Climate Monitoring and 

Diagnostics Laboratory 

No. 21 

Summary Report 1992 

U.S DEPARTMENT 

OF COMMERCE 

NATIONAL 

OCEANIC AND 

ATMOSPHERIC 

ADMINISTRATION 

ENVIRONMENTAL 

RESEARCH 

LABORATORIES 

•, f • 

. 

. l 
Climate Monitoring 

and Diagnostics Laboratory 

No. 21 

Summary Report 1992 

James T. Peterson, Editor 

Rita M. Rosson, Assistant Editor 

Boulder, Colorado 

December 1993 

U.S. DEPARTMENT OF COMMERCE 

Ronald H. Brown, Secretary 

National Oceanic and Atmospheric Administration 

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

Environmental Research Laboratories 

Alan R. Thomas, 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 l'\ational Technical lnfonnation Service. 5285 Port Hoyal Road 

Springfield, VA 22161 

II 
Contents 

CMDL Staff, 1992 ............................................................................................................................................ vi 

CMDL Station Information ............................................................................................................................... vu 

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

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

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

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

1.2. Barrow .. .. .. . ..... ... .. . .. . .. .. . . . . .. . . .. . . . .. .. ... ... ..... ... ... .. ..... . .. .. .. . . . . . .... ... .. .. . ... . .. . . . . . . .. ... . .. . .. .. . . . .. . . .. ... . . ... . . . . . . . . . . 7 

1.2. 1. Operations............................................ ................................................................................. 7 

1.2.2. Programs .. . . . . .. .. . . . . . . .. . . . . . ... .. . . . .. .. . ... .. .. . .. .... . . . . . . . . .. . . .. . . . . ... . . . . ... . ... ... . . . . ... . . . . ... . . . .. . . . .. . . . . . . . . . . . .. .. .. . 7 

1.3. Samoa ........................ ....................................................................... ................................................ 9 

1.3.1. Operations............................................................................................................................. 9 

1.3.2. Programs............................................................................................................................... 10 

1.4. South Pole ........................................................................................................................................ 12 

1.4 .1. Operations .. . .. . .. . . . . .. .. . .. .. . . . . .. .. . . .. . .. . .. .. . .. .. . . . . . .. .. .. . . . .. . . .. . .. . . .. .. . . .. . .. . .. .. .. . . .. . .. . . . . . . . . . .. .. . . .. . . . . . . . . .. . . 12 

1.4.2. Programs ............................................................................... ................................................ 13 

1.5. References .............................................. .......................................................................................... 15 

2. Carbon Cycle Division................................................................................................................................ 16 

2.1. Continuing Programs . .. . .. ... .. . ... . . . ...... .. ... .. . .. ... .. ... .. . .. . . . .... .. .. . . .... . . .... . . . . . .. . . . . . . ... . . ... . . . .. . . .. .. . . . . . . . . . . . . . . . . . . 16 

2.1.1. In Situ Carbon Dioxide Measurements .................................................................................. 16 

2.1.2. Flask Sample Carbon Dioxide Measurements ........................................ ................................ 17 

2. 1.3. In Situ Methane Measurements ............................................................................................. 19 

2. 1.4. A ask Measurements of Methane .. ...... ..... .. ..... .. .. .. ...... .... .. .. .... .. .. . ... .... . .. .. .. ..... .. .... .. .. .. .. . . .. .. .. . 20 

2. 1.5. In Situ Carbon Monoxide Measurements................................................................................ 22 

2. 1.6. Flask Measurements of Carbon Monoxide.............................................................................. 23 

2.2. Reference Gas Standards................................................................................................................... 24 

2.2.1. Carbon Dioxide...................................................................................................................... 24 

2.2.2. Carbon Monoxide................................................................................................................... 25 

2.3. New Measurement Programs............................................................................................................. 26 

2.3 .1. Measurements of Carbon Dioxide on a Very Tall Tower........ ................................................ 26 

2.3.2. Flask Samples From Aircraft.................................................................................................. 27 

2.4. Data Management.............................................................................................................................. 28 

2.5. References ........................................................................................................................................ 29 

3. Aerosols, Radiation, Ozone, and Water Vapor Division.............................................................................. 30 

3.1. Continuing Programs........................................................................................................................ 30 

3 .1.1. Surface Aerosols . . .. ... .. ... .. ......... ........ .. ..... ...... .... .. ... .. ...... . .. .. ......... .. .... .. ... .. .. ... . ... .. .... . .. .. .. . .... . 30 

3.1.2. Lidar Observations of Aerosols.............................................................................................. 34 

3.1.3. Total Ozone Observations...................................................................................................... 34 

3.1.4. UmkehrObservations..... ........................................................................................................ 36 

3.1.5. Calibration of CMDL Dobson Spectrophotometers ................................................................ 36 

3.1.6. Validation of TOMS and Satellite Instrument Ozone Data..................................................... 39 

3.1.7. Tropospheric Ozone............................................................................................................... 39 

3.1.8. Ozonesonde Observations ......... ........... ................................. ...................... ................ ... ...... .. 40 

3.1.9. Stratospheric Water Vapor ..................................................................................................... 41 

3.1.10. Surface Radiation................................................................................................................... 42 

3.1 .11. Solar Radiation Facility ....................................... .......... ....... ...................... ... ........ ... ..... ........ 45 

3. 1.12. Atmospheric Trajectory Analysis........................................................................................... 46 

111 
3.2. Special Project - A Decrease in Arctic Haze at BRW......................................................................... 47 

3.3. References .......................................................................... ................... ...... ..................................... 49 

4. Acquisition and Data Management Division .............................................................................................. 51 

4. 1. Continuing Programs ........................................................................................................................ 51 

4.1. 1. Station Climatology ............................................. ........... ........................... ........................... 51 

4.1.2. Data Management ........................................................... .............. ........................................ 58 

4.2. Reference ......................................................................................................................................... 58 

5. Nitrous Oxide and Halocarbons Division .................................................................................................... 59 

5.1. Continuing Programs ........................................................................................................................ 59 

5. 1.1. Flask Samples ....................................................................................................................... 59 

5. 1.2. RITS Continuous Gas Chromatograph Systems at CMDL Baseline 

Stations and Niwot Ridge................................................................................................. 59 

5.1.3. Low Electron Attachment Potential Species (LEAPS)............................................................ 61 

5.1.4. Alternative Halocarbon Measurements............................................................................. ...... 61 

5.1.5. Gravimetric Standards............................................................................................................ 65 

5.2. Special Projects ......................................................... ....................................................................... 67 

5.2.1. Aircraft Measurements of the CFCs....................................................................................... 67 

5.2.2. Ocean/Atmosphere Exchange of Trace Compounds............................... ................................ 69 

5.2.3. Software Development........................................................................................................... 73 

5.3. References .................................................................................. ...................... ........... ... ........... ....... 74 

6. Director's Office .............. ........................... ......................... ................ ................... ......... ................ ... ....... 76 

6.1. Introduction....................................................................................................................................... 76 

6.2. Methods............................................................................................................... .............................. 76 

6.3. Results............................. .................................................................................................................. 77 

6.3.1. Stratospheric Aerosol Optical Depth ...................................................................................... 77 

6.3.2. Stratospheric Aerosol Measurements...................................................................................... 77 

6.4. Discussion............................................................................................................................ ............. 79 

6.5. References......................................................................................................................................... 80 

7. Cooperative Programs ......................................................... ......................... ... ..... . ................ ..................... 81 

Antarctic Ultraviolet Spectroradiometer Monitoring Program: South Pole and Barrow 

Contrasts in UV Irradiance 

C.R. Booth, T. B. Lucas, J.R. Tusson JV, J.11. Morrow, and T. Mastechkina ........................... 81 

Lidar Observations of Volcanic Aerosol Layers and Polar Stratospheric Clouds at 

South Pole, 1990, 199 1, and 1992 

M. Cacciani, P. DiGirolamo, A. DiSarra, G. Fiacco, D. Fua, P. Colagrande, 

and G. Panegrossi ............ ................................................ .................................... ........ ....... 84 

Fine Sulfur Concentrations at the Mauna Loa Observatory and Other Hawaiian Sites 

T.A. Cahill............................................................................................................................. 86 

Artifi cial Windsh ielding of Precipitation Gauges in the Arctic 

G.P. Clagett................................................... ........................................................................ 92 

A Comparison of Aerosol Size Distributions and Nephelometer Measurements 

at Mauna Loa Observatory 

A. Clarke and B. Bodhaine .... ...... ........ ....................... .... ............. ... ...... ........ ...................... .... 93 

Improved MFOV Performance at Mauna Loa 

P.F. llein, J.M. Davis, and S.K. Cox...................................................................................... 97 

Atmospheric Methane at Cape Meares, Oregon 

M.A.K. Khalil and RA. Rasmussen ................................................................................. ....... 100 

Radioactivi ty in the Surface Air at BRW, MLO, SMO, and SPO during 1992 

R.J. Larsen and C.G. Sanderson...................................................................... ....................... 102 

iv 
Tomsk-7 Debris at BRW: Detection and Transport 

H.N. Lee. RJ. Larsen, and C.G. Sanderson............................................................................ 104 

Ultrahigh Resolution Infrared Solar Spectra from Mauna Loa Observatory 

F J. Murcray, SJ. David. R.D. Blatherwick, A. Goldman. and D.G. Murcray ........................ 106 

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. Simmonds............................................................................................................ 108 

The 13C/12C of Atmospheric Methane 

P. Quay. J. Stutsman, and D. Wilbur ...................................................................................... 111 

Non Seasalt Sulfate to Methanesulfonate Ratios at American Samoa 

D.L. Savoie and J.M. Prospero.................................................................................. ............. 112 

USGS Barrow Observatory 

J. Townshend.... ..................................................................................................................... 115 

Separation of Local From Distant Pollution at MLO Using PB-212 

S. Whittles/one, SD. Schery, and Y. li ................................................................................... 116 

Recent Interannual Variations in C02 in Both Hemispheres 

T.P. Whorf. C.D. Keeling, and D.M. Wahlen........... ............................................................... 119 

8. International Activities, 1992 ..................................................................................................................... 123 

9. Publications and Presentations by CMDL Staff, 1992 . .. ...... ..... .. .. ......... ... .. .. ... .......... .... ...... .. ..... .. .. .. .... ... .. . 126 

10. Acronyms and Abbreviations ..................................................................................................................... 129 

v 
Director's Office 

Eldon Ferguson, Direcior 

James T. Peterson, Deputy Director 

Donna Leise, Adminislrative Officer 

Sandra Howe, Adminisirative Assistant 

Carole Brandes, Secretary 

Ellen Hardman, Secretary 

Rita Rosson, Editorial Assistant 

Denise Theede, Program Clerk 

Special Projects 

Howard Bridgman, Visiiing Scientist 

M. Kisley, CIRES 

Craig Quincy, CIRES 

Mark Serreze, CIRES 

Pairick Sheridan, CIRES 

Spencer Shiotani, Physical Science Aid 

Ludmilla Sokolik, NRC Post Doctorate 

Aerosols, Radiation, Ozone & \Vater 

Vapor Division 

David Hofmann, Chief 

Ji II Foose, Secretary 

Jennifer Barnell, Physical Science Aid 

Barry Bodhaine, Metc.:>rologist 

Paul Chilson, Physical Science Aid 

John DeLuisi, Meteorologist 

Ellsworth Dullon, Meteorologist 

Robert Evans, CI RES 

Jason Gingerich, Physical Science Aid 

Robert Grass, CIRES 

Rudy Haas, Mathematician 

Bradley Halter, CIRES 

Joyce Harris, Physical Scienlist 

Todd Idler, Physical Science Aid 

Gloria Koenig, Computer Programmer 

Walter Komhyr, Physicist 

Thomas Kotsines, Physical Science Aid 

Jeffrey Lathrop, Physica l Scientist 

Kent Leonard, CIRES 

David Longenecker, ClRES 

Donald Nelson, Meteorologist 

John Ogren, Physical Scientist 

Samuel Oltmans, Physicist 

Micheal O'Neill, CIRES 

Greg Orleans, Phyical Science Aid 

Gina Palmer, Physical Science Aid 

Frank Polacek, Ill, Meteorological 

Technician 

Gayland Pounder, Physical Science Aid 

Dorothy Quincy, CIRES 

Scott Sanberg, Electronic Technician 

CMDL Staff, 1992 

Scott Sio, Physical Science Aid 

Robert Stone, CJRES 

David Theisen, Physical Science Aid 

Holger V6mel, CJRES 

Byron Wells, Physical Science Aid 

James Wendell, Electronic Technician 

Acquisition and Data 

Management Division 

Gary Herbert, Chief 

Sheri Cox, Secretary 

Mark Bieniulis, CIRES 

Thomas Mefford, CIRES 

Kenneth Thaut, Electronic Technician 

Carbon Cycle Division 

Pieter Tans, Chief 

Carol Brandes, Secretary 

Trey Moody, Secretary 

Peter Bakwin, CIRES 

Phillipe Ciais, NRC 

Thomas Conway, Research Chemis1 

Wya1t Coy, CIRES 

Mario DiCino, Physical Science Aid 

Edward Dlugokencky, CIR.ES 

Douglas Guenther, CIRES 

Duane Ki1zis, CIRES 

Patricia Lang, Physical Scieniist 

Terry Lesoing, CIRES 

Martin Manning, Visiting Scieniist 

Kenneth Masarie, CIRES 

Paul Novelli, CIRES 

Aaron Pauon, CO-OP 

Nonnan Siuer, Physical Science Aid 

Michael Stavish, CO-OP 

Kirk Thoning, Physicist 

Michael Trolier, JNSTAAR 

Lee Waterman, Research Chemist 

Ni Zhang, CIRES 

Conglong Zhao, CIRES 

Nitrous Oxide and Halocarbons Division 

James Elkins, Chief 

Carol Brandes, Secretary 

Trey Moody, Secretary 

Thomas Baring, Physical Science Aid 

James Butler, Research Chemist 

Scoll Cummings, CIRES 

Jennie Dolan, C.U. Work S1udy 

Andrew Duang, C.U. Work Siudy 

Geoffrey Duuon, CIRES 

Timothy Gilpin, NRC 

vi 

Arnold Hayden, CIRES Student 

Garry Holcomb, Eleclronic Engineer 

Krislen Kauffman, C.U. Work Study 

Jilrgen Lobert, CIRES 

Richard Myers, Physical Science 

Technician 

Steve Monlzka, Research Chemist 

Jae W. Nam, C.U. Work Siudy 

Phuong Nguyen, CIRES S1udent 

Matthew Nowick, C.U. Work Study 

William Siurges, CIRES 

Thomas Swanson, CIRES 

Thayne Thompson, Physicist 

Tina Waller, C.U. Work S1udy 

Observatory Operations Division 

Bernard Mendonca, Chief 

Sheri Cox, Secretary 

Daniel Endres, Station Chief, Ba rrow 

Christropher Churylo, Electronic 

Engineer 

Bradley Halter, Physical Scientist 

Russell Schnell, Director, ~!auna Loa 

Judith Pereira, Program Support 

Technician 

John Chin, Physicist 

Thomas DeFoor, Electronic Engineer 

Melody Keaunui, Clerk 

Darryl Kuniyuki, NOAA Jr. Fellow 

Steven Ryan, Physical Scientist 

Robert Uchida, Electronic Technician 

Alice Wall, Physical Science Aid 

Alan Yoshinaga, Chemist 

Carl Farmer, Station Chief, Samoa 

Mark Winey, Electronic Engineer 

Dale Tysor, NOAA Corps, South Pole 

David Gaines, Electronic Engineer 

Kaiherine, McNiu, NOAA Corps, 

Raymond Dunn, Elecironic Engineer 

Carl Groeneveld, NOAA Corps 

Thomas Jacobs, NOAA Corps 
CMDL Station Information 

Name: Darrow (BRW) Mauna Loa (MLO) 

Latitude: 71.323 19.539 

Longitude: 156.609 155.578 

Elevation: 8m 3397 m 

Time Zone: GMT-9 GMT-10 

Office Hours: 8:00 am-5:00 pm 8:00 am-5:00 pm 

Telephone 

Office hours: (907) 852-6500 (808) 961-3788 

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

Postal Address: Officer in Charge U.S. Dept. of Commerce 

NOAA/ERL/CMDL NOAA - Mauna Loa Observatory 

Pouch 8888 P.O. Box 275 

Barrow, AK 99723 Hilo, HI 96720 

Freight Address: Same as above U.S. Dept. of Commerce 

NOAA - Mauna Loa Observatory 

154 Waianucnue Ave. 

Hilo, HI 96720 

Name: Samoa (SMO) South Pole (SPO) 

Latitude: -14.232 -89.997 

Longitude: 170.563 -1 02.0 

Elevation: 77 m 2841 m 

Time Zone: GMT-11 GMT+12 

Office Hours: 8:00 am-5:00 pm 8:00 am - 5:00 pm 

Telephone: 

Office hours: 011 (684)622-7455 Relayed through CMDL Boulder 

After hours: 011 (684) 699-9953 

Fax: 011(684)699-4440 

Postal Address: U.S. Dept. of Commerce Officer in Charge 

NOAA - CMDL Samoa Observatory NOAA/CMDL Clean Air Facility S-257 

Pago Pago, American Samoa 96799 PSC 468 Box 402 

FPO AP 96598-5402 

Freight Address: Same as above Same as above 

vii 

1. Observatory Operations Division 

1.1. MAU~A LOA OBSERVATORY 

R. C. SCHNELL 

1.1.1. OPERATIONS 

Two, month-long MLOPEX intensive study periods and 

the MLO electrical upgrade dominated the non-routine 

MLO activities during 1992. MLOPEX is an NCARorganized free troposphere photochemistry experiment 

focusing on odd-nitrogen, odd-oxygen, and odd-hydrogen 

chemistry. The study utilized instruments mounted in four 

large ocean shipping containers; the equipment was 

operated by up to 25 scientists and support crew. 

Additional instruments for the study were mounted on the 

MLO meteorological tower. The AEC building was used 

by NCAR as a communication and data analysis center. 

Study periods occurred in April and July after which the 

instruments and containers were r emoved from the MLO 

site. It is expected that the results from the MLOPEX 

studies will provide valuable information on the sources, 

ages, and recent flow histories of air masses enveloping 

MLO in various seasons. 

The MLO electrical upgrade consisted of re-installing all 

of the outdoor power disrrihution and data transmission 

cables into buried conduits. In addition, all buildings, the 

meteorological and air sampling towers, and the HAO 

faci lity were connected into a single, well-built grounding 

network. This construction began in April and lasted 

throughout the year. 

A major upgrade of our computing faci lity occurred at 

the Hilo facili ty with the acquisition and installation of a 

VAX 4000 computer (provided by the NDSC program), 

three 486 PC's, and a high-capac ity laser printer. All of the 

computers and printers in the Hilo offices have been 

connected with an Ethernet LAN, including the third floor 

office and basement labs. 

MLO will be host to a Network for the Detection of 

Stratospheric Change (NDSC) facility to be built cast of the 

observatory . NDSC is a set of high-quality, rcmotcsounding research stations for observing and understanding 

the physical and chemical state of the stratosphere. Plans 

for the ,..5000 ft2 building and land acquisition were 

essentially completed in 1992. 

Siting plans were developed for the future installation of 

the Global Oscillation Network Group (GONG) facility 

designed to study the core of the sun. This 5-year project 

by the National Solar Observatory, Tucson, Arizona, will 

include the installation of an unmanned trailer and solar 

tracker. 

In 1992 MLO was visited by 393 signed-in guests. This 

number was influenced (on the high side) by the MLOPEX 

activities. Few of the visitors coming to MLO are 

opportune walk-ins. Instead, most are knowledgeable in 

science and have MLO as their destination. About 50% of 

our visitors in 1992 were from Europe or Asia. 

1.1.2. PROGRA:'llS 

Three new CMDL programs were added in 1992: column 

water vapor, continuous CO, and UVB at 280-320 nm. 

Smaller changes in programs included discontinuing 3-L 

evacuated fl asks for C02, CH4 , CO, 13C, 180 of C02 at 

MLO and increasing the size of flasks from 0.5 L to 3.0 L 

for the same gases at Cape Kumukahi. These programs 

have added 15% and one mountain staff day per week to 

the MLO workload over 1991 . 

Table 1.1 summarizes the programs in operation at MLO 

during 1992. Details of some of the programs are as 

follows: 

Carbon Dioxide 

The CMDL Siemens Ullramat-3 IR C02 analyzer and the 

SIO Applied Physics IR C02 analyzer were operated in 

parallel without major problems throughout the year. 

Routine maintenance and calibrations were undertaken on 

both instruments as scheduled. 

The preliminary average MLO C02 concentration for 

1992 was 356.2 ppm. The C02 annual growth rate between 

1991 and 1992 was approximately 0.75 ppm. Compared to 

the previous year's growth rate of 1.3 ppm per year, this is 

a significant difference, a 42% drop. 

Outgassing 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 down slope wind 

regime. The erratic concentrations in the data resulting 

from venting events were easily identified 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 Thoni11g et al. [1 989). 

The frequency of monthly occurrences of observable 

outgassing from volcanic vents on Mauna Loa for 1992 are 

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

past 5 years are listed in Table 1.3. 

