. Monthly composite samples for each site are formed 

by adding together one half of each of the weekly filter 

samples. These monthly composite samples arc compressed 

into 45-cm3 plastic planchets and are routinely analyzed for 

several gamma-ray emitting radionuclidcs using either n-typc 

low-energy coaxial, HPGe detectors or p-type coaxial 

high-resolution, germanium lithium or HPGe detectors. 

Detailed information on SASP is periodically published 

[Larsen and.Sanderson, 1991]. 

RESULTS 

The results of the analyses of several radionuclides and the 

total gamma-ray activities for the monthly composite samples 

from filters collected at BRW, MLO, SMO, and SPO during 

1993 arc reported in Table 1. The total gamma-ray activities 

are reported in units of counts per minute (cpm) per cubic 

meter of sampled air referenced to 15°C and 1 Atm. The 

surface air concentrations of 7Bc and 210Pb arc reported in 

millibecquerels (mBq) per standard cubic meter of air, and 

95Zr, 137Cs, and 144Ce are reported in microbccquerels (μBq) 

per cubic meter of air referenced to 15°C and I Atm. TI1c 

concentrations are reported as corrected for radioactive decay 

to tht: midpoint of the month of collection. Unforrunatcly, the 

bulk of the air filter samples collected at SPO during I 993 have 

been "lost" during transit to EML. 

Table 1. Monthly Surface Air Concentrations of Radionuclides at BRW, MLO, SMO, and SPO during 1993 

Site Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. 

Nuclide: Gamma (cpm m"3

) 

BRW <0.01 <0.0 1 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.0 1 <0.0 1 <0.0 1 <0.01 

MLO <0.01 <0.0 1 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.0 1 <0.01 

SMO <0.0 1 <0.0 1 <0.01 <0.01 <0.01 <0.01 • <0.01 <0.01 <0.01 <0.0 1 <0.01 

SPO <0.01 • • • • • • • • <0.0 1 

Nuclide: 7Bc (mBq m"3

) 

BRW 1.4 1.4 1.6 2.3 1.8 0.6 o.s• 0.5 0.9 1.6 1.7 2.5 

MLO 4.7 8.0 7.5 7.1 7.2 7.1 7.0 5.5 5.0 6.0 7.2 7.0 

SMO 1.3 2.2 1.3 0.8 2.0 2.5 • 2.5 n 3.7 2.5 2.0 

SPO 6.8 • • • • • • • • • 5.9 

Nuclide: 95Zr (mBq m"3

) 

BRW <6.2 <3.3 <4.4 <I.I <37. <5.1 <29. <3.6 <5.1 <7.3 <5.7 <13. 

MLO <5.4 <8.9 <12. <6.9 <12. <2.5 <45. <19. <14. <2.7 <11. <14. 

SMO <7.6 <6.5 <7.7 <9.3 <20. <14. • <4.6 <5.7 <4.8 <4.9 <4.7 

SPO <30. • • • • • • • • • <11. 

118 
Table 1. Monthly Surface Air Concentrations of Radionuclides at BRW, MLO, SMO, and SPO during 1993---Continued 

Site Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec. 

Nuclide: 137Cs (mBq m"

3

) 

13RW <1.3 <0.9 <1.1 0.9a <1.9 <0.5 <0.6 <0.7 <I. I <2.0 <0.6 <1.7 

Y!LO <1.2 <2.1 <2.0 <2.0 <1.4 <0.8 <4.1 <3.4 <2.5 <0.8 <3.1 <3.6 

s~o <2.2 <2.3 <1.4 <1.6 <1.3 <1.6 <0.9 <1.3 <1.2 <1.6 <1.8 

SPO <1.2 • • • • • • • <2.0 

Nuclide: 144Ce (mBq m'

3

) 

13RW <5.5 <3.3 <4.6 <2.1 <11. <2.1 <3.6 <2.5 <4.5 <9.0 <3.0 <9.2 

MLO <5.3 <9.9 <8.0 <8.1 <6.7 <3.4 <18. <18. <12. <3.1 <13. <18. 

SMO <9.3 <11. <6.5 <6.9 <7.2 <8.2 • <3.9 <5.4 <5.8 <6.6 <7.6 

SPO <5.8 • • • • • • • • <9.4 • 

Nuclide: 210Pb (mBq m"

3

) 

13RW 0.78 0.80 0.67 

MLO 0. 17' 0.31 0.49 

SMO 0.03' 0.05• 0.02b 

sro 0.03' .. .. 

•No data 

Uncertainty is< 20% except: 

~Uncertainty is between 20% and 50% 

Uncertainty is between 50% and 100% 

cUncertainty is> 100% 

DISSCUSSION 

0.38 0.26 

0.54 0.43 

0.02b 0.05• 

.. 

During 1993 the re was one reported significant release of 

anthropogenic radionuclides into the atmosphere. On April 6, 

1993, radioactivity was accidentally released into the 

atmosphere during an explosion and fire at a reprocess-ing 

plant in the Tomsk-7 military nuclear complex located 16 km 

north of the Siberian city of Tomsk. Details about the release 

of nuclear materials from this accident and the atmospheric 

transport and detection of the debris have been previously 

reported [Lee et al., 1993; Larsen et al., 1994]. We suggest 

that the detection of 137Cs at BRW during April (see Table I) 

represents traces of the Tomsk-7 debris released during this 

accident [Larsen et al., 1994]. 

The seasonal cycles of 7Be and 210Pb continue to follow 

those observed in previous years [Feely et al., 1989; Larsen 

and Feely, 1986]. 

/\cknowledgment. We wish to thank the CMDL staff at BRW, MLO, 

SMO, and SPO for the collection of air filter samples for SASP. 

0.05 0.1 1 0.06 0.09 0.23 0.35 0.59 

0.49 0.27" 0.1 8 0.23 0.26 0.22 0.2 1 

0.04" 0.05c 0.09 0.08 o.os 0.05 .. 

119 

0.03° 

REFERENCES 

Feely, H.W., R.J. Larsen and C.G. Sanderson, Factors that cause seasonal 

variations in Beryllium-? concentrations in surface air, J. Environ. 

Radioact., 9, 223-249 (1989). 

Larsen, R. J. and H. W. Feely, Seasonal variations of 2t0Pb and 7fk at 

Mauna Loa and Barrow, in Geophysical Monitoring for Climatic 

Change, No. 14, Summary Report 1985, edited by R.C. Schnell and 

R.M. Rosson, pp. 127-130, NOAA Environmental Research 

Laboratories, 13oulder, Colorado, 1986. 

Larsen, R. J. and C. G. Sanderson , E:>.1L surface air sampling progrJ111, 

1989 data, U.S. DOE Report EML-541 (available from :\TIS, 

Springfield, VA) 1991. 

Larsen, R. J., C. G. Sanderson, 11. :-./. Lee, K. :>.!. Decker and 11. L. Beck, 

Fission products detected in Alaska following the Tomsk-7 accident, 

J . Environ. Radioactivity, Letter 10 Editor, 23. 1994. 

Lee, II. N., R. J. Larsen and C. G. Sanderson, Tomsk-7 debris at UR\V: 

detection and transport, in Climate Monitoring and Diagnostir.s 

Laboratory No. 21 Summary Report 1992, edited by J.T. Peterson and 

R.M. Rosson, pp. I 02- 103, NOAA Environmental Research 

Laboratories, Boulder, CO, 1993. 
Exposure Experiment, South Pole 

J.E. MAK 

Lawrence Livermore Na tional Laboratory, Livermore, California 94551 -9900 

C.A.M. BRENNINKMEIJER 

Max Planck /n stitut fur Chemie, Mainz, Germany 

J.R. SOUTIION 

Cente r for Acee/era/or Mass Speclrom etry , La wre nce Li ve rmore National Laboratory, Livermore, Ca lifo rn ia 94551-9900 

The scope of this project is 10 directly detect and 

quantify the production rate of atmospheric 14C. Carbon14 is not only used for dating organic materials, it can also 

be used as a tracer of OH chemistry (in the form of 14CO). 

In the latter case, if the inventory of l4CO is measured and 

the production rate known, then the sink rate , which is 

oxidation by OH, can be calculated. Allhough cascade 

calcul ations have constrained the 14CO production rate to 

±20%, it is of interest to measure this rate directly. 

14CO is produced from the reaction: 

14N + n ~ 14C + p 

which is immed iately followed by 

14C + 0 2 14 O + 0 (>90% yield). 

The methodology takes advantage of gas handling 

techniques previously developed by these authors. A 

known amount of CO carrier gas was mi xed in with zero 

air and compressed into a suite of cylinders, some of 

which were placed 1 m above the surface at SPO. There 

they sat, exposed to incoming cosmic rays. The 

cylinders were removed about 11 months later and 

brought back to the isotope laboratory in New Zealand 

where the CO was extracted and measured for 14C 

content at Lawrence Livermore's Center for Accelerator 

Mass Spectrometry. During the same period, cylinders 

were exposed at Scott Base, on Mount Cook, New 

Zealand , and at various heights on the Boulder 

Atmospheric Observatory tower in Colorado. The latter 

was 10 constrain the surface effect that is known 10 

c ause an increase in the thermal neutron flux for a 

distance of about 150 m. 

Monte Carlo simulations arc currently being 

120 

performed at LLNL to estimate any effects from the 

mass of the cylinders used as well as the ground effect. 

These simulation s indicate tha t the effect from the 

cylinders is small. The experimental results arc st ill 

being analyzed, and preliminary analyses s how tha t the 

amounts of 14C produced at the South Pole would be 

easil y delectable for an exposure ti me of about 6 

months. To our knowledge, this is the second time 

direct 14C detection was achieved and the firs! time a 

ground effect was accounted for by direct measurement. 

This is an ongoing cooperative project. 
Correlations in Short-Term Variations in Atmospheric 

Oxygen and Carbon Dioxide at Mauna Loa Observatory 

ANDREW C. MANNING Ai\D RALPH F. KEELING 

Scripps Institution of Oceanography, UCSD, la Jolla, California 92093-0236 

Since J anuary 1991, SIO has measured atmospheric 0 2 and 

C02 from flask samples collected by station personnel al MLO 

at roughly 2-week intervals. Samples were collected in 

triplicate in 5-L glass flasks, which were flushed overnight and 

closed off the next day, then shipped back to La Joll a where 

they were analysed for 02 and C02 concentrations. The results 

of this program, from J anuary 1991 through to the end of 1993, 

are shown in Figure 1. 

Keeling and Shertz (1992] and Keeling et al. (1993) have 

discussed various aspects of these 0 2/N2 and C02 data, 

including reasons for the observed seasonal cycles in both C02 

and 02/N2; the larger seasonal amplitude in OiJN2 than C02; 

.. 

E " 

.. 

<J 

0. 

N 

7. 

....... N 

0 

'O 

> 

E 

0. 

0. 

- •o l •o 

- 10 0 L 

..14 0 I - 1&0 

- 1110 

2 01') ~ 

-»• I :'!IHI f 

3 1\4 ~ 

300 

3 .. ~ ~ 

3~2 ,,,, 

~ 

- .. 

f l l'l!llk 0 1\lft 

CMDL cot Dote 

filled Curvf' 5 

;:---..::·~~· ,.;,: .. ,·., • • J l ·.· ·. ·1 . 

l 

N :H S\.. 0 

u ,. , . I 

o .. .-..i. .... ....__... __ .. ···--~~ ~---4 ~- .......... ~~ ....... _ ....... I '"" • rr J·1I ('rt J,,n ._r , Jul nrt Jan •rt J,11 O· I ' "'" Apr Jul Utt Ja to • 1·r I ol 1 Ja ,.. 

l !lO!l l!J90 l!l!ll t9!J2 l'l!l:I 

f-ig. 1. Measurements of d(020.li) and C02 from air samples 

collected at ~fauna Loa. 0 2 concentration changes are reported as 

changes in the 0 2/N2 ratio of the air sample. We report this ratio 

relative to a reference as: 

li(Oi/Ni)=( (02/Ni)sampte -t)• 

(02 / N 2)refereoce 

and multiply this by 1 Q6 and express the result in units of "per 

mcg". In these units, 4.8 per meg is equivalent to 1 ppmV. Flask 

concentrations for a given date (usually three flasks per date) were 

3veragcd resulting in a single concentration for each sample date. 

The scale of the axes were adjusted in such a way that visually, 

differences in C02 can be directly compared with differences in 02 

on a mole fraction basis. For C02, supplementary data from C.YIDL 

fla sks arc shown going back to 1989, with some overlap when the 

sampling program first began. The curves shown (from which all 

residuals arc calculated) were calculated with a least-squares fit to a 

function of two harmonics (annual and semi-annual periodicity) and 

a stiff Reinsch spline. 

121 

the interannual decrease in OifN2; and the resultant 

implications of these phenomena to the global carbon cycle. In 

1992, after slightly more than 1 year of data had been 

collected, Keeling and Shertz (1991 ] pointed out that there 

appeared to be greater relative short-term variability in 0 2/N2 

at MLO than at other sites, but were unsure of the cause. This 

paper will try to establish whet.her the residuals of the llask 

data from the smooth curves fitted through the data are due to 

experimental artifacts or real atmospheric variability; that is, 

whether there is some problem with the sampling procedure 

used to collect the air samples at MLO or whether there arc one 

or more natural processes affecting the air at :-.lLO, and in a 

mariner not seen at other SIO stations. 

The sampling procedure al MLO is slightly different from 

lhal at our other sites. Because samples arc collected at an 

altitude of about 3400 m, a back pressure regulator is used to 

ensure that our flask samples are pressurized to 760 torr, 

consistent with samples collected al our sea-level sites. Despite 

this procedural difference, however, we have found evidence to 

suggest that a significant fraction of the short-term variability 

in 0 2/N2 at MLO is due to real atmospheric variability . 

This evidence comes from looking at short-tem1 covariations 

in OiJN2 and C02. As a measure of short-term variability, we 

have computed the residuals in 02/N2 and C02 relative to 

smooth curves through the data. The curves consist of a 

two-harmonic fit to account for seasonality and a stiff, Rcimc/1 

(1967] spline to account for intcrannual variations. A 

correlation plot of these residuals is shown in Figure 2, and 

although there is some scatter, a clear negative corrcl:nion can 

be seen. Statistically speaking, the linear least-squares fit line 

shown gives an r2 value of 0.37; thus a minimum of 37% of the 

variance in the 0 2/N2 residuals can be explained by the 

variance in the C02 residuals. TI1c probability of these data 

being a random collec tion of points, and still resulting in an r2 

of 0.37, is less than 0.00 l. 

This statistically significant correlation between 0 2/N2 and 

C02 could e ither be caused by real atmospheric variations in 

OifN2 and C02, or by systematic flask sampling problems 

which are influencing both 02/N2 and C02 simultaneously. 

This latter possibility can be eliminated by a comparison of our 

C02 data with concurrent data measured by a continuous 

infrared C02 analyzer al MLO operated by C.D. Kccling's 

group. We calculated residuals of the steady C02 data 

obtained from that instrument relative 10 the same smooth 

curves that are fitted to our C02 data and correlated those 

residuals with our own C02 residuals. This correlation resulted 

in an r2 value of 0.78, showing that almost 80% of the 

variability in our C02 data was also seen in the C.D. Keeling 

data, hence suggesting that most of the short-tern\ variability in 

our C02 data is due to real atmospheric variations. 
20 

I 5 

• 

- 1 0 -0.5 . 

.--- • Dec - Ma r flask data 

• All other months 

- least-squares fil 

0 5 1.0 

C02 residuals/ ppmV 

r'ig . 2 . C02 and 0 2/N2 residuals of the fla sk data from the smooth 

curves of Figure I arc shown plotted against each oth er. Samples 

were included only if they were collected durin g a period of stead y 

C0 2 concentration, as defi ned by C.D. Keeling's group using their 

continuous C02 analyzer at MLO; as a result only 37 sampling 

dates, from an original 59, were used. A clea r negative correlation 

can be seen. 

Additionally, a correlation of our OifN2 data with C.D. 

Keeping 's C02 data produced an r2 value of 0.36. This is 

almost identical to the correlation with our own C02 data that 

had the advantage of being taken from the same flask samples 

as the 0 2/N2 data. 

Having shown that a significant fraction of the short-term 

variability in 0 2/N2 and C02 at MLO is due to atmospheric 

changes, we now ask the question: what may be causing these 

background variations? Heimann et al. [section 5.5, 1989) 

have shown that a significant fraction of the C02 variability at 

MLO is related to changing synoptic weather patterns in the 

area. Particularly important may be variations in north-south 

transport, since for much of the year, due to both seasonal and 

anthropogenic differences, air masses to the north of MLO 

have large differences in 0 2/N2 and C02 concentrations 

relative to air masses to the south. Keeling, et al. [section 2, 

1989) have also shown that the zonal mean C02 concentration 

122 

at the latitude of MLO is almost identical to the actual C02 

concentration measured at MLO, hence further suggesting that 

longitudinal variations are not as important as north-south 

variations. Although there is no direct measurement of these 

north-south gradients at MLO, their magnitude can be 

estimated based on the differences in OiJN2 and C02 that exist 

between midlatitude sites in each hemisphere; La Jolla, 

California, at 32.9"N, and Cape Grim, Tasmania, at 40.7"S. 

Curves for these sites are shown in Figure 3 . 

If variations in north-south transport are in fact causing the 

short-term variability at MLO, then we would expect the ratio 

of the instantaneous OifN2 and C02 gradients (shown in Figure 

3) to be roughly equal to tJ1e ratio of the short-tcm1 

covariations in OifN2 and C02. In other words, we would 

expect the ratio of the two vertical lines shown in Figure 3 lO 

be roughly equal to the slope of the envelope of the flask 

residuals shown in Figure 2, for the san1c time period. In the 

period from December through March, when the ratio of the 

north-south gradient is at its most stable, the average absolute 

value of this north-south 02/N2 versus C02 ratio is 15 ± 3 per 

meg ppmV·l, while a least squares fit to the flask residuals 

over this period results in a slope of 17 ± 4 per mcg ppm V· l. 