The weekly C02, CH4, and other gas sampling programs, 

using flasks at MLO and at Cape Kumukahi, were carried 

out according to schedule throughout the year, without 

problems. 
TABLE I.I. Summary of Measurement Programs at MLO in 1992 

Gases 

C02 

co 

CII4 

Surface 03 

Total 0 3 

03 profiles 

Program 

CfC-11, CfC- 12, t'\20 

CFC- I I, CFC-12, N20 , 

CC14,Cll3CCl3 CfC-113 

Cll313r, llCfC-22, CFC- 11 3 

cc1 •• CII3CCl3, CFC-113 

llalon-1211, llalon-1301 

N20 

Radon 

Aerosols 

Condensation nuclei 

Optical properties 

Stratospheric and upper tropospheric aerosols 

13lack carbon 

Total suspended particles 

Solar Radiation 

Global irradiance 

Direct irradiance 

Diffuse irradiance 

Turbidity 

Ultrav iolet radiation 

UV solar radiation (ARL) 

Column water vapor 

Meteorology 

Air temperature 

Temperature g radient 

Dewpoint tempe rature 

Relative humidity 

Instrument 

Siemens Ultramat-3 IR analyzer 

3-L glass flaskst 

0.5-L glass flasks, through analyzer 

Trace Analy tical RGA3 

reduction gas analyzer no. RS 

0.5-L glass fla sks, MAKS pump unit (MLO) 

3-L glass fl asks (Kumakahi) 

Carle automated GC no. 6 

Dasibi ozone meter 

Dobson spectrophotometer no. 76 

Dobson spectrophotometer no. 76 

(automated Umkehr method) 

13alloonborne ECC sonde 

300-mL stainless steel fla sks 

JIP5890 automated GC 

0.8-L stainless-steel fla sks 

Shimadzu automated GCl 

Two-filter system 

Poll ak CNC 

TSI CNC• 

four-wavelength nephelometer•: 

450, 550, 700, 850 nm 

Lidar, 694.3 nm 

Aethe lometer 

lligh-volume sampler 

Eppley pyranometers with Q, 

OG I, and RG8 filters 

Eppley pyrheliometer (2) with Q filt er 

Eppley pyrheliomete r with Q, OG I, 

RG2, and RG8 filters 

Eppley/Kendall active cavity radiometer 

Eppley pyrgeometer with shading disk 

and Q filter• 

J-202 and J-314 su nphotometers with 

380-, 500-, 778-, 862-nm narrowband filte rs 

PMOD three-wave length sun photometer•: 

380, 500, 778 nm; narrowband 

Robinson-13erger UV radiometer (erythema) 

Yankee Environmental UVl3, pyranometer 

(280-320 nm) 

2 wavelength tracking sunpho tometer 

Aspirated thermistor•, 2- and 40-m heights 

Max.-min. thermometers, 2 -m hei ght 

II )'grothermograph 

Aspirated thermistors•, 2- and 40-m heights 

Dewpoint hygrometer•, 2-m height 

I lygrothermograph 

2 

Sampling Frequency 

Continuous 

I pa ir wk· 1 

I pair wk· 1 

Con tinuous (5/92) 

I pa ir wk·

1 

I sample (24 min)"1 

Contin uous 

3 day· 1, weekdays 

2 day·I 

I wk"1 

I pair wk·1 

I sample (h)"1 

Monthly 

I samplc(h)" 1 

Continuous integrated 

30-min samples 

I day·1 

Continuous 

Continuo us 

1-3 profiles wk·t 

Continuous 

2 samples (mo)"1 

Continuous 

Continuous 

3 day· 1 

I mo·

1 

Continuous 

3 day·1, weekdays 

Continuous 

Continuous 

Continuous (10/92) 

Continuous (4/92) 

Continuous 

1 day·l 

Continuous 

Continuous 

Continuous 

Con tinuous 
TABLE I.I. Summary of Measurement Programs al MLO in 1992-Continued 

Program 

Meteorology· Con tinued 

Pressure 

Wind (speed and direction) 

Planeiary boundary layer meteorology 

(PI3L MET) 

Precipitation 

Toial percepiible water 

Precipitation Chemistry 

pll 

Conductivity 

Chemical components 

Cooperative Programs 

C02 (SIO) 

C02 , llC, N2 0 (SIO) 

C02 • CO, Cil4 , 13C/12C (CSIRO) 

Total suspended particles (DOE) 

Cll4 (13C/12C) (Univ. of Washington) 

Uhraviolel radiation (Smithsoni an) 

Solar aureole intensity (CSU) 

Precipi1a1ion colleciion (DOE) 

Precipitation collection for organic acid 

analysis (Univ. of Virginia) 

Wet-dry deposiiion (IS\VS, !\ADP) 

Aerosol chemistry, upslope-downslope 

discrimination (Univ. of Washington) 

Aerosol chemistry (Univ. of Calif.-Davis) 

Various trace gases (OGIST) 

Sulfate, nitrate, aerosols (URI) 

Radon (ANSTO) 

Formation of 3J!e (\VIIOI) 

Solar speclra (Univ. of Denver) 

0 2/N2 (NCAR) 

All instruments are at 1'.ILO unless indica1cd. 

Instrument 

Capacitance transducer• 

Mercurial barometer 

Bendix Aerovane•, 8.5- and 40-m heights 

Wind vane , cup anemometer, and aspira1cd RTD 

thermometer (direction, speed, 1empera1ure at 

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

Rain gauge, 8-in 

Rain gauge, 8-in;t 

Rain gauge, tipping bucket• 

Fosken JR hygrometer• 

pll meter 

Conductivity bridge 

Ion chromatograph 

Applied Physics IR analyzer 

5-L evacua1ed glass flaskst 

Pressurized glass flask sample 

lligh-volume sampler (I filter wk.1

) 

35-L evacuated flask 

8-wavelength UV radiometer: 290-325 nm; 

narrowband 

Mu hi-aperture tracking photometer: 

2, 5 , I 0, 20, 30' fields of view 

Exposed collection pails 

Aerochemetric automatic collector 

Aerochemetric automatic collector and 

weighing-bucket rain gauge 

Nuclepore filters 

Programmed filter sampler 

Stainless steel flaskst 

Filter system 

Aerosol scavenging of Rn daughters 

Closed cylinder 

FTIR spectrometer 

Th ree 5-L glass flasks 

•Data from this instrumcnt recorded and processed by CA~IS. 

tMLO and Kumukahi. 

~Kulani Mauka 

3 

Sampling Frequency 

Continuous 

5 wk" 1 

Continuous 

Continuous 

5 wk "

1 

I wk· 1 

Continuous 

Continuous 

Daily 

Daily 

As needed 

Continuous 

I pair wk"1 

I mo·1 

Continuous 

I mo·1 

Continuous 

Continuous 

Integrated monthly s~mple 

Colleciion after each 

rain event 

Integrated 7 -day sample 

Inactive 

Integrated 3-day sample 

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

I SCI wk" 1 (3 flasks) 

Daily, 2000-0600 LST 

Continuous; integrated 

30-min samples 

Continuous 12-mo ambient 

exposure from l /90 

I wk· 1 

I wk' 1 
TABLE 1.2. Estimated Mauna Loa Venting Episodes (Total Time in Hours) at MLO in 1992* 

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

0 0 2 2 0 2 6 4 0 3 3 23 

•Criteria: C02 SD ~1.0 ppm; wind direction sector 135'-225'; wind speed ~1.35 m s·t. 

TABLE 1.3. C02 Venting Events From 1988 Tluough 1992 

Year 

1988 

1989 

1990 

1991 

1992 

Methane 

Total Time (Hours) 

200 

84 

48 

26 

23 

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 taken every 24 

minutes. The instrument functioned well during the year. 

The CH4 data continued to show clearly defined cycles of 

varying frequencies. The typical diurnal cycle was well 

correlated with up- and downslope winds, with the marine 

boundary layer air having the higher CH4 concentrations. 

There were also multi-day or synoptic scale CH4 cycles 

observed that apparently relate to different air mass source 

regions. The MLO CH4 measurements show CH4 lost its 

upward trend in 1992 compared with 1991 's gradual 

increase. The MLO 1992 monthly average CH4 value was 

-1725 ppb with the maximum occurring in March (-1735 

ppb). There were decreases in CH4 concentrations below 

the annual average in August (to -1710 ppb), September (to 

-1720 ppb) and October (to -1720 ppb). 

Carbon Al onoxide 

A Trace Analytical RGA3 reduction gas analyzer for the 

continuous measurement of CO mixing ratios was installed 

in May. System operations and chromatographic data 

logging are handled by an HP3396A integrator. The system 

has worked well since installation. 

Ozo11e Al 011itoring 

The 1992 MLO ozone monitoring program consists of 

three measurement phases: continuous MLO surface ozone 

monitoring using a Dasibi model 1003-AH UV absorption 

ozone monitor; daily total and Umkchr ozone profile 

measurements using a computer-based automated Dobson 

instrument (Dobson no. 76); and ozone profile 

measurements based on weekly ascents of balloon-borne 

4 

ECC ozonesondcs released from the NWS station at the 

Hilo airport. In addition to the daily automated Umkchr 

measurements and 5-day-a-wcek total ozone measurements, 

five special early morning AD-CD direct sun observations 

were completed in 1993. The Dasibi ozone monitor 

performed in a fully satisfactory manner and provided a 

continuous, high-quality record of station-level ozone 

concentrations for the entire year. The weekly ozonesonde 

flights were coordinated with lidar observations to provide 

further opportunities to study the effects of the Pinatubo 

aerosol cloud on ozone chemistry. 

Halocarbons and Nitrous Oxide 

The RITS system had its annual major maintenance in 

February 1992. During this time a Best UPS was installed, 

valves were replaced or serviced on the HP-GC, leaking 

solenoids were replaced, older plastic (pneumatic) lines on 

the valves were replaced, and a back-flush needle valve 

was installed on the HP-GC. In addition, the low value 

reading was adjusted on the Shimadzu GC, and the air lines 

on the tower were fitted with beaker cover protectors. 

During this maintenance operation, the computer crashed 

and a replacement was shipped from Boulder (a bad power 

supply and back plane were replaced). The keyboard was 

also sent back to Boulder later for repair. 

Comparison air supply option tests were conducted from 

April 17 to May 4 for various pump, tower air line, and 

aluminum stack configurations. From these tests, a minor 

leak problem was detected in the 41 El valve in conjunction 

with the Valeo valve in the stream select unit. This was 

repaired. In June the mid-tower air line was installed as 

AIR2 and the aluminum stack pump unit was disconnected 

from the system. In July the Best UPS frequency windows 

were expanded to allow greater flexibility for incoming 

power. Prior to this expansion, preset values were too 

narrow for the Helco power delivered to the station. 

In general, the RITS computer experienced problems 

throughout the year before and after the UPS installation. 

It was hoped that the UPS installation would alleviate some 

of the earlier computer "glitch" problems as it did with the 

power problems to the entire system. This was not the 

case, as computer hang ups continued through 1992. The 

ASCII conversion program, which allows MLO personnel to 

look at the data more closely, had some problems in early 1992 

but was successfully modified at MLO in late 1992. 
Aerosol Mo11itori11g 

The TSI unit is a continuous expansion CNC in which 

condensation occurs in a butyl alcohol vapor chamber and 

single particle counting statistics are used as a basis for the 

CN concentration calculations. The instrument has 

continued to display higher counts than the Pollak since its 

return from the company in 1991. This instrument will be 

compared to a second TSI in early 1993. 

The aethalomcter performed satisfactorily during 1992. 

There was some local contamination of the data during the 

latter half of the year when the observatory electrical 

upgrade contractor was using diesel equipment at MLO. 

The 4-wavelength nephelometer 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 in service on February 26. The system 

performed without any problems the remainder of the year. 

Radon 

The CMDL/DOE radon program completed its second 

year of operation, collecting quality data 87% of the tot al 

hours in 1992. Experiments with a sister instrument at the 

DOE/EML lab in New York in the fall of 1992 isolated the 

source of thoron contamination as being in the welds in the 

aluminum chamber and housings. A thi ck coating of epoxy 

was applied to the MLO instrument welds in December that 

completely eliminated the thoron contamination. This 

brought the instrument sensitivity down from more than 

50mBq/m3 to less that 15mBq m3 for a 30-minute sample. 

Results from the first 30 months of operation are 

summarized in Figures I. I and 1.2. A strong seasonal 

cycle is seen at MLO. Downslope March monthly averages 

arc highest at 300mBq m3 with a minimum in October of 

less than lOmBq m3. Radon emanating from soils at lower 

altitudes on Hawaii is typically transported in the daytime 

upslope winds, with concentrations averaging over IOOmBq 

m3. 

Solar Radiation 

Two water-vapor meters built by the University of 

Arizona were put on the solar dome spar on April 2. The 

instruments measure narrow-band solar radiation at 870 nm 

and 940 nm. The station pyranometer was replaced on 

October 27. The solar dome controller and related sensors 

were damaged when the building was being rewired as part 

of the station electrical upgrade; this caused loss of 

automated operation for the remainder of 1992. 

Fifty-seven hand-held sunphotometer instrument calibrations were performed during the year. The broadband 

atmospheric transmission factor increased from 0.86 in 

January to 0.90 in December as the Pinatubo aerosol 

continued to fall out of the atmosphere. 

The old Robertson-Berger erythema meter, in use for 

many years at MLO, was replaced with a newer model 500 

RB meter. An IBM PC is now being used as a data 

acquisition system for the newer R-B meter. 

5 

1000 

~ I 

~ t I 

11 

I 

M" 100 I " ' 

E 

--CT 

al 

.§. 

I' z 

0 

0 

~ 10 

'1 

1 -to--.,-,,,.....,.....,-,--,-,-..,.,-'T""T...,.-'T""T-r-.,...,...,...."r-,_,..-,-'T""T...,.-...-l 

91 92 93 

YEAR 

Fig. I. I. Nightly average radon concentrations between 00 and 07 

LST measu red by the CMDL/DOE radon instrument at MLO during 

its first 30 months of operation . The heavy solid line is a 60-day 

running geometric mean. Synoptic-scale variability is primarily 

caused by changes in air trajectories coming from continental 

sources. 

M' 

ID 

~ 

§. 

z 

0 

0 

~ 

2 3 4 5 6 7 8 9 10 11 12 

MONTH 

Fig. 1.2. Seasonal representation of Figure I. I data, shown by 

monthly geometric means±.! cr. The ri ght-hand sca le (with arbitrary 

zero) relates radon loss to the 3.8 day radon half-life . All else being 

equal, this suggests that continental air reaches MLO 2 to 3 weeks 

faster during the spring Asian dust season than in the fall. Only 7 

day s' data were averaged for October. 
A Yankee Environmental UVB instrument was installed 

on September 17 and connected to CAMS ASR channels 6 

and 7. This UVB pyranometer measures global solar UVB 

irradiance from 280 nm to 330 nm. 

Computers/Network 

A VAX 4000 computer was installed in November and an 

Ethernet LAN set up to connect all the PC's in the Hilo 

office. A network printer was connected to the system. A 

dial-in modem connection to the VAX and a 486 PC was 

put in place so MLO staff can cal l in and work on the 

system from home. We are now waiting for a NASA 

Internet connection to establish a network between Boulder 

and MLO. 

MLO Database 

Subsequent to the addition of the VAX computer, several 

large, integrated data bases were created along with utility 

programs to convert the data and read the data bases for 

analysis. More data bases are being added on a monthly 

basis. The data bases currently stored in the VAX along 

with the period covered: mlohrsall - all hourly data from 

1985 until 1999 (contains all CAMS data, RITS, CH4 , black 

carbon, radon, Scripps C02, and other future projects up to 

100 parameters (master. hrs); m\ominmsd - minimum data 

from solar dome (only when dome is open); mlo3mnall - 3-

minute data for solar radiation data (or other parameters); 

mlo30mall - 30-minute data; mlohrshis - data starting 

January 1, 1958; mlowkyall - weekly data; and mlowkyproprofile data (ozonesonde, lidar, and NWS soundings). 

Meteorology 

A Planetary Boundary Layer System (PBL) was installed 

and activated January 15, 1992. The system measures wind 

speed, wind direction, and temperature at the 3, 5, 10, 20, 

30, and 40 meter levels. Sensors arc scanned by a 386 

computer at I-second intervals, and I-minute averages are 

displayed and stored by the computer. Frequent 

anemometer problems were experienced in the early stages, 

but the system has operated trouble-free after all the 

sensors were overhauled. 

There were no changes in the standard meteorological 

observations program. The routine monitoring of wind 

speed, wind direction, temperatures, dew point, and 

atmospheric pressure was carried out during the year 

without major problems. The mercury barometer was 

moved to a more stable location in the middle of the MLO 

building on November 9. Weekly dewpoint and 

temperature comparisons and semi-annual calibrations 

revealed no discrepancies in the data. 

l'recipitatio11 Chemistry 

The MLO modified program of precipitation chemistry 

collection and analyses continued throughout 1992 within 

the basic MLO operational routine. This program consists 

of a weekly integrated precipitation sample from the 

6 

Hilo NWS station and the collection of precipitation event 

samples at MLO. Analyses of these samples are 

undertaken in the Hilo Laboratory for pH, conductivity, and 

several ions using currently ava il able equipment. 

Lidar 

Lidar operations continued on a regul ar weekly basis up 

to November 4 on which date a major electrical breakdown 

occurred during an observation. The lidar was out of 

service until February l, 1993. As shown in Figure 1.3, 

stratospheric aerosols from the June 15-16, 1991, eruption 

of Mt. Pinatubo continued to decrease over the year with a 

more rapid decline beginning in mid-October. 

Cooperative Programs 

The cooperative programs continued without any major 

changes from 199 1 except for the University of 

Washington's aerosol chemistry program that went into 

inactive status due to malfunctions in the control system. 

No replacement was received in 1992. The 0 2/N2 nask 

sampling program (NCAR) matured in 1992 having passed 

through a shakedown period in late 1991. The NCAR CTask 

program did not send any flasks in 1992 and was 

subsequently discontinued. Weekly sunrise solar spectra 

FTIR measurements (University of Denver) were conducted 

throughout the year. A second staff member has been fully 

trained in the FTIR spectrometer operation. This program 

has also now settled into a mature phase. 

M LO cooperative programs are listed in Table I. I. It is 

the consensus of the !\!LO staff that cooperative program 

activities now consume 50% of MLO non-administrative 

staff time. 

~2 NOAA/CMDL/MLO 

RUBY LIDAR 

I/):; 

., ' 0: • 

z .! 

INTEGRATED NRBS 

15 8 - 33 OKM 

YEAR 

f ig. 1.3. Stratospheric column aerosol backscatter record from the 

MLO lidar. The El Chichon and Pinatubo aerosols arc the most 

significant inputs in the past two decades. Note the rapid decrease 

in the Pinatubo aerosols beginning in October 1992. 
1.2. BARROW OBSERVATORY 

D. ENDRES 

1.2.1. OPERATIONS 

January 1992 marked the start of the 20th year of data 

collection at BRW. 

BRW serves as part of the training for the CMDL SPO 

crew each year. This year the NOAA Corps officer was in 

BRW for training during February and March and again 

during June and July. The electronics technician was here 

during July and August. 

A new third-party support agreement with the DEW Line 

site was negotiated this year with a greatly reduced road 

maintenance schedule. 

A gate for the observatory road is being planned to 

control the increased traffic on the observatory road. On 

several occasions the station was used as a starting point 

for 4-wheel drive vehicles to gain access to the tundra. 

In October the electronics technician left for a new 

position and was replaced in November. 

Polar bears were seen in record numbers during the fall 

with as many as 30 bears sighted at the dump on several 

occasions. 

During the winter of 1992-1993 the road was left drifted 

with snow due to the extreme cost of snow removal. 

Station personnel started skiing to the station when there 

were no known bears in the area. The road closure helped 

to keep traffic off the road. 

Last year an offshore exploratory oil rig was stationed 

east of the station about 32 km out. ARCO Alaska moved 

it during the summer of 1992. To date, no effects have 

been noted in the BRW data set. 

With the help of the MASC Engineering Office in 

Boulder, plans for a new BRW Observatory building were 

completed. The plans call for about a 50% increase in 

building size, with the old observatory building to be used 

for warm storage and/or co-op projects. Funds for the 

construction of a new observatory have not yet been 

obtained. A standing request to secure funds from the 

Department of Commerce NOAA Capital Improvement 

Appropriations is pending. 

The 1985 Chevy Suburban was returned to GSA in 

Anchorage and a 1992 Ford pick-up was issued to BRW. 

The DEW Line allowed us access to a stall in their garage. 

This gave us a place to park the truck during the day with 

enough room left on the side for the snow machines. The 

snow machines are particularly useful during the winter 

when access to the observatory by car can become difficult. 

All vehicles ran fine during the year with normal 

maintenance. 

The bathroom in Apartment A was remodeled by station 

personnel during Apri l to finish the government housing 

upgrade. A problem in the apartment occurred when a 

broken pipe was found in the wall that called for extensive 

repair to the plumbing. In spite of the break, no structural 

7 

damage was found to the house. In a separate incident, a 

pipe under the house, about 3.6 m long, froze and cracked 

in several places. Station personnel replaced and replumbed the pipe and installed insulation to correct the 

situation. 

1.2.2. PROGRAMS 

Table 1.4 summarizes the 1992 measurement programs at 

BRW. Operational highlights are as follows: 

Aerosols 

The nephelometer ran well all year with only minor 

maintenance required. Aerosol backscatter, as measured by the 

nephelometer, showed the typical springtime high with no 

substantial deviation from the past record. 

The Tygon tubing on the inlet to the TSI CNC was replaced 

with copper tubing. It was decided to keep the diameter of the 

tubing at 3/8 inch (9.525 mm) i.d. There is less particle loss 

due to static electricity in the copper tubing than in the Tygon 

tubing. 

The lamp was replaced in the aethalometer when the data 

began to show erratic values. The problem was cleared up and 

the aethalometer continues to collect black carbon data. A very 

good correlation has been shown between black carbon and 

C02 data [Hansen, 1989]. 

Solar Radiation 

The first sunrise of the year occurred on January 23. For the 

first few weeks of the solar year the elevation angle is too low 

for quality direct sun observations. All global instruments 

were returned to service at sunrise and worked well throughout 

the year. 

Backlash in the rack and pinion gears for the solar tracke,r 

was adjusted and the tracker experienced no problems this 

year. 

The quartz and the RG8 pyranometers, along with the 

pyrheliometer, were returned to Boulder during November for 

calibration. The FWNIP was calibrated. 

Carbon Cycle 

C02 NDJR. The Barrow C02 mixing ratio reached a high 

this year of over 360 ppm. A peak is seen each spring with 

a summer minimum occurring during September and 

October. During the fall oi 1991 the C02 system was 

upgraded to a Siemens Ultramar 5E [Ferguson and Rosson, 

1991). The Siemens NDIR ran fine all year with minimal 

downtime. 

C/14 • Batteries were changed in the CH4 UPS. The local 

ut ilities co-op experienced problems with the generators 

that caused several outages late in 1991. During April a 

member of the CMDL Carbon Cycle Division arrived to 

upgrade the system by replacing the gas chromatograph. 

Several modifications were made to the internal plumbing 

of the GC along with program updates. Late in the year 

there was a problem with noisy data. Changing the 

diaphragm m the air sample pumps apparently 
TABLE 1.4. Summary of Measurement Programs at BRW in 1992 

Gases 

C02 

C02, CI14 , CO 

Cl14 

Surface 0 3 

Total 0 3 

Program 

Cf-C-11 , Cf-C- 12, Cf-C- 11 3, N20 

111211, 111301, IICFC-22 

CFC- I I , CFC- 12, Cf-C- 11 3, N2 0, 

CCl4 • Cl13CCl3 

N20 

co 

Aerosols 

Condensation nuclei 

Optical properties 

Black carbon 

Solar and Terrestrial Radiation 

Global irradiance 

Direct irradiance 

Terrestri al (IR) radiation 

Albedo 

Meteorology 

Air temperature 

Dewpoint tempe rature 

Pressure 

Wind (speed and direction) 

Precipitation 

Cooperative Programs 

Total su rface particu lates (DOE) 

Precipitation gauge (USDA) 

Magneti c fi e lds (USGS) 

Various trace gases (OG IST) 

13c, tso. C02 (CS!RO) 

C02. 13C, N10 (S!O) 

CH4 (Univ. of Calif., Irvine) 

Earthquake detection 

(Univ. of Alaska) 

t3CII4 (13C/t 2C) (Univ. of Washington) 

Ultra low frequency waves (Univ. of Tokyo) 

UV monitor (NSf-) 

Magnetic fi elds (NAVSWC) 

0 2 in air (Univ. of Rhode Island) 

Instrume nt 

Siemens Ultramat 5E analy zer 

3-L glass flasks 

0.5-L glass flasks, through ana lyzer 

0.5-L glass flasks, P3 pump unit 

Carle automated GC 

Dasibi ozone meter 

Dobson spectrophotometer no. 91 

300-mL stainless steel fl asks 

800-mL stainless steel fl asks 

HP5890 automated GC 

Shimadzu automated GC 

Trace Analy tical GC 

Pollak CNC 

T.S.I. CNC 

Four-wavelength nephelometer 

Aethalometer 

Eppley pyranometers with Q and RG8 filters 

T racking NIP 

Eppley pyrheliometer with Q, OG 1, 

RG2, and RG8 filte rs 

Eppley pyrgeometer 

Eppley pyranomcter and pyrgeomete r 

Thermistor, 2 levels 

Max.-min. thermometers 

Dewpoint hygrometer 

Capacitance transducer 

Mercurial barometer 

Bendix Aerovanc 

Rain gauge, tipping bucket 

lligh-volume sampler ( I filter wk·l) 

Wyoming shielded precipitation gauge. 

1\ipher shield , Alter shield, 2 buckets 

3-Component fluxgate magnetometer and total field 

proton magnetometer 

Stainless steel flasks 

5-L glass fl asks 

5-L evacuated glass fl asks 

Various stainless steel flasks 

Seismograph 

35-L stainless steel flasks 

Magnetometer 

UV spectrometer 31Ie sensors 

3-L glass fl asks 

8 

Samplin g Frequency 

Continuous 

I pair wk·t 

1 pair wk·l 

1 pair wk·l 

I sample (12 min)'t 

Continuous 

3 day-I 

1 pair wk·I 

1 pair month·! 

1 sample (0.5 h)'t 

1 sample (0.5 h)·I 

I sample (6 min)·t 

I day· 1 

Continuous 

Continuou s 

Continuous 

Continuous 

Continuous 

Discre te 

Continuous 

Continuous 

Continuous 

1 day·t 

Continuo us 

Continuous 

Discre te 

Continuous 

Continuous 

I mo·l 

Co ntinuo us 

I set wk·t (3 fl asks sei·t) 

I pair (2 wk)·I 

1 pair wk·I 

1 set (3 mo)·t 

Continuous, check 

site I wk·I 

I (2 wk)'' 

Continuous 

1 scan per 0.5 hour 

Contin uous 

1 pair (2 wk)'t 
cleared up the problem. The system ran fine the rest of the 

year. 

CO. Another member of the CMDL Carbon Cycle 

Division came to BRW to upgrade the CO system. The CO 

detector uses HgO to reduce CO to C02 and Hg. Mercury 

vapor absorbs UV light and produces a signal proportional 

to levels of CO. The system ran fine all year. 

Flask Samples. Flasks were exposed on a weekly basis. 

C02. CH2. and CO are measured from the flask samples. 

An offset between the CMDL 3-L flasks and the MAKS 

flasks was noted and is currently under investigation by 

CMDL Boulder personnel. 

Meteorology 

Winds as high as 96.5 km ph (60 mph) were recorded 

during a blizzard in November. During December a series 

of six low-pressure cells moved across the Arctic raising 

temperatures to as high as -6"C ( +20" F). All instrumentation ran fine during the year. Aerovane and temperature 

probe calibrations were performed at 6-month intervals 

with no drift in calibration found. 

Ozone 

Surface Ozone. Barrow 0 3 measurements are a two-part 

program with surface level measurements made by the 

Dasibi ozone meter. Springtime data often show a 

minimum and have been seen to reach levels down to zero. 

The most likely cause is the build up of Br in ocean water 

during the winter and when it is released into the 

atmosphere and undergut:s photochemical disassociation 

during spring break up destroying ozone in the process. On 

a longer time scale, an overall increase in average surface 

ozone amounts has been shown for BRW and it may be the 

by-product of NO emissions from the Prudhoe Bay oil 

fields [Jaffe, 1991). 

Total Ozone. Ozone observations began in late February 

when the sun angle became high enough to produce reliable 

signals. A possible problem with high humidity was 

discussed and it was decided to build and install a dryer 

system. With the dryer system, air is pushed through a 

desiccant and blown through the Dobson. Whenever 

practical, zenith observations were taken in conjunction 

with direct sun observations to produce a data set for 

analysis of the difference between the data from direct sun 

and zenith observations. 

The observational year was concluded on October 8 when 

the sun angle decreased to levels too low for observations. 

Halocarbons 

In situ measurements. Problems with the GC data 

acquisition system locking up continue to plague the 

station. Generally good data was collected except for the 

episodes of unexplained failures. A power down reset was 

the only thing that would work to restart the system after 

lockups. 

9 

BRW data along with that from other remote long-term 

CMDL monitoring sites, show a decrease in the rate of 

increase in global CFC's. The seasonal cycle of CFC 

mixing ratios was still seen in the BRW data set. 

Flask samples. When flasks were available, they were 

exposed on a weekly basis and returned to Boulder for 

analysis. Measured compounds included CFC's, HCFC'S, 

and the LEAPS gases. 

Cooperative Programs 

Only programs with problems or unusual occurrences are 

mentioned in this section. 

The DOE began preliminary discussions with BRW and 

UlC/NARL regarding the possibility of using the BRW 

Observatory and surrounding area as part of the 

ARM/CART site. The ARM program is part of an effort by 

the DOE to resolve uncertainties about global climate 

change and the role of clouds on any possible change. 

Instrumentation will collect data to determine the 

interactions of sunlight, radiant energy, and clouds on 

temperature, weather, and climate. A l 0-year project is 

being planned. 

USDA/SCS Snow Survey gages froze again during the 

winter of 1991-1992 because the fluid used could not 

handle the cold temperatures. During the summer of 1992 

a switch was made to a different type of solution that has a 

lower freezing point. 

The University of Rhode Island began collecting flask 

samples of ambient air in BRW for analysis of 0 2/N2 and 

C02. Oz fluxes mirror those of COz. By measuring 0 2 

concentrations, important information about the fate of 

fossil fuel C02 can be gained as well as the information 

regarding the fertility of the ocean. 

Several new projects are being planned for BRW in the 

coming year. The University of Washington is planning to 

have high-pressure cylinders filled at BRW for analysis of 

14C in CO at the University of Washington. The measurements will provide information about photochemical 

influences on tropospherical OH radical concentrations. 

A project is being planned by the U.S. Interagency Arctic 

Buoy Program to set up and calibrate ice buoys at BRW. 

1.3. SMllOA 

C. FARMER 

1.3.1. 0PERAT!Oi\S 

The past year at the observatory was spent doing many 

of the hurricane recovery chores that were not completed 

immediately following Hurricane Val. Most measurement 

programs were cont inued during the year without any 

major difficulties. It was the middle of the year before all 

of the main CMDL programs were back to normal with the 

replacement of the C02 sampling mast at the point area. 
The only item that still needed altention was the 

replacement of the Hi-Vol sampling enclosure for EML 

and the maximum/minimum temperature shelter. 

There were more problems with the generator during the 

year. The starter shorted out and in doing so caused many 

other problems, the most serious of which required the 

replacement of the radiator that had been replaced just 1 

year earlier and the replacement of the injectors that were 

damaged due to water gelling in the fuel. The old radiator 

was returned to Caterpillar in hopes that they would 

replace it under warranty but they did not. The starter 

burned out and also had to be replaced. Most of these 

repairs and modifications were performed by the 

observatory personnel. 

Much of the hurricane damage on the island went 

unrcpaired for the year, especialJy the roads. The 

condition of the road to the observatory worsened further 

with the passage of a period of unusually heavy rain in 

April of more than 580 mm (23 inches) and the passage of 

a hurricane near the islands during the last week in 

December when again heavy rains and flooding occurred. 

Because the balleries were no longer holding a charge, 

the PY array was disconnected during August. New 

baltcrics were requested but because of their high 

replacement cost, they could not be purchased and were 

not in place by the end of the year. This created few 

problems for the CAMS and other equipment that normalJy 

used the solar PY power, until the end of the year when the 

island power began going off and on quite often. Because 

of the degradation of the island power, the:: data acquisition 

units had a high failure rate. They began experiencing 

many autorcstarts, the bram Jost messages, and several 

circuit board failures occurred with alJ units. This problem 

was finally dealt with by running extension cords lo the 

Ekto building and using the UPS power available there. 

We had a smalJ problem with the new chief in Tula 

vilJage when the rent payments for March and April were 

delayed in the mail. He threatened to change alJ of the 

locks at the observatory. Luckily the check for April 

arrived in time for the Station Chief to persuade him not lo 

Jock us out. 

1.3.2. PROGRA~IS 

Table 1.5 summarizes the programs at SMO for 1992. 

Further descriptions of some of the programs folJow. 

Carbon Dioxide 

The sampling mast that was broken during Hurricane 

Val was replaced during July. Until that time the 

temporary sampling mast that was configured after 

Hurricane Ofa had been in use since early January. 

There appeared to be linle difference in the C02 data 

when the winds were within the clean air sector except 

possibly there was a slight decrease in the standard 

deviations of the hourly averages. 

10 

A shortage of working tanks occurred near the end of the 

year. The new tanks were supposed to arrive in early 

December but failed to make the ship. The system was 

kept running by switching in old working tank standards 

for about 1 week at a time, working the remaining pressure 

levels of the working tanks lo lower than normal levels 

before they were shipped back to Boulder for final 

concentration level checks. 

The flask sampling program continued throughout the 

year without any major difficulties. The only significant 

change to the regular flask sampling program was the 

switch to the 2.5-L flasks for the MAKS unit and the 

discontinuance of the 3-L flasks. 

Surface Ozone 

There were many problems with this program during the 

year. A new instrument was shipped in February to the 

observatory only to develop immediate problems because 

of its newer design it ran cooler, causing a condensation 

problem that evcntualJy led to its return to Boulder. The 

old instrument was refurbished in Boulder, was returned to 

Samoa, and was put back into service. There were also 

problems with the chart recorder hanging up on several 

occasions and it was finalJy replaced. There was also a 

great deal of data Jost due to the continued failure of the 

ozone board in the data acquisition unit. This problem 

worsened when the PY array had 10 be shut down. 

Total Ozone 

There were no serious difficuhies with the operation of 

Dobson spectrophotometer no. 42 during the year. An 

expanded program was started in March to include zenith 

observations after each direct sun observation to improve 

the algorithm to convert the zenith observations to ozone 

values. This program was continued through the end of the 

year. 

Halocarbons and Nitrous Oxide 

There were problems during the year with the halocarbon 

and N20 gas chromatographs. However, Joss of data was 

kept 10 a minimum in most circumstances. These 

problems included the Joss of a power supply in the 

computer, the continued problem of the water removal 

system gelling plugged up, problems with the air 

compressor, and a temperature control problem with the 

N20 gas chromatograph. The source of the fine powdery 

substance that was plugging up the water removal system 

was determined to be the traps themselves, although the 

presence of the material upstream of the traps seems to 

contradict this. New stainless-steel traps were instalJed 

and appeared to be working well; however, there was 

eventually a problem with them plugging up as well. To 

keep the system from being affected by the regular low 

voltages experienced during the evening hours and power 

outages, the UPS continued to work without difficulty. 

Several other minor problems were encountered during the 

year. 
TABLE 1.5. Summary of Measurement Programs at SMO in 1992 

Surface 0 3 

Total 0 3 

Program 

CFC-I I, CFC-12, N20 

CFC-I I, CFC-12, N20, CCl4 , 

CH3CCl3 

N20 

LEAPS Gases H-1301, H-1211, CFC-113, 

CFC-22 

HCOOH, CH3COOH, HCI, HN03, CH3S03H 

Aerosols 

Condensation nuclei 

Solar Radiation 

Global irradiance 

Direct irradiance 

Meteorology 

Air temperature 

Dewpoint temperature 

Pressure 

Wind (speed and direction) 

Precipitation 

Precipitation Chemistry 

pH 

Conductivity 

Anions (NO), S04) 

Cooperative Programs 

C02 , 13C, N20 (SIO) 

GAGE project: CFC- I I, CFC-12, 

N2 0, CH3CCl3, CCl4 (SIO) 

Various trace gases (OGIST) 

Wet deposition (NADP) 

Bulk deposition (EML) 

Hi-vol sampler (EML) 

Hi-vol sampler (SEASPAN Project) 

CHd'3C/'2C ratio) (Univ. of Wash.) 

Light hydrocarbons (UC!) 

Instrument 

Siemens Ultramat-5E analyzer 

3-L glass flasks 

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 steel flasks 

HP5890 automated GC 

Shimadzu automated GC 

1-L stainless-steel flasks 

Condensation sampling with ion 

chromatographic analysis 

Pollak CNC 

G.E. CNC 

Eppley pyranometers with Q and RG8 filters 

Eppley pyrheliometer with Q filter 

Eppley pyrheliometer with Q. OG 1, 

RG2, and RG8 filters 

Thermistors (2) 

Max.-min. thermometers 

Polished mirror 

Capacitance transducer 

Mercurial barometer 

Bendix Aerovane 

Rain gauge, weighing bucket 

Rain gauge, tipping bucket 

Rain gauge, plastic bulk 

HASL Chemetrics wet/dry collector 

Fisher model 805 meter 

Beckman model RC- 16C meter 

Dionex QIC ion chromatograph 

5-L evacuated glass fl asks 

HP5880 gas chromatograph 

Stainless steel flasks 

HASL Chemetrics wet-dry collector 

Plastic bucket 

High-volume sampler 

High-volume sampler 

30-L pressurized cylinder 

1-L evacuated stainless steel flasks 

11 

Sampling Frequency 

Continuous 

I pair wk"1 

1 pair wk-t 

I pair wk"1 

Continuous 

4 day-I 

I pair wk-I 

I sample (h)-t 

I pair mo·! 

I pair mo-t 

Discrete 

I day-I 

Continuous 

Continuous 

Continuous 

Discrete 

Continuous 

l day-I 

Continuous 

Continuous 

1 wk-I 

Continuous 

Continuous 

Continuous 

1 day-I 

1 day-I 

1 day-I (CMDL); 

I wk-I (NADP) 

1 day·'(CMDL); 

I wk-I (NADP) 

1 day-I (CMDL) 

3 flasks wk-I 

1 h-1 

3 flasks wk- 1 

(3 flasks set·I) 

1 wk-I 

Continuous (I bucket mo-I) 

Continuous (I filter wk-I) 

Continuous (I filter wk-I) 

Biweekly 

3-4 flasks qtrl 
Flask air sampling continued on a weekly basis when 

flasks were available. Either 300-ml (weekly) or 1-L 

(monthly) flasks were used. 

Aerosols 

The aerosol program continued at the observatory with 

the addition of a TSI condensation nucleus counter. There 

were several problems initially encountered with the unit 

and the acquisition of the data from it, but it was up and 

running by May. The other component of the aerosol 

program, the GE condensation nucleus counter, ran 

throughout most of the year experiencing problems typical 

of past years. 

Solar Radiation 

This program had few problems during the year. There 

was some difficulty with the tracking NIP staying aligned 

during the middle of the year, the reason for which was 

never clear. 

Meteorology 

After Hurricane Val destroyed the weather shelter, the 

maximum/minimum thermometers remained underneath 

the carport for the entire year. This obviously was not an 

ideal location for the thermometers, but without a shelter, 

this temporary site was required. One result of this 

temporary location was that during the year many people 

who came up to the observatory after hours began taking or 

breaking the thermometers due to their conspicuous 

location. All the other meteorological-shelter instruments 

performed well during the year. 

Problems with the Aerovane were suspected when the 

measured wind speed was not as high as it appeared to be. 

The Aerovane readings were checked against a hand-held 

anemometer to verify that the measured wind speeds were 

below expected values. The problem was due to the 

degaussing of the magnet in the instrument. Later in the 

year during the passage of a hurricane near the island, the 

direction was affected causing the direction to shift by 

about +20°. Later tests have verified this to be the case. 

Precipitation Chemistry 

When it rained, daily precipitation samples continued to 

be collected during the year. All analyses were performed 

at the observatory. Samples are no longer being shipped to 

MLO for further analyses. Analysis is performed using a 

Dionex QIC ion chromatograph on loan from the 

University of Washington. 

Cooperati1•e Programs 

The cooperative program that again involved the most 

time during the year was the gas chromatographs operated 

by SIO. All problems were dealt with and the system ran 

well throughout most of the year. Most all other programs 

operated without difficulty for the year. The National 

Acid Deposition Program was discontinued during the year 

with the last sample being taken in October. 

12 

1.4. SOUTH POLE 0IlSERVATORY 

D. TYSOR 

1.4.1. 0PERATIO:'\S 

CMDL's most remote baseline observatory is located at 

the Amundsen-Scott South Pole Station (SPO). The SPO is 

located 200 m from the geographic South Pole on the polar 

plateau at an elevation of 2835 m. The extreme 

environment of the polar plateau adds to the remoteness of 

the station. With an average year-round temperature of 

-49"C, planes can land only during a short summer season 

(approximately November I-February 15). This report 

will cover dates from November l, 1991-November 1, 

1992, a time-frame consistent with the rotation dates for 

incoming and outgoing observatory staff. 

The SPO is housed in the Clean Air Facility (CAF), a 

building located several hundred meters grid northeast of 

the main dome structure of the United State's Antarctic 

station. This location is optimal for the sampling of 

atmospheric constituents because the wind blows from a 

clean air sector a large percentage of the time. 

While most of the CMDL SPO operations are located at 

the CAF, the SPO balloon programs were carried out in the 

Balloon Inflation Tower located "down wind" of the 

station. Antarctic Support Associates (ASA) computer 

facilities located in the main dome, were also used by the 

CMDL program. 

NSF is the United States' agency tasked with managing 

all of our country's Antarctic science projects. NSF funds 

provide the base support for research, transportation, and 

logistics for university and government agencies as well as 

for the civilian contractors, ASA, to help develop, 

maintain, and improve America's presence on the continent. 

This year's support facilities that had an impact or future 

impact on CMDL's program included the following: 

A ceilomcter (for measuring cloud base heights) was 

purchased by the U.S. Navy and installed on the roof of 

CAF. Although the instrument is to be operated and 

maintained by ASA, software was written that allowed 

CMDL to collect raw data from this instrument. This data 

may be able to contribute to several of NOAA's programs 

including solar radiation (radiation budget), aerosols 

(tropospheric/surface), as well as for its intended purpose 

for meteorology (cloud base heights). 

The upgrades on the station power plant continued during 

the 1991-1992 season. In previous years, power has been a 

problem at the Pole when blackouts and brownouts were 

quite common. The station is perhaps one season away 

from completing the power plant upgrade, but during the 

year station power was very clean and there were only a 

few unscheduled blackouts. During the summer, a new 

two-story building on stilts was constructed in an area 

known as "summer camp." This structure and others like it 

represent the future design of new buildings at the Pole and 

as such could eventually be used as the next CAF. The 
current CAF is over 1 S years old and is scheduled to be 

replaced in the next few years. 

CMDL scientific data from the Pole is sent out via the 

ATS-3 satellite. This satellite was also used for phone 

traffic into the United States via Malabar, Florida. When 

available, the LES-8 and LES-9 satellites were used to 

transmit additional data from the Pole. The SPO data ranks 

second in the priority list of all project data currently being 

transmitted from the Pole, so data transmittal went 

smoothly. 

1.4.2. PROGRAMS 

Table 1.6 is a summary of the measurement programs at 

SPO during 1992. The following is a short discussion of 

the various programs. 

Aerosols 

Most of the aerosol equipment functioned well during the 

year. The aethalometer performed well in its task of 

measuring carbon aerosols, but was returned to Boulder in 

Dec em bcr 1991 for refurbishing. 

The 4-wavelength nephelometcr measures the optical 

properties of aerosols and ran well except during high 

winds. For some unexplained reason, all four channels 

would drop out when winds exceeded 30 knots. When the 

wind speed decreased, the instrument would automatically 

begin collecting data again. 

The TSI condensation nuclei counter (CNC) also 

performed poorly during high winds exhibiting erratic 

behavior. A blown driver card was the only hardware 

replacement required for the TSI. The in strument 

functioned perfectly during low wind conditions. 

The Pollak CNC observations took several days to 

stabil ize after the instrument was watered, but after the 

Pollak had time to dry out, the results began to agree with 

the TSI CNC. 

CAMS 

Data is collected for the various programs using the 

Control and Monitoring System (CAMS). The CAMS units 

all functioned very well during low wind conditions. 

However, during high winds especially in the winter, the 

C02 unit had one autorcstart and the ASR (Aerosol, Solar 

Radiation) unit had numerous ones. 