This agreement suggests that the north-south transport may 

indeed be implicated as a source of variability at MLO. 

However, this analysis is hardly conclusive because we have 

only 3 years worth of data to work with, and we arc close to the 

level of our experimental uncertainty. Also , the rapid seasonal 

variations in the interhemispheric gradient complicates the 

analysis. 

N 

7. 

'-N 

0 

-0 

> 

E 

0. 

a. 

o"' 

u 

14!0 

140 

- UJO 

- 160 

- 200 t - 220 

, .. 

,., 

JOO 

,.. 

J 02 

,.. 

"' J<O 

· · Le Jolla (32 g•N) Filled Curves 

-- Cllipe Crim ('4. 0 7•S ) rilled Curves 

ln1erhemupher1c C02 1red1en \ 

. / . _.- .. ·J' .-- " •, ' ' ' I \ I 

·~- ,, ,, 

Ja n Apr Joi Or i J111 &pr Jul Ori Jan Apr Jul Ort J. n Av• Jul Ou Jan Apt h1I nc1 J. 11 

19 fl9 1990 199 1 1Hll2 199:1 

Fig 3. Seasonal patterns of 0 2/N2 and C02 as observed al La Jolla, 

Califo rn ia , and Cape Grim, Ta smania, Australia. The curves " 'e fits 

to fl ask data (not shown) sim ilar lo tho se shown in r'igure I for 

MLO, except that the seasonality is represented here by four 

harmonics instead of two. The difference between 0 2/N2, and C02 

concentrations at these two sites can be taken as a measure of th e 

interhemispheri c gradient between the midd le latitudes in th e 

northern and southern hemispheres. The vertical lines show 

examples of the north-south gradient in 0 2/N2 in the top plot, and 

C02 in the bottom plot. These gradients change rapidly with time, 

due to opposing seasonal changes in the two hemispheres. 
In conclusion, we have shown that a significant fraction of 

the short-term variability in our C02 and OJJN2 data at MLO 

can be explained by real atmospheric variability rather than by 

artifacts of our flask sampling procedure or analysis. We have 

suggested that this variability may be related to seasonal 

north-south concentration gradients that exist in the tropics as a 

result of opposing seasonal variations at middle latitudes in 

either hemisphere and have given statistical evidence to 

support this. If we are correct, we would expect to see high 

variability at other tropical sites as well. We have recently 

started collecting flask samples at two additional tropical sites 

supported by NOAA personnel, one at Cape Kumukahi, also in 

Hawaii, but at sea level, and another in American Samoa, at a 

latitude of 14.3'S. The Cape Kurnukahi site should help to 

eliminate the parameter of variable altitude, which can have an 

effect on results obtained, as shown for C02 in Keeling et al., 

[section 2, 1989]. These new sites, along with the continuing 

MLO data should, over time, help to clarify the interpretations 

put forward in this paper. 

REFERENCES 

Heimann, M., C.D. Keeling, C.J. Tucker, A three dimensional 

model of atmospheric C02 transpo rt based on observed winds: 

3. Seasonal cycle and synoptic time scale variations, in in the 

Pacific and the Western Americas, edited by D.1-1. Peterson, 

pp. 277-303. American Geophysical Un ion, Washington, DC, 

1989. 

Keeling, C.D., S.C. Piper, and M. Heimann, A three dimensional 

model of atmospheric C02 transport based on observed winds: 

4. Mean annua l gradients and interannual va riations, in 

Geophysical Monograph 55, Aspects of Climate Variability 

in the Pacific and the Western Americas, edited by D.H. 

Peterson, pp. 305-363, American Geophysical Union, 

Washington, DC, 1989. 

Keeling, R.F., and S .R. Shertz, Va riations in atmospheric 

molecular oxygen at Mauna Loa, in Climate Monitoring and 

Diagnostics laboratory, No. 20, Summary Report 1991, 

edited by E.F. ferguson and R.M. Rosson, pp. 103-104, NOAA 

Environmental Research Laboratories, nouldcr. CO, 1992. 

Keeling, R.F., and S.R. Shcrtz, Seasonal and intcrannual 

variations in atmospheric oxygen and implications for the 

global carbon cycle, Nature, 358, 723 , 1992. 

Keeling, R.F., R.P. Najjar, M.L. Bender, and P.P. Tans, What 

atmospheric oxygen measurements can tell us about the global 

carbon cycle, Global Biogeochem. Cycles, 7, 37-67, 1993. 

Reinsch, C.H., Smoothing by spline functions, Numer. Math., JO, 

177 -183, 1967. 

123 

York, D., Least squares fitting of a straight line, Can . J. Phys .. 

44, 1079, 1966. 
Artificial Windshielding of Precipitation Gauges in the Arctic 

RICHARD J. MCCLURE 

Soil Conservation Service, Anchorage, Alaska 99508-4362 

INTRODUCTION 

Precipitation gauges c an provide good measurements 

of the wa ter equ ivalent of snow precipitation, provided 

the gauge is protected or shielded from wind effects. 

Unfortunately, there are no standard.s for collecting 

snow precipitation. Gauges located in exposed and 

windy areas may be totally unshielded, partially 

shielded by one or more buildings, or equipped with one 

of several types of artificial shields. The various 

shielding options in common use, therefore, produce a 

wide range of gauge catch e ffi c iency. Also, the various 

studies of artificial shi elds in the United States and 

Canada have produced a wide r ange of results. This 

must be, in part, due to the wide range of weather 

conditions under which the various studies have been 

conducted. A lingering problem is applying the results 

to the local conditions of Alaska's tundra regions. 

METHODS 

A study of the windshield alternatives, under th e 

unique conditions of Al aska's Arctic coastal region. was 

set up at the CMDL facil ity at Barrow during September 

1989. Snowfall catches from four newly installed 

precipitation storage gauges were compared with that 

from an existing storage gauge protected by a Wyoming 

shield (l/anson, 1988]. Two of the new gauges were 

shielded-one with a Nipher shield [Goodison et al., 

1983] and the other with an Aller shield [Alter, 

1937]-and two were unshielded. One of the 

unshi elded gauges was serviced on an event basis, the 

same as the three shielded gauges. The other 

unshielded gauge was treated as if it were a remote 

gauge, allowing rime to build up and dissipate n atur ally 

to see what effects rime had on the overall catch. The 

four newly installed gauges are 20.3 cm in diameter x 

100 cm tall, mounted with the orifice 2 m above the 

normal ground surface. The existing Wyoming-sh ielded 

gauge is 30.5 cm in diameter x 2-m tall and is equipped 

with a Leupold-Stevens water-level recorder. 

RESULT S 

The 1992-1993 winter season total prec1p1tation 1s 

available for comparison of the 5 gauges. Th e results 

for the period October 2, 1992 through May 6, 1993 are 

as follows: The Wyoming -sh ielded gauge caught a total 

of 105.7 mm of snowfall precipitation during the 

period. The Nipher-shielded gauge caught 100.8 mm or 

95% of the Wyoming-shielded gauge. Th e Altershielded gauge caught 38.1 mm or 36% of the 

Wyoming-shielded gauge. The unshielded but serviced 

gauge caught 19.3 mm or 18% of the Wyoming-shielded 

gauge. The unshielded and non-serviced gauge caught 

14.2 mm or 13% of the Wyoming-shielded gauge. The 

results continue to confirm the Aller-shielded and 

uns hielded gauges catch one-third or less of the catch of 

the Wyoming-shielded and Nipher-shi eldcd precipitation gauges. 

Acknowledgment. Apprecia1ion is expressed lo D. Endres. 

Station Chief, Barro w, Alaska, who serv iced 1hc prccipi1:11ion 

gauges and collected the snow samples. 

R EFEREl'iCES 

124 

Alter, S.C., Shield storage precipita1ion gauges, Mon, Weather 

Rev., 65, 262-265, 1937. 

Goodison, B.E., V.R. Turner, and J.E. l\lctcalfe, A niphe r-t ype 

shield for recording p recipitation gauges, l'rocecdings, 5th 

Symposium on Meteorological Observations and /nstru. 

mentation, Toronto , Ontario, Canada, pp. 2-126, American 

Meteorological Society, Boston, 1983. 

Hanson, C.L., Precipitation measured by gauges protected by 

the Wyoming shield and the dual-gauge system, l'roceedings, 

56th Western Snow Conference, Kalispell, l\lontana, pp . 17~· 

177, Colorado State Un ive rsity, Fort Collins, CO, 1988. 
Lidar Measurements of Stratospheric Ozone, Temperature, and Aerosol 

Profiles at Mauna Loa 

I. STUART MCDERMID, MARTHA SCHMOE, ERIC W. SIRKO, AND T. D ANIEL W ALS H 

Jet Propulsion Laboratory, California Institute of Technology , Table Mountain Facility, \Vrightwood, California 92397.0367 

1. I NTRO DUCTION 

Mauna Loa Observatory (MLO) has been designated 

as a primary site within the Network for the Detection 

of Strato spheric Change (NDSC) and as such, wi ll 

eventually host a complement of instruments for 

stratospheric observations. JPL has developed and 

operated a lidar system for NDSC to measure 

stratospheric profiles of ozone, tempera ture, and 

aerosols at its Table Mountain Facility (TMF) in 

southern Cal ifornia [McDermid et al., 1990a, 1991 ]. 

The TMF lidar has been in continuous operation since 

1988 and has undergone extensive testing and validation 

[McDermid et al., 1990b, c,d] . Based on the success of 

the TMF lidar a new, and somewhat improved, system 

was constructed for deployment at MLO. This new 

lidar is housed in a transportable facility and was built 

and tested at TMF before being moved intact to MLO in 

June 1993 in advance of the new NDSC facili ty being 

completed there. 

2 . INSTRUMENT ATION 

The new lidar is substantially similar to that at TMF 

and has been full y described elsewhere [McDermid et 

al., 1990a, 1991]. The major improvements for the 

MLO lidar are the addit ion of Raman receiver channels 

at 332 nm and 385 nm [McGee et al., 1993]. and an 

optical chopper to reduce signal-induced-noise. The 

Raman channels are used to obtain ozone and 

temperature profiles in regions of aerosol layers, a 

measurement that was not possible with the TMF 

implementation. The aerosol backscatter ratio profi le is 

also obtained from comparison of the lidar returns at 

353 nm and 385 nm, thus e liminating the need for a 

reference atmospheric density profile. 

3. RESULTS 

The lidar measurements are made at night as the 

cloud conditions permit. Typically measurements were 

obtained about three nights per week. The incidence of 

high altitude cirrus clouds is a limiting factor in the 

total number of measurements that can be achieved. 

3.1. OZONE 

Three separate ozone profi Jes are generated from the 

high intensity Rayleigh/M ie DIAL pair, low intensity 

Rayleigh/Mic pair, and Raman pair. These profiles are 

then combined , taking into account the location of 

aerosol layers and the rel ative errors for each profile, to 

make a single ozone profile that can extend from about 

15 km to 60 km altitude. An example is shown in 

Figure 1. The error bars at the bottom of the profile 

are relatively l arge because this region is obtained from 

the Raman pair that has the weakest signal but is not 

affected by the aerosol layers. 

3.2. T EMPERATURE 

Temperature profiles are obtained in the same manner 

as with the TMF lidar except that add itional information 

is available using the 385 nm Raman channe l. This data 

can be used to extend the temperature profile 

downwards to almost 20 km alt itude. As for the ozone 

profile, the error bars from the Raman data arc 

relatively large but temperature profile information is 

obtained in a region where it was not previously 

possible from lidar measurements. Figure 2 shows an 

example of a temperature profile obtained with the 

MLO lidar. 

3.3. AEROSO LS 

The Raman-channel data at 385 nm provides a 

measure of the atmospheric relative density profile . 

45 

4-0 

E 

~ JS 

w 

0 

::J 

::: 30 

-' 

< 

25 

20 

15...._~._ ........................ ~ ....................................... ~ ............................ ......... 

1.00E+lD 1.0DE+l 1 1.0DE+12 

OZONE NUMBER DENSITY (cm-3) 

1.00E+lJ 

Fig. I. MLO ozone profile for J anuary 27, 1994 . 

125 
BO 

75 

70 

&S 

60 

E' 

-==- 55 

w 

0 50 :J 

II- 45 _J 

<!; 

40 

35 

30 

25 

20 

200 220 240 260 280 

TEMPERATURE (K) 

Fig. 2. MLO temperature profile for January 27, 1994. 

Dashed line is the CIRA reference atmosphere model. 

This can be used, together with the Rayleigh/Mie 

scattered data at 353 nm, to calculate a backscattering 

ratio that does not depend on an atmospheric model 

such as is typically the case. If the relative density 

profile is normalized, for example by using r esults from 

a coincident balloon sonde, then absolute backscatter 

cross sections can be deduced. Figure 3 shows an 

example of an aerosol backscatter ratio profile. At the 

latitude of MLO there are still considerable aerosol 

layers up to at least 30 km altitude. 

J5 

E 

~ 

-""-

w 

0 JO :J 

II-

_J 

<!; 25 

20 

15 ..... ~~....1~~~ ..... ~~~ ...... ~~~ ..... ~~--'~~~-' 

O.B 0.9 1 1.1 1.2 1.3 1.4 

BACKSCATTER RATIO (353 nm) 

Fig. 3. MLO aerosol profile for January 27, 1994. 

3.4. INTERCOMPARISONS 

Figure 4 shows an example where the lidar ozone 

profile has been converted from number density versus 

absolute altitude to mixing ratio versus pressure altitude 

using both the lidar and CIRA model atmospheric 

temperature/pressure profiles and then compared with 

results from UARS-MLS. The two c losest MLS profiles 

are used. For these two examples, the ozone profile has 

a slightly different shape ·but the agreement between the 

lidar and MLS is very good in both cases and over the 

entire range of the lidar measurement. This provides 

confidence in the Raman augmentation and in both the 

temperature and density measurements since both arc 

required for the conversion to mixing ratio and pressure 

altitudes. 

0 

Cl. 

6 

Q) 

.... 

::> 

t/l 

t/l 

~ 

a.. 10 

x 0 

XO 

- Lidor (Model T) 

- Lidor (Lidor T) 

0 UARS-MLS ( 1) 

X UARS-MLS (2) 

100"--e--....................................... _.... .......... __..__._ ............................................ ..... 

0 2 3 4 5 6 7 8 

Ozone Mixing Ratio (ppmv) 

10 11 

Fig. 4. Lidar MLO ozone profile converted to mixing ratio and 

comparison with two closest UARS overpasses (January 19, 

1994). 

Acknowledgments. The work described here was carried out by 

the Jet Propulsion Laboratory, California Institute of 

Technology, under an agreement with the National Aeronautics 

and Space Administration . We are grateful to the staff at \llLO 

for the ir extensive efforts in preparing a site for the liclar 

faci lity and for their continuing support of this program. 

4. REFERENCES 

McDermid, I. S., S. M. Godin, and L. 0. Lindquist, Ground-based 

laser DIAL system for long-term measurements of stratospheric 

ozone, Appl. Opt .. 29, 3603-3612, 1990a. 

McDermid, I. S., S. M. Godin, P. H. Wang, and M. P. McCormick, 

Comparison of stratospheric ozone profi les and their seasonal 

variations as measured by lidar and SAGE II during 1988, J. 

Geophys. Res., 95 , 5606-5612, 1990b. 

126 
McDermid, l.S., S.M. Godin, L.O. Li ndquist, T.D. Walsh, J. 

Burris, J. Butler, R. Ferrare, D. Whiteman, and T.J. McGee, 

Measurement intercomparison of the JPL and GSFC 

stratospheric ozone lidar systems, Appl. Opt., 29, 467 1-4676, 

l990c. 

McDermid , l.S., S.M. Godin, R.A. Barnes, C.L. Parsons, A. 

Torres, M.P. McCormick, W.P. Chu, P. Wang, J. Butler, P. 

Newman, J. Burris, R. Ferrare, D. Whiteman, and T.J. McGee, 

Comparison of ozone profiles from ground-based lidar, ECC 

balloon sonde, ROCOZ-A rocket ozonesonde, and SAGE II 

satellite measurements, J . Geophys. Res., 95, 10,037-10,042, 

1990d. 

McDermid, l.S., D.A. Hane r, M.M. Kleiman , T.D. Walsh, and M.L. 

White, Differential absorption lidar systems for tropospheri c 

and stratospheric ozone meas urements, Opt. Eng., 30, 22-30 , 

199 1. 

McGee, T.J., M.R. Gross, R.A. Ferra re. W.S. Heaps, and U.N. 

Singh, Raman lida r measurements of stra tospheric ozone in th e 

presence of volcanic aerosols, G~ophys. Res. Lett., 20, 955-958 , 

1993. 

127 
Strontium-90 Deposition at SMO and MLO Through 1990 

M. MONETTI 

Environmental Measurements Laboratory, U.S. Department of Energy, New York, NewYork 10014 ·3621 

INTRODUCTION 

Depositi on samples have been collected at American 

Samoa (SMO) since 1965 and Mauna Loa, Hawai i 

(MLO) since 1959 for the Environmental Measurements 

Laboratory's (EML) Global Fallout Program. Sampling 

at both locations has been supported by CMDL for the 

majori ty of these years through a cooperative 

agreement. These samples, along with others collected 

in our global network, were regul arly analyzed for 90Sr. 