Carbon Dioxide 

The Siemans IR analyzer that measures in situ baseline 

C02 concentrations worked without fail for the entire year. 

The chart recorder failed on occasion, but was easily fixed 

with the replacement of a few electronic components. 

The through-analyzer flask program samples the same air 

that is analyzed by the Siemans equipment. The flasks 

were saved throughout the winter and were returned to 

Boulder in the summer for analysis and comparison with 

the Sicmans' data. A second C02 fl ask program involved 

the use of a portable MAKS unit. Samples arc collected 

13 

outside simultaneously with the SIO program flasks and the 

MAKS flasks are shipped back to Boulder in the summer 

along with the through-analyzer flasks. All C02 flasks 

compared well with the Sicmans analyzer data. 

Dobson Ozone Spectrophotometer 

The Dobson ozone spectrophotometer measures the total 

ozone in a column of air. The measurements are 

normalized to ozone concentrations in a vertical column 

over the station. This equipment is normally operational in 

the summertime when the sun is several degrees above the 

horizon and in the wintertime when the moon is full. The 

instrument was operational 100% of the operational 

window. Missed observations were usually due to poor 

weather conditions, i.e., blowing snow or thick overcast 

skies. 

Meteorology 

Meteorology equipment includes instruments to measure 

temperature, pressure, frost-point temperature, and wind 

speed and direction as well as the CAMS units for 

recording all of the data. After replacing the CAMS 

anemometer board early in the season, the meteorology 

equipment functioned well throughout the rest of the year. 

NOAH - Halocarbons 

The gas chromatograph system that measures CFC's in 

the atmosphere, was reworked during the summer and ran 

almost continuously for the rest of the year. Minor 

computer problems and valve realignments account for the 

small amount of down-time in the winter. The flask 

sampling program ran smoothly. 

Ozonesonde Balloons 

This program was the year's most challenging. Extensive 

data was collected on stratospheric ozone even though there 

was a telemetry reception problem with the ground 

equipment. Balloons were launched in high winds with 

greater success than in previous years. 

Solar Radiation 

The side-by-side comparison of Soviet versus American 

solar radiation instruments was completed in the summer. 

The Soviet equipment was removed and returned to 

Boulder. The tracker for the normal incidence 

pyrhcliomcter had a few problems, but the data still 

compared well with the manually operated instrument. No 

pyrgeometcr data was collected after both instruments 

malfunctioned in the winter. 

Water Vapor Balloo11s 

Like the ozoncsonde program, this balloon program 

suffered from the telemetry problems mentioned earlier. 

Other problems included faulty timers that are supposed to 

fire, causing a slow descent for the balloons. The correct 

functioning of the timers is particularly important as the 

most valuable water vapor data is collected during descent. 
TABLE 1.6. Summary of Measurement Programs at SPO in 1992 

Surface 0 3 

Total 0 3 

Ozone profiles 

Program 

CFC-I I, CFC-12, CFC- 113, N10. CH3CCl3, CC14 

CFC-I I, CFC-12, N20, CFC-113, CCl4 , CH3CCl3 

CFC-I I, CFC-12, N20, CFC-113, CCI,, CH3CCl3 

H- 1301 , H-1211,F-22,F113 

Water vapor 

Aerosols 

Condensation nuclei 

Optical properties 

Carbon aerosols 

Solar and Terrestrial Radiation 

Global irradiance 

Direct irradiance 

Alhedo 

Terrestrial Radiation 

Global irradiance 

Albedo 

Meteorology 

Air temperature 

Pressure 

Wind (speed and direction) 

Frost-point temperature 

Cooperative Programs 

C02. !3C, N10 (SIO) 

Total surface particulates (DOE) 

Various trace gases (OGIST) 

t4C (ARL) 

Interhemispheric t3C/1 4C (CSIRO) 

Polar stratospheric clouds (Univ. of Rome) 

0 2, N2 (NCAR) 

Instrument 

Siemans IR analyzer 

0.5-L glass flasks, through analyzer 

0.5-L glass flasks, MAKS pump unit 

Dasibi ozone meter 

Dobson spectrophotometer no. 82 

Balloonbome ECC sonde 

Shimadzu automated mini-2 GCs 

300-mL stainless steel flasks 

850-mL stainless steel flasks 

Balloonbome sonde 

Pollack CNC 

TS! CNC 

Four-wavelength nephelometer 

Aethalometer 

Eppley pyranometers with Q and RG8 filters 

Eppley pyranometer with Q filter 

Net radiometer 

Eppley pyrheliometer with Q, OGI, RG2, 

and RG8 filters 

Eppley pyrheliometers with Q and 

RG8 filters 

Eppley pyranometers with Q and RG8 filters 

filters, downward facing 

Eppley pyrgeometer 

Eppley pyrgeometer, downward facing 

Platinum resistor, 2- and 20-m heights 

Capacitance transducer 

Mercurial barometer 

Bendix Aerovane 

Hygrometer 

5-L evacuated glass flasks 

High-volume sampler 

Stainless-steel fla sks 

3,000 psi spheres 

5-L glass flasks 

Optical lidar 

Air sampling pump and flasks 

Sampling Frequency 

Continuous 

1 pair twice mo·I 

1 pair twice mo·I 

Continuous 

2 day·l 

I wk-I, summer, autumn, 

winter; I (3 day)-1, spring 

I sample (2 h)-1 

3 pair mo·I, summer 

I pair mo·t, summer, winter 

6 times yrl 

I day-I 

Continuous 

Continuous 

Continuous, summer 

Continuous, summer 

Continuous, summer 

Continuous, summer 

Discre te, summer 

Continuous, summer 

Continuous. summer 

Continuous 

Continuous 

Continuous 

Continuous 

1 timewk-1 

Continuous 

Continuous 

2 mo·! (3 flasks sample·!) 

Continuous 

(4 filters mo·l) 

I week·l (2 flasks set·l) 

500 psi day-I, summer 

I or 2 flasks mo·I 

I week·2 

I mo·I (3 fl asks set·l). summer 

Cooperative Programs 

The Commonwealth Scientific and Industrial Research 

Organization (CSIRO) and the Oregon Graduate Institute of 

Science and Technology (OGIST) flask sampling programs, 

which sample for various trace gases, both ran smoothly. 

The flasks for the Scripps Institute of Oceanography 

(SIO) C02 program lost their vacuum after the 1990-1991 

season. This resulted in contaminated flask samples early 

in the summer. The program had no problems after new 

flasks were shipped in. The Department of Energy (DOE) 

14 
pump ran flawlessly. Fillers were collecled lhal were laler 

sampled for lolal surface parliculales. 

The NOAA Air Resources Laboralory (ARL) 14C pump 

had no problems, but was removed in lhe early summer. 

This long-term project was terminated at the request of lhe 

P.I. who decided lo end lhe program in Anlarclica. 

The NCAR air sampling pump was subject to leaks, but 

several samples were able to be collected. These flask 

samples were later analyzed for oxygen to nilrogen ratios. 

This program to determine global oxygen concentrations in 

the atmosphere was starled this year as a feasibility study. 

Depending on the initial results, the program may be 

continu-:d irHo th~ f'lt'.!!'! ye2!'£. 

The Universily of Rome lidar projecl was given its own 

projecl number (S-256), bul NOAA continued assisting 

with lhe collection of data for this project. During lhe 

summer, a more powerful laser was installed. The 

instrument ran with no problems during the year. 

In summary, the CMDL programs ran well over the year. 

The ozone and solar radiation measurements gave pertinent 

data that helped to quantify and describe .ozone depletion 

over Antarelica and lhe volcanic dust veil from Mt. 

15 

Pinatubo and Mt. Hudson that spread globally and warmed 

the stratosphere while slightly cooling the troposphere. All 

the trace gas measurements continued to exhibit the 

buildup in the atmosphere but at a slower rate for the 

halocarbons. 

REFERENCES 

Ferguson, E.E., and R.M. Rosson (Eds.), Climate Monitoring and 

Diagnostics i.Aboratory No. 19: Swrvruuy Report 1990, 133 pp., 

NOAA Environmental Research Laboratories, Boulder, Colorado, 

1991. 

H!n£-:!1, A.D.A., T.!. Ccr?'-'-'!j', L.P. S~::!e, B.A. Bodhainc, K.\V. 

Thoning, P. Tans, and T. Novakov, Correlations among combustion 

effluent species at Barrow, Alaska: Aerosol black carbon, carbon 

dioxide, and methane, J. Atmos. Chem., 9, 283-299, 1989. 

Jaffe, D.A., R.E. Honrath, J.A. Herring, S.-M. Li, and J.D. Kahl, 

Measurements of nitrogen oxides at Barrow, Alaska during 

spring: Evidence for regional and northern hemispheric sources 

of pollution, J. Geophys. Res., 96, 7395-7405, 1991. 

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

dioxide at Mauna Loa Observatory, 2, Analysis of NOAA GMCC 

Data 1974- 1985, J. Geophys. Res., 94(06), 8549-8565, 1989. 
2. Carbon Cycle Division 

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

P.M. LANG, K.A. MASARIE, P.C. NOVELLI, K.W. THONING, 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 1992 as in previous years. 

Monthly and annual mean C02 mixing ratios [in the WMO 

1985 mole fraction scale (X85)] are given in Table 2.1. 

These values are provisional, pending final calibrations of 

station standards. Preliminary selected daily average C02 

mixing ratios for 1992 are plotted versus time for the four 

observatories in Figure 2.1. 

The C02 in-situ systems operated during 1992 from a 

low of 93.5% at SMO to a high 98.5% of the year at MLO. 

BRW operated 97.8% of the time and SPO 95.0%. This is 

based on the number of valid hourly averaged C02 mixing 

ratios that were calculated for the year, taking into account 

missing data due to reference gas calibrations during the 

year. The major loss of data at SPO was due to 

temperature instability in the Clean Air Facility, which 

affected the stability of the C02 NDIR analyzer. A failure 

of the SMO CAMS unit in December resulted in 4 days of 

lost data. In December 1991, typhoon Val struck SMO, 

damaging the C02 intake mast at the point. A temporary 

intake line was erected on the point so that C02 monitoring 

could resume. Power outages in January accounted for 5 

days of Jost data. In July, a new, stronger 23-m high mast 

was installed. 

TABLE 2.1. Provisional Monthy Mean C02 Mixing Ratios 

From Continuous Analyzer Data (ppmv, Relative to 

Dry Air WMO X85 Mole Fraction Scale) 

Jan. 

Feb 

March 

April 

May 

June 

July 

Aug. 

Sept. 

Oct. 

~OV. 

Dec. 

Year 

BRW 

361.62 

362.21 

362.48 

362.55 

362.77 

360.42 

353.58 

347.09 

347.69 

353.66 

357.24 

361.05 

357.70 

MLO 

356.02 

356.79 

357.60 

358.75 

359.33 

359.15 

356.68 

354.74 

352.76 

353. 16 

354.09 

355.34 

356.20 

SMO 

354.20 

354.56 

354.78 

354.58 

354.63 

354.87 

355.35 

355.31 

354.96 

355.05 

354.78 

355.25 

354.86 

SPO 

353.05 

352.80 

352.68 

352.90 

353.25 

353.65 

354.09 

354.47 

354.66 

354.67 

354.49 

354.22 

353.74 

16 

340~~~~~~~~~~~~~~~~~~~~ 

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 

365 

355 

350 e 

a. 345.__~~~~~~~~~~~~~~~~~~~ 

.9: JAN FEB MAR APR MAY JUN JUL AUG.SEP OCT NOV DEC 

N 360 8 Samoa 

355 1-J..')°J"'"'!v~N-~~-,,,,. 

350 1--~~ ~~~~~~~~~~~~~~~--' 

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 

South Pole 

351 .__~~~~~~~~~~~~~~~~~~~ 

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 

Fig. 2.1. Preliminary selected daily mean mixing ratios at the four 

CMDL observatories. 

The growth rate of C02, as measured by the observatory 

systems, was smaller than average in 1991 and 1992. 

Figure 2.2 shows the instantaneous growth rate with the 

annual cycles removed at the four CMDL observatories for 

the years 1980 through 1992. These curves were obtained 

using methods similar to Thoning et al. [1989]; they are the 

derivative of a curve that is a combination of a function 

consisting of a quadratic polynomial, four annual harmonic 

terms, and low pass filtering of the residuals to remove 

high frequency variations. Annual cycles were removed by 

not including the derivatives of the four annual harmonic 

terms. The BRW growth rate, which typically has greater 

fluctuations than the other sites, appeared lo be negative 

for most of 1992. The low growth rate at BRW is also 

apparent when comparing the annual mean difference 

between BRW and SPO. In 1991, this difference was 5.1 

ppm, but for 1992 it was only 4.0 ppm. 
L<g•nd 

- Burow 

- - Mauna Loa 

~ 

- - South Pok 

-1~_,_~_.___,~_.__~..___,_~_.___,.~_.__~....__,_~_.___, 

80 81 82 83 S4 8, 86 87 88 89 90 91 92 93 

Year 

Fig. 2.2. The variat;on of the C02 growth rate for the period 1980-

1992. The curves are the lime derivatives of the deseasonalized, 

smoothed daily mean data for the four CMDL observatories. 

2.1.2. FLASK SAMPLE CARBON DIOXIDE MEASURE· 

MENTS 

Measurements of the global distribution of atmospheric 

C02 by flask sampling continued in 1992. Table 2.2 lists 

33 sites of the CMDL cooperative flask sampling network 

where flask samples were collected in 1992. Carbon 

dioxide mixing ratios (as well as CH4 , CO, and isotopic 

ratios) were measured in the CMDL Boulder laboratories. 

Provisional annual mean C02 mixing ratios for 1992 and 

revised values for 1990 and 1991 are given in Table 2.2. 

The first annual means for the recently started programs at 

Izafia, Canary Islands; Mace Head, Ireland; Qinghai, China; 

and Ulaan Uul, Mongolia are included in Table 2.2. Flask 

sampling at Heimaey, Iceland, was also begun in late 1992. 

The Iceland site was chosen to replace Ocean Station M 

which is expected to cease operation in the next year. 

Sampling on regular voyages of the containerships 

Southland Star and Wellington Star continued in 1992. 

Since the ships sample similar regions of the Pacific 

Ocean, the annual mean C02 mixing ratios for 1990 

through 1992 from both ships were combined into 5-degree 

latitude bins centered on latitudes from 30"N to 35'S 

(Table 2.3). 

The flask sampling program in the South China Sea, 

begun in 1991, continued in 1992. Flask samples are 

collected at 3-degree latitude intervals from 3"N to 21 'N 

on regular voyages of the Chevron refined product carrier 

Carla A. Hills. It is hoped that this intensive sampling 

program (averaging more than one sample per day) will 

help quantify the large CH4 source due to rice production 

in southeast Asia. Annual mean C02 mixing ratios for 

1992, the first complete year of sampling, are presented in 

Table 2.4. 

The conversion of the flask sampling network to the 

2.5-L Teflon 0-ring stopcock flasks and the MAKS sampler 

continued in 1992. These changes, together with an 

17 

TABLE 2.2. Provisional 1990-1992 Annual Mean 

C02 Mixing Ratios From Network Sites 

C02 (ppm) 

Code Station 1990 1991 1992 

ALT Alen, N.W.T., Canada 355.5 357.2 357.5 

AMS Amsterdam Island 352.5 I I [) 

ASC Ascension Island 352.9 353.9 355.1 

AZR Terceira Island, Azores 353.2 355.8 [) 

BME Bermuda (east coast) 355.2 356.1 357.0 

BMW Bermuda (west coast) 355.l 356.6 356.3 

BRW Barrow, Alaska 356.0 357.6 357.5 

CBA Cold Bay, Alaska 355.3 357.3 357.3 

CGO Cape Grim, Tasmania 351.6 352.8 353.5 

CHR Christmas Island 354.3 355.4 356.4 

CMO Cape Meares, Oregon 355.4 356.7 356.3 

GM! Guam, Mariana Islands 354.2 356.1 356.3 

HBA Halley Bay, Antarctica I I I I [) 

IZO Izaiia Observatory, Tenerife I I 356.2 

KEY Key Biscayne, Florida 355.9 356.5 357.3 

KUM Cape Kumukahi, Hawaii 354.3 355.8 356.3 

MBC Mould Bay, Canada 356.0 357.6 357.4 

MHT Mace Head, Ireland [) 356.1 

MID Midway Island 355.2 357.0 356.8 

MLO Mauna Loa, Hawaii 354.1 355.5 356.4 

NWR Niwot Ridge, Colorado 354.7 356.1 356.8 

PSA Palmer Station, Antarctica 351.9 353.2 354.2 

QPC Qinghai Province, China I I 356.6 

RPB Ragged Point, Barbados 354.7 355.9 355.9 

SEY Mah~ Island, Seychelles 353.3 353.9 354.8 

SGl South Georgia Island CI CI I I 

SHM Shemya Island, Alaska 355.0 356.7 357.l 

SMO American Samoa 352.8 354.2 354.9 

SPO South Pole, Antarctica 351.8 353.1 354.1 

STM Ocean Station M 354.8 356.5 356.5 

SYO Syowa Station, Antarctica 352.3 353.3 354.2 

TAP Tae-ahn Peninsula, S. Korea I I 359.8 360.6 

UUM Ulaan Uul, Mongolia 356.3 

Square brackets indicate insufficient data to calculate annual mean. 

increased emphasis on face-to-face training, have resulted 

in a significant increase in sample quality. An objective 

criterion for successful flask sample collection is that the 

two members of the sample pair, collected in series, agree 

to within 0.5 ppm. Figure 2.3 shows the percentage of 

samples meeting this criterion ("good pairs") for all sites 

during 1987-1992. The percentage of good pairs has 

increased from .,.75% to 90%, if the shipboard flasks are 

excluded. The somewhat lower percentage of good pairs 

for shipboard sampling is probably due to the use of 

evacuated flasks rather than the MAKS sampler (for the 

convenience of the ship personnel) and the presence of 

contamination sources on the ships. 

The most notable feature of the 1992 C02 flask data is a 

decrease in the C02 growth rate, particularly in the 

northern hemisphere. The flask data from Mould Bay, 

Canada (76' 15'N, 119' 21'W) and Cold Bay, Alaska (55" 

12'N, 162" 43'W) are shown in Figures 2.4 and 2 .5 as 
TABLE 2.3. Provisional 1990-1992 Annual Mean 

C02 Mixing Ratios From the Southland Star and 

W e/lington Star Shipboard Flasks 

C02 (ppm) 

Latitude 1990 1991 1992 

30"N 354.6 356.5 357.1 

25'N 354.4 356.l 357.0 

20'N 354.9 356.0 356.8 

15'N 354.7 356.0 356.9 

IO"N 355.0 356.2 357.1 

5"N 354.9 355.9 356.9 

Equator 354.9 355.7 356.4 

5·s 354 .9 355.4 356.1 

!O'S 354.1 355.0 355.6 

15·s 353.0 354.4 355.4 

20'S 352.5 353.8 354.9 

25'S 352.5 353.7 354.5 

30'S 352.3 353.4 354.4 

35'S 352.1 353.7 354.5 

examples. The trend curves for both sites (dotted lines) 

show that the increase in C02 levelled off in late 1991, and 

essentially no C02 increase was observed in 1992. 

The spatial distribution of the 1992 C02 growth rate 

anomaly is shown in Table 2.5. The mean growth rates for 

1981-1992 and 1991-1992 were calculated from annual 

averages based on flask data smoothed in space and time. 

The global C02 growth in 1991-1992 was less than half of 

the 1981-1992 mean. From 30° to 90°N, C02 did not 

increase from 1991 to 1992. From the C02 data alone it is 

difficult to explain the 1992 C02 growth rate anomaly. 

Although 1992 fossil fuel C02 emission data are not yet 

available, it is extremely unlikely that fossil fuel C02 

emissions decreased enough to account for the observed 

northern hemisphere results. An increased C02 sink in the 

terrestrial biosphere is a possible explanation, and is 

supported by deeper than usual C02 drawdowns during the 

summer of 1992, observed at several flask network sites. 

TABLE 2.4. Provisional 1992 Annual Mean C02 Mixing 

Ratios From the Carla A. Hills Shipboard Flasks 

Latitude C02 (ppm) 

3"N 357.6 

6"N 357.0 

9"N 357.2 

12"N 357.6 

15"N 358.2 

18"N 358.5 

2l'N 359.I 

18 

ICC 

9C 

80 

70 

60 

50 

• O 

JO 

20 

10 

0 

j 

~ 

1987 

-

Tete 

-

·gee 1989 

r 

fl 

• 1: 

1990 1991 1992 

Fig. 2.3. The percentage of fla sk samples collected each year from 

1987 to 1992 meeting the good pair criterion for C02 (difference 

between flasks flushed and filled in series less than 0.5 ppm). The 

shaded bar represents the percentage of good pairs from both Jandbased and shipboard samples, and the solid bar represents only the 

land-based samples. 

Similarly, an increase in the flux of atmospheric C02 into 

the oceans could have occurred as a result of cooler sea 

surface temperatures. The cooling is due to the aerosol 

cloud produced by the eruption of Mt. Pinatubo. Work is 

currently being done to improve on these speculations 

using a 2-D model to calculate the latitude distribution of 

C02 sources and sinks. In addition, the measurements of 

13C/12C in C02 from flask network sites begun in 1990 

should be extremely valuable in distinguishing between 

marine and terrestrial effects. 

370 

360 

e JSO 0. 

.9: 

ON 

u )<() 

~·---/4 l 

·"" . "' \ i \ • "" I ' < l J " ' I . \ , 

-r1--ti I· ·! -- ~ ,; ~ ·' . \I t . '• r ~ • )JO .. -- - --- ---

320 --·-12 16 II 90 92 

YEAR 

Fig. 2.4. Flask sample C02 data for Mould Bay, Canada, 1981-

1993. Each square symbol represents the average of a retained pair 

or a retained single flask. The dashed-dot curve is a combination of 

curve fits to and digital filtering of the data that shows both low and 

high frequency variability in the data. The dotted curve shows only 

the long-term trend with the mean seasonality removed. Note the 

absence of an increase in C02 from 1991 to 1992 (dotted curve). 
)70 

)6() 

e )lO 

Q, 

~ 

0 

u HO 

HO 

. > . : 

.. ·-~ . \ ./.-; --u':\·- " ~ • -~! 

• 1 ! 1 \ ·~ I : I 1 \ ·_LJ·~ .. ,, ?: :i ;, ~ 

~ 1\_ \ ·1 . • I : I I I I : ' I \ ".t,; ~i :, .. : . .~+ --i i~ .. ..I. ·;., r 1 I ~ \t ft i : ': ·; l_.' i\ \ f I 1

". \,: ; ; '.I :.· ~ ~ . I I I ' ' _ ____._L• - ·->-• 1 : -'t,' -- -..--~ __ , ---ic----1 

; ! ii : : : l . : ~: ~; ~ 

1 2 ' ··--·- --------+---1 

)20 ------

80 12 16 81 90 92 

YEAR 

Figure 2.5. Flask sample C02 data for Cold Bay, Alaska, 1981-

1993. The symbols and curves are the same as in Figure 2.4. 

Again, note the absence of an increase in C02 from 1991 to 1992 

(dotted curve). 

TABLE 2.5. Comparison of 1981-1992 and 

1991 -1992 C02 Growth Rates (ppm yrl) 

Global 3o·s.9o·s 3o·s.o o.3o·N 3o·N-9o·N 

1981-1992 1.43 

1991-1992 0.59 

1.38 

0.91 

1.42 

0.87 

1.45 

0.58 

2.1.3. IN SITU METHANE MEASUREMENTS 

1.47 

0.03 

Semi-continuous measurements of atmospheric CH4 

continued at BRW and MLO in 1992. As before, the 

sampling frequency was 60 samples per day. 

A rebuilt GC, designated Carle 5, was installed at BRW 

on May 14, 1992. It included modifications designed to 

make the GC system more robust and easier to maintain, 

and to improve the measurement precision. Carle 5 was 

modified in Boulder and then installed at BRW. In Boulder 

the catalyst used to convert CO and C02 to CH4 in a stream 

of H2 and a 4-port, 2-position valve used to divert the gas 

flow to the catalyst were removed from the GC. This 

change greatly simplified the procedure for balancing the 

carrier gas flow rate at the FID for the two positions of the 

sampling valve. The GC framework was extensively 

modified to install a Valeo Instruments 10-port sample 

valve instead of the factory equipped Carle valve. 

Compared with Carle valves, Valeo valves are easier to 

align and maintain, and they are more robust. The sample 

loop was increased from about 3 ml (STP) to about 6 mL 

(STP). A 10-mL (STP) sample loop was experimented 

with, but this amount of sample overloaded the columns. 

The final important modification was a switch from a 

column sequence reversal chromatographic method to a 

backflush of the silica gel pre-column. The combined 

result of these changes was an improvement in 

measurement precision from about 0.2% to 0.1 % (reported 

as lcr of the me an of 20 replicate measurements). 

19 

As before, a rule-based expert system (AMIE) was used 

to evaluate the quality of the in situ measurements 

[Masarie et al., 1991]. During 1992, 5.7% of the data from 

BRW and 11.3% of the data from MLO were flagged by 

AMIE. Daily averaged dry air CH4 mixing ratios for 1992 

in ppb (where 1 ppb = 1 part in 109) are shown in Figure 

2.6a for BRW and Figure 2.6b for MLO. The daily means 

exclude all values flagged by AMIE, but they are not 

constrained by wind speed or direction. 

General features in the data are similar to previous 

years. At BRW, large CH4 mixing ratios are observed 

when the wind direction is outside the clean air sector 

(defined as 020 to 110), as air masses elevated in CH4 due 

to anthropogenic activities pass over the site. Much of the 

noise in the data is removed when the data are constrained 

to wind directions within the clean air sector. At MLO, 

large variability (up to 50 ppb in 2 days) in the CH4 mixing 

ratio occurring on synoptic time scales has been attributed 

to transport affects by Harris et al. [1992]. Air masses 

rapidly transported from Asia to MLO in about a week 

elevate the CH4 mixing ratio at MLO compared with air 

masses that have resided over the tropical Pacific Ocean. 

At MLO a diurnal cycle in the CH4 mixing ratio related 

to the local meteorology is seen also. After sunrise, the 

mountain warms which results in air being drawn up from 

the boundary layer to the sampling site. With this air 

comes CH4 mixing ratios that are z30 ppb higher than 

during nighttime when air representative of the free 

troposphere is sampled. The effects of the 

upslope/downslope phenomenon on the mixing ratio of CH4 

are shown in Figure 2.7a for August 19 to 21, 1992. The 

same pattern is observed for the dew point temperature in 

111<0 1al 

lllOO 

~ 

b 

1860 

1

1

820 

780 

JI~~~ ~~Jv 17• 0 

...,.. FEB MAR 

- MAY J.1< .J..l. >W SEP CIC! rm ct:C 

1780 lb) 

~ 

b 

ISM 

.)loJI FEB ,...,. ""' """ JJ• .J..l. .....:; SEP OCl rm ct:C 

1992 

Fig. 2.6. Unselected, daily mean CH4 mixing ratios for 1992: (a) 

BRW and (b) MLO. Gaps in the da1a are due to instrument 

malfunction. Please note the change in vertical scale between (a) 

and (b). 
The average pair difference, based on 2481 pairs, was (0.3 

(a) ± 5.0) ppb. 

,..... 

.D 

Q. 

Q. 

~ 

-£ 

u 

1740 

1730 

1720 

1710 

1700 

1690 

MLO and Cape Kumukahi, Hawaii (KUM) are two 

sampling sites on the Island of Hawaii approximately 90 

km apart, with MLO at an elevation of 3394 m and KUM at 

sea level. These sites provide a unique opportunity to look 

for vertical differences in the mixing ratios and seasonal 

cycles. The annual mean CH4 mixing ratios for 1984 to 

1992 are, on average, (16.0 ± 4.5) ppb larger at KUM than 

MLO (where the uncertainty is lo of the mean). A detailed 

examination of the data suggests that the vertical gradient 

averaged over the measurement period varies with the time 

of year from ==20 ppb during fall, winter, and spring to ==6 

8 

6 

4 

~ 

(b) ppb during summer. Detrended, seasonal cycles 

determined from the flask sample data and averaged over 

the period 1983 through 1992 are shown in Figure 2.8 for 

MLO and KUM. As shown in the figure, the seasonal 

cycles at both sites have roughly the same phase, reaching 

2 c 

·o 

0. 0 

J: -2 0 " 

-4 

-6 

-8 

6 12 18 0 6 12 18 0 

Fig. 2.7. Hourly averaged va lues for CH4 (a) and dew point (b) for 

MLO spanning the period August 19 to 21, 1992. The diurnal cycle 

results from differences in vertical transport between day and night 

at the observatory. 

Figure 2.7b; higher dewpoints are indicative of moist air 

moving up from the marine boundary layer to the sampling 

site. 

2.1.4 FLASK MEASUREMENTS OF METHANE 

During 1992, the determination of the global 

distribution of atmospheric CH4 continued. Measurements 

of CH4 were made covering all or part of 1992 from 

samples collected at 34 sites and three ships participating 

in the CMDL Carbon Cycle Division cooperative air 

sampling network. Sampling was started at three new sites 

during the year: Vestmannaeyjar, Iceland (October), 

Grifton, North Carolina (July), and Ulaan Uul, Mongolia 

(January). At the time of writing, no samples were 

received for 1992 from Halley Bay, Antarctica, and South 

Georgeia Island, and only part of 1992 was covered for 

Azores (January) and Crozet (January to June). Provisional 

annual mean values are shown for sites in the cooperative 

air sampling network in Tables 2.6, and 2.7. 

We continued to determine CH4 mixing ratios from both 

flasks of a sample pair using the Carle 7 analysis system. 

In 1992, 6300 flasks were analyzed for atmospheric CH4. 

20 

their minima at nearly the same time, but the amplitude of 

the seasonal cycle at KUM is ==12 ppb (or 40%) larger than 

at MLO. The appearance of the minima at similar times is 

TABLE 2.6. Provisional 1992 Annual Mean CH4 

Mixing Ratios From the Flask Network Sites 

Code Station CH4 (ppm) 

ALT Alert, N.W.T., Canada 1802.1 

ASC Ascension Island 1677.2 

AZR Terceira Island, Azores (] 

BME Bermuda (east coast) I769.8 

BMW Bermuda (west coast) 1760.9 

BRW Barrow, Alaska 1806.5 

CBA Cold Bay, Alaska 1794.3 

CGO Cape Grim, Tasmania 1666.2 

CHR Christmas Island 1692.4 

CMO Cape Meares, Oregon 1776.5 

GM! Guam, Mariana Islands 1726.2 

HBA Halley Bay, Antarctica [I 

IZO Izaiia Observatory, Tenerife 1746.8 

KEY Key Biscayne, Florida 1755.0 

KUM Cape Kumukahi, Hawaii 1741.5 

MBC Mould Bay, Canada 1802.8 

MHT Mace Head, Ireland 1782.2 

MID Midway Island 1756.5 

MLO Mauna Loa, Hawaii 1724.0 

NWR Ni wot Ridge, Colorado 1756.2 

PSA Palmer Station, Antarctica 1667.6 

QPC Qinghai Province, China I765.8 

RPB Ragged Point, Barbados 1729.2 

SEY Mahe Island, Seychelles 1689.0 

SGI South Georgia Island [ l 

SHM Shemya Island, Alaska 1795.0 

SMO American Samoa 1668.7 

SPO South Pole, Antarctica 1666.9 

STM Ocean Station M 1793.8 

SYO Syowa Station, Antarctica 1667.7 

TAP Tae-ahn Peninsula, S. Korea 1829.3 

Square brackets indicate insufficient data to calculate annual mean. 
TABLE 2.7. Annual Mean CH4 Mixing Ratios 

From Shipboard Air Sampling 

Latitude CH4 (ppb) 

Southland Star and Wellington Star 

35"S 

3o· s 

25"S 

2o· s 

15"S 

1o·s 

s·s 

Equator 

5"N 

lO"N 

15"N 

20"N 

25"N 

30"N 

3"N 

6°N 

9"N 

12"N 

15"N 

!8°N 

21"N 

1672.2 

1669.3 

1668.3 

1668.3 

1670.0 

1672.7 

1682.8 

1690.7 

1702.1 

1721.6 

17347 

1749.4 

1758.8 

1769.7 

Carla A. Hills 

1719.9 

1723.7 

1727.7 

1738.4 

1739.0 

1746.3 

1762.1 

likely due to the fact that the CH4 sink (reaction with 

hydroxyl radical, OH) occurs throughout the atmosphere. 

This is unlike C02, where the minimum at KUM precedes 

the minimum at MLO by about 3 weeks because the 

drawdown in C02 is due to photosynthesis which occurs 

JO 

IS 

~ 10 

i 

u 

-s 

-10 

·IS 

-20 

Kl.M 

. 

M..0 

' I 

--- ... 

J/oJl F(B >WI - MAY JJ" .U. >UJ SEP OCT tCV OCC 

Fig. 2.8. Average, detrended seasonal cycles for MLO (dashed 

line) and KUM (solid line) determined from the flask data. The 

curves are based on data from the period 1983 to 1992. 

21 

entirely at the surface, within the atmospheric boundary 

layer. Although it is not surprising that the amplitudes of 

the seasonal cycles at these two sites are different, a model 

of atmospheric chemistry and transport is necessary to 

quantitatively explain the observations. 

New air sampling sites located near important CH4 

source regions are being used to place better constraints on 

regional sources and sinks of CH4. CH4 data from one of 

these sites, Tae-ahn Peninsula in South Korea (TAP), are 

shown in Figure 2.9 for 1991 and 1992. The important 

features in the time series are the lack of a seasonal cycle 

in the average CH4 mixing ratio and the near-simultaneous 

appearance of the highest and the lowest values during the 

summer. Analysis of atmospheric trajectories shows that 

the lowest values observed during the summer are 

associated with southeasterly flow off the tropical Pacific 

Ocean. Values observed at TAP at such times are typical 

of values observed at KUM. During June to August, 

northwesterly flow from the peat-rich wetlands located in 

the maritime provinces of the former Soviet Union elevate 

CH4 at TAP by about 80 ppb above the annual mean. 

Analysis of the TAP observations using a 3-D atmospheric 

CH4 model (in collaboration with I. Fung and Y. Chung) 

suggests that CH4 emissions from the Far East Russian 

wetlands may be about two times those of Alaskan 

wetlands. Also using the 3-D model, the data were used to 

constrain the global CH4 emissions from rice cultivation to 

=100 Tg CH4 yrt. 

The flask sample data were smoothed using techniques 

described in Steele et al. (1992) to obtain biweekly, zonally 

averaged data used to study CH4 trends on large spatial 

scales (e.g. global, hemispheric, or semihemispheric). 

Time series of global and hemispheric values are shown in 

Figure 2.10. The lines approximate the trends. The main 

features in the data are the strong latitudinal gradient with 

values in the northern hemisphere always higher than those 

1g50 

1900 

1850 

~ 1800 

"6 1750 

1700 

1650 

. ·.·· ., 

1991 

. . . 

..... 

... . . . . . . . . .. . .. 

1992 

. ... .... .. 

Fig. 2.9. Methane mixing ratios (ppb) for TAP from air samples 

collected as part of the CMDL cooperative air sampling network. 
~ 

b 

1780 

~ 

tHO 

Q.. 

1700 

SH 

16eo 

1!>40 

Fig. 2.10. Biweekly CH4 mixing ratios (symbols) for global and 

northern and southern hemispheres determined from zonally 

smoothed flask network data. The line represents the long-term 

trend in atmospheric CH4 . 

in the southern hemisphere, the seasonal variation in both 

hemispheres, and the long-term trend. The globally 

averaged values show a seasonal cycle which is a 

combination of the seasonal cycles in the two hemispheres. 

Based on these surface measurements, the global burden of 

atmospheric CH4 undergoes a seasonal variation of about 

43 Tg CH4 , where 1 Tg = 1012 g. The regular seasonal 

cycle in the southern hemisphere is due to the seasonality 

in the photochemical oxidation of CH4 by OH. The more 

complex seasonal cycle in the northern hemisphere arises 

through interactions between seasonal sources and sinks. 

A decrease in the global growth rate of atmospheric 

CH4 over the period of these measurements from about 14 

ppb yrl in 1984 to less than 10 ppb yrl in 1992 was 

observed. It is confidently observed that the decrease is 

not related to measurement or sampling problems. In 

Figure 2. 11, the instantaneous growth rate curves for 

semihemispheres obtained using methods as described by 

Steele et al. [ 1992] are shown for 1983 to 1992. The 

semihemispheres represent the latitude regions HNH = 30-

90'N, LNH = 0-30' N, LSH = 0-30'S, and HSH = 30-90'S. 

While the rates of decrease of the growth rates for the 

semihemispheres LSH, LNH, and HSH are somewhat 

similar, the growth rate in the HNH has fallen off about a 

factor of 3 faster than the others. The growth rate is 

affected by both sources and sinks of CH4. The 

observation that the growth rate is falling off much more 

rapidly in the high latitudes of the northern hemisphere, 

where most of the industrialized world lives, suggests to us 

that changes in emissions of anthropogenic sources are 

largely responsible for the change in the CH4 growth rate. 

In particular, the component of the global methane source 

that is most amenable to rapid reductions by human 

intervention is that associated with fossil fuel exploitation. 

...: 

i 

.. .., 

.. 

([ 

5 

> 10 0 

\3 

iS 

.... .... .... .... , 

' ' ' ' ' ' ' ' ' ' 

1911) 1964 196~ 1986 1987 1988 1969 1990 1991 1992 

Fig. 2.11. Growth rate variations for four semihemispheres, each 

containing equal volumes of the atmosphere. The figure highlights 

the mo re rapid decrease in the CH4 growth rate in the high latitudes 

of the nonhem hemisphere than in the other semihemispheres. 

22 

2.1.5. IN SITU CARBON MONOXIDE MEASUREMENTS 

In 1992 quasi-continuous in situ measurements of CO 

were made at BRW using a Trace Analytical ROA installed 

at the observatory in September 1991. The analysis, gas 

chromatography followed by mercuric oxide reduction 

detection, requires about 3 minutes. Chromatographic data 

were stored on a diskette, and mixing ratios were calculated 

from the raw data using a 2-point, linear calibration scheme 

(standards had mixing ratios of 75.3 and 178.8 ppb CO). 

The standards were referenced to the CMDL CO-standard 

scale. The instrument was operational 93% of the time; in 

March 1992 components of the chromatograph and detector 

were replaced. 

Preliminary hourly-averaged CO mixing ratios for 1992 

are shown Figure 2. l 2a. The data were not constrained for 

wind speed or direction. The time series shows higher CO 

mixing ratios in the winter, and lower levels in the summer, 

which is a seasonal cycle typical of CO. The in situ time 

series exhibits periods of low variability in CO levels 

punctuated by short-term increases or decreases. 

Comparison of CO to C02 for January 1992 (Fig. 2.12b, c) 

shows the mixing ratios of both gases often change rapidly 

at the same time; these episodes are are called "events." In 

winter, events classified as originating from very distant 

sources (based upon wind direction) had CO/C02 ratios 

(ppb/ppm) of between 6 and 10 (r2 from 0.8 to 0.9); higher 

ratios of between 6 and 22 (r2 from 0.6 to 0.8) were 

observed, and, based upon wind direction, were attributed 

to local emissions. It has been suggested that in winter, 

trace gases and aerosols from non-local sources at BRW 

originate largely from Western Russia and Eastern Europe 

[Lowenthal and Rahn, 1985; Halter et al., 1985). In the 

absence of significant sinks for either gas, CO/C02 ratios 
! ~E1~-.~H~Jd 

---~ 

~ ~~l ~;;:;;;:; 

: :F;;:~;:=~}:i 1 2 J • 5 e 1 e v 101112u 1n51ai11e1v20:ri.222J2•2s2021211NJOJ1 

JAN 92 

Fig. 2.12. (a) In situ hourly average CO mixing ratios at BRW for 

1992. (b) In situ hourly average CO mixing ratios at BRW for 

January 1992. (c) In situ hourly average C02 mixing ratios at 

BRW for January 1992. 

may represent emission ratios from these areas. The 

average wintertime ratio for events within the designated 

clean air sector was 8.5. These ratios are about a factor of 

2 lower than those estimated for the Northeastern United 

States and Western Europe [P. Bakwin el al., manuscript in 

preparation]. The lower value may reflect a number of 

differences between the United States/Western Europe and 

Eastern Europe/Russia, including population densities, 

differences in fossil fuel usage, or a source of C02 not 

sufficiently accounted for (wintertime respiration). In 

summer the situation is quite different. The CO/C02 ratios 

at Barrow are lower than in winter and show much less 

correlation (r2 ranges from 0.1 to 0.9). In summer, CO is 

lost to oxidation by OH, and C02 is certainly depressed due 

to photosynthesis. As a result, the CO/C02 ratio can be 

both positive and negative. 

A CO analysis system, similar to that operating at 

BRW, was installed at MLO in June 1992. Five to six 

mixing ratios were calculated every hour using a piecewise 

linear calibration scheme. The three standards used were 

referenced to the CMDL scale and had mixing ratios of 

81.6, 124.6, and 185.6 ppb. Beginning in July 1992, the 

system was operating 92% of the time. Figure 2.13 shows 

140 

20 

s 0 

..U... 92 - DEC 92 N 0 

Fig . 2.13. In situ hourly average CO mixing ratios at MLO. 

23 

preliminary data collected during 1992. Mixing ratios at 

MLO are, as expected from previous studies [Novelli el al., 

1992, among others], lower than those observed at BRW. 

In winter the background CO levels reach about 130 ppb; in 

summer levels of 65 ppb are found. 

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 air 

sampling program. Measurements were made only in air 

from sites where glass flasks with Teflon 0-ring stopcocks 

were used. Table 2.8 provides the fixed sites where CO 

was measured in 1992, the date of the first sample collected 

for CO, and where possible, the 1992 annual mean value 

for the site. Samples for CO were also collected during 

crossings of the Pacific Ocean by ships of the Blue Star 

Line and on the South China Sea between Singapore and 

Hong Kong on board the tanker Carla A. Hills of the 

Chevron Shipping Company. Analysis of air from all of 

these flask samples for CO and H2 was made on a semiautomated Trace Analytical RGA, which shared a common 

flask sampling carousel, data collection and analysis 

system, and valve switching control with the gas 

chromatograph used for the flask measurements of 

methane. CH4, CO, and H2 analyses used a common 

reference gas. From January to March, the reference gas 

standard AAL-17269 (118.5 ppb) was used and from May 

to December, the reference gas AAL-17270 (112.9 ppb) 

was used. Both standards consisted of chemically dried 

(using phosphorous pentoxide on an inert support) air 

collected at Niwot Ridge, Colorado, and both were 

calibrated against the CMDL CO secondary standards. 

Hydrogen was referenced to an arbitrary scale awaiting the 

preparation of accurate standards. The precision of the CO 

method, estimated as the difference of mixing ratios 

determined for each flask in a (near-) simultaneously 

collected pair of flasks, was typically 2 ppb or better. 

The response characteristics of the instrument used for 

flask analysis were non-linear from 0 to 250 ppb. 

Therefore, CO mixing ratios were calculated using a multipoint calibration curve. A suite of 6-8 standards, and one 

sample of zero air passed through a CO scrubber (Schutze 

reagent), were analyzed twice monthly, and all standard 

response data were normalized to the response of a single 

flask analysis standard (AAL-17269 or AAL-17270). 

These response ratios were fit using a polynomial function. 

CO in flask samples was determined by first calculating the 

ratio of the area of the sample to that of the standard. 

Using the calibration curve and these ratios, a mixing ratio 

for each sample was calculated. 

The annual mean CO values were calculated for stations 

that had a complete data set for 1992 (Table 2.8). These 

mean values were calculated from a curve fit to the 

measurements [Thoning et al., 1989] that reduces the 

effects of short-term variability of the individual samples 

and of inhomogeneous sampling density through the year. 