Strontium-90 is a radioac tive fission product, and most 

of the 90Sr measured in deposition samples were 

produced as a result of atmospheric nuclear weapons 

testing. Strontium-90 is an important radionuclide from 

a health perspective because it has a long half-life (28 

years), is produced in rel atively large quantities during 

nuclear fission reactions, and has a high bioaccumulation potential. The data generated by this 

program are used to determine the distribution and 

inventories of 90Sr deposited on the earth's surface. 

Many factors controlling the transport and fate of 

atmospherically released radionuclides have been 

revealed by th is program. The r esults are periodically 

published in EML reports [Monetti and Larsen, 1991]. 

MATERIAL AND METHODS 

Deposition samples have been collected at MLO and 

SMO using two different collectors, either an ion-exchange 

column or a 23-L polyethylene bucket. Using either 

method, the collectors are exposed to bulk (wet and dry) 

atmospheric deposition, and a new sample is collected each 

month . The ion-exchange columns were used at MLO and 

at SMO until 1976. The column was packed with Dowex50\V ion-exchange resin that efficiently removes 90Sr and 

other cations from the aqueous phase of the sample, while 

the particulates are trapped in the paper pulp. The column 

was placed in a wooden housing unit, and a polyethylene 

funnel with a diameter of 30 cm was attached to the top of 

the column. Presently, an open 23-L polyethylene bucket 

with a diameter of 29 cm is being used as a deposition 

sampler at both locations. The precipitation samples 

collected are shipped to EML and are passed through an 

ion-exchange column. The contents of the columns are 

analyzed for 90Sr using established radiochemical 

procedures [Chieco et al., 1992]. 

128 

RESULTS 

The annual 90Sr deposition data through 1990 for 

MLO and SMO are summarized in Figure 1. The 

deposition is reported in uni ts of activity per unit area 

(Bq 90Sr m-2). Samples were not collected at SMO 

prior to 1965, therefore, no data are shown in the 

corresponding positions on the graph. In al l other 

instances, a lack of data indicates that the samples 

contained 90Sr activ ities that were below the detection 

limit. 

DISCUSSIO N 

The trend of 90Sr deposition at MLO, shown in Figure 

I, is characteristic of the depositional history 

throughout most of the world [Larsen, 1984]. There is 

generally a 1963 maximum value as a result of the large 

number and high fission yield of the 1962 weapons 

tests. Reduced 90Sr deposition is observed at both 

locations for the years 1965 to 1986. The deposit ional 

trends during these years were similar at both MLO and 

SMO, however 90Sr deposi tion was apparently higher at 

SMO. Little 90Sr was deposited at either sampling site 

following the last atmospheric weapons test conducted 

by China late in 1980. Strontium-90 result ing from the 

Chernobyl accident in April of 1986 was not found at 

either location due to the regional nature of this event 

and its related contamin ant transport. Any 90Sr 

deposited after 1982 is appa rently due to resuspension 

N' 

'e 

r::1" 150 

~ 

c: 

0 

:~ 100 

0 

Q. 

Cl> 

0 

(j, 50 

0 

a> 

0 Mauna Loa, Hawaii 

• American Samoa 

59 60 &1 61 '-' &i 65 66 61 68 69 10 1 l n n 1.- 1s 76 n 11 79 so i 1 u n &.1 ss 1611 u 19 90 

Year 

Fig. I. Annual 90Sr deposition at Mauna Loa, Ha waii, and 

American Samoa from 1959 to 1990. 
processes and is insignificant compared to historic 

deposits. The 90Sr inventory at the end of 1990 determined 

from the MLO deposition data is 290 Bq 

m-2. A total inventory cannot be calculated for SMO 

because there is no SMO data available during the peak 

deposition period prior to 1965. MLO and SMO are just 

two sites of the many locations where deposition samples 

arc collected for EML's Global Fallout Program. Using 

data from all the sampling stations enables us to determine 

the global distribution and magnitude of 90Sr deposition _ 

Acknowledgment. I wish to thank the CMDL staff at MLO and SMO 

who have continued to provide EML with deposition samples for all 

of the years our program has been in operation. 

129 

REFERENCES 

Ch ieco, N.A., D.C. Bogen, and E.O. Knutson (eds.), EML 

Procedures Manual, 27th Edition, HASL-300, Vol. 1, pp. 4.5-

195 to 4.5-236, U.S. Department of Energy , Environmental 

Measurements Laboratory, New York, 1992. 

Larsen, R.J., Graphic presentation of quarterly 90Sr fallout data 

1954 -1982, EML-424 , 186 pp., U.S. Department of Energy, 

Environmental Measu rements Laboratory, New York, 1984. 

Monetti, M.A., and R.J. Larsen, Worldwide Deposition of 

Strontium-90 through 1986, EML-533, 31 pp., U.S. 

Department of Energy, Environmental Measurements 

Laboratory, New York, 1991. 
Results from the Mauna Loa Ultrahigh Resolution 

Infrared Solar Spectrometer 

FRANKJ. MURCRAY, SHELLEJ. DAVID, RONALDD. B LATHERWICK, 

DAVID G. MURCRAY , AND AARON GOLDMAN 

University of Denver, Department of Physics, Denver, Colorado 80208 

CURTIS P. RINSLAND 

NASA Langley Research Center, Hampton, Virginia 23681 

INTRODUCTION 

The Network for Detection of Stratospheric Change 

(NDSC) ultrahigh resolution infrared solar spectrometer 

system continued operation in 1993 with only minor 

problems. The instrument and data analysis technique 

were described in the 1991 Summary Report [Ferguson 

and Rosson, 1992]. The instrument is operated once per 

week (usually Wednesdays) at sunrise by the MLO staff. 

The spectra cover two regions: 750 to 1250 cm·t (8 to 

13 μm) and 2500 to 3100 cm· t (3.1 to 4 μm ). 

University of Denver personnel visited the site three 

times during the year to make special measurements and 

carry out adjustments. 

The spectrometer system began routine operation in 

November, 1991, so we now have 2 years of data. This 

is sufficient to begin the study of seasonal cycles and 

trends. 

RESULTS AND DISCUSSION 

We are currently analyzing the infrared spectra for 

total column amounts of several gases. In some cases, 

altitude information can also be recovered. Although 

this instrument is intended primarily for monitoring of 

stratospheric chemistry, many tropospheric gases are 

also observed. An example of this is ethane (C2H6). 

Eth ane is released from the surface in a variety of 

processes, some of them related to human activity. 

Destruction of ethane in the troposphere is due to 

oxidation by OH radicals. The ethane concentration 

falls off rapidly in the stratosphere. This, coupled with 

the high tropopause over MLO, means that total column 

amounts measured by infrared solar absorption spectra 

are almost entirely tropospheric. 

Spectra were analyzed for the vertical column amount 

of ethane using an absorption feature at 2976.77 cm·l. 

An example spectrum and a fit are shown in Figure 1. 

The spectral filling routine adjusts several parameters, 

including amounts of interfering gases like ozone and 

methane. Spectra from 71 days have been processed, 

and the results are shown in Figure 2. The seasonal 

effect is expected, and the model prediction of 

Kanakidou et al. [ 1991] is shown on the figure for 3 

months. 

130 

1.0~ 

> 

.~ /i.1 .... 

.. 

" t> §, 0. 9 

/

./ v 

·q3/ i ti) ·-

....... _ Eest Fit 

I v ' -- !l.e~S\.!red 

I a. , C:-14 • 03 

0.8 '----'----'----'-----''-----'----' 

2976.s 2976.6 2•1 ~u 2ns.e ;;;s.11 z•n.o ;,;n.1 

~ • b . . . . i _: ~'\v"·""':"-"\f"--,dy'=-~l -2 t • · I ~s;s.s 2sis.s ;;;;s.7 2975.e ::;s.> ;;sn.c ;sn.1 

Vta·.renumber 

-I 

(c::1 ) 

Fig. I. A small section of an infrare d solar absorption 

spectrum is shown in the lop panel (dolled line) along with the 

best fit modeled spectrum (solid line). The absorption marked 

PQ3 is due to ethane, the smaller features arc methane o r ozone 

as indicated. The bottom panel shows the ex perimental 

spectrum minus the calculated on an expanded scale. 

HN03 is one of the stratospheric gases that is 

routinely monitored. The total vertical column of 

HN03 over the period from November 1991 lo October 

1993 is shown in Figure 3. Mount Pinatubo erupted in 

July 1991 , shortly before routine operation of the 

instrument began. Also shown in the figure is the 

aerosol loading of the stratosphere (as observed by the 

SAGE satellite) during the same period. The effect of 

the Mount Pinatubo aerosol on the HN03 column is 

clear, indicating that significant reactions arc occurring 

on the aerosol surface. We also show the ozone amount 
...--.. N 

I 

s 

0 

[/) 

0 

...... 

::J 

0 

0 

...... 

0 

s 

L."l 

0 

....... 

...._,, 

~ 

8 

;j 

0 

u 

....... 

('j 

~ 

0 

E-< 

<.'.) 

::i:: 

C\l 

u 

20 

15 

5 

0 

0 1991 

1992 

1993 

Fit 

~fode 

J FMAMJ J ASOND 

Month 

Fig. 2. Vert ical column amounts of er.h ane detennincd from the 

infrared spectra. Error bars show the random compone nt of 

uncertainties in the me asurement. The best fit curve (solid line) is a 

cosine with amplitude 0.37 and maximum in mid-March , added to 

the average column of 8.44 x 101s. Model values are from 

Kanakidou et al., 199 1. 

in this figure to indicate that no large c hange in ozone 

column occurred, although our data is not suffic ient to 

determine small changes. The observed c hange in 

HN03 agrees well with similar observations from New 

Zeal and [Koi ke et al ., 1994]. 

Continued operation of the instrument is planned for 

next year. 

131 

.. ... . o, :. r1 i . . . . . .. ... ,1• .... . . . ... ~ .. . 10 . • t \ . . 6 · .. .. E 

u 

9 c; 

E 

~ 

8 .. f 4 

~ "" i 

8 

6 

5 7 [l 

~ 6 

t: c; 

E 

~ 

0 

... ..... I 

6 4 , ..•..•... Lo z 

~ ~ 

31 

... 

•. 

-.r .. • A<rosol ........ •.. 21 .. •· . ~ 

l I; . I . . 

" 

300 ~ 

8 

200 ~ c: 100 E 

< "L'.-,~~~~~~~~~~~-.~~~,.-,---,-.~-f, 0 

10/ 15 01/14 04/IS 07/IS 10/IS 01114 04/ 16 07/16 10116 

1991 1992 

Fig. 3. Vertical column amounts of ozone and IIN03 over MLO, 

along with the month ly mean tota l aerosol loading 

(μm2km/cm3) observed by SAGE in the 15 10 35 km region between 

10°N and 20°N. The solid line through the 111'\03 values has a 

slop e of 15% per year. 

Acknowledgments. We continue to be particularly grateful to 

the MLO sta ff for the dedication and skill in operating our 

instrument. 

R EFER ENCES 

Ferguson, E.E. and R.M. Rosson (Eds.), Climate Monitoring and 

Diagnostics laboratory No. 20: Summary Report 1991, pp 115-

11 6, NOAA Environmental Research Laboratories, Boulder, CO, 

1992. 

Kanakidou, M., H.J3. Singh, K.M. Valentin and P.J. Cru1zen, /I. two 

dimensional study of ethane and propane oxidation in the 

troposphere,!. Geophys. Res., 97(08), 15,395-15,413, 1991. 

Ko ike, M., N.B. Jones, W.A . Mauhews, P.V. Johnston, R.L. 

McKenzie, D. Kinn ison and J. Rodriguez, Impact of Pinatubo 

aerosols on the partitioning betwee n N02 and HN0 3 , Geophys. 

Res. Lei/., 21, 597-600, 1994. 
UV-B Optical Depths at Manna Loa: Relative Contribution of Ozone and Aerosols 

PATRICK J. NEALE, DAVID L. CORRELL, VERNON R. GOODRICH, AND DOUGLASS R. HA YES, JR. 

Smithsonian Environmental Research Cenler, Edgewater, Maryland 21037 

Our laboratory has been monitoring surface spectral 

UV-B irradiance at Mauna Loa since fall of 1984. The 

instrument is similar to a radiometer in operation in 

Edgewater, Maryland [Correll et al., 1992]. The 

instrument measures UV-B irradiance in a series of 

eight, 5-nm band passes (290-325 nm) and records 1-

m inute averages. Operation is continuous except for an 

annual break of about 1 month when the instrument is 

returned Lo Maryland for calibration. Our primary 

objective is to monitor long-term changes in incident 

solar UV-B irradiance. To accomplish this, a complete 

review of instrument calibrations over the period of 

operation is underway. Publication of our UV-B record 

will await the completion of this review. 

While a record of absolute irradiance is presently not 

available, we nevertheless undertook preliminary 

analyses to assess the utility of the data set in regard to 

increasing our understanding of how different 

atmospheric factors control the intensity of surface UVB. This was accomplished by calculating a relative 

optical depth for UV-B irradiance and statistically 

analyzing the relationship between such optical depth 

and parallel records of primary properties affecting 

atmospheric transparency to UV-B: total column ozone 

and aerosol optical depth. 

Sunphotometers are commonly used for measurements 

of total optical depth, but usually are not designed to 

operate in the UV-B spectral region. On the other hand, 

the SERC radiometer measures total global irradiance as 

opposed to direct normal beam irradiance that is 

typically used for calculation of optical depth via Beer's 

law. Even so, an approximate optical depth can be 

estimated using the relationship: 

(1) 

where !(A.) is surface irradiance, ! 0(A.) is direct normal 

irradiance at the top of the atmosphere, 0s is the solarzenith angle, and 'C is total optical depth. Operationally, 

-c can be estimated as the slope of a linear regression of 

log(I(A.)!cos(0s)) on sec 0s. Since the diffuse (sky) 

component of !(A.) does not completely obey eq. (1) 

[Box and Deepak, 1979], the regression slope is termed 

"relative optical depth." The differences between 

relative and true optical depth are further discussed 

below. 

For the analysis we chose measurements from 

morning to midday, for 0s <54". The analysis was done 

on days for which (1) morning to midday data were 

recorded, (2) c lear sky conditions prevailed, (3) aerosol 

optical depth (-ca) at 500 nm was measured (data kindly 

132 

provided by CMDL and further d escribed in Dutton et 

al. [1994]), and (4) total column ozone was measured 

on the same day or day immedi ately before and after, 

i.e., by the MLO Dobson spectrometer. If ozone was 

not measured on the same day, it was estimated by 

interpolation. Clear sky cond itions were ascertained by 

the lack of deviations from a log-linear relationship, 

additionally 'Ca at 500 nm was generally only estimated 

for clear sky mornings [Dutton et al., 1994]. No slope 

was estimated unless at least 50 1-minute averages 

could be entered into the regression analysis. 

We focused on two parts of the record with 

contrasting conditions in terms of aerosol optical depth, 

a period from mid-1984 through 1985 when aerosol 

optical depth was low, i.e., near historic background 

levels, and 1991 through mid-1992 during which aerosol 

turbidity markedly increased due to the eruption of Mt. 

Pinatubo [Dutton et al., 1994]. A total of 208 days 

during these two periods met the crite ri a for analysis. 

A time-series of regression slopes for channels with 

nominal center wavelengths between 300 and 325 nm is 

shown in Figure I. The results show several expected 

features for UV-B optical depths. First, optical depths 

vary by almost an order-of-magnitude over this spectral 

range with the largest depths associated with the 

shortest wavelengths. Second, there is significant 

seasonal variation of about 20-30% around the annual 

mean that is in phase with the seasonal variation in total 

ozone concentration (data not shown). Third, optical 

depths increase following the eruption of Mt. Pinatubo 

in June 1991 cf. [Du/Ion et al., 1994]. 

The quantitative relationship between our estimated 

relative optical depth, ozone, and aerosol turbidity was 

analyzed via multiple linear regression. This is based 

on the assumption that total optical depth is the sum of 

components due to Rayleigh scattering, ozone, and 

aerosols, the last two components being time va riable . 

By analogy, relative optical depth would be ex plained 

by the model: 

(2) 

where 'Cp is relative optical depth, /03] is total column 

ozone and 'ta is aerosol turbidity at 500 nm, and A, B, 

and C are constants. The results of the regression 

analysis applied to 'Cp estimated from .the 1984-1992 

SERC UV-B radiometer record are given in Table 1. 

The proportion of variation in Tp explained by the 

regression varied from 50% at 325 nm to 77% at 305 

nm. All regressions were highly statistically 

significant, and all coefficients were significantly 
Fig. I. Time series of relative optical depths in six UV-B bands 

(5 nm full bandwidth at half maximum) as estimated from 

morning-midday data rt:cor<lt:<l on lht: SERC UV-B ra<liomt:le r. 

Upper (A) graph for 300-, 305-, and 310-nm bands, bottom (B) 

gra ph for the 315-, 320-, and 325-nm bands. Note the different 

abscissa scales. Although data has been recorded more-or-less 

continuously since 1984, only periods between 1984-1986 and 

1991-1992 were used in the present analysis. Vertical line 

indicates date of Mt. Pinatubo eruption. 

different from zero, except for th e coeffi cient of 'ta for 

'tp at 300 nm. The coefficient A is analogous to a0 )._, the 

s pectral absorption coefficient for ozone. Estimates for 

the coeffi cient A were approximately equal to or 

exceeded effective a0 ).., Table 1, [Molina and Molina, 

1986]. except at 300 nm. The estimate for A may 

generally be greater than a0 A. when •p has been 

estimated from total (direct plus diffuse) irradiance. 

Attenuation of the diffuse component of /().,) will be 

over longer mean optical paths than for the direc t beam 

irradiance, e.g. , Perliski and Solomon (1 993). The 

estimate of A for the 300-nm channel may be less than 

a 0 :>,. at 300 nm due to the probable red-shift of effective 

center wavelength of this channel with respect to the 

filter center wavelength (300.6 nm) as discussed by 

Corre ll et al. (1992). 