Annual means for 1992 were plotted versus station latitude 
TABLE 2.8. Flask Network Sites for CO Analysis 

and Preliminary Annual Mean CO Levels (ppb) 

First Annual 

Code Station Latitude Sample• Meant 

ALT Alert, N.W.T., Canada 82°N April 1992 

ASC Ascension Island gos Feb. 1989 80.8 (1.8) 

BAL Baltic Sea Cruises 55°N Aug. 1992 

BME Bermuda (east coast) 32°N June 1991 135.5 (2.5) 

BMW Bermuda (west coast) 32°N July 1991 132.6 (2.3) 

BRW Barrow, Alaska 7 1°N July 1988 139.4 (I.I) 

CBA Cold Bay, Alaska 55°N April 1992 

CGO Cape Grim, Tasmania 41°S June 1991 54.5 (0.4)t 

CHR Christmas Island 2°N Dec. 1989 72.9 (0.8)t 

CMO Cape Meares, Oregon 45°N Jan. 1992 139.4 (3.0) 

GM! Guam, Mariana Islands 13°N Oct. 1989 98.5 (1.6) 

ICE Iceland 63°N Oct. 1992 

!TN Griffton, N. Carolina 35°N July 1992 

Tower 

IZO Izaiia Observatory, 28°N Nov. 1991 110.8 (1.2) 

Tenerife 

KEY Key Biscayne, Florida 25°N Aug. 1991 120.6 (2.4) 

KUM Cape Kumukahi, Hawaii 20°N June 1989 105.0 (1.7) 

MBC Mould Bay, Canada 76°N Feb. 1992 

MHT Mace Head, Ireland 54°N Junel991 133.8 (2.9) 

MID Midway Island 28°N Jan. 1992 120.6 (1.9) 

MLO Mauna Loa, Hawaii 20°N July 1989 96.4 (1.7) 

NWR Niwot Ridge, Colorado 40°N Dec. 1988 125.8 (1.8) 

PSA Palmer Station, 65°S 

Antarctica 

QPC Qinghai Province, China 36°N July 1991 135.9 (3.8) 

RPB Ragged Point, Barbados )JON March 1993 

SEY Mahe Island, Seychelles 4°S Sept. 1990 84.3 (1.4) 

SMO American Samoa 14°S Sept. 1988 57.0 (0.5) 

TAP Tae-ahn Peninsula, 36°N Nov. 1990 285.5 (24) 

S. Korea 

UUM Ulaan Uul, Mongolia 44°N Jan. 1992 181.4 (2.0)§ 

•Tue month and year air samples were first collected in a glass 

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

tPreliminary 1992 mean mill:ing ratios and the standard error are 

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

as described in Novelli et al., 1991. 

tMean value for 11 months of data; no samples available for I 

month. 

§Mean value from 10 months of data; no samples available for 2 

months. 

to evaluate the latitudinal vanat1on of CO (Figure 2 . 14). 

Generally CO values decreased from north to south. 

However there were some interesting exceptions. The 

greatest annual mean CO levels were observed in the midand high-northern latitudes. Annual mean CO mixing 

ratios were about the same from 7 1 'N (Barrow) to 32'N 

(Bermuda). Further south, carbon monoxide levels 

decreased to about 55 ppb at 40' S (SMO, CGO). The 

lifetime of tropospheric CO varies widely with season and 

latitude. At high latitudes CO is largely conserved in 

winter and is destroyed by reaction with OH during the 

24 

175 

150 

" t t • .D 125 a. • ~ • 0 • u 100 • c 

0 " ., 

:::; 75 • 0 

::> 

c 

c • • <: 50 

25 

0 

-80 -60 -40 -20 0 20 40 60 80 

Latitude 

Fig. 2.14. Latitudinal distribution of CO. Annual means for 1992 

were calculated by laking weekly values from a smoothed curve fit 

to the data, then calculating monthly means, and annual means from 

the monthly means as described by Novelli et al. [ 1992). 

summer. In the tropics CO has a lifetime of 1-2 months 

due to the high OH radical concentration. The latitudinal 

distribution reported here would suggest there are large 

regions of the troposphere that are relatively well mixed on 

time scales comparable to CO lifetimes. However, a 

comparison of annual mean CO values at stations with 

similar latitude and different longitude (for example Key 

Biscayne, Florida, Midway Island, and Izaiia Observatory, 

Tenerife at about 25°-28°N, or Tae-ahn Peninsula, S. Korea 

and Qinghai Province, China at 36°N) sometimes shows 

substantial longitudinal variations in CO. These 

differences probably reflect regional scale anthropogenic 

impacts on CO levels at some locations. Similarly, 

biomass burning in Africa may directly impact CO levels at 

some downwind sites (e.g., Ascension Island and Mahe 

Island, Seychelles, but not Christmas Island). 

2.2. REFERENCE GAS STANDARDS 

2.2.1. CARBON DIOXIDE 

The calibrations of COi-in-air reference gas tanks 

continued in 1991; on 154 days, 308 tanks were calibrated. 

The filling of high-pressure cyl inders with dry air from 

Niwot Ridge for use as reference gases continued in 1991. 

The set of 15 reference gases stored in large aluminum 

cylinders, which will eventually become the CMDL 

primary C02 standards, were calibrated by the Scripps 

Insti tute of Oceanography (SIO) in 1992. The NOAA 

secondary COi-in-air standards were also shipped to SIO 

for calibration in 1992. 
The transfer calibration system was revised in 1992 to 

allow more calibrations to be performed using the same 

amount of standard reference gases. Figure 2.15 shows the 

new system. A Valeo 16-port stream selection valve 

replaced an array of eight solenoid valves for switching the 

appropriate gas to the NDIR analyzer. The number of 

unknown gas tanks being calibrated was increased from two 

to four, while still using four known standards. Now either 

two or four unknowns can be calibrated at one time, with 

the time for each calibration being 2 hours and 24 minutes 

and 3 hours and 12 minutes respectively. 

Construction of a system for making manometric 

measurements of the mole fraction of C02 in standard 

gases continued in 1992. Extensive modifications to the 

system were made. Tests showed unstable adsorption 

effects from the small amounts of polymers used in the 

system, even when using dry air, which created instability 

in the measurement of the volumes containing the air 

sample and the C02 sample. Based on this, it was decided 

to replace all the polymer parts with glass. This involved 

installing standard greased stopcocks in place of metal 

valves. These stopcocks are connected lo an air-driven 

NDIR C02 

Chart Recorder Analyzer 

rotary actuator, which turns the handle of the stopcock 90 

degrees. 

Some small changes in the response of the Ruska 

quartz-spiral pressure gauge were observed but 

unexplained. A deadweight pressure gauge purchased by 

the Carbon Cycle Division in 1992 was used to calibrate 

the pressure gauges in the system. A history of calibrations 

was begun so that the long-term stability of the gauge 

calibration can be observed. 

2.2.2. CARBON MONOXIDE 

The CMDL primary CO standards were prepared 

gravimetrically and were propagated to a set of secondary 

CO-in-air standards [Novelli et al., 1991). These 

secondaries were used to calibrate a set of tertiary 

standards. These make up the CMDL working standards. 

In March 1992 three CO-in-air standards were prepared by 

the CMDL NOAH Division using gravimetric methods 

(mixing ratios of 48.0, 99.9 and 147.2 ppb). The secondary 

and tertiary standards were then calibrated using the new 

gravimetric standards. The CO values assigned to 

Mass Flow Controller 

O - 1000 cc/min 

Auxiliary outlet 

HP 3478A 

Vottmeter 

1.9 - :-- r-+ I 

I From To manometer 1 manometer 

I 

I 

I 

I 

I 

I I 

Zero gas 1 , H20 Trap : 

1 · ..... :x--· · -- ----- rr-~== =========~ = = ============= ~ Edwards 1605 1

1 1 1 111 I Flow oontroller 11 1 

111 

IEEE-488 111 

111 

111 

HP 340 Unix workstation = 

.::::: 

o a • • o ana •o•• ooeo 

.. --- ......... ---- ---- HP 3488A Switch/Control Unit 

Fig. 2.15. Diagram of C02 transfer calibration system. 

25 

8 

Valeo 16 port 

stream selection valve 

a a a 

Unknowns 
TABLE 2.9. CO Mixing Ratios* Assigned to Standards Based Upon Different Calibration Procedures 

Cylinder ID 

Type 

Fill Datet 

Grav) 

(ppb); 

Second 

(ppb)§ 

Grav II 

(ppb) .. 

AAL-17269 

CC68734 

CC61344 

CC73110 

CC73198 

CC89259 

CC89580 

CC71607 

NWR, Nov. 1987 

NWR, Dec. 1988 

NWR, Dec. 1988 

NWR, Jan. 1990 

NWR,Jan.1990 

SM,Jan.1990 

SM, June 1990 

NWR, Sept. 1991 

118.5 (0.6) 

159.7 (1.5) 

181.5 (1.5) 

202.4 (0.9) 

179.3 (1.7) 

117.6 (0.9) 

159.5 (1.0) 

182.3 (1.3) 

200.7 (2.1) 

178.8 (0.9) 

117.0 (0.6) 

160.1 (1.8) 

181.5 (1.7) 

202.6 ( 1.9) 

179.3 (J.7) 

34.9 (1.9) 31.9 (1.7) 

50.7 (I.I) 

133.8 (2.0) 

32.2 (1.5) 

49.9 (0.6) 

134.4 (1.4) 

*Mixing ratios are in units of parts per billion by mole fraction (ppb). Values represent the mean of several calibrations; the standard deviations of 

the means are presented in parentheses. 

tType of air in tank and fill date. NWR indicates the cylinder was filled at Niwol Ridge, Colorado; SM indicates the standard was purchased from 

Scou Marrin, Inc. 

;Grav) = Mixing ratios assigned based upon calibration against the 17 gravimetric standards prepared 1989-1990 as described by Novelli el al., 

1991. 

§Second= Mixing ratios assigned to cylinders based solely upon calibration against other secondary standards using CO values based upon Grav I. 

••Grav II= Mix.ing ratios assigned to cylinders based upon calibration against the gravimetric standards prepared in March 1992. 

standards using either a 1-, 2- or multi-point calibration, 

and using either the primary. secondary or new 

gravimetrics show no significant difference (Table 2.9.). 

The intercalibrations of the CMDL working standards show 

that the reference values assigned to the standards were 

propagated with a precision of at least 1 %. Comparison of 

gravimetric standards made at different times, with 

different materials, and by different people suggests an 

accuracy of 1 %. In general, the working standards appear 

stable with respect to CO over time scales of at least 

several years. 

2.3. NEW MEASUREMENT PROGRAMS 

2.3.1. MEASUREMENTS OF CARBON DIOXIDE ON A 

VERY TALL TOWER 

Measurements of C02 on a 610-m tall television and 

radio transmitter tower in a rural area of eastern North 

Carolina (35' 21' 55" N, 77" 23' 38" W, 9 m above sea 

level) began in June 1992. Use of the tower and space in 

the transmitter building for our analytical and data 

acquisition equipment were donated free of charge by 

American Family Broadcasting, Inc. 

Tubes for trace gas sampling were mounted on the 

tower with inlets at 51, 123, and 496 m height, and sensors 

for wind speed and direction, temperature and humidity 

were placed at the same three levels. Three C02 analyzers 

arc located within the transmitter building at the base of the 

tower, with an analyzer dedicated to continuous sampling 

from each altitude. Flask samples are collected weekly 

from the 496 m level for analysis for CH4 , C02, CO and 

813C in C02. In addition, concentrations of radon-222 are 

being measured by scientists from the University of North 

Carolina. Radon-222 originates in the soil from decay of 

radium-226 and has a half-life of 3.8 days, making it an 

26 

excellent tracer for soil/atmosphere gas exchange and for 

continental air masses. Sampling and calibration sequences 

are controlled and data are read and pre-processed using a 

PC. One-half hour averages of the data are computed and 

transmitted to Boulder each day by modem. 

Figure 2.16 shows the mean diurnal cycle for C02 at 

each height for periods of several days in June 1992 and 

January 1993. In summer the concentration gradient is 

positive upwards in the afternoon because of vigorous 

photosynthetic uptake of C02 at the surface. At night a 

shallow inversion forms, and concentrations at 51 m 

rapidly increase because of plant and soil respiration and 

industrial emissions, often reaching in excess of 400 ppm. 

Radon-222 concentrations also build up near the surface at 

night. The diurnal cycle is damped at higher altitudes; the 

magnitude is typically 7-10 ppm at 496 m in summer. A 

morning pulse of C02 is evident at 123 and 496 m as C02 

stored in the nocturnal stable layer is mixed upward with 

the onset of convection. The nocturnal build-up at low 

altitudes is reflected in 10-20 ppm higher daily mean C02 

concentrations at 51 m than at 496 m in summer. In winter 

the biologically driven surface sources and sinks are much 

smaller and the diurnal variation at all altitudes is greatly 

reduced. Clearly. biological activity dominates industrial 

C02 sources at this rural site in summer. 

A time series of the daily minimum C02 concentration 

at 496 m is shown in Figure 2.17. The daily minimum, 

which generally occurs in late afternoon , may reasonably 

approximate the average for the daytime convective 

boundary layer (e.g., 2-3 km depth), since vertical 

gradients above 496 m are likely to be small. The time 

series of daily mean concentrations shows a similar pattern, 

but the values are typically 2-8 ppm higher. Monthly 

statistics for the daily minimums and means are given in 

Table 2.10. 

Day-to-day changes in the daily minimums (or means) 

are large, as much as 15-20 ppm in the summer, probably 
reflecting changes in air-mass back trajectory and the vigor 

of vertical mixing. Also in summer, the biological source 

and sink strengths are strongly dependent on 

meteorological parameters such as temperature and 

illumination. The monthly medians change smoothly, 

confirming that these data will be useful for comparison 

with the CMDL "background" (remote) sites. The 

magnitude of the seasonal cycle is about 15 ppm, with a 

sharp minimum in August and a broad maximum in 

January-April. Starting in about the last week of April, 

concentrations begin to drop rapidly as photosynthetic 

activity increases towards summer levels. 

30 

25 -

E 

Q. 20 

s 

C\J 

15 

0 10 () 

5 

0 

-5 

30 

25 

E 20 a. 

s 15 

C\J 

0 10 () 

5 

0 

-5 

0 

0 

r 

I I 

{ 

I (a) 

I 

I I 51 m 

I I 123 m 

496 m 

J I 

I /'\ ,/ I 

/ /---~ 

/ _,,.1 \ 

/// ~ 

.I 

·-·-----------·-·-·······- -·-···-········· 

6 12 18 

Time of Day (GMT) 

51 m 

123 m 

496m 

--- -: :;:-_-: ~ --:::::----- ............ --- ~ 

6 12 18 

Time of Day (GMT) 

24 

(b) 

..... 

24 

Fig. 2.16. Mean diurnal cycles of C02 at 51, 123, and 496 m above the 

ground on the tower in eastern North Carolina for (a) June 14-21, 1992, 

(b) January 18-February 1, 1993. The daily mean at 496 m for each day 

has been subtracted from the data and the data were binned in I-hour 

intervals. Time is given as GMT, which is 5 hours ahead of local 

standard time. 

27 

0 

,...._ 

C') 

0 

E <.D 

C') 

Q. 

Q. 

C\J 0 lO 

0 C') 

() 

0 

"'<t 

C') 

0 

C') 

C') 

. ·'\. : ,, ··~·· ·· ~· ~ r;~·~r .. > ·~x-i~:·--· .... .,., ... . J "~, . ,,, ~ 

: ... l .. : f~ .. ·~· " '.:~ ~T··r.- :·· 

·: · 

1992 

Jun 

1992 

Sep 

1992 

Dec 

1993 

Mar 

1993 

Jun 

Fig. 2.17. Daily minimum C02 mixing ratios at 496 m above the 

ground on the North Carolina tower for June 14, 1992, to May 31 , 

1993. Medians and the upper and lower quartiles for each month 

are also shown (and are summarized in Table 2.10). 

2.3.2 FLASK SAMPLES FROM AIRCRAFT 

This year marked the beginning of operation of the 

Aircraft Sampling Project. The intent of this project is to 

measure biweekly profiles of C02. CH4, and CO in the 

troposphere over continental sites to determine vertical 

mixing rates and identify trace gas sources and sinks. The 

operation may also be useful for studying boundary layer 

dynamics and species ratios of anthropogenic sources. 

To make sample collection economically feasible, the 

project relies on a highly automated sampling system that 

requires a minimum of labor to operate and can be flown 

on inexpensive and available aircraft. The current system 

consists of two aluminum cases, each about 25 cm x 50 cm 

x 75 cm and each weighing about 30 kg. One case contains 

compressors and batteries, making the system completely 

self-powered and operable up to 12000 m. The other case 

contains 20 1-L glass sampling flasks and a microcontroller 

to actuate the sample valves at pre-programmed altitudes, 

based on inputs from a Global Positioning System receiver 

and a barometric altimeter. The system can be installed in 

a light aircraft by one person in less than 15 minutes and 

operates unattended or with minimal pilot interaction. 

After a sampling flight, the flask case is plugged into an 

automated analysis system, which sequentially measures 

the samples with no further operator intervention. 

Our first sampling site using this system is located over 

Carr, Colorado, about 100 km north of Boulder (40.9°N, 

104.8°W). Test flights began in March, and regularly 

scheduled twice-monthly flights commenced in November. 

A low-cost single-engine plane was used to take samples up 

to 7600 m. Figure 2.18 shows a typical C02 profile. The 

combined sampling and analysis method yields a precision 

of about 0.07 ppm C02. 5 ppb CH4 and 3 ppb CO. After a 
TABLE 2.10. Monthly Statistics for Daily Minimum and Mean C02 (ppm) 496 m Above the Ground on the North Carolina Tower 

Daily Minimum 

Month Year Mean Std. Dev. N Median LQ 

July 1992 347.00 5.62 31 347.38 343.02 

Aug. 1992 342.85 6.42 31 340.70 338.96 

Sept. 1992 345.37 4.46 22 346.99 342.19 

Oct. 1992 352.12 4.08 31 351.24 349.23 

Nov. 1992 357 .26 2.58 27 356.55 355.47 

Dec. 1992 359.11 2.24 29 359.68 357.20 

Jan. 1993 360.89 3.21 29 360.07 358.45 

Feb. 1993 361.28 2.21 17 361.28 359.56 

March 1993 362.02 2.41 23 362.00 359.87 

April 1993 360.91 2.28 30 360.99 359.04 

May 1993 353.71 3.66 31 353.10 350.67 

year of sampling and a full seasonal cycle of data has been 

obtained, the vertical mixing rate and seasonal averages for 

C02. CH4, and CO can be estimated. 

2.4. DATA MANAGEMENT 

Considerable effort was made in 1992 lo define and 

implement a Jong-term Carbon Cycle Division flask data 

management strategy. Annually, more than 5500 air 

samples are collected in glass flasks from over 30 different 

locations and shipped lo Boulder where they are analyzed 

for several trace gns species. Air collecled into a single 

2.5-L glass flask is currently analyzed for C02, CH4 , CO, 

H2 within our Jab, and for Cl802 and 13C02 by the Stable 

Isotope Laboratory at the Institute of Arctic and Alpine 

Research (INSTAAR, University of Colorado). Future 

flask measurement projects include N20 by CMDL and 

t3CH4 by INSTAAR. Each flask has a unique sample 

history that includes sampling location, date and time, flask 

identification number, sample collection method, and 

sampling wind speed and direction. Each analysis produces 

a mixing ratio or isotopic ratio, a flag, and additional 

analysis information. The proliferation of flask data from 

the various measurement projects has lead us to consider a 

data management strategy that (1) will allow timely 

comparisons of ambient mixing ratios or isotopic ratios of 

the measured species; (2) will easily accommodate all 

existing and future trace gas measurements made from air 

collected in flasks; (3) will continue to provide the 

individual measurement programs the independence 

necessary to best maintain their data; (4) will require 

minimal software modifications; and (5) can be maintained 

by a primary and secondary database manager. After 

considering several strategies, including commercially 

available relational database management packages, 

management software that could provide the necessary 

flexibility with relatively Jillie disruption Lo the projects 

and minimal modifications lo existing software was 

developed in-house. 

The strategy adopted is simple and features a search key 

that is common to all files containing analysis results for 

Daily Mean 

UQ Mean Std. Dev. N Median LQ UQ 

351.71 353.86 4.42 25 353.96 351.22 356.84 

346.44 348.77 6.47 29 349.14 343.15 354.09 

348.55 349.83 4.44 18 351.10 346.47 352.54 

355.48 356.29 5.19 30 354.99 352.31 359.71 

358.88 361.40 4.32 29 360.45 358.11 363.29 

360.32 361.88 3.12 29 361.33 359.80 363.66 

362.57 364.06 3.78 28 363.21 361.60 366.03 

362.31 364.76 2.83 17 364.08 362.53 367.61 

364.03 365.51 3.48 23 364.58 362.90 368.64 

362.44 363.61 2.94 27 363.34 361.76 365.19 

356.88 357.77 3.53 30 358.35 354.58 361.08 

28 

an air sample collected in a flask. For a given air sample, 

results will exist in one daily analysis file and one 

processed site file for each project analyzing the sample. 

Search keys used by relational database packages are often 

non-repeating consecutive integers. To satisfy the above 

mentioned requirements, a key that uniquely identifies a 

flask sampling event was built. This 31-character key 

includes the sampling location, GMT date and Lime, flask 

id number, and sample collection method as shown below 

for an air sample collected at MLO. 

MLO 1992 12 18 20 07 2340-66 P 

The only condition required of current and future flask 

measurement projects is Lhal analysis resuhs residing in the 

daily analysis files and processed site files must be 

preceded by the 31-characler search key. Once this 

condition is satisfied, the primary Lask becomes one of 

10 

8 

........ 

E 6 6 

v 

-0 

:::> 

4 0 

0 0 0 

0 0 

2 0 0 

0 

353 354 355 356 357 

C02 mixing ratio (ppm) 

Fig. 2.18. Vertical profile for C02 over Carr, Colorado, from 

December 10, 1992. (Altitude is in km above sea level.) Square 

symbols represent individual flask measurements. The solid line is 

drawn through the average of two samples collected in succession at 

each a ltitude. 
ensuring that the integrity of the 31-character search key is 

maintained everywhere it exists. This is accomplished by 

restricting access to the search key. 