The coefficient B is interpreted as an overall 

proportion between 'ta at 500 nm and ae rosol optical 

depth in each of the UV-B b ands. Generally, aerosol 

opti cal depth obeys an inverse power l aw (Angstrom) 

133 

TABLE 1. Results of Regression Analysis of 1, Using Eq. 2 

A. aol A B c R2 

300.6 9.34 6.17 NS 0.63 68 

304.8 5.42 5.04 0.76 0.19 77 

310.7 2.45 2.72 0.51 0.24 66 

314.6 1.46 2.66 0.66 0.08 63 

320.l 0.68 1.45 0.43 0.13 57 

325.2 0.33 1.12 0.38 0.12 50 

Wavelength (A) is the computed center wavelength for the band 

interference filter. a0 / is the absorption coefficient for total column 

ozone (units, a1rn-l cm at NTP). A, B, and Care the filled coefficients of 

eq. 2, and R2 is the coefficient of determination (given in %). Ozone 

absorption is estimated from the spectral integrals of Molina and Molina 

[1986] assuming a stratosphere temperature of -40"C and normal surface 

temperature of l 8°C. All regressions were significantly different from 

zero, n = 208. NS =not significant. 

relationship with wavelength, arising from a Junge-type 

size distribution of aerosols [Angstrom, 1961). Thus it 

may be surprising at first sight to find that estimated B 

in all bands is less than one. However, the variation of 

'ta at MLO was dominated by Mt. Pinatubo stratospheric 

aerosols, at least during the selected period [Dutton et 

al., 1994). These aerosols were inferred to have a 

narrow size r ange, in contrast with the Junge-ty pe 

distribution of background aerosols [Dutton et al., 

1994]. Furthermore, our regression analysis (eq . 2) 

does not explicitly consider that relative airmass (m,) 

for aerosol a ttenuation will be decreased at the altitude 

of MLO. This was not attempted since we did not h ave 

a basis to estimate m,, i.e., vertical distributions of 

aerosols. However, we would expect m, to range 

between sec e, and 0.67 sec e,. the latter being the 

altitude adjusted Rayleigh m, using the expression of 

Bird and Riordan (1986). 

Finally, the constant term in the regression model, C, 

represents all time-constant contributions to optical 

depth, primarily attenuation due to Rayle igh 

(molecu lar) scattering. However, the estimated Cs arc 

very much lower than the theoretical Rayleigh 

contribution at these wavelengths [Bird and Riordan, 

1986). Again, this is expected since our estimation of 

•p includes diffuse irradiance, which mainly arises from 

Ray leigh scatterin g. 

Overall, the results of the regression analysis conform 

to expectations g iven the approximate nature of the 

model. Thus we conclude that our record can provide 

an indication of the relative importance of ozone and 

aerosol variation in causing variations in incident solar 

UV-B. One quantitative indicator of the relative 

importance of these two variables is the proportion of 

variance in 'tp explained by each variable in the 

regression eq. (2). The fractional contribution of each 

factor was obtained by (1) performing a second 

regression including A but omitting B (i.e. , the term for 
't 0 ); the R2 of this equation is the variance explained by 

ozone alone, and (2) the difference between the former 

R2 and the R2 for the full equation is the variance 

explained by 'ta. Such a "step-wise" approach can be 

used because variations in ozone and aerosol optical 

depth in this record are not correlated. The results are 

shown in Figure 2. Aerosol optical depth is seen to 

have a significant, though secondary, contribution to 

UV-B optical depth with the importance of aerosols 

increasing (and importance of ozone decreasing) at the 

longer wavelengths. Between 315 and 325 nm, aerosol 

optical depth accounts for almost 20% of the variation 

in total optical depth at MLO. 

-';!2, 0 

-

"'O 

Q) 

c: 

·co 

c.. 

x 

Q) 

Q) 

u 

c: 

co 

·;:::: 

co 

> 

80 

70 

60 

50 

40 

30 

20 

10 

0 

300.6 304.8 310.7 314.6 320.1 325.2 

Filter Center Wavelength (nm) 

Fig. 2. Partitioning of the total coefficient of determination (R2) 

for the regression of relative optical depth against total column 

ozone and aerosol optical depth at 500 nm. The dark, upper bar is 

the variance explained by total column ozone; the light, lower bar is 

the variance explained by aerosol optical depth. 

This preliminary analysis of our record of UV-B 

measurements at MLO suggests that volcanic aerosols 

can contribute significantly to the variation in UV-B 

irradiance. Aerosol-forced variation in UV-B is 

probably of less importance during periods inbetween 

eruptions, due to the high-altitude, pristine nature of the 

MLO site. These pristine conditions actually make it 

easier to detect an aerosol-related event when it does 

occur such as documented by [Dull on et al. , 1994]. An 

understanding of the interaction between aerosols, 

ozone, and UV-B will assist in the analysis of trends at 

sites with more complex variations in atmospheric 

conditions such as at our Maryland site. Thus in the 

future we will be extending this preliminary analysis 

over the complete MLO record. 

REFERENCES 

Angstrom, A., Technique of determining the tu rbidity of the 

atmosphere, Tellus, 13, 214-231, 1961. 

Bird, R.E., and C. Riordan, Simple solar spectral model for direct 

and diffuse irradiance on horizontal and tilted planes at the 

Earth's surface for cloudless atmospheres, J. Clim. Appl. 

Meteorol., 25, 87-97, 1986. 

Box, M.A., and A. Deepak, Atmospheric scatte ring corrections to 

solar radiometry, Appl. Opt., 18, 1941 -1949, 1979. 

134 

Correll, D.L., C.O. Clark, B. Goldberg, V.R. Goodrich, D.R. Hayes 

Jr., W.H. Klein, and W.D. Schecher, Spectral Ultraviolet-13 

radiation fluxes at the earth's surface: long-term variations at 

39"N, 77"\V,J. Geophys. Res., 97, 7579-7591, 1992. 

Dutton, E.G., P. Reddy, S. Ryan, and J.J. DeLuisi, Features and 

effects of aerosol optical depth observed at Mauna Loa, llawaii: 

1982- 1992, J. Geophys. Res., 99, 8295-8306, 1994. 

Molina, L.T., and M.J. Molina, Absolute absorption cross sections 

of ozone in the 185- to 350- nm wavelength range, J. Geophys. 

Res., 91 , 14,501-14,508, 1986. 

Perliski, L.M., and S. Solomon, On the evaluation of air mass 

factors for atmospheric near-ultraviolet and visible absorption 

spectroscopy,J. Geophys. Res., 98, 10,363- 10,374, 1993. 
Advanced Global Atmospheric Gases Experiment (AGAGE) 

R.G. PRINN 

Massachusetts Institute of Technolog y, Cambridge, Massachusetts 02139 

R.F. WEISS 

Scripps Institution of Oceanography, Un iversity of California , La Jolla, California 92093 

F .N . ALYEA AND D.M. CUNNOLD 

Georgia Institu te of Technology, Atmospheric Sciences, Atlanta, Georgia 30332 

P.J. FRASER AND L.P. STEELE 

CS/R O, Division of Atmospheric Research, Victoria, Australia 3195 

P.G. SIMMONDS 

University of Bristol, School of Chemistry, Bristol, United Kingdom BSB ITS 

INTRODUCTION 

Continuous high frequency gas chromatographic 

measurements of two biogenic/anthropogenic gases 

(C H4, NiO) and five anthropogenic gases (CFCJ3, 

CF2Cl2. CH3CCl3 , CF2CICFCl2. and CCJ4) are being 

carried out at globally-distributed sites in order to 

quantitatively determine the source and sink strengths 

and circulation of these chemically and radiatively 

important long-lived gases. The current station 

locations arc Cape Grim, Tasmania (41 ·s, 145"E), Point 

Matatula, American Samoa (14 °S, 171"E), Ragged 

Point, Barbados (13"N, 59"W), and Mace Head, Ireland 

(53"N, JO' W). Stations also previously existed at Cape 

Meares, Oregon (45'N, 124"W) and Adrigole, Ireland 

(52"N, lO"W). The current Mace Head station replaced 

the Adrigole station and a station is planned at Trinidad 

Head, California (4 1 "N, 124"W) to repl ace Cape 

Meares. The program, which began in 1978, is 

conveni ently divided into three parts associated with 

three changes in instrumentation: the Atmospheric 

Lifetime Experiment (A LE) that utilized HewlcttPackard HP5 840 gas chromatographs, the Global 

Atmospheric Gases Experiment (GAGE) that utilizes 

HP5880 gas chromatographs, and the Advanced 

(AGAGE) phase that has recently begun using a new 

fully-automated system from the Scripps Institution of 

Oceanography (SIO) containing a custom-designed 

sample module and HP5890 and Carle Instruments gas 

chromatographic components. Finally, a new Finnigan 

gas chromatograph-mass spectrometer system for 

measuring hydrochlorofluorocarbons (HCFCs) and 

hydrofluorocarbons is being installed at Mace Head 

with another planned for Cape Grim. 

1993-1994 UPDATE 

The da ta for the seven Jong-lived gases measured in 

GAGE during 1993-1994 con tinue to be generally of 

135 

good quality. Some signifi cant conclusions have been 

made over the past year as a result of analyzing the 

data. First, 13 years of ALE/GAGE CCl3F and CC12F2 

measurements have been analyzed and pub! ishcd 

[Cunnold et al., 1994]. Comparisons are made against 

shipboard measurements made by SIO and archived air 

samples collected at Cape Grim, Tasmania, since 1978. 

CCl3F in the lower troposphere was increasing at an 

average rate of 9.2 ppt yr·l over July 1978 to June 1988. 

CCl2F2 was increasing at an average 17. 3 ppt yr· I in the 

lower troposphere over the same period. However, 

between July 1988 and June 1991 the increases of CC13F 

and CCl2F2 in th is region have averaged just 7 .0 ppt yr· 

t and 15.7 ppt yr-I, respectively. The rate of increase 

has been decreasing 2.4 ppt yr·2 and 2. 9 ppt 

yr·2 over this 3-year period. Based on recent scenarios 

of the worldwide releases of these compounds and using 

the calibration scale SIO 1993, the equilibrium lifetimes 

are estimated to be 44 :~ years and 180 0 years fo r 

CCl3F and CCl2F2 respectively. Using these lifetime 

estimates and a two-dimensional model, it is estimated 

that global releases of these two chlorofluorocarbons 

(CFCs) in 1990 were 249 ± 28 x 106 kg for CC13F and 

366 ± 30 x 106 kg for CCl2F2. It is also e st imated tha t 

combined releases of these chlorofluorocarbons in 1990 

were 2 1 ± 5% less than those in 1986. 

Second, recent analysis of 15 1/ 2 ye ars o f ALE/GAGE 

CH3CCJ3 data ( 1978-1993) has shown that global 

concentrations arc decreasing rapidly and arc 

approximately consistent with report ed industria l 

emissions decreases [Prinn et al., 199-l). The 

concentration decreases (about 12% globall y) began in 

1991 in the northern hemisphere and in 1992- 1993 in 

the southern hemisphere consistent with the 

predominantly northern hemisphere industrial emissions 

and expected intcrhemispheric mixing times. 

Interpretation of the data using optimal estimation 

inverse techniques, together with new SIO 1993 

calibrations for this gas and recent estimates of 
industrial CH3CC13 emissions, indicate a tropospheric 

lifetime of about 4.85 years which is a significantly 

lower lifetime than that reported previously [Prinn et 

al .• 1992) that was based on 12 years of data and the old 

(17% greater) calibration. 

Operations at SMO will soon make the transition 

from the GAGE instrument to the new AGAGE system, 

with the actual schedule depending upon plans for the 

replacement of the existing laboratory building at this 

site. During 1993-1994 the GAGE HP5880 continued to 

be operated by the CMDL station personnel in 

collaboration with SIO. Operations were quite smooth 

and uneventful during this period, with most problems 

being of a routine maintenance and repair nature. 

Through the results obtained at SMO where ambient 

atmospheric water vapor concentrations are high, we 

have become aware that the quality of the HP5880 

electron capture chromatography is sometimes degraded 

by poor performance of the Nafion drier [Foulger and 

Simmonds, 1979] configuration used in GAGE, in which 

pellets of molecular sieve are used to absorb water in 

the space surrounding the drier tube. As a result, in 

1994 we modified all of the GAGE driers to use the 

same Nafion drier method used for the AGAGE 

instruments, in which the drier tube is surrounded by a 

countercurrent flow of dry "zero air." 

The new in strument systems for AGAGE represent a 

significant technological advance. All operations and 

data acquisition are by a Sun Microsystems workstation 

computer using custom runfile architecture, signal 

processing and integration routines, and storing all the 

data and chromatograms digitally. The instrument 

measures its own non-linearity for all the AGAGE gases 

on a regular basis using a pressure-programmed 

constant- volume injec tion system and a single gas 

standard. All channels of the instrument are fitted with 

prccolumns to avoid column contamination by lateelut ing gases, and as a result the frequency of 

measurement has been increased three-fold versus 

GAGE. Precision is also greatly improved over the 

GAGE instruments with lcr relative precisions on the 

order of 0.05% for the rapidly eluting gases CH4, 

CCl2F2. N10. and CCl3F. The system work s 

interactively with its uninterruptible power supply so 

that controlled shutdown and startup of the entire 

instrument and sampling system are assured when there 

arc extended power outages. The new AGAGE 

instruments arc now operational at Cape Grim and at 

Mace Head, and the remaining instruments will be 

installed at the other stations within the coming year. 

Another major component of the AGAGE program is 

the development of new absolute calibration scales. 

This work is being done using an extension of the 

"bootstrap" calibration method used earlier at SIO. In 

the AGAGE work, an all-metal high-vacuum system is 

used to mix gravimetrically determined aliquots of pure 

CFCs with about 12 L of gravimetrically determined 

pure nitrous ox ide. This mixture is prepared at roughly 

136 

the ambient atmospheric mole ratios of these gases. A 

small aliquot (-0.4 cm3) of this mixture is then 

introduced using a separate pressure/vacuum system , 

fitted with a high-pressure chromatographic sampling 

valve, into a 35-L electropolished stain less steel 

canister to which about 10 torr of water vapor has been 

added to reduce wall reactions and adsorption. The 

canister is then filled with about 40 atmospheres of repurified "zero air" to bring the nitrous oxide mo le 

fraction to a near-ambient value. The resulting ni trous 

ox ide concentration is then calibrated gas chromatographically against existing SIO standards, and the CFC 

concentrations are determined by multiplying the 

measured nitrous oxide mole fraction by the gravimetric 

CFC nitrous oxide ratios of the original mixture. In this 

way, we have been able to obtain improved accuracy for 

all AGAGE gases, b11t especially for the lower vapor 

pressure and more adsorptive gases. AGAGE and 

CMDL are now engaged in an active intcrcalibration 

program for all the AGAGE gases as well as for methyl 

halides and some HCFCs. 

DATA ACCESS 

The ALE/GAGE/AGAGE data are archived at the 

DOE Carbon Dioxide Information Analysis Center at 

Oak Ridge and are available to interested scientists. 

Potent ial users of the data should contact CDIAC 

(Internet: CDP@ORNL.GOV). 

Acknowledgments. The AGAGE is supported b)• :-IASA gran ts 

NAGW-732 and NAGW-2034, l\OAA Contract NA85 -

RAC05103, CSlRO, Australian Dureau of i\leteorology, th e 

U.K. Department of Environment, and the i\l1erna1ive 

Fluorocarbons Environmental Acceptability Study. We thank 

th e CMDL staff at Samoa for their continued e xce ll en t loca l 

support of our instrumentation there. 

REFERENCES 

Cunnold, D.M., P.J. Fraser, R.F. Weiss, R.G. Prinn, P.G. Simmonds, 

0. R. Miller, F. N. Alyea, and A. J. Crawford, Global trends and 

annual releases of CC13F and CCI2F2 estimated from ALE/GAGE 

and other measurements from July 1978 10 June 1991, J. 

Geophys. Res., 99, 11 07-1126, 1994. 

Fou lger, D.E., and P.G. Simmonds, Drier for field use in the 

determination of trace atmosphe ri c gases, Anal. Chem., 51 , 

1089-1090, 1979. 

Prinn, R., D. Cunnold, P. Simmonds, F. Al yea, R. IJoldi, i\. 

Crawford, P. Fraser, D. Gutzler, D. Hartley, R. Rosen, and R. 

Rasmussen, Global average co ncen trati on and trend for 

hydroxyl radicals deduced from ALE/GAGE trichloroethane 

(methyl chloroform) data, J. Geophys. Res., 97 , 2445-2461, 

1992. 

Prinn, R.G., R.F. Weiss, 13 .R. Miller, J. l!uang, f-.:\. Alyea, 

D.M. Cunnold, D.E. Hartley, P.J. Fraser, and P.G. Simmonds, 

Global weighted-average concentration and trend for OH 

based on IS 1/2 years o f ALE/GAGE Cll 3CCl 3 data, paper 

presented al the 2nd IGAC 8th CACGP Symposium, FujiYoshida, Japan, September 5, 1994 . 
The 13C/12C of Atmospheric Methane 

PAUL Q UAY, JOHN STUTSMAN, AND D AVID WILBUR 

School of Ocean ography, University of Washington, Seal/le, 98195 

INTRODUCTION 

For the past 6 years we have been measuring the 

13C/12C o f atmospheric C H4 on air samples collected at 

three CMDL sites (BRW, MLO, and SMO) and on the 

Washington coast at 48. N 126"W. 

The 13C/12C of atmospheric CH4 is a tracer th at can 

distinguish between CH4 input from bacterial and nonbacterial CH4 sources. Bacterial CH4 is microbially 

produced in anox ic environments likes swamps, bogs, 

rice paddies, and the rumens of cows. Non-bacterial 

CH4 sources include thermogenically produced natural 

gas and CH4 produced during the incomplete oxidation 

of plant material during biomass burning. Bacterial 

CH4 has a o13C of about -60%0 (versus PDB) whereas 

the ol3C of natural gas and CH4 produced from biomass 

burning arc about -40 and -27%0, respectively [Quay et 

al., 1991 ]. 

The spatial and temporal variations in the 13C/12C of 

atmospheric CH4 depend on the variations o f the relative 

streng th and l3C/12C of the CH4 sources and sinks. Over 

intcrannual time scales the trends in the l3C/12C of 

atmospheric CH4 indicate changes in the source 

composition, i.e., the relative strength of bacterial versus 

non-bacterial CH4 sources. Because CH4 will likely 

contribute about 15% o f the radiative forcing during the 

next century [Wigley and Raper, 1992], it is important to 

quantify the strength of the individual CH4 sources, 

currently known to about ±50% and to determine whether 

the CH4 source strengths are changing with time. This 

latter point has been underscored by the recently observed 

slowdown in the rate of CH4 increase in the atmosphere 

[Dlugokencky et al., 1994). 

METHODS 

The a ir samples are collected at approximately 2-

wcck intervals, u sing pre-evacuated stainless steel 

flasks e ither 15- or 30-L in volume. The CH4 is 

ex trac ted from air in our laboratory using the procedure 

developed by Stevens and Rust [1982). Briefly, the air 

is metered into a high-vacuum extraction line through a 

series of liquid nitrogen traps to remove H20 , C02, and 

N20. The air then passes through a bed of Schutze's 

reagent, 120 5 on silica, to oxidize CO to C02 that is 

trapped cryogenically. Then the CH4 in the air is 

combusted over platinized silica at 800"C to C02 which 

is then trapped cryogenically. The yield of the 

procedure, determined from stand ards, is 100 ± 2% (n = 

114). The 13C/12C of the C02 derived from C H4 is 

137 

measured on a Finnigan MAT 251 gas ratio isotope 

mass spectrometer. The overall measurement precision 

is about ±0. l %0. We obtain a ol3C of -41.73%0 (versus 

PDB) for NBS-16. 

R ESULTS AND DISCUSS ION 

The seasonal cycle in the 513C of CH4 is greatest at 71 "N 

(BRW), with an amplitude of -0.6%0, and decreases 

southward to 14"S (SMO) where we measure no significant 

seasonal trend, i.e. <0.1%o (Figure 1). The seasonal trends 

at 71 "N and 48"N can be approximated roughly by a single 

harmonic with an annual period. Episodes of high CH4 

concentrations associated with very depleted ol3C values 

occur at these two sites in September-October of each year 

and are due to input of bacterial methane. Generally, at the 

northern hemisphere sites the lowest 513C values occur in 

the fall and the highest values occur in the summer. This 

trend toward higher summert ime ol3C values is expected if 

CH4 oxidation by OH primarily controls the seasonal cycle 

because the l2C H4 molecules react at a slightly faster rate 

(1.0054x) than the 13CH4 molecules [Cantrell ct al., 1990] . 

The annual mean l)l3C values increase southward from 

about -47 .8%0 at 7 1 "N Lo -47 .3%o at 14" S. 

We calculate a global average ol3C of CH4 of 

approximately -47.5%0. The mean global ol3C value, 

when combined with the l4C content of atmospheric 

CH4, y ields estimates of the proportion of bacterial , 

non-bacterial, and fossil CH4 source strengths [Quay ct 

al., 1991 ). We estimate that bacterial CH4 sources 

contribute - 70%, fossil CH4 sources -20%, and biomass 

burning - 10% of the total CH4 input. 

Although the seasonal cycle in ol3C dominates the 

time-series measurements in the northern h..:misphere, 

there is evidence for a slight interannual increase up 

until 1992. Measurements at all four time-series 

locations indicate an increase in ol3C and , when 

combined and area weighted, y ield an average rate of 

approximately 0.04 ± 0.02%0 per year. A 1)13C increase 

indicates the ratio of bacterial to non-bacterial CH~ 

source strength is decreasing. In 1993 , however, there 

has been a leveling of the ol3C trend at the northern 

sites and a decrease al SMO. This trend is similar 10 

the recent ol3C decrease observed at Baring Head, New 

Zealand (4l"S) and Scott Base, Antarctica (78 ") by 

Lowe et al. (1994], who attribute the decrease 10 a 

reduction of the CH4 released from biomass burning . 

Measuring the interannual change in the 1)13C of 

atmospheric CH4 at sever al sites over the longer te rm 

will be a useful indicator of changes in the proportion of 
-47.45 

a;- - 47.70 

0 

n. 

~ -47.95 

~ -48.20 

l>? -48.45 

o; 

.,, -48.70 

-48.95 

-47.2 

a;- - 47.4 

0 

n. 

~ -47.6 

-.! -47.8 ~ 

w -48.0 

ti 

"'-48.2 

-.&8.4 

1988 

PT. BARROW 

(71 •N 156•W) 

OLYMPIC PENINSULA 

(A8•N 126•W) 

a;-

0 

n. 

., 

> 

8 

~ 

l>? 

ti 

"' 

a;-

0 

n. 

~ 

8 

~ 

l>? 

u 

.,, 

- 4 7.0 

-47.2 

- •7.4 

-47 6 

- 47.8 

- 46.0 

-46.2 

-46.4 

-48.6 1966 1989 

- 46.6 

-47.0 

- 47.2 

- 47.4 

- 47.6 

- 47.6 

-46.0 

-48 2 

-48 4 

1966 1969 

MAUNALOA 

(19°N 155•W) 

1990 1991 

SAMOA 

( 1 4•S 1 700W) 

1990 1991 

1992 . 199J 

1992 199.) 

Fig. I. The time se ries of the l)t3C o f atmospheric CH4 measured at BRW, Olympic Pe ninsu la, MLO, and SMO since 1988. 

bacterial and non-bacterial CH4 inputs. These isotopic 

records should help us detennine why the rate of methane 

increase has slowed so dramatically over the last few years. 

R EFERENCES 

Dlugokencky, E.J., K.A. Maserie, P.M. Lang, P.P. Tans, L.P. 

Steele and E.G. Nisbet, A d ramatic decrease in th e growth 

rate of atmospheric methane in the northern hemisphere 

during 1992, Geophys. Res. Lett., 21, 45-48, 1994. 

Cantrell, C.A., R.E. Sheller, A.II. '.'vl:cDaniel, J.G Calvert, J.A. 

Davidson, D.C. Lowe, S.C. Tyler, R.J. Cicerone and J.P. 

Greenberg, Carbon kin eti c isotope effect in the oxidatio n of 

methane by the hyd roxy l radica l, J . Geophys. Res., 95, 

22,455-22,462, 1990. 

138 

Lowe , D.C., C.A.M. Brcnninkmeijer, G.W. Brailsford, K.R . 

Lassey, A.J. Gomez and E.G. Nisbe t, Concentration and tJc 

record s of atmo spheri c methane in New Zealand and 

Anta rcti ca: evidence fo r c hanges in methane sources, J. 

Geophys. Res., 99, 16,913-16,920, 1994. 

Quay, P.O., S.L. King, J. Stutsman, D.0. Wilbur, L.P. Steele, I. 

Fu ng, R.11 . Gammon, T.A . Brown , G.W. f-a rwell, P.M. 

Grootes, and F.1-1 . Schmidt, Carbon isotopic composit ion of 

atmospheric methane: f-ossi l and biomass burning source 

strengths, Global Diogeochem. Cycles, 5, 25-4 7, 1991. 

Stevens, C.M. and F.E. Rust, The carbon isotopic compositi on 

of a tm ospheric methane, J. Geophys. Res., 87, 4879-4882, 

1982. 

Wigley, T.M.L. and S.C.13 . Raper, Impl icatio ns for c limate and 

sea level of revised IPCC emission scenarios, Na111re, 357, 

293-300, 1992. 
Point Barrow Geomagnetic Observatory 

J.F. SCARZELLO 

Naval Surface Warfare Center, Electromagnetic Fields Branch, Silver Spring, Maryland 20903.5640 

As part of the U.S. Navy's Ice Experiment 1-91, a 

permanent Geomagnetic Observatory was established at 

Point Barrow, Alaska, on March 21, 1991. The Point 

Barrow Geomagnetic Observatory (PBGMO) was designed 

and established by Naval Surface Warfare Center (NSWC), 

Electromagnetic Fields Branch, to be a permanent facility 

that acquires ambient noise using slate-of-the-art and 

experimental magnetic sensors. This program is sponsored 

by the Office of Naval Research, Ocean, Atmosphere, and 

Space Science Technology Department. The observatory 

was established lo measure the high level geomagnetic 

activity (1991 to 1993) generally associated with sunspot 

maximum periods and to provide data for al least the next 

decade. The PBGMO sensors are located on U.S. Air Force 

properly, near the NOAA Climate Monitoring and 

Diagnostics Laboratory that provides support and housing 

for the observatory electronics. The U.S. Geological 

Survcy's geomagnetic observatory is about 1/2 km west and 

uses less sensitive proton precession magnetometers. 

The PBGMO has three helium-3 magnetometers and 

three triaxial nuxgate magnetometers arranged to form two 

orthogonal gradiometer axes, north-south and east-west 

magnetic with baselines of 152 m (500 feet). The sensor 

and its electronics are mounted on a tray inside a PVC tube 

that is put inside a 203-mm (8-inch) diameter fiberglass 

waterproof housing. The fiberglass tube has a welded 

aluminum pipe sh ie ld (open ends) and is put inside a nonmagnetic wooden box. A non-magnetic wooden fence was 

built around the sensor to mark its location and protect it 

from animals and adventuresome snowmobilers. Two RG8/U cables are required lo provide power to and obtain 

signals from each sensor. The six cables are routed to the 

CMDL facility building where NOAA has provided NSWC 

with a table in a comer of one room and access to a phone 

line. The U.S. Air Force Long Range Radar Site provides 

space for storage, lodging, and other logistical support. 

Data from the Point Barrow helium-3 and fluxgat e 

sensors are recorded on magnetic tape cartridges (March 

1991 lo January 1994) and most recently, (January 1994 to 

present) on optical disk storage medium because of the 

volume of data obtained from continuously sampling the 

ambient noise and to easily access data records. Data tapes 

and cartridges have been shipped to NSWC, White Oak site 

by NOAA personnel. 

The PBGMO electronics were originally designed to 

pump the helium-3 sensors once a day, assuming the 

helium-3 nuclear magnetic resonance magnetometer T2 

times would be greater than 24 hours. Unfortunately, only 

one of the three worked reliably greater than 24 hours, so a 

12-hour repump time was programmed, resulting in a 10-

minute loss of data from an otherwise continuous data 

record. Trips lo repair one helium-3 sensor and up-grade 

139 

software, electronics, and assure that sensors have greater 

than 12 hours T2 time were made on September 30, 1991. 

and again in January 1994 . The hclium-3 magnetometers, 

designed and built by Texas Instruments, Inc .. McKinney, 

Texas, have a noise level of nominally I picotcsla. (1 

picotesla = 10" Oersted= IO" nanotesla = IO" gamma). 

All observatory functions are controlled by a type 386 

personal computer with a magnetic tape drive and a Ricoh 

Optical Drive, uninterruptable power supply, modem phone 

line for program control, and instant access from White 

Oak. An electronics power supply sensor interface cabinet 

contains three power supplies that power each sensor 

separately. 

THE DATA 

The initial measured data contained some glitches and 

incomplete data records that have been corrected resulting 

in almost continuous data records from April 1991 to the 

present. Each data file contains all sensor information 

sampled at 2.34 Hz and identified by year (last digit), 

month (2 digits), day (2 digits) hours Zulu (2 digits) and 

lens of minutes to define the standard half hour file. The 

helium-3 NMR magnetometer measures the absolute value 

of the total ambient field, and at this location it is 

nominally 57,450 nT with slight variations associated with 

sensor location, i.e., sensor no. l measures 35 nT more than 

sensor no. 3, and sensor no. 2 is l 0 nT less than sensor no. 

3. 

In addition to the total field helium sensor information, 

each of the three sensors has a fluxgale magnetometer. 

Activity indices are computed from the triaxial fluxgate 

magnetometers over a 23-hour period. The indices arc the 

change in component field amplitude in nanotesla measured 

in a 2.5-minute period. Display software has been 

developed to plot the field value from all sensors and 

components and the gradient field from each sensor pair, 

i.e., 1-2, 2-3, and 1-3 for one 30-minute data segment. 

THE FUTURE 

The present plan is to operate the PBGMO for al least the 

next decade. Some upgrading is planned for the helium-3 

and fluxgate magnetometers, enhancing data recording 

reliability, and testing experimental sensors and systems. 

Data reduction, which includes transferring magnetic tape 

cartridge data to optical disks, appears to be the most 

efficient storage and distribution mechanism and will be 

done in FY95. Software development has been started lo 

define a set of geomagnetic noise parameters, lo 

automatically scan through the archived data, and to select 

out data segments of interest for further examination. 
USGS Barrow Observatory 

JACK TOWNSHEND 

U.S. Geological Survey, College Obesrvatory, Fairbanks, Alaska 99775-5160 

The Barrow Magnetic Observatory is the northernmost of 

this agency's (U.S. Geological Survey) 12 continuouslyrecording, digital magnetic observatories. As such, it 

serves as a singularly important site in a global network of 

observing stations whose combined data define the 

planetary magnetic field and track its secular change. 

Ground stations such as the Barrow ·Observatory are 

controls for field modeling by harmonic analysis, essential 

reference stations for airborne and satellite surveys, and 

absolute calibration locations for field survey 

instrumentation. 

The primary instrumentation operated is an EDA FM100BR Triaxial fluxgate magnetometer, an EDA PPM-105 

proton free-precession magnetometer, an Observatory 

Magnetometer Interface System (OMIS), and several piermounted instruments for absolute control observations. 

In August 1993 the USGS and NOAA negotiated a 

Memorandum of Agreement (MOA) to have CMDL 

personnel at Barrow service the USGS BRW equipment, 

make instrument observations, and provide some logistic 

support. 

The principal investigator for the Barrow Observatory in 

1993 was Jack Townshend. The coinvestigator in 1993 was 

Robert Hammond. In 1994, Johnny Dickey is the 

coinvestigator. The Barrow Magnetic Observatory receives 

its authorization to operate from the USGS Branch of 

Earthquakes and Geomagnetic Information in Golden, 

Colorado. 

Parts of the NOAA-USGS MOA are presented below to 

provide some history and background of our joint Barrow 

operations. 

For many years, the Naval Arctic Research Laboratory 

(NARL) was the source of electrical power, road maintenance, 

transportation, and lodging support. Effective October 1, 1984, 

this support was no longer assured as the Navy began the 

process of transferring ownership of NARL to the Ukpeagvik 

Inupiat Corporation (UIC). 

Individual withdrawal applications for land occupied by 

each agency's project was approved by BLM and published 

in the Federal Register. Withdrawal file numbers are 

NOAA-F-81469 and USGS-F-81490. Transfer of the land 

to the USGS and NOAA was made effective April 2, 1991, 

and published in the Federal Register, Volume 56, Number 

63, page 13413, dated April 2, 1991. 

A third-party agreement was set up between NOAA, 

USGS, and the Department of the Air Force, now located at 

11 TCW/LGOX, 6900 9th St. Suite 301 , Elmendorf AFB, 

Alaska 99506-2270, to provide support for electrical power, 

road service, transportation, vehicle repair, lodging, and 

meals through their DEW System Station at Barrow, Alaska 

(Pow-Main). This agreement (Inter-Agency MOA between 

NOAA and USGS) will be an attachment to the "Support 

Agreement" between USAF, NOAA and USGS. NOAA is 

authorized by the USGS to be signatory to the "Support 

Agreement" with the USAF, since they want only one 

signature on the document. 

Subsequently NOAA and USGS agreed to get power 

from the Barrow Utilities and Electric Co-op, Inc., 

(BUEGI), through the Ukpeagvik Inupiat 

Corporation/Northern Arctic Research Laboratory 

(UIC/NARL) facility. 

NOAA and the USGS shall continue to acquire electrical 

power from the Barrow Utilities and Electric Co-op., l nc. 

(BUECI). During emergencies and times then when power 

is not available from BUECI, it is the intent of NOAA and 

USGS to receive electrical power from the Air Force DEW 

Line. 

Under the terms of the MOA, NOAA agrees to have the 

CMDL personnel at Barrow do the following: 

Weekly 

140 

Check facilities for any noticeable damage or unusual 

conditions and report anything that may seem out of the 

ordinary to the College Observatory, Fairbanks, check the 

Observatory instruments and equipment, and make routine 

rotations on specific forms supplied. 

Monthly 

Make six sets of magnetic absolute observations with a 

Declination Inclination Magnetometer (DIM); make one set 

of Scale Value Observations on the Observatory 

Magnetometer Interface System (OMIS) Fluxgatc 

Magnetometer; change digital magnetic, and analog paper 

tapes; and send all data, computations, observations, and 

tapes to the USGS office. 

Unscheduled 

Perform minor trouble shooting and make adjustments to 

equipment when USGS technical personnel provide 

instructions by telephone. 