The search key is created by one (and only one) 

software package within the Carbon Cycle Division. 

Before an air sample is analyzed, the flask must proceed 

through a check-in procedure. This procedure is semiautomatic and has two primary functions. The first 

function is to maintain a flask inventory, i.e., tracking 

when, where, and how each flask was shipped from and 

returned to Boulder. The second function is to introduce 

each flask's sampling history into a computer data base; it 

is here that the 31-character search key is created. During 

a measurement, the analysis software simply requests the 

flask identification code, and upon entry, receives the 

search key from the database. This software then uses the 

search key in creating the data files resulting from the 

analysis. The search key is propagated to the various 

measurement projects as the air sample is analyzed. At no 

time may the individual measurement projects modify the 

search key. If an error in the search key is suspected, then 

the original sample sheet is annotated and the problem is 

resolved at a later time. 

The search key may be edited by one (and only one) 

software package within the Carbon Cycle Division. Every 

2 weeks the original sample sheets of flasks analyzed 

during this period are collected and collated. The sample 

history from each sample sheet is compared with the 

history recorded during the check-in procedure; annotations 

made during analyses are also addressed at this time. Any 

necessary changes to the search key are made at this time 

by the primary database manager using a single software 

package. This package replaces the incorrect search key 

with the edited key everywhere that the key exists and 

documents each action in a log file. All personnel 

responsible for maintaining the various measurement 

databases are automatically notified of the changes made 

by the database manager by electronic mailing of the log 

file. 

This flask data management strategy has been fully 

implemented. The benefits of this strategy are already 

29 

quite clear. The various measurement project data bases 

remain independent, but are easily related by the search 

key. The integrity of the search key is maintained by 

restricting access to both personnel and software. New 

measurement programs can develop independently but 

integrate easily by satisfying the single design constraint 

based on the search key. Considerable time is saved when 

search-key errors are corrected everywhere by the data base 

manager. And finally, software written for the statistical 

and graphical analysis of flask data can be speciesindependent, providing powerful analysis tools to a greater 

number of flask measurement programs. 

2.5. REFERENCES 

Halter, B.C., J.M. Harris, and K.A. Rahn, A study o f winter 

variability in carbon dioxide and Arctic haze aerosols at 

Barrow, Alaska, Atmos. Environ., 19, 2033-2037, 1985. 

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

S. Whittlestonc, and L.P. Steele, Variations in atmospheric 

methane at Mauna Loa Observatory related to long-range 

transpon, J. Geophys. Res., 97, 6003-6010, 1992. 

Lowenthal, D.H., and K.A. Rahn, Regional sources of pollution 

aerosol at Barrow, Alaska, during winter 1979-80 as determined 

from elemental tracers, Atmos. Environ., 19, 2011-2024, 1985. 

Masaric, K.A., L.P. Steele, P.M. Lang, A Ruic-based expen system 

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

chromatographic measurements of atmospheric methane, 

NOAA Tech. Memo, ERL CMDL-3, Boulder, CO, 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-

10,750, 1992. 

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

evaluation of a gravimetric reference scale for measurements of 

atmospheric carbon monoxide, J. Geophys. Res., 96, 13,109-

13,121, 1991. 

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

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

atmospheric methane during the 1980s, Nature, 358, 3 13-316, 

1992. 

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

dioxide at Mauna Loa Observatory 2. Analysis of the NOAA 

GMCC data, 1974-1985,J. Geophys. Res., 94, 8549-8565, 1989. 
3. Aerosol, Radiation, Ozone, and Water Vapor Division 

B. BODHAINE, E. DUTION, R. EVANS, R. GRASS, J. HARRIS, D. HOFMANN, W. KOMl!YR, 

D. NELSON, J. OGREN, ANDS . 0LTMANS 

3.1. CONTINUil'G PROGRAMS 

3.1.1. SURFACE AEROSOLS 

3.1.1.1. BASELINE OBSERVATIONS 

Operations 

The aerosol monitoring program at BRW, MLO, SMO, 

and SPO continued during 1992 as in previous years. 

Condensation nucleus (CN) concentration was measured 

continuously with TSI (butanol-based) CN counters at 

BRW, MLO, SMO, and SPO. Daily calibration points were 

provided by Pollak CN counters at all stations. TSI CN 

counters have been operated at BRW since March 1990, 

MLO since May 1988, SMO since May 1992, and SPO 

since January 1989. After TSI CN counter installation at 

each station, G.E. CN counter operation was continued for 

a 1-year comparison, and then G.E. CN counter operation 

was terminated. At the end of 1992 all G.E. CN counters 

had been discontinued. Aerosol scattering extinction 

coefficient (o5p) at 450-, 550-, 700-, and 850-nm 

wavelengths was measured continuously at BRW, MLO, 

and SPO with four-wavelength 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. Table 3.1 shows the time periods of operation of the 

CN counters and nephelometers at the four baseline 

stations. 

Figure 3.1 shows daily geometric means of CN 

concentration (lower portion of each plot), Osp (middle 

portion of each plot), and Angstrom exponent (upper 

portion of each plot) at the CMDL stations for 1992. Two 

independent values of Angstrom exponent (a) were 

calculated from the 450-, 550-, and 700-nm channels of Osp 

data using the relation a = -61og05p/6logA, where a is 

TABLE 3. 1. Operation of Aerosol Instrumentation at 

BRW, MLO, SMO, and SPO 

Station Pollak CN G.E.CN TSICN 4-A. Neph. 

BRW May 1976- May 1976- March 1990- May 1976-

Present Mar. 1991 Present Present 

MLO Jan. 1974- Jan. 1974- June 1988- Jan. 1974-

Present June 1989 Present Present 

S'.\10 June 1977- Junel977- May 1992- June 1977-

Present Dec. 1992 Present Mar. 1991 

SPO Jan. 1974- Jan. 1974- Jan. 1989 Jan. 1979-

Present Dec. 1989 Present Present 

30 

Angstrom exponent and A is wavelength. These averages 

were calculated only if data for all three wavelengths were 

available. The interpretation of a in terms of aerosol size 

distribution was discussed by Bodhaine and Deluisi 

(1985). Monthly geometric means of the 1991 aerosol data 

are listed in Table 3.2. A graphical presentation of the 

monthly geometric means of the entire data record for the 

four stations is shown in Figure 3.2. 

Discussion 

The BRW data in Figure 3.1 show a Osp maximum of 

about 3 x 10-5 m·l during spring , typical of the well-known 

Arctic Haze. Minimum values of Osp below 10-6 m·l 

occurred in July-August. The BRW long-term record 

shown in Figure 3.2 clearly shows this annual cycle in Osp• 

with springtime monthly means of about 10-5 m·l 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 another maximum in late summer or early fall. The 

1992 annual geometric mean for CN is 228 cm·3 and the 

annual mean for Osp (550 nm) is 4.62 x 10-6 m·l. Note that 

the G.E. counter CN record is shown as a solid line and the 

TSI counter CN record is shown as a dashed line. The 

individual squares plotted on the CN graph are monthly 

means of Pollak counter observations. These are shown 

separately because the TSI and Pollak counter give 

independent data sets, whereas the G.E. counter was 

calibrated using the Pollak counter data. Numerous gaps in 

the data are apparent because of the averaging process 

excluding data if local pollution is evident or if winds are 

not from the clean air sector. The BRW aerosol data set 

was presented by Quakenbush and Bodhaine (1986]. 

The MLO Osp data shown in Figure 3.1 are typical with 

the highest values in April and May and lower values in 

fall and winter. Large events are apparent 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]. Osp values were generally higher since 

the installation 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 375 cm-3; the annual 

mean of Osp (550 nm) is 8.58 x 10·7 m·l. 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). 
Aero1ol Data tor Barrow Aero1ol Data tor Sa9>a 

~ i kl! bh1 .. t~d: ii J !~!:I~ ~ ~ i I ..I .. I .. I.. I ... 1 ...1 ...1 .. J . .I. . J . .I. .. I 

1it~l':1 ~J'j . t l J ~~ 1.f ~ M: 1 1 i I .. I .. I ..I .. I ... 1 ...1 ...1 ..J . .I. . J . .I. .. I 

I~H: ~:'. l':~~ . J1.id .. '{I ~ ~J+ :l r f.1E1 .. 

1

J .t.1'1 P•B Jiii.• .t.P• 1111.T J UJI JUL .t.UC: B•P OCT NOT D•C J .t.H P•B Jiii.• .t.P• §f Jiii. T 1 UJI 

~.1.+±+:tJ-j 1 VL .t.UG B•P OCT ROT D•C 

111112 111112 

J.t.1'1 PD 11.U .t.Pll 1111.T IUJI l l1L .t.UC: UP OCT NOT DSC 

111112 UR rD Kil .t.P11 lilT 101' lUL .t.UO al' OCT KOY Dmc 111112 

f-ig. 3.1. Daily geometric means of cr,P and CN data at l3RW, MLO, SMO, and SPO for 1992. Data for MLO arc included only for 0000-0800 LST. 

for each station, CN concentration (lower) is shown as a sol id line, and daily mean Pollak counte r data are shown as small squares. The cr,P data 

{middle) arc shown for 450 {doncd), 550 {solid), and 700 nm {dashed). Angstrom exponents {alpha) were calculated from 450- and 550-nm {doued) 

and 550- and 700-nm {solid) o,P data. 

The SMO CN data continue as in previous years with no 

significanl annual cycle or long-term trend. The SMO 

1992 annual mean is about 207 cm-3 for CN concen trat ion , 

representative of the background marine boundary layer in 

that region. The SMO ncphclomcter was removed from 

service in March 1991. The SMO data record was 

presented by Bodhaine and Deluisi ( 1985]. 

The SPO Osp and CN data arc shown in Figure 3.1. 

These data show a strong annual cycle reaching a 

maximum in the austral summer and a minimum in the 

winter, simil ar lo previous years. The Osp data show 

fairly clean values in the fall and events resulting from 

the transport of sea-salt particles in July and September. 

31 

Because of instrumen t problems, some dala are missing 

in the winter and fall. Referring to the long-term data 

set for SPO shown in Figure 3.2, the Osp data generally 

show intermed iate values in the austral summe r and 

fall, and large events, sometimes exceeding 10·6 m·l, in 

!ale winter. These large aerosol events are caused by 

the transport of sea sail in the upper troposphere from 

stormy regions near the Antarctic coast to the interior 

of the cont inent. The SPO 1992 annual means are about 

69 cm-3 for CN and 4.41 x 10-7 m·l for Osp (550 nm). 

Analyses of the SPO data were presented by Bodhaine et 

al. (1986, 1987]. The complete data set was presented 

by Bodha ine and Shanahan [1990). 
TABLE 3.2. Monthly Geometric Means of CN concentration (cm·3) and Osp (m-1) at 450, 

550, and 700 nm for BRW, MLO, SMO, and SPO During 1992 

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

BRIV 

CN 204 354 346 263 338 100 363 354 83 162 245 208 

cr,P (450) 1.17-5 1.48-5 1.70-5 1.15-5 3.63-6 2.57-6 1.62-6 2.04-6 1.62-6 4.57-6 9.55-6 1.02-5 

cr,P (550) 1.05-5 1.29-5 1.48-5 9.77-6 2.75-6 1.95-6 1.35-6 1.86-6 1.05-6 3.89-6 9.33-6 9.33-6 

cr,P (700) 7.76-6 9.33-6 1.07-5 6.92-6 1.7-6 1.12-6 9.55-7 1.55-6 7.24-7 2.88-6 7.76-6 6.92-6 

MLO 

CN 398 380 407 338 309 380 380 436 426 354 331 380 

cr,P (450) 7.08-7 1.15-6 3.8-6 4.07-6 2.4-6 1.35-6 1.00-6 8.32-7 6.61-7 5.13-7 6.17-7 6.17-7 

cr,P (550) 5.13-7 7.08-7 3.09-6 3.24-6 2.04-6 1.07-6 7.76-7 6.17-7 5.01-7 3.63-7 5.01-7 4.57-7 

cr,P (700) 3.55-7 4.17-7 2.45-6 2.45-6 1.70-6 8.51-7 5.89-7 4.37-7 3.39-7 2.82-7 3.72-7 3.55-7 

SMO 

CN 213 190 151 263 251 154 208 218 223 223 194 229 

SPO 

CN 181 275 154 34 22 22 13 25 53 162 213 169 

cr,P (450) 2.40-6 1.35-6 5.25-7 3.55-7 2.45-7 2.29-7 7.24-7 I.I 0-6 7.76-7 9.12-7 4.79-7 

cr,P (550) 1.86-6 9.77-7 3.31-7 2.14-7 1.38-7 1.23-7 5.75-7 8.32-7 5.89-7 6.31-7 3.16-7 

cr,P (700) 1.29-6 5.89-7 1.95-7 1.29-7 8.13-8 6.17-8 4.37-7 6.03-7 4.68-7 5.25-7 2.51-7 

A compact exponenti al format is used for cr,P such th at 1.78-5 = 1.78 • 10-5. 

3.1.1.2. REGIONAL 0IlSERVATIONS 

In order to address questions concerning climate forcing 

by anthropogenic aerosol particles [Charlson et al., 1992; 

Penner et al., 1993], CMDL is establishing a network of 

four regional aerosol monitoring stations. Two of the 

stations are located in marine locations and two in 

continental locations; for each category one site is 

relatively free of anthropogenic influences and the other is 

frequently perturbed by anthropogenic aerosols. Table 3.3 

lists the four sites, their characteristics, and their current 

status (June 1993). Each station operates in close 

coll aboration with a local university or government agency 

that provides on-site support for the measurements. 

The scientific questions that define the context of the 

measurements al these sites include: 

• What are the sign, mechanism, magnitude, 

and spatial distribution of the climate 

anthropogenic aerosol particles? 

uncertainty, 

forcing by 

• 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 size and 

chemical-composition distributions of the partic les? 

• What is the sensitivity of the forcing and its spatial 

distribution to changes in these parameters? 

32 

• How has the forcing 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. 

Recognizing this, the strategy of the CMDL regional 

aerosol measurement program is to determine means, 

variability, and possible trends of key optical, chemical, 

and microphysical properties for a number of important 

aerosol types. 

The measurements wi ll provide ground-truth for satellite 

measurements and global models, as well as key aerosol 

parameters for global-scale models (e.g., scattering 

efficiency of sulfate particles, hemispheric backscattering 

fraction). An important aspect of this strategy is that the 

chemical measurements are linked to the physical 

measurements 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), the cloud condensation nucleus 

number concentration (Nccn), aerosol optical depth (o), and 

components of the aerosol extinction coefficient (total 

scattering O"sp• backwards hemispheric scattering Obsp• and 

absorption o.p). Size-resolved impactor and filter samples 
.. 

I 

Aeroeol Data for Barrow 

I -' " A • . j 

~ A'-" : I .I} .Y l. ~ ...... ·,\} r<J..t μ11 fr,ll JU VJ! , l. ~ Ai Ull 

~ \. ~ ./ \ 11'"' ·~· •'\. I/~ , -.. ~I I• ~- i./~ ., r ~~ ' ~ ~ , t1 

Tl n Tl Tl IO 11 • IO N • IO '7 IO • It tl t I 

YllAB 

Aeroeol Data for Sa..,a 

7T U 71 IO 11 • IO N IO IO 9' IO IO U tl U 

YllAB 

Aeroeol Data tor M&uaa Loa A•r•••I Data fer lloutk Pol• 

~rn1111111m ~~11111~•~11 

]~H#r+H IE !Mf±t±H ~~11111 ~ fftH#l1 ii !~I " 

lttfffftfffflffE 

" " " " " • al •• " •• " • • •• .. .. 

!~wtMM##M1#M1~ ,. " " " ,. " • 11 •• " •• ., .... 11 .. 

Fig. 3.2. Monthly geometric means of a,P and CN data for the entire data record. Data for MLO are included only for 0000-0800 LST. The a,P data 

(middle) arc shown for 450 (dolled), 550 (solid), and 700 nm (dashed). Angstrom exponents (alpha) were calculated from 450- and 550-run (doucd), 

and 550- and 700-run (solid) cr,P data. Note that G. E. CN counter data are shown as a solid line, TS! CN counter data are shown as a dashed line, and 

Pollak CN counter data are shown as small squares. 

TABLE 3.3. CMDL Regional Aerosol Monitoring Sites 

Category Perturbed Marine Perturbed Continental Clean Continental Clean Marine 

Location Sable Island, Bondville, Illino is Laramie, Wyoming Cheeka Peak , Washington 

Nova Scotia, Canada 

Collaborating Atmospheric Environ- University of Illinois, University of Wyoming University of Washington 

institute mcnt Service, Canada Illinois State Water Survey 

Status Operational August 1992 Planned for operations Site feasibility measure- Operationa l, May 1993 

late- 1993 ments began April 1993 

Current measure- N,01, a, 0 (3A.), size- N,

01• 0'10 (3A.), size- N,o•• a,o (3A.) N,0 ., a ,0 and ab•o (I A.), sizements (June 1993) resolved),8 (4A.), size- resolvcd),8 (SA.) , size- resolved), 8 (4A.), sizeresolved chemica l resolved chemical resolved chemical 

composition composition composition 

33 
(submicrometer and supermicrometer size fractions) will be 

obtained for gravimetric and chemical (ion 

chromatographic) 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. 

Because of the early developmental state of the regional 

aerosol measurement program, the limited amount of 

monthly-averaged data obtained in 1992 will be included in 

the 1993 CMDL Summary Report. An example of the sizeresol ved measurements of the aerosol light scattering 

coefficient at Sable Island is shown in Figure 3.3. The 

Sable Island site was chosen to allow characterization of 

anthropogenically-perturbed marine aerosols, but air mass 

trajectories from clean marine and clean continental areas 

are also frequently encountered at the site. Clean marine 

air was encountered at the beginning of the period shown in 

Figure 3.3, resulting in low particle number concentrations 

and light scattering coefficients. The contributions to Osp 

of the sub- and super-micrometer size fractions were about 

equal. The large peaks on September 12 are due to 

contamination by local sources on the island; a automatic 

control algorithm in the sampling system prevents 

contamination of the filter samples during such periods. 

After several days the air trajectories came from 

northeastern Canada, causing higher particle number 

concentrations but similar levels of cr5P' Air trajectories 

bringing polluted air from the eastern United States were 

observed at the end of the period, yielding much higher 

values of N101 and Osp- Submicrometer particles dominated 

the light scattering coefficient, although a substantial 

increase of light scattering from supennicrometer particles 

was also observed. 

2.0E-4 

1.5E-4 ..... 

-'e 

- 1.0E-4 Q. 

b. 

5.0E-5 

O.OE+-0 

10 11 12 13 14 15 16 17 18 19 

Oats (September, 1992) 

f 

.2. 

1 

5000 

2500 

0 

Fig. 3. 3. Observed total particle nwnber concentration (lower pane) and 

size-resolved aerosol light scattering coefficient (upper pane, 550 nm 

wavelength, solid line for 0-1 μrn diameter particles, circles for 1-10 μrn 

particles) at Sable Island, Canada, September 10-19, 1992. 

34 

3.1.2. LIDAR OBSERVATIONS OF AEROSOLS 

(See 1.1.2. for report on Mauna Loa lidar data.) 

3.1.3. TOTAL OZONE OBSERVATIONS 

Total ozone observations continued throughout 1992 at 

15 of 16 stations that comprise the U.S. Dobson 

spectrophotometer network (Table 3.4). Of the 15 stations, 

5 were operated by CMDL personnel, 4 by the NWS, 2 are 

domestic cooperative stations, and 4 are foreign 

cooperative stations. The Dobson spectrophotometer, 

operated at Florida State University in Tallahassee until 

November 1989, was relocated in 1992 to the Municipal 

Airport in Tall ahassee. NWS staff made routine total 

ozone observations at Tallahassee begining in March 1993. 

The Poker Flat Research Range instrument fai led in May 

and the instrument was shipped to Boulder for repair and 

re-calibration. In early June the instrument was returned, 

but problems in the computer system driving this 

automated instrument and problems with the operations at 

the Range in general kept the instrument from making any 

useful observations through the rest of the year. At the end 

of the summer, the instrument and shelter were moved to 

the roof of the Geophysical Institute, University of Alaska, 

for installation early in 1993. 

A semi-automated method of operation for the Dobson 

ozone spectrophotometer was developed by CMDL. The 

system uses an encoder and a counter to read the R-dial 

position and a computer to guide the operator through the 

observations and record the data. The operator is given a 

total ozone value at the end of the observation. The 

advantage is that the data is in a format ready for 

processing or transmission by electronic mail. Instrument 

no. 82 was equipped with this system at SPO where the 

need for the system was greatest as all the data arc 

transmitted by satellite to CMDL. 

Provisional daily 1992 total ozone amounts applicable to 

local apparent noon for stations listed in Table 3.4 were 

archived at the World Ozone Data Center (WODC), 4905 

Dufferin Street, Downsview, Ontario M3H 5T4 , Canada, in 

Ozone Data for the World. Table 3.5 lists mean monthly 

total ozone amounts measured at the various stations. 

(Monthly means are derived for stations where observations 

were made during at least 10 days each month.) Ozone 

values shown for MLO for July-October may be too high 

by about 2.5%; more work is needed to assess the exact 

measurement errors. Ozone values in the table are 

expressed in the Bass-Paur ( 1985] ozone absorption 

coefficient scale [Komhyr et al., 1993a]. adopted for use by 

the WMO beginning January 1, 1992. The Bass-Paur 

coefficients yield ozone amounts 0.9743 times as large as 

those derived from the use of the Vigrou.x ( 1957] ozone 

absorption coefficients. 