For the services supplied by NOAA in the previously 

mentioned items, the USGS will reimburse NOAA for the 

time required to perform the work, travel time required to 

get to and from USGS facilities and instruments, and a 

reasonable amount for unplanned c ircumstances because of 

emergencies, weather, etc. Supplies and materials arc not 

included in this agreement. USGS will pay for or 

reimburse NOAA for supplies or materials needed. 
A New Rugged High Sensitivity Radon Monitor for Remote Stations 

STEWART WHITTLESTONE 

Australian Nuclear Science and Tech nology Organization, Menai NS\V 2234, Australia 

STEVE RYAN 

NOAA Mauna Loa Observatory, Hilo, Hawaii 97621-0275 

INTRODUCTION 

The radon detector which was operated for ANSTO by 

MLO, was installed in April 1989 to provide a full year 

of radon concentrations to assess the utility of such 

information to the CMDL baseline monitoring program. 

After a year the data proved to be of interest, and the 

instrument was easy to operate so it was left in place. 

Over the 5 years to April 1994, several publications 

have drawn on data from the radon program 

[Wh i11lestone, 1985, 1990, Whittlestone et al., 1991, 

1992, 1993; Gras and Whittlestone, 1992). Radon has 

been established as a valuable measurement for 

characterizing air masses and should continue to be 

measured at MLO. 

Scientifically it would be desirable to expand 

CMDL's radon measurement program to other stations. 

The major inhibition to this process has been financial, 

but there was also concern that the instrument was more 

complex than would be desirable at some stations. 

MLO is environmentally re latively benign and, because 

of its size, has the technical capability to maintain a 

relatively complex instrument. Simply installing a 

duplicate of the first MLO radon detector would not 

guarantee success at another observatory. ANSTO has, 

therefore, been developing an instrument better suited 

to more remote sites. 

MLO has provided an e xcellent opportunity to assess 

the requirements of a radon detector, partly because it 

has much in common with other stations that could 

benefit from radon measurements, and partly because it 

has two radon detectors (ANSTO's and EML's), each 

with different c haracteristics. ANSTO's new design is 

superior in all ways to its old one, and it incorporates 

some of the better qualities of the EML instrume nt . In 

line with the design objectives, the main respects in 

which the new instrument is superi or to either of the 

others is in initial cost, simplic ity, low power 

consumpti on, and freedom from routine maintenance. 

In April 1994 the ANSTO radon detector at MLO was 

re -built to become the second detector of its type. The 

first was installed at Cape Grim in February 1994. 

Prior to this, only a small laboratory prototype had been 

operated. It is therefore pleasing to be able to report 

that the new system has performed to specification and 

required no operator intervention between its 

installation and writing of this report (July 1994). A 

detailed report on the new design is being prepared by 

S. Whittlestone et al, 1994. 

141 

DETECTOR DESIG N 

High-sensi tivi ty radon detectors work on the "twofilter" principle. Five stages are involved: (1) All radon 

decay products are fi ltered from the inlet a ir by the first 

fi lter; (2) the air passes through a delay chamber whe re 

a known proportion of the radon decays; (3) the decay 

products, which have a concentration proportional to 

that of the radon, are collected on the second filter; (4) 

the decay of the radon decay products on the filter is 

converted to electronic pulses; and (5) a data 

acquisition and control ·system collects the data and 

monitors essential operating parameters. 

For brevity the EML detec tor will be designated "E", 

the old ANSTO detector "Al" and the new one "A2". 

Little discussion is required of stage 1. All the 

instruments have similar fi lters for filter 1, but rather 

different fl ow rates, being 400-, 90-, and 40-L min· I for 

E, A2 and Al respectivel y. 

Stage 2 involves impunam design consideration s 

because it is necessary to stop the radon decay products 

from being plated out on the walls of the delay 

chamber. E uses the approach of moving the air so fast 

that the decay products do not have time to stick. In E's 

design this means that high flow rates ( 400 L min· I) are 

needed in all flow paths, resulting in high pumping 

power. Al h ad an aerosol injected into the air stream. 

The decay products became attached to the aerosol 

which was much less likely to plate out, so it was 

possible to use a low flow rate (40 L min·l). A2 uses 

the high flow rate idea, but has an internal flow loop 

which means that the high flow is only through a very 

low impedance filter. The result is that A2 has the 

simplicity of E but an even lower pumping power than 

Al. At 25 watts, the power is about an order o f 

magnitude less than E or A 1. 

In stage 3, the second filter, A2 aga in takes the 

simpler of the approaches used in E and A I. In this 

case it is Al's fixed filter that is used . But an important 

step is taken here by using a very fine wire screen that 

is just as effective as a filter for collecting the decay 

products, but offers much less flow impedance. This is 

the only part of the detector tha t requires routine 

maintenance, and it should be replaced or cleaned every 

l or 2 years. 

The fixed filter has two advantages over the movingfilter design. One is the inherent simplicity. Nothing 

moves and no external control is required. The other 

advantage is that all the decay products on the filter are 
counted, whereas in a moving-filter system, about half 

of them decay during sampling before the filter is 

moved to the counter. Fixed-filter detectors are, 

therefore, more efficient. 

The disadvantage of the fixed filter is that the time 

response is slow. A 1 took about 90 minutes to reach 

50% of maximum count rate, whereas E indicates the 

concentration in well-defined half-hour intervals. A2 is 

much faster than A 1 for reasons that are too complex to 

explain here. It reaches 50% of maximum response in 

30 minutes. 

There are applications where the slow response time 

of Al makes it necessary to use design E. Many of 

those applications would be adequately served by design 

A2, making it unnecessary to compromise on efficiency 

and increase complexity, as E does, in order to gain the 

required time response. Stage 4, counting the decay 

products, is practically identical for all three systems. 

It involves a zinc sulfide screen scintillator with a 

photomultiplier to detect the alpha particles, followed 

by pulse amplifiers, and discriminators. 

In the final stage, 5, which includes data acquisition 

and control, E and Al need active control of moderately 

complex systems: a filter tape transport mechanism and 

particle counter respectively. A2 has no devices to 

control and in its simplest configuration needs to record 

only pulses from the alpha counter. Only a very simple 

device is needed. Real-time requirements could be met 

by a simple, robust data logger. 

RESULTS 

Figure 1 is an example of the results obtained from 

the new detector (A2) and the EML detector (E). There 

is no question that A2 is measuring radon. However 

well a l aboratory prototype works, performance must be 

obtained in the field. The agreement between the 

results will be considered first. Correlation analysis 

shows that overall, the correlation coefficient between 

them is 0.79. The data were grouped using different 

criteria: groups with a wide range of concentrations had 

the best correlations. The period shown with its 

concentration range of about 50 to 500 mBq m-3, had a 

correlation coefficient of 0.87, whereas groups with 

ranges 50 to 300 typically had correlation coefficients 

of about 0.65. These are consistent with correlations 

observed between detectors E and Al that ranged from 

0.55 for narrow concentration ranges to 0.97 when the 

concentrations reached 1000 mBq m-3. There is some 

evidence in this limited data set that the correlation is 

better between E and A2 than E and Al, as expected 

because of the improved time resolution of A2. 

It is instructive to examine the differences between 

the results. At concentrations below 100 mBq m-3, the 

agreement is poor, which can be attributed mainly to 

counting statistical error. At 60 mBq m-3 the error on a 

1-hour value for Eis 30% and for A2 is 15%. At higher 

concentrations, differences are smaller, but not as small 

142 

400 II 

".' 

E --new ANSTO detector J ' ' CT 

m - - - - EML detector • ',: 

.s I 

z 200 0 

i= 

< I 

a: I 

I- I 

z I I 

w I I 

(.) I I 

z I I 

0 I I 

(.) I 

z I I 

0 •' " 0 •' II 

< 60 •' II 

a: ~ u 

I 

I ' 

40._ ____ __. ______ ....._ ______ .._ ____ __J ______ _._ ______ 

125 126 127 

DAY of 1994 (major ticks at midnight) 

Fig. I. Radon concentrations at MLO measured by ANSTO and 

EML instruments. 

as could be expected on the basis of counting statistics. 

These differences arc attributed to the better time 

resolution of E. 

CONCLUSIONS 

A new design of baseline radon detectors brought the 

cost and maintenance requirements down to about the 

cost of meteorological instruments. Given the power of 

radon measurements to characterize air samples at 

remote stations, it is recommended that such 

measurements be viewed as a necessary component of 

their basic instrumentation. 

The new design has been proven in the field al MLO. 

It has achieved the same sensitivity as the previou s 

ANSTO radon detector for about half the capital cost, a 

tenth of the power consumption, and reduction o f 

routine maintenance from weekly to once per year. 

Because of the simplicity of the design, it is reasonable 

to expect that unscheduled breakdowns should be less 

frequent and diagnosis should be much easier. 

While the new detector is superior to the old ANSTO 

design in all respects, the EML design would be 

preferred in situations when time resolution is o f prime 

importance and concentrations of interest arc more than 

100 mBq m-3. At MLO, where the demand s o f 

instrument maintenance can be met easily , it ts 

desirable to have both detectors because there are rapid 

concentration changes, long periods when the 

concentration is more than 100 mBq m-3, and periods 

when the concentration is lower than 100 mBq m-3 and 

higher sensitivity is necessary. 

For a new installation at stations less well staffed 

than MLO and with a more demanding environment, the 

new design is to be preferred on cost and maintenance 

considerations. At Samoa, South Pole, and Barrow, 
Jong periods of very low radon concentrations could be 

ant icipated, which gives a scientific preference for the 

more sensitive instrument. 

Acknowledgments. The authors are grateful to CMDL for housing 

the equipment and assisting with its operation. The radon detector 

upgrade kit was built by B. Stenhouse of ANSTO. 

REFERENCES 

Gras J., and S. Whittlestone, Radon and CN: Complementary tracers of 

polluted air masses at coastal and island sites, J. Radioanal. Nucl. 

Chem., 161, 293-306, 1992. 

Whittlestone S., Radon measurements as an aid to the interpretation of 

atmospheric monitoring, J. Atmos. Chem., 3, 187-201, 1985. 

Whittlestone S., Radon from distant continents detected at the Mauna 

Loa Observatory, in Climate Monitoring and Diagnostics Laboratory 

No. 18 Summary Report 1989, pp. 131-133, NOAA Environmental 

Research Laboratories, Boulder, CO, 1990. 

Whittlestone S., L.P. Steele, and S. Ryan, Radon as a baseline selection 

criterion at Mauna Loa Observatory, in Climate Monitoring and 

Diagnostics Laboratory No. 1.9 Summary Report 1990, pp. 120-123, 

NOAA Environmental Research Laboratories, Boulder, CO, 1991. 

Whittlestone S., S.D. Schery, and Y. Li, Separation of loca l from 

distant pollution at MLO usi ng Pb-212", in Climate Monitoring 

and Diagnostics Laboratory No. 21 Summary Report 1992, pp. 

11 6- 118, NOAA Environmental Research Laboratories, Boulder, 

co. 1993. 

143 

Whiulestone S., E. Robinson, and S. Ryan, Radon at the Mauna Loa 

Observatory: Transport from distant continents, Atmos. Environ. 

26A(2), 251-260, 1992. 
7. International Activities, 1993 

In July, Eldon Ferguson attended and particip ated in 

the International Symposium on Modern Chemistry in 

Beijing, China. In November, he lectured at the 

Department of Chemistry and · interacted and 

collaborated on research in atmospheric ion chemistry 

and air-sea exchange of C02 at the University of 

Canterbury, Christchurch, New Zealand. 

In April, Russ Schnell spent 1 week in northern 

Siberia at Cherskiy, Russia, co-leading a group of 

NOAA, EPA, and DOE scientists and administrators in a 

research logistics demonstration project. The group 

flew on chartered Russian aircraft including an AN-74 

(jet), AN-26 (twin turboprop), and AN-2 (single engine 

biplane) to Lest the aircraft capabilities for future Arctic 

air research projects. Doug Guenther, also a member of 

the group, determined the feasibility of utilizing 

Russian aviation resources to carryout out flask 

sampling of trace gases. Russ Schnell attended the 

International Global Aerosol Program workshop in 

Geneva, June 28-July 2, 1993, as a member of two 

Expert Panels drafting the overall IGAP program plan. 

October 4-8 Russ Schnell attended and presented papers 

on AGASP and CMDL Arctic meteorological data sets 

at the International Symposium on the Ecological 

Effects of Arctic Air Contaminants, Reykjavik, Iceland. 

Bernard Mendonca traveled to Geneva, Switzerland, 

in January to attend the first organizational meeting for 

the establishment of the WMO GAW stations. In March 

he traveled Lo Munich, Germany, Lo attend the 

Harmonization of Environmental Measurement (HEM) 

Programme and Tt ::hnical Advisory Group Meeting as a 

member of the programme and technical advisory group 

of the United Nations Environment Programme (UNEP). 

In March and April Bernard traveled Lo Buenos Aires, 

Argentina, and Sao Paulo, Brazil, to continue in the 

organization and establishment of GAW stations. 

Bernard traveled Lo Geneva in June and again in 

October to aid the WMO Secretarial staff in station 

logistics and purch asing of equipment for the GAW 

stations. 

In April and May, Dave Hofmann traveled Lo 

Obcrpfaffenhofen, Germany, to discuss research results 

at the Institute for Atmospheric Physics. D. Hofmann 

presented a paper entitled "Twenty years of 

balloonborne tropospheric aerosol measurements at 

Laramie , Wyoming" at the First International Global 

Atmospheric Chemistry Program (ICAG) Scientific 

Conference in Eilal, Israel. Next, he visited the 

Institute for Atmospheric Environment Research in 

Garmisch, Germany, Lo conduct research and present a 

paper entitled "Possible impact of the commercial jet 

fleet on the upper tropospheric aerosol" al the XVIII 

General Assembly of the European Geophysical Society 

in Wiesbaden, Germany. D. Hofmann then visited the 

Max Planck Institute (MPI) in Heidelberg before 

attending the MPI sponsored IPCC WGI Workshop on 

The Impact on Climate of Ozone Change and Aerosols 

held in Hamburg. 

D. Hofmann attended two WMO meetings. The first 

was the June meeting of the Stratospheric Aerosol 

working group of the International Global Aerosol 

Program at WMO headquarters in Geneva, Switzerland. 

The second meeting was comprised of authors for the 

United Nations Environment Program Ozone Trends 

Report and was held in September in Cambridge, 

England. In late October and early November, D. 

Hofmann attended a meeting at the CSIRO Cape Grim 

Baseline Air Pollution Station in Hoban, Tasmania, 

Australia. 

H. Vomel participated in the NATO Advanced Study 

Institute on Low Temperature Chemistry of the Atmosphere 

in Maratea/Sapri, Italy. He presented a paper entitl ed 

"Balloon-borne obser.vations of stratospheric and upper 

tropospheric water vapor in the tropics and over 

Antarctica." While in Europe, H. Vomel also visited 

Grossforschungsanlage in Jiilich, Germany, to work with 

Dieter Kley on the use of their atmospheric test for 

calibrating ozonesondc pumps and the frost-point 

hygrometer. M. O'Neill accompanied H. Vomcl to carry 

out balloonbome water vapor and ozone measurements 

from aboard the research vessel Joh11 I/. Vickers. 

Mike O'Neill visited Christmas Island, Republic of 

Kiribati, on March 18-29 and Terciera, Azores, on July 

28-September 9 to discuss C02/CH4 /CO sampling with 

local sample takers. 

The University of Stockholm invited John Ogren to 

present a seminar "Measurements of the sizcdcpcndence of the scavenging efficiency of aerosol 

particles by fog droplets" in January. While in Sweden, 

John consulted with colleagues on the measurements 

done at the Swedish baseline station on Spitsbergen and 

worked with faculty and students on evaluation of 

cloud/aerosol measurement data. 

144 

In September, Sam Oltmans attended a workshop on 

European Ozonesondc Records and presented results on 

North American ozonesonde trend s in Jlilich, Germany. 

B. Evans and W. D. Komhyr traveled to Hradcc 

Kralove in the new Czech Republic to attend the Dobson 

Workshop and lntercomparison in May. 

In June, W.D. Komhyr attended the High Latitude 

Optics Symposium in Troms~. Norway, to present an 

invited paper enti tled, "U.S.A. Dobson Spectrophotometer Total Ozone Program, 1962-1992." In 

November, W.D. Komhyr traveled to Thessaloniki, 

Greece, to participate in a WMO Meeting of Experts on 

Homogenizing Total Ozone Records for Ozone 

Assessments and Early Warning of Ozone Changes. 

B. Bodhaine and J. Wendell traveled to the remote 

Sable Island Regional Climate Monitoring Station off 

the coast of Newfoundland, Canada, in July to install 
new and to test and calibrate existing aerosol 

instrumentation. In late October, J. Wendell installed a 

new solar radiation data acquisition system at South 

Pole, Antarctica. 

M. Lucarelli from Australia (CSIRO) and R. Knobben 

from New Zealand (NIWA) worked with D. Guenther from 

April to June to build four of the CMDL-design aircraft 

sampling apparatus. Under an agreement, CSIRO and 

NIWA each received a complete sampling system. 

In May, L. Haszpra from the Institute for 

Atmospheric Physics in Budapest, Hungary, came to 

Boulder for 25 days. The purpose of the visit was to 

prepare a paper for presentation at the 4th International 

Conference on COz. 

Pieter Tans, Jim Peterson , and Michael Trolier 

attended the WMO C02 Experts Meeting held on 

September 6-11 in Rome, Italy. 

Peter B akwin , Philippe Ciais, Jim Peterson, Pieter 

Tans, and Michael Trolier participated in the 4th 

International C02 Conference in Carqueiranne, France, 

on September 13- 17. Each presented a paper (see 

Publications and Presentations). 

The program to bring flask-sampling network personnel 

to Boulder was continued. In preparation for establishing a 

sampling site in Malta, H. Galea from the Ministry of 

Environment, Pollution Control Co-ordinating Unit, 

Vittoriosa, visited Boulder September 8-12. Likewise, H. 

Munoz, Direcion Meteorologica de Chile, was invited to 

Boulder in connection with establishing a cooperative 

program for collecting air sampl~s on Easter Island. 

Sampling began in January 1994. Taking advantage of his 

trip to Washington, DC, arrangements were made for D. 

Dagvadorj, Mongolian Hydro-Meteorological Research 

Institute, to make a side trip to Boulder on December 18-21 

to discuss the results to date of sampling for about 2 years 

at Ulaan Uul. 

The South China Sea air sampling aboard the Chevron 

tanker Carla A. Hills terminated in February after 19 

months of continuous collecti ons. The vessel's charter 

was not renewed by Caltex. The Blue St ar Line vessels, 

We llington Star and Southland Star were withdrawn 

from trans-Pacific service in Jul y and August, 

respectively. L. Waterman traveled to Los Angeles to 

join the Blue Star Line vessel California Star on 

October 16-31 to train ship's officers to col lect air 

samples and to restart Operation Pac ific Air that had 

been in hiatus since August. The practice of collecting 

samples at 5• latitude intervals will be continued and a 

single pair in the middle of the Tasman Sea for each 

crossing was added to the protocol. L. Waterman 

disembarked at Botany Bay, NSW, and visi ted Glass 

Expansion Pty. Ltd ., Hawthorn, Victoria, and CSIRO, 

Aspendalc, Victoria, on November 2. Glass Expansion 

manufacturers one of the best glass o-ring seal valves 

currently on the market. From November 12-26, L. 

Waterman sailed on the Great Promise from Singapore 

to Hong Kong and return to restart the South China Sea 

program. The protocol for collect ing pairs of evacuated 

samples every 3• of latitude on all runs, north and 

south, was reestablished. 

P. Novelli continued intercomparisons of CO 

standards begun in 1991 . The current round of 

comparisons, begun in July, involves ten laboratories in 

eight countries and will be completed in January 1995. 

Four cylinders of standard gases are being sent from 

one collabora tor to the next in Australia, Brazil, 

Germany, Hong Kong, Japan, New Zealand, South 

Africa, and the United States (Colorado, Maryland, and 

Virginia). The objective of the intercomparisons, 

sponsored by NASA, is to create an internally consistent 

set of ground based measurements to wh ich 

measurements from space can be compared. 

145 
8. Publications and Presentations by CMDL Staff, 1993 

Bakwin, P.S., Measurements of carbon dioxide on a very tall 

tower, paper presented at the 4th International Conference on 

C02 sponsored by WMO Global Atmosphere Watch, 

Carqueiranne, France, September 13-17, 1993. 

Bodhaine, B.A, The U.S. aerosol monitoring program in 

Antarctica, Proceedings, 4th Workshop Italian Research on 

Antarctic Atmosphere, Porano, Italy, October 21-23, 1991, 

Italian Physical Society, Bologna, Italy, 15-25, 1993. 

Bodhaine, B.A., and E.G. Dutton, A long-term decrease in 

Arctic Haze at Barrow, Alaska, Geophys. Res. Lett., 20, 947-

950,1993. 

Bodhaine, B.A., B.I. Nazarov, and A.K. Shukurov, Comparison 

of aerosol concentrations at Fedchenko Glacier and 

Dushanbe, in JOINT SOVIET-AMERICAN EXPERIMENT 

ON ARID AEROSOL, G.S. Golitsyn (ed.), Hydrometeoizdat, 

St. Petersburg, Russia, 181-184, 1993. 

Bojkov, R., W.D. Komhyr, A. Lapworth, and K. Vanicek, 

Dobson data re-evaluation handbook, NOAA Tech. Report 

NESDIS 74, 140 pp., 1993. 

Butler, J.H., J.E. Elkins, T.M. Thompson, B.D. Hall, J.H. 

Lobert, T.H. Swanson, V. Korapalov, poster presentation at 

the Biannual Meeting of the Oceanographic Society, Seattle, 

WA, April 2-16, 1933. 

Cess, R.D., S. Nemesure, E.G. Dutton, J.J. DeLuisi, G.L. 

Potier, and J.-J. Morcrette, The impact of clouds on the 

shortwave radiation budget of the surface-atmosphere 

system: Interfacing measurements and models, J. Clim., 

6(2), 308-316, 1993. 

Chiou, E.W., M.P. McCormick, L.R. McMaster, W.P. Chu, 

J.C. Larsen, D. Rind, and S. Oltmans, Intercomparison of 

stratospheric water vapor observed by satellite experiments: 

Stratospheric Aerosol and Gas Experiment II versus Limb 

Infrared Monitor of the Stratosphere and Atmospheric Trace 

Molecule Spectroscopy, J. Geophys. Res., 98(D3), 4875-

4887, 1993. 

Chu, W.P., E.W. Chiou, J.C. Larsen, L.W. Thomason, D. Rind, 

J.J. Buglia, S. Oltmans, M.P. McCormick, and L.M. 

McMaster, Algorithms and sens1llv1ty analyses for 

Stratospheric Aerosol and Gas Experiment II water vapor 

retrieval, J. Geophys. Res., 98(D3 ), 4857-4866, 1993. 

Ciais, P., P. Tans, M. Trolier, and J.W.C. White, Global carbon 

cycle modeling: The distribution of the sources and sinks of 

C02 from 13C isotope measurements in the remote 

troposphere, paper presented at the 4th International 

Conference on C02 sponsored by WMO Global Atmosphere 

Watch, Carqueiranne, France, September 13-17, 1993. 

Conway, T.J., L.P. Steele, and P.C. Novelli, Correlations 

among atmospheric C02. CH4 and CO in the Arctic, March 

1989, Atmos. Env., 27A(l7!18), 2881-2894, 1993. 

Davidson, C.I., and R.C. Schnell, Introduction: On arctic air, 

snow, and ice chemistry, Atmos. Env., 27A{17118), 2695-

2699, 1993. 

Davidson, C.I., J.-L. Jaffrezo. B.W. Mosher, J.E. Dibb, R.D. 

Borys, B.A. Bodhaine, R.A. Rasmussen, C.F. Boutron, U. 

Gorlach. H. Cachier, J. Ducret, J.-L. Colin, N.Z. Heidam, K. 

146 

Kemp, and R. Hillamo, Chemical constituents in the air and 

snow at Dye 3, Greenland: I, Seasonal variations, Atmos. 

Env., 27A, 2709-2722, 1993. 

Davidson, C.I., J.-L. Jaffrezo. B.W. Mosher, J.E. Dibb, R.D. 

Borys, B.A. Bodhaine, R.A. Rasmussen, C.F. Boutron, U. 

Gorlach. H. Cachier, J. Ducret, J.-L. Colin, N.Z. Heidam, K. 

Kemp, and R. Hillamo, Chemical constituents in the air and 

snow at Dye 3, Greenland: II, Seasonal variations, Atmos. 

Env., 27A, 2723-2737, 1993. 

DeLuisi, J.J., D.U. Longenecker, C.L. Mateer, and W.P. Chu, 

Estimation of solar backscatter ultraviolet albedo using 

ground-based Umkehr measurements, J. Geophys. Res., 

98(D2), 2985-2993, 1993. 

Dlugokencky, E.J., J.M. Harris, Y.M. Chung, P.P. Tans, and 

LY. Fung, The relationship between the methane seasonal 

cycle and regional sources and sinks at Tae-ahn Peninsula, 

Korea, Atmos. Environ., 27A, 2115-2120, 1993. 

Dlugokencky, E.J., P.M. Lang, K.A. Masarie, L.P. Steele, and 

E.G. Nisbit, A dramatic decrease in the growth rate of 

atmospheric methane in the Northern Hemisphere during 

1992, paper presented at the Fall American Geophysical 

Union Meeting, San Francisco, CA, December 10, 1993. 

Dutton, E.G. An extended comparison between LOWfRAN7 

computed and observed broadband thermal irradianccs: 

Global extreme and intermediate surface conditions, J. 

Atmos. Oceanic Technol., 10(3), 326-336, 1993. 

Elkins, J., Facts and myths over ozone depletion and the CFCs, 

paper presented at the NOAA Sea Grant Meeting-New 

England Region, Durham, NH, November 9, 1993. 

Elkins, J.W., T.M. Thompson, T.H. Swanson, J.H. Butler, B.D. 

Hall, S.O. Cummings, D.A. Fisher, and A.G. Raffo, 

Decrease in the growth rates of atmospheric 

chlorofluorocarbons 11 and 12, Nature, 364, 780-783, I 993. 

Ferguson, E.E, Processes associated with stratospheric ozone 

decrease: homogeneous chemistry, in The Role of the 

Stratosphere in Global Change, M.-L. Chanin (ed.), NATO 

ASI Series, Vol. 18, Sprmger-Verlag, Berlin Heidelberg 47-

64, 1993. 

Gillette, D.A., and B.A. Bodhaine, U.S. results from a joint 

US/USSR experiment for the study of desert dust and its 

impact on local meteorological conditions and climate, in 

JOINT SOVIET-AMERICAN EXPERIMENT ON AIUD 

AEROSOL, G.S. Golitsyn (ed.), Hydromcteoizdat, St. 

Petersburg, Russia, 7-22, 1993. 

Gillette, D.A .. B.A. Bodhaine, and D. Mackinnon, Transport 

and deposition of desert dust in the Kafirnigan River Valley 

(fadzhikistan) from Shaartuz to Esanbay: Measurements and 

a simple model, Atmos. Env., 27A( 16), 2545-2552, 1993. 

Gleason, J.F., PK. Bhartia, J.R. Herman, R. McPeters, P. 

Newman, R.S. Stolarski, L. Flynn, G. Labow, D. Larko, C. 

Seftor, C. Wellemeyer, W.D. Komhyr, A.J. Miller, and W. 

Planet, Record low global ozone in 1992, Science, 260, 523-

526, 1993. 

Goldan, P.D., W.C. Kuster, F.C. Fehsenfeld, and S.A. 

Montzka, The observation of a C5 alcohol emission in a 
North American pine forest, Geophys. Res. Lett., 20(11 ), 

1039-1042, 1993. 

Gunter, R.L., A.D.A. Hansen, J.F. Boatman, B.A. Bodhaine, 

R.C. Schnell, and D.M. Garvey, Airborne measurements of 

aerosol optical properties over south-central New Mexico, 

Atmos., Env., 27A(8), 1363-1368, 1993. 

Hansen, A.D.A., R.C. Schnell, A.V. Polissar, and G.S. 

Golitsyn, Aerosol measurements over the East Siberian Sea, 

paper presented at the 5th Symposium on Arctic Air 

Chemistry, Copenhagen, Denmark, September 8-10, 1992, 

NERI Tech. Report. No. 70, National Environmental 

Research Institute, Roskilde, Denmark, 1993. 

Hansen, A.D.A., V.N. Kapustin, V.M. Kopeikin, D.A. Gillette, 

and B.A. Bodhaine, Optical absorption by aerosol black 

carbon and dust in a desert region of Central Asia, Atmos. 

Env., 27A, 2527-2531 , 1993. 

Hansen, A.D.A., V.N. Kapustin, V.M. Kopeikin, D.A. Gillette, 

and B.A. Bodhaine, Optical absorption by aerosol black 

carbon and dust in a desert region of Central Asia, in JOINT 

SOVIET-AMERICAN EXPERIMENT ON ARID AEROSOL, 

G.S. Golitsyn (ed.), Hydrometeoizdat, St. Petersburg, 

Russia, 195-105, 1993, 

Herbert, G.A., P.S. Sheridan, R.C. Schnell, M.Z. Bieniulis, 

B.A. Bodhaine, Analysis of meteorological conditions 

during AGASP-IV, March 30-April 23, 1992, NOAA Tech 

MemoERLCMDL-5, 118pp., 1993. 

Herbert, G.A., R.C. Schnell, B.J.B. SLUnder, B.A. Bodhaine, 

S.J. Oltmans, and M.Z. Bieniulis, Meteorology and aerosol 

distribution during AGASP-III: The "Haze" flights (March 

16-30, 1989), NOAA Tech. Menw. ERL CMDL-6, 103 pp., 

1993. 

Hewitl, C.N., and W.T. Sturges (eds.), Global Atnwspheric 

Chemical Change, Elsevier, London, 470 pp., 1993. 

Hofmann, D.J, Twenty years of balloon-borne tropospheric 

aerosol measurements at Laramie, Wyoming, J. Geophys. 

Res., 98(D7), 12,753-12,766, 1993. 

Hofmann, D.J., Possible impact of the commercial jet fleet on 

the upper tropospheric aerosol, paper presented al the wvn 

General Assembly of the European Geophysical Society in 

Wiesbaden, Germany, Institute for Atmospheric 

Environment Research in Garmisch, Germany, May 3-7, 

1993. 

Hofmann, D.J., and S.J. Oltmans, J.M. Harris, W.D. Komhyr, 

J.A. Latluop, T. DeFoor, and D. Kuniyuki, Ozonesonde 

measurements at Hilo, Hawaii, following the eruption of 

Pinatubo, Geophys. Res. Lett., 20( 15), 1555-1558, 1993. 

Johnson, J.E. , V.M. Koropalov, K.E. Pickering, A.M. 

Thompson, N. Bond, and J.W. Elkins, SAGA-3 Experiment: 

Overview and meteorological and oceanographic conditions, 

J. Geophys. Res., 98(D9), 16,893-16,908, 1993. 

Kahl, J.D.W., D.J. Charlevoix, N.A. Zaitseva, R.C. Schnell, 

and M.C. Serreze, Absence of evidence for greenhouse 

warming over the Arctic Ocean in the past 40 years, Nature, 

361, 335-337, 1993. 

Kahl, J.D.W., M.C. Serreze, R.S. Stone, S. Shiotani, M. Kisley, 

and R.C. Schnell, Tropospheric temperature trends in the 

Arctic: 1958-1986, J. Geophys. Res., 98(D7), 12,825-12,838, 

1993. 

147 

Kaufman, Y.G., S.S. Khmelevtsov, and T.E. DeFoor, Lidar 

measurements of stratospheric aerosols during the SAGA 3 

expedition,]. Geophys. Res., 98(D9), 16,909-16,913, 1993. 

Keeling, R.F., R.G. Najjar, M.L. Bender, and P.P. Tans, What 

atmospheric oxygen measurements can tell us about the 

global carbon cycle, Glob. Biogeochem. Cycles, 7, 37-67, 

1993. 

Khalsa, S.J., J.R. Key, R.C. Schnell, J.D. Kahl, M.C. Serreze, 

and J. Bates, Final Report: Development and trend analyses 

of an Arctic TOVS temperature sounding record, Report to 

NASA, Contract NA26GP0186, 28 pp., (available from 

CIRES, University of Colorado, Boulder), 1993. 

Komhyr, W.D., U.S.A. Dobson Spectrophotometer Total 

Ozone Program, 1962-1992, paper presented at the High 

Latitude Optics Symposium in Tromsi;!, Norway, June 1993 

Komhyr, W.D., C.L. Mateer, and R.D. Hudson, Effective BassPaur 1985 ozone absorption coefficients for use with Dobson 

ozone spectrophotometers, J. Geophys. Res., 198(Dl 1 ). 

20,451-20,465, 1993. 

Larsen, J.C., E.W. Chiou, W.P. Chu, M.P. McCormick, L.R. 

McMaster, S. Oltmans, and D. Rind, A comparison of the 

Stratospheric Aerosol and Gas Experiment II tropospheric 

water vapor to radiosonde measurements, J. Geophys. Res., 

98(D3), 4897-4917, 1993. 

Lobert, J.M., and D.H. Scharffe, N10-and CH4-emissionen aus 

biomasseverbrennung , in EMISSIONEN DER TREIBHAUSGASE DISTICKSTOFFOXID UND METHAN IN 

DEUTSCHLAND, M. Schon, R. Walz, G. Angerer, K. 

Batcher, E. Bohm, T. Hillenbrand, H. Hiessl, and J. Reichert 

(eds.), Erick Schidt Verlag, Berlin, 110-132, 1993. 

Lobert, J.M., and J. Warnatz, Emissions from the combustion 

process in vegetation, in Fire in the EnvironmenJ: The 

Ecological Atnwspheric, and Climatic Importance of 

Vegetation Fires, P.J. Crutzen and J.G. Goldammer (eds.}, 

Wiley, New York, 15-37, 1993. 

McCormick, E.W. Chiou, L.R. McMaster, W.P. Chu, J.C. 

Larsen, D. Rind, and S. Oltmans, Annual variations of water 

vapor in the stratosphere and upper troposphere observed by 

the Stratospheric Aerosol and Gas Experiment II., J. 

Geophys. Res., 98(D3), 4867-4874, 1993. 

Miller, J.M., J.L. Moody, J.M. Harris, and A. Gaudry, A 10-

year trajectory flow climatology for Amsterdam Island, 

1980-1989,Atmos. Env., 27A(12), 1909-1916, 1993. 

Montzka, S.A., M. Trainer, P.O. Goldan , W.C. Kuster, and 

F.C. Fehsenfeld, Isoprene and its oxidation products, methyl 

vinyl ketone and methacrolein, in the rural troposphere, J. 

Geophys. Res., 98(Dl), 1101-1 111, 1993. 

Montzka, S.A., R.C. Myers, J.H. Butler, and J.W. Elkins, 

Global tropospheric distribution and calibration scale of 

HCFC-22, Geophys. Res. Lett., 20(8), 703-706, 1993. 

Noone, K.B., K.J. Noone, J. Heintzenberg, J. Strom, and J.A. 

Ogren, In situ observations of cirrus cloud microphysical 

properties using the counterflow virtual impactor, J. Atnws. 

Oceanic Technol., 10, 294-303, 1993. 

Ogren, J. Measurements of the size-dependence of the 

scavenging efficiency of aerosol particles by fog droplets, 

seminar presented at the University of Stockholm, Sweden, 

January 1993. 
Oltmans, S.A, Climatology of Arctic and Antarctic 

tropospheric ozone, in The Tropospheric Chemistry of Ozone 

in the Polar Regions, H. Niki and K.H. Becker (eds.), 

Springer-Ver lag, Berlin Heidelberg, 25-40, 1993. 

Oltmans, S.J, Climatology of the Arctic and Antarctic 

tropospheric ozone, in The Tropospheric Chemistry of Ozone 

in the Polar Regions, H. Niki and K.H. Becker (eds.), NATO 

AS! Series, 17, Springer-Verlag, Berlin, 25-40, 1993, 

Oncley, S.P .. A.C. Delany, T.W. Horst, and P.P. Tans, 

Verification of flux measurement using relaxed eddy 

accumulation, Atmos. E11viro11., 27A, 2417-2426, 1993. 

Pachenko, M.V., S.A. Terpugova, B.A. Bodhaine, A.A. lsakov, 

M.A. Sviridenkov, l.N. Sokolik, E.V. Romashova, B.I. 

Nazarov, A.K. Shukurov, E.l. Christyakova, and T.C. 

Johnson, Optical investigations of dust storms during 

U.S.S.R.-U.S. experiments in Tadzhikistan, 1989, Atmos. 

Env., 27A(16), 2503-2508, 1993. 

Parungo, F., C. Nagamoto, G. Herbert, J. Harris, R. Schnell, P. 

Sheridan, and N. Zhang, Individual particle analyses of 

Arctic aerosol samples collected during AGASP-ffi, Atmos. 

Env., 27(171]8), 2825-2837, 1993. 

Penner, J.E., R.J. Charlson, J.M. Hales, N. Laulainen, R. 

Leifer, T. Novakov, J. Ogren, L.F. Radke, S.E. Schwartz, 

and L. Travis, Quantifying and minimizing uncertainty of 

climate forcing by anthropogenic aerosols, DOE!NBB-0092T 

UC-402, U.S. Department of Energy, Washington, DC, 53 

pp .. 1993. 

Peterson, J.T., and R.M. Rosson (eds.), Climate Monitoring 

and Diagnostics Laboratory No. 21 Swnmary Report 1992, 

Environmental Research Laboratories, Boulder, CO 131 pp., 

1993. 

Peterson, J.T., K.W. Thoning, and P.P. Tans, Continuous 

atmospheric carbon dioxide measurements at Barrow, 

Alaska, 1973-1992, paper presented at the 4th 

International Conference on C02 sponsored by WMO 

Global Atmosphere Watch, Carqueiranne, France, 

September 13-17, 1993. 

Proffitt, M.H., K. Aikin, J.J. Margitan, M . Loewenstein, J.R. 

Podolskc, A. Weaver, K.R. Chan, H. Fast, and J.W. Elkins, 

Ozone loss inside the northern polar vortex during the 1991-

1992 winter, Science, 261, 1150-1154, 1993. 

Rind, D., E.-W. Chiou, W. Chu, S. Oltmans, J. Lerner, J. 

Larsen, M.P. McCormick, and L. McMaster, Overview of 

the Stratospheric Aerosol and Gas Experiment II water vapor 

observations: method, validation, and data characteristics. J. 

Geophys. Res., 98(D3), 4835-4856, 1993. 

Russell, P.B., J.M. Livingston, E.G. Dutton, R.F. Pueschel, 

J.A. Reagan, T.E. DcFoor, M.A. Box, D. Allen, P. 

Pilewskie, B.M. Herman, S.A. Kinne, and D.J. Hofmann, 

Pinatubo and pre-Pinatubo optical depth spectra: Mauna 

Loa measurements, comparisons, inferred particle size 

distributions, radiative effects, and relationship to lidar 

data, J. Geophys. Res., 198(DJ2), 22,969-22,985, 1993. 

Salawitch, R.J., S.C. Wofsy, E.W. Gottlieb, L.R. Lait, P.A. 

Newman, M.R. Schober!, M. Loewenstein, J.R. Podolske, 

S.E. Strahan, M.H. Proffitt, C.R. Webster, R.D. May, D.W. 

Fahey, D.Baurngardner, J.E. Dye, J.C. Wilson, K.K. Kelly, 

J.W. Elkins, K.R. Chan, and J.G. Anderson, Chemical loss 

of ozone in the Arctic polar vortex in the winter of 1991-

1992, Science, 261, 1146-1149,1993. 

Schnell, R.C., Are biological ice nuclei important in drought 

processes, past thoughts, present perspectives?, paper 

presented at Sixth International Conference on Biological Ice 

Nuclei, Univ. of Wyoming, Laramie, August 4-16, 1993. 

Schnell, R.C., P.J. Sheridan, B.A. Bodhaine, E.G. Dutton, and 

J.D. Kahl, Arctic gas and aerosol data sets from AGASP and 

the Barrow Baseline Station, Proceedings, Int. Symposium, 

Ecological Effects of Arctic Airborne Contaminants, 

Reykjavik, Iceland, 25 pp., USA CRREL Special Report 92-

93, October 4-8, 1993. 

Sheridan, P.J. R.C. Schnell, W.H. Zoller, N.D. Carlson, R.A. 

Rasmussen, J.M. Harris, and H. Sievering, Composition of 

Br-containing aerosols and gases related to boundary layer 

ozone destruction in the Arctic, Atmos. Env., 27A(17118), 

2839-2849, 1993. 

Sheridan, P.J., C.E. Quincy, and R.C. Schnell, Optical 

properties of aerosols in the Kuwait oil fire smoke plume, 

May-June 1991, NOM Data Report, ERL, CMDL-10, 

NOAA, Boulder, CO, 154 pp., 1993. 

Sheridan, P.J., R.C. Schnell, and D.W. Garvey, Analytical 

electron microscope analysis of aerosol sampled over White 

Sands Missile Range, NM, 1989, Atmos. Environ., 271\(8), 

1169-1183, 1993. 

Sheridan, P.J., R.C. Schnell, J.D. Kahl, J.F. Boatman, and D.M. 

Garvey, Microanalysis of the aerosol collected over southcentral New Mexico during the ALIVE field experiment, 

May-December, 1989, submitted, Atmos. Environ., 27A, 

1169-1183, 1993. 

Sheridan, P.J., R.C. Schnell, W.H. Zoller, N.D. Carlson, R.A. 

148 

Rasmussen, J.M. Harris, and H. Sicvering, Composition of 

Br- containing aerosols and gases related to boundary layer 

ozone destruction in the Arctic, Atmos. E11viron., 27A, 2839-

2849, 1993. 

Stone, R.S., J.R. Key, and E.G. Dutton, Properties and decay of 

stratospheric aerosols in the Arctic following the 1991 

eruptions of Mount Pinatubo, Geophys. Res. Lett., 20(21 ), 

2359-2362, 1993. 

Sturges, W.T, Halocarbons in the Arctic and Antarctic 

Atmosphere, in The Tropospheric Chemistry of Ozo11e in the 

Polar Regions, H. Niki, and K.H. Becker (eds.), SpringcrVerlag, New York, 117-130, 1993. 

Sturges, W.T., and J.W. Elkins, The use of adsorbents to 

collect selected halocarbons and hydrohalocarbons of 

environmental interest from large air volumes, J. 

Chromatogr., 642, 123-134, 1993. 

Sturges, W.T., C.W. Sullivan, R.C. Schnell, L.E. Heidt, and 

W.H. Pollock, Bromoalkane production by Antarctic ice 

algae, Tel/us, 45B, 120-126, 1993. 

Sturges, W.T., J.F. Hooper, L.A. Barrie, and R.C. Schnell , 

Stable lead isotope ratios in Alaskan Arctic aerosols, A1mos. 

Environ .. 27A, 2865-2837, 1993. 

Sturges, W.T., R.C. Schnell, G.S. Dutton, S.R. Garcia, and J.A. 

Lind, Spring measurements of tropospheric bromine at 

Barrow, Alaska, Geophys. Res. Lett., 20(2), 201-204, 1993. 

Sturges, W.T., R.C. Schnell, S. Landsbcrger, S.J. Oltmans, 

J.M. Harris, and S.-M. Li, Chemical and meteorological 
influences on surface ozone destruction at Barrow, Alaska, 

during spring 1989, Atmos. Env., 27A(l7118), 2851-2863, 

1993. 

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American Chemical Society Meeting, Denver, CO, March 

29, 1993. 

Tans, P.P., An observational strategy for assessing the role of 

terrestrial ecosystems in the global carbon cycle: Scaling 

down to regional levels, in Scaling Physiological Processes 

J.R. Ehleringer and C.B. Field (eds.), pp. 179-190, Academic 

Press, 1993. 

Tans, P.P., J.A. Berry, and R.F. Keeling, Oceanic 13C/12C 

observations, a new window on C02 uptake by the 

oceans, Glob. Bioeochem. Cycles, 7, 353-368, 1993. 

Tans, P.P., T.J. Conway, D.R. Kitzis, K.A. Masarie, M. 

Stavish, L.S. Waterman, J.C. White, and N. Zhang, 

Evidence for interannual variability of the carbon cycle 

for measurements of the CMDL Cooperative Global 

Flask Network, paper presented at the 4th International 

Conference on C02 sponsored by WMO Global 

Atmosphere Watch, Carquciranne, France, September 

13-17, 1993. 

Trolier, M., J.W.C. White, P.P. Tans, and P.A. Gcmcry, 

Monitoring the stable isotopic compos1t1on of 

atmospheric C02: Data from NOAA/Cl\IDL nask 

sampling network, paper presented at the 4th 

International Conference on C02 sponsored by Wl\10 

Global Atmosphere Watch, Carqueiranne, France, 

September 13-17, 1993. 

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upper tropospheric water vapor in the tropics and over 

Antarctica, paper presented at the NATO Advanced Study 

Institute on Low Temperature Chemistry of the Atmosphere 

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149 

Anderson, P. Newman, L.Lait, M.R. Schoeberl, J.W. Elkins, 

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1993. 
AASE 

ACATS 

AEC 

A GASP 

AL 

ALE/GAGE 

ALIAS 

ALT 

ANS TO 

AOML 

ARL 

ARM 

ASA 

AS ASP 

ASH OE 

ASL 

ASR 

ATLAS 

ATMOS 

BAO 

BC 

BSRN 

BRW 

CAF 

CAMS 

CART 

CD-ROM 

CFC 

CFC-11 

CFC-12 

CGO 

CI RES 

CMDL 

CN 

CNC 

CSIRO/DAR 

CSU 

DAS 

DB 

DEW 

DMS 

DOE 

DOY 

DU 

ECC 

ECO 

EC-GC 

ECMWF 

EML 

ENSO 

ERL 

9. Acronyms and Abbreviations 

Airborne Arctic stratospheric Expedition 

Airborne Chromatograph for Atmospheric Trace Species 

Atomic Energy Commision 

Arctic Gas and Aerosol Sampling Program 

Aeronomy Laboratory, Boulder, Colorado (ERL) 

Atmospheric Lifetime Experiment/Global Atmospheric Gases Experiment 

aircraft laser infrared absorption spectrometer 

Alert, Northwest Territories, Canada 

Australian Nuclear Science and Technology Organization 

Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida (ERL) 

Air Resources Laboratory, Silver Spring, Maryland (ERL) 

Atmospheric Radiation Measurement program 

Antarctic Support Associates, Inc. 

Active Scattering Aerosol Spectrometer Probe 

Airborne Southern Hemisphere Ozone Experiment 

above sea level 

aerosol solar radiation 

airborne turnable laser absorption spectrometer 

Atmospheric Trace Molecule Spectroscopy 

Boulder Atmospheric Observatory 

black carbon 

Baseline Surface Radition Network 

Barrow Observatory, Barrow, Alaska (CMDL) 

Clean Air Facility 

Control and Monitoring System 

Cloud And Radiation Testbed 

compact disk-read only memory 

chi oro fl uorcarbon 

trichlorofluoromethane 

dichlorodifluoromethane 

Cape Grim, Tasmania, baseline station 

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder 

Climate Monitoring and Diagnostics Laboratory (ERL) 

condensation nuclei 

condensation nucleus counter 

Commonwealth Scientific and Industrial Research Organization/Division of Atmospheric Research, Australia 

Colorado State University, Fort Collins, Colorado 

data acquisition system 

direct-beam [irradiance] 

distant early warning 

dimethyl sulfide 

Department of Energy 

day of year 

Dobson units 

electrochemical concentration cell 

electron capture detector 

electron capture-gas chromatograph 

European Center for Medium-Range Weather Forecasts 

Environmental Measurements Laboratory 

El Nino/Southern Oscillation 

Environmental Research Laboratories, Boulder, Colorado (NOAA) 

150 
FID 

FPO 

FTIR 

FTS 

FW 

GAGE 

GAW 

GC 

GE 

GMT 

GOES 

GSA 

HAO 

HCFC 

HCFC-22 

HCFC-14 lb 

HOFC-142b 

H- 1211 

H- 1301 

HFC 

HP 

HST 

INSTAAR 

IR 

ISWS 

JPL 

KUM 

LAN 

LEAD EX 

LEAPS 

LES 

LLNL 

LO WESS 

LPM 

LST 

MAKS 

MAESA 

METOP 

MLO 

MLOPEX 

MOA 

MRI 

MS 

MSL 

NADP 

NASA 

NAVSWC 

NCAR 

NDSC 

NOIR 

NIP 

NOAA 

NOAH 

NSF 

flame ionization detector 

flame photometric detector 

Fourier transform infrared (spectroscopy) 

File Transfer System 

filter wheel 

Global Atmospheric Gases Experiment 

Global Atmosphere Watch 

gas chromatograph 

General Electric 

Greenwich Mean Time 

Geostationary Operational Environmental Satellite 

General Services Administration 

High Altitude Observatory 

hydrochloroflurocarbon 

CHClF2 

CH3CCl2F 

CH3CCIF2 

CBrClF2 

CBrF3 

hydroflurocarbon 

Hewlett-Packard 

Hawaii standard time 

Institute for Arctic and Alpine Research, University of Colorado, Boulder 

infrared 

Illinois State Water Survey 

Jet Propulsion Laboratories 

Cape Kumukahi, Hawaii 

local area network 

Leads Experiment 

Low Electron Attachment Potential Species 

Lincoln Experimental Satellite 

Lawrence Livermore National Laboratories 

Locally Weighted Least Squares 

liters per minute 

local standard time 

Martin and Kitzis Sampler (portable air sampler) 

Measurements for Assessing the Effects of Stratosperic Aircraft 

Meteorological Operational Mission (polar satellite series) 

Mauna Loa Observatory, Hawaii (CMDL) 

MLO Photochemical Experiment 

Memorandum of Agreement 

Meteorology Research, Inc . 

mass spectrometer 

mean sea level 

National Atmospheric Deposition Program 

National Aeronautics and Space Administration 

Naval Surface Warfare Center, Department of Defense 

National Center for Atmospheric Research 

Network for the Detection of Stratospheric Change 

non-dispersive infrared analyzer 

normal incidence pyrheliometer 

National Oceanic and Atmospheric Administration (U.S. Department. of Commerce) 

Nitrous Oxide And Halocarbons Division (CMDL) 

National Science Foundation 

151 
NWR 

NWS 

NOS 

o.d. 

OGIST 

OH 

ONR 

PBL 

PC 

PI 

PMEL 

PMOD 

PSP 

QBO 

RASS 

RITS 

RGA 

RSD 

RV 

SBUV 

scs 

s.d. 

SESAME 

SEAS PAN 

SIO 

SMO 

SOI 

SPADE 

SPO 

SRB 

SRF 

SRF 

SST 

STP 

TDLS 

TOMS 

TSI 

TSL 

UARS 

UCI 

UPS 

URAS 

URI 

USDA 

USGS 

UT 

UV 

UVB 

VMS 

\VD 

\VS 

\VOCE 

\VHOI 

WMO 

Niwot Ridge, Colorado 

National Weather Service 

National Ocean Service 

outside di ameter 

Oregon Graduate Institute of Science and Technology 

hydrox yl radical 

Office of Naval Research 

planetary boundary layer 

personal computer 

Principal investigator 

Pacific Marine Environmental Laboratory (ERL) 

Physikalisch-Meteorologisches Observatorium Davos (World Radiation Center) 

Precision Spectral Pyranometer 

quasi-biennial oscillation 

Radio Acoustic Sounding System 

Radi atively Important Trace Spec ies 

reduction gas analyzer 

residual standard deviation 

Recreational vehicle 

solar backscattered ultraviolet (satellite ozone instrument) 

Soil Conservation Service, Anchorage, Alaska 

standard deviation 

Second European Stratospheric Arctic Middle Latitude Experiment 

SEAREX South Pacific Aerosol Network 

Scripps Institution of Oceanography 

Samoa Observatory, American Samoa (CMDL) 

Southern Oscillation Index 

Stratospheric Photochemistry, Aerosols. and Dynamics Expedition 

South Pole Observatory, Antarctica (CMDL) 

surface radiation budget 

Solar Radiation Facility (CMDL) 

spectral response function 

sea-surface temperature 

standard temperature and pressure (0° and l atm) 

tunable diode laser spectroscopy 

Total Ozone Mapping Spectrometer 

Thermo Systems Incorporated 

Technical Services Laboratory 

Upper Atmosphere Research Satellite 

University of California, Irvine 

uninteruptable power supply 

[a commercial C02 analyzer) 

University of Rhode Island 

United States Department of Agriculture 

United States Geological Survey 

universal time 

ultraviolet 

ultraviolet B spectral band 

Virtual Memory System 

wind d irection 

wind speed 

World Ocean Circulation Experiment 

Woods Hole Oceanographic Institute 

World Meteorological Organization 

152 

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