Because of the need for "ground truth" validation of 

satellite instrument ozone data and the desirability of 

obtaining reliable information on ozone trends during past 

decades, the NOAA National Environmental Satellite, Data, 
TABLE 3.4. U.S. Dobson Ozone Spectrophotometer Station Network for 1992 

Station Period of Record Instrument No. Agency 

Bismarck, Nonh Dakota• Jan. 1, 1963-present 33 NOAA 

Caribou, Maine• Jan. 1, 1963-present 34 NOAA 

Wallops Is., Virginia• July 1, 1967-present 38 NOAA; NASA 

SMO• Dec. 19, 1975-present 42 NOAA 

Tallahassee, Florida• May 2, 1964-Nov. 30, 1989; 58 NOAA; Florida State University 

Nov. 1, 1992-present 

Boulder, Colorado• Sept. 1, 1966-present 61 NOAA 

Poker Flat, Alaska March 6, 1984-present 63 NOAA; University of Alaska 

Lauder, New Zealand Jan. 29, 1987-present 72 NOAA; DSIR 

MLO• Jan. 2, 1964-present 76 NOAA 

Nashville, Tennessee• Jan. 2, 1963-present 79 NOAA 

Perth, Australia July 30, 1984-present 81 NOAA; Australian Bureau Meteorologi 

SPO Nov. 17, 1961-present 82 NOAA 

Haute Provence, France Sept. 2, 1983-present 85 NOAA; CNRS 

lluancayo, Peru Feb. 14, 1964-present 87 NOAA; !GP 

BRW June 6, 1986-present 91 NOAA 

Fresno, California• June 22, 1983-present 94 NOAA 

•Stations where total ozone data were tentatively re-evaluated. 

TABLE 3.5. Provisional 1992 Monthly Mean Total Ozone Amounts (m-atm-cm) 

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

Bismarck, ND 337 346 354 347 331 328 321 302 297 272 307 320 

Caribou, ME 353 364 375 384 346 354 335 311 278 293 285 302 

Wallops Is., VA 314 323 337 331 338 322 299 293 278 284 254 262 

SMO 251 249 247 237 234 235 233 238 240 239 248 249 

Tallahassee, FL 

Boulder, CO 324 325 336 318 308 299 296 287 276 270 290 285 

Poker Fial, AK 423 404 397 333 

Lauder, New Zealand 290 284 278 266 309 [358] 367 350 318 289 

MLO 236 255 265 279 284 279 (267) (266) (258) (250) (241) (230) 

Nashville, TN 303 317 327 319 333 318 297 303 284 288 268 262 

Perth, Australia 282 274 271 273 [277] 324 318 307 290 

SPO 278 262 (286] [254] (260] [244] (257] - 185 180 269 

Haute Provence, France 296 332 329 362 346 340 [33 1] (286] 285 291 262 292 

Huancayo, Peru 242 245 241 235 227 221 224 237 247 245 248 248 

BRW [260] 417 416 384 330 291 301 314 325 

Fresno, CA 310 321 346 309 315 325 301 297 281 270 263 278 

Monthly mean ozone values in square brackets are derived from observations made on fewer than 10 days per month. 

Values in parentheses may be too high by about 2.5%. 

and Information Service, in cooperation with the WMO, 

embarked on an international project to optimize the 

quality of Dobson spectrophotometer data of the global 

Dobson instrument network in 1991. To this end, a 

"Dobson Data Re-evaluation Handbook" [Komhyr et al., 

l 993b J was prepared outlining procedures to be followed in 

re-evaluating the data. For Dobson instruments that were 

periodically calibrated throughout the years relative to 

World Primary Standard Dobson Instrument 83, as have 

been the instruments of the U.S . station network, the 

"Handbook" specifies procedures for correcting the data for 

instrument spectral calibration changes arising from aging 

of optical components, optical contamination, cobalt filter 

35 

corrosion by humidity, and optical wedge calibration 

changes. 

Reevaluation of the U.S. data began in 1991. To date, 

data from 9 of 16 stations identified in Table 3.4 were 

tentatively reprocessed. The method involved use of 

updated initial and final calibrations (relative to Dobson 

instrument 83) as well as the determination, from quasisimultaneous direct-sun and zenith-sky observations, of 

corrections to empirical charts, from which total ozone 

amounts are derived from observations on the clear or 

cloudy zenith sky. Resulting data are improved compared 

with those originally archived at the WODC, with monthly 

means generally differing from the archived values on 
average by not more than about ±2%. Portions of the 

records, however, are subject to additional refinement. 

Maximum errors within these data portions are estimated 

not to exceed ±2%. 

Figure 3.4 plots 1979-1992 ozone anomaly data (i.e., 

monthly mean ozone deviations from monthly normals) for 

14 of the 15 operating CMDL ozone stations. Data used in 

the analysis are the tentatively re-evaluated data for 8 of 

the 14 stations (see Table 3.4), but provisional data as 

archived at the WODC for the remaining 6 stations. The 

plots exhibit several interesting features. The two most 

northerly stations, e.g., Point Barrow and Poker Flat, 

Alaska, show downward ozone trends of -0.38 and -0.47% 

yrl , respectively, based on sparse data obtained during 

springtime seasons of the years when observations were 

made. (The trend at Poker Flat is not statistically 

significant at the 95% confidence interval [!-statistic]). 

Stations on the U.S. mainland (Caribou, Bismarck, 

Boulder, Wallops Island, and Nashville) with complete 

1979-1992 records show downward ozone trends ranging 

from -0.33 to -0.46 % yrl. Data from Fresno, also on the 

U.S. mainland, exhibit a non-statistically significant 

downward trend of -0.22% yr·l over the 9-year record of 

observations. At Haute Provence Observatory, the 9-year 

record yields a large downward trend of -0.62% yr-1, 

primarily because of unusually low ozone that occurred 

there in the spring of 1990 and in 1992. Smaller trends, 

ranging from 0.03 to -0.20% yrl are evident for the nearequatorial stations of MLO, Huancayo, and SMO. The two 

southern hemisphere stations of Perth and Lauder exhibit 

positive ozone trends that likely result, at least in part, from the 

shortness of the records. 

Monthly mean total ozone amounts measured at SPO 

during October 15-31 time intervals of 1962-1991 are 

plotted in Figure 3.5. (Mid-October is when Dobson 

spectrophotometer total ozone observations first become 

possible at SPO following the polar night.) The October 

1992 mean ozone value of 185 DU was higher than the 

corresponding 1991 value of 162 DU. This larger ozone 

amount resulted most likely from the relative proximity to 

SPO of the polar vortex boundary in 1992 than in 1993. 

The SPO November 1992 mean total ozone (180 DU) was 

considerably lower in 1992 than in 1991 (289 DU). 

The CMDL Dobson spectrophotometer observations 

show low ozone values in 1992, similar to those reported 

for the TOMS satellite instrument Gleason et al. (1993). 

While the TOMS total ozone record is relatively short, 

allowing comparison of recent decreases in ozone with 

ozone amounts measured only since 1978, the CMDL 

Dobson instrument data date back for a number of the 

stations to the 1960s and 1970s, a time when atmospheric 

ozone destruction was minimal due to anthropogenic 

chlorofluorocarbons. Recent and past Dobson instrument 

total ozone data from the six contiguous U.S. stations of 

Nashville, Fresno, Wallops Island, Boulder, Bismarck, 

Caribou, and from MLO in Hawaii and SMO in the South 

Pacific, are compared in Figure 3.6. The solid lines in the 

plots are percent decreases in 1992 monthly mean total 

36 

ozone amounts relative to Jong-term normal monthly means 

for the eight stations. For all stations except Fresno, the 

normal monthly means were derived from data obtained at 

the stations through 1985 (see Table 3.4). For the shorter 

Fresno record, the monthly normals were obtained from 

1984-1991 data. Dashed lines in Figure 3.6 represent 

standard deviations (±la) of the normal monthly means. 

Note that nearly all monthly means fall below long-term 

normal ozone levels to values as low as about -10%. The 

mean 1992 ozone deficiency for the eight stations is 4.7%. 

For the record as a whole, the monthly mean ozone values 

fell below one standard deviation of the normal monthly 

means 66% of the time and below two standard deviations 

38% of the time. 

3.1.4. UMKEHR 0IlSERVATIONS 

Umkehr observations with automated Dobson ozone 

spectrophotometers continued during 1992 at Boulder, 

Haute Provence, Lauder, MLO, Perth, and Poker Flat. 

Table 3.6 lists the number of observations at!empted and 

the number that yielded useful data. Observations with 

excessive cloud interference were not useful. Umkehr data 

quality during 1992 was adversely affected by aerosol 

particles still remaining in the stratosphere following the 

June 1991 eruption of Mt. Pinatubo in the Philippines. 

Umkehr observations at Poker Flat were only made during 

March and Apri l 1992. An instrument mechanical failure, 

followed by multiple failures in the controlling computer 

system, kept the station out of operation. The instrument 

and shelter were moved to the Geophysical Institute at the 

University of Alaska, Fairbanks, for observations starting 

in 1993. Both Lauder and Perth missed many weeks of 

observations in June, July, and August while the 

instruments were in Boulder for recalibration. Umkehr 

data for 1991 has not been archived at the WMO World 

Ozone Data Center, since a correction for the interference 

from the Mt. Pinatubo aerosols has not been determined. 

3.1.5. CALIIlRATION OF CMDL DOBSON SPECTROPHOTOMETERS 

Three Dobson ozone spectrophotometers of the CMDL 

network and three others were calibrated during 1992. 

Table 3.7 lists all the instruments calibrated and the 

resulting calibration difference expressed as a percent 

ozone difference. This percentage difference is calculated 

between measurements from the test instrument and the 

standard instrument with the ADDSGQP observation type 

at aμ value of 2, and a total ozone value of 300 DU, before 

any repair or calibration adjustment is made. All 

calibrations were performed in Boulder relative to the 

NOAA world primary standard Dobson spectrophotometer 

83 and to secondary standard Dobson spectrophotometer 

65. 

Instrument 63 from Poker Flat Research Range had a 

failure of one of the bands holding the optical wedge in 

place. The instrument was repaired with an attempt to 
~ :x -+-----+-----_,_ ___ __,.___---.-

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~"' ~N 

~o 

l2S 7'SW TREND, -0.201 t 0.01 X I YEAR 

OM~ 

__, HUANCAYO ~ ~~--,~~ ....----, ~--.- ....----,~~~....----.~~--+ O' 

~ ~-t-~~~~~-'-~~~~~.L.-~~~~~'--~--.-

"' N 

I 

MS VIW TREND, -0 180 t ~ X I YEAR 

SAMOA _,_-.---,~~--,.---.---,..--,~~--,.--~--...--,~-.---+ 

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

:ns 116E TREND, 0.69~ t 0.213 X I YEAR 

~ 

0 

l(l 

I 

PERTI-t ~--'-~-.~~~~.--~~~.---.--.-~.---.--.--+ 

~ 

"' N 

0 

l(l 

I 

~5S VOE TREND. 0 311 1 0.~7~ X I YEAR 

LAUDEJI f_._~~.---r--.-~.,..-~--...~,.---.---...~~-.---..--+ 

1979 1983 1987 1991 

YEAR 

f-'ig. 3.4. To1al ozone anomaly data derived from Dobson spec1ropho1omc1cr observa1ions. Leas1-squares linear regression lines have been filled 10 the 

dala ob1ained through 1992. Unccrtain1ies in indica1ed ozone !rends arc 95% confidence in1ervals (1-s1a1is1ic). 

37 
19.0 1910 1980 1990 

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

19.0 1910 19!0 1990 

YEA~ 

Fig. 3.5. SPO mean total ozone amounts for October 15-31 time 

intervals of 1962-1992. 

- 0 

~ --

°' ........ c; IG . . E •, ... . ··. _ ....... , ... .... ... ....... ,, , . .. 0 '-.... z 0 ·····--············ 

> :s .. .. ti!) 

c:: • 0 

:E 

e 0 

-• ~ ~ Fresno 

a • • c 

.9 

E 0 

0 - &t: ' . CD IO '· ..... . ,-.... , a .. , , . . . ' 

c ..... .. .... . cg ··--· '· ..... .r. 0 u 

CD 

c 

2 IO • 

0 

N 0 0) 

0) -• 

- IO Ceribou -• J M J s 0 J M J s 

replace the wedge back into the correct position, based on 

the results of standard lamp tests, before the comparison 

with a standard. A wedge calibration after the comparison 

showed that the wedge had been replaced very close to the 

original position, based on the observation that after the 

wedge was cleaned, the wedge density curve was the same 

as the 1989 curve. Instrument 81 from Perth, Australia, 

had worn bearings in the wedge drive assembly replaced. 

Instrument 72 from Lauder, New Zealand, was accidentally 

damaged by oil on the optical wedge, thus the result in 

Table 3.7 is misleading. A wedge calibration defined the 

problem completely, and an interim calibration could be 

applied to the data for the period when the oil was on the 

wedge. This time period was known to the day. 

Three non-CMDL instruments were calibrated by CMDL 

in 1992. The results are listed in Table 3.7. Instrument 99 

from Argentina was sent to Boulder after the instrument 

was damaged by a falJ that resulted in a broken band on the 

wedge. A repair was attempted on site, but the correct 

0 

.. ,--..... . IO 

. . . . . .. ·-··- . " ... .. .... ........ . ... ···-" ... _ ', .... 0 

IO • 

2 • 

Samoa IO 

.. 

• 

2 

. ,. . .. ·., IO .. . '•" . ' . .. ... .... ____ , .. 0 

IO 

• 

g 

• 

, 

• J s D 0 

fig. 3.6. January 1992-:\lay 1993 percent decreases in monthl>• mean total ozone amount at six contiguous U.S. stations an<l in llawaii an<l 

Samoa relative to long-term normal monthly means. Dashed lines arc standard deviations (I a) of the normal monthly means. 

38 
TABLE 3.6. Umkehr Observation Frequency During 1992 

S1a1ion To1al No. Tola! No. 

S1a1ion Coordinales Obs. Made Useful Obs. 

Iloulder 40°N, 1os 0w S32 200 

Hame Provence 43•s. 110°E 44S 21S 

Lauder 4S0 S, 170°E SI I IS8 

~!LO 20°N, !S6°W S80 413 

Penh 32°S, l 16°E 427 199 

Poker fla1 6S0 N, 147°\V 77 22 

TAB LE 3. 7. Dobson Oz.one Speclropholomelcrs 

Calibrated in 1992 

Inslrumcnl Calibra1ion Calibralion Corr. 

S1a1ion Number Dale !\'ceded (%)• 

Poker Flat (now UAF) 63 May IS -1.3 

Perlh Airpon, Auslralia 81 June 19 -0.8 

Lauder, Auslralia 72 July 14 -1.4 

Argenlina 99 July 27 -0.S 

Melbourne, Auslralia !OS June 19 -0.8 

Tsukuba, Japan 116 June 28 -0.S 

•Applicable loμ= 2 and 300 DU ozone 

band was nol available. The results in lhe table arc 

therefore, less reliable when considering ex.isling data: 

Inslrumenl 105 is a W/\10 regional standard owned and 

operated by the Australian Bureau of Meteorology in 

Melbourne. Inslrumenl 116 is the standard for the 

Japanese network and is operated by the Acrological 

Observatory, Tsukuba, Japan. 

The calibration of instrument 82 was verified and the 

instrument sent lo SPO as a replacement for instrument 80. 

While both instruments were on station, observations were 

made with both inslrumenls in overlapping time periods. 

The results showed that both instruments produced ozone 

values that agreed within I%. 

A Shimadzu-built copy of lhe Dobson ozone 

spectrophotometer, owned by the WMO, was rebuilt in 

Boulder for subsequent use in Lagos, Nigeria. As most of 

this instrument's construction was different than that of the 

British-built Dobson instrument, a great amount of 

ingenuity was used lo gel the optical pans aligned 

correctly. The instrument calibration was excellent after 

rebuilding. 

C/\IDL developed a semi-automated version of a twolamp wedge calibrator lhat increased the speed of a wedge 

calibration from 2 days lo one-half day. 

3.1.6. VALIDATIO:\ OF TO~lS A:\D SATELLITE 

l:\STRU:'>IE:\T 0ZO:\E DATA 

World primary standard Dobson inslrumcnl 83, 

maintained by C/\IDL, operated in June-August 1992 al 

/\ILO in an ongoing program lo assess its cal ibration and lo 

39 

provide "ground-truth" data for verification of ozone 

measurements made by the NASA TOMS and SBUV 

instruments from aboard the Nimbus 7 satellite. While 

large differences were observed between Dobson 

instrument 83 and TOMS data prior to 1987, development 

of a wavelength pair justification technique [llerman et al., 

1991) has rendered data from the two kinds of instruments 

highly compatible. TOMS corrected (Version 6) data and 

Dobson instrument 83 data for 1979-1992 are compared in 

Figure 3. 7, showing agreement lO within aboul ±0.5%. 

The long-term ozone measurement precision of Dobson 

instrument 83 is currently estimated 10 be± 1 %. 

3.1.7. TROPOSPHERIC 0ZO:\E 

The CMDL network of surface ozone measurements 

includes the four baseline observatories; three AEROCE 

sites (Bermuda, Barbados, and Mace Head, Ireland); Niwot 

Ridge; and Westman Islands, Iceland. The station at 

Reykjavik, Iceland, continues operation under the direction 

of the Icelandic Meteorological Office. The data from this 

site arc heavily inOucnccd by its in-city location and the 

data arc more difficult lo interpret as regionally 

representative. Figure 3.8 shows the diurnal cycle (shown 

as deviations from the daily mean) for Reykjavik (a) and 

Westman Islands (b). Al Reykjavik, there is a large 

variation with minimum values in the day and highest 

values very early in the morning. Al Westman Islands, on 

the other hand, there is no significant diurnal cycle that is 

consistent wi1h the fact thal it is removed from local or 

regional pollution sources on a small island south of the 

main island of Iceland. At Reykjavik, lhe diurnal cycle 

appears to be driven by daily automobile traffic paucrns 

and the titration of ozone by nitric oxide (NO) [0/1ma11s 

and Levy, 1993]. 

Interestingly, at Reykjavik the average concentration for 

0307 LST is very similar to the daily average at Westman 

Islands indicating that for -.clatively unpolluted conditions 

the broad scale pallerns determine important features such 

as the seasonal variation [ 0/1mans and Levy, 1993]. The 

long-term trend pauerns reported last year [Ferguson and 

Rosson, 1992) for the four observatories are nol altered by 

the addition of the 1992 data. A fuller discussion of the 

surface ozone measurements can be found in 0/1mans and 

~ I J 4 ····l ···· i .. ...... . .1 .. .... r·r·····'-··f'·t···1 .... . 

:0 

~ 2 t 6 World standard 

0.. 

O'--~...J.....~---1~~-'--~-+-~---1~~_._~_._~_..J 

1915 19ao 1982 1984 1gss 1988 1990 1992 1994 

Year 

fig. 3.7. Percenl differences bclwcen TO'.\IS and World S1andard 

Dobson lnslrumenl 83 lol31 ozone amounls measured al ~!LO 

during months of Junc·Augusl 1979-1992. 
lf) 

0 

lf) 

0 

Q_ 

QJ 

Q_ 

> lf) 

0 

I 

~~~~~~~~~~~~~ O' SON 

!-- lf) 

0: I 

a::: 0 2 1 6 8 10 12 11 16 18 20 22 21 

(..9 

z U1 

x .... - b) 

I: [") -

L...J N- z 

~~~~~~~~~~8898~~~~~~~~~~ 0 

N 

0 0-

-;' -

~-

[") - I 

T- SON 

U1 

I I I I I I I I I I I I I 

0 2 1 6 8 10 12 11 16 18 20 22 24 

LST 

Fig. 3.8. Average hourly depanures from 1he daily mean of the surface 

01onc mixing ra1io (ppbv) for 1he 3 monlhs of Seplemlx:r, Ociobcr, and 

\'uvember al (a) Reykjavik and (b) Weslman lsl,mds, Iceland. 

Levy I 1993). The monthly mean mixing ratios from each 

site arc summariLed in Table 3.8. For l'\ILO, the averages 

arc based on the period from 00-08 LST (downslope now) 

and al Re) kjavik for 03-07 LST. 

3.1.8. 0ZONESONDE 0DSERVATIONS 

After reestablishing weekly ozone vertical profile 

measurements at Hilo, Hawaii, and Boulder, Colorado, in 

1991, in response to the eruption of Mt. Pinatubo, the 

sounding program was continued at these sites as well as 

SPO in 1992. 

Two significant effects of the Mt. Pinatubo eruption on 

stratospheric ozone were found. At SPO there was 

additional springtime ozone depletion in 1992, particularly 

in the lower stratosphere. Figure 3.9 shows the vertical 

profile of the ozone partial pressure over South Pole at a 

date near the minimum in column ozone amount for the 

years 1986-1992. In 1992 (the open stars), there is 

significantly less ozone in the layer from 10-15 km than in 

previous years. In addition, in the region from 14-17 km, 

ozone has essentially been completely destroyed in 1992. 

In 1990, similar near complete ozone Joss in this region 

was also seen but the lower stratospheric destruction was 

not. Evidence of unusual ozone loss was also seen in 1991 

in the lowest part of the stratosphere. The 1991 reduction 

in this region was attributed to the enhanced ozone 

destroying effects of volcanic aerosol from the Mt. Hudson 

(46°S) eruption in August 1991 [llofmann et al., 1992]. 

The presence of enhanced aerosols, cold polar 

stratospheric temperatures (but not cold enough to form 

polar stratospheric clouds at 10-15 km), and high levels of 

ch lorine from human manufactured chloronuorocarbons 

allowed ozone destruction in a region where it had not 

previously been seen. By winter 1992 the volcanic aerosol 

from Mt. Pinatubo, which was ejected to much higher 

altitudes than that from Mt. Hudson, had settled into the 

10-18 km region over Antarctica [Cacciani et al., 1993). 

In 1991 the l\lt. Pinatubo aerosol probably did not 

penetrate the Antarctic polar vortex at these levels. In late 

winter and spring 1992, ozone declined more rapidly than 

in previous years. The course of this decline is shown in 

Figure 3.10 which shows profiles from late August through 

the minimum value achieved on October 11. The column 

amount of 105 DU, obtained by integrating the data from 

the profile measurements, is the lowest ever measured over 

South Pole and may well repn:senl the lowest column 

amount measured anywhere [l/ofmrmn and Oltmans, 1993). 

TAnLE 3.8. l\lonthly Mean Surface ozone Mixing Ratios (ppbv) During 1992 

S1a1ion Jan. Feb. :'-larch April :'-IJ) 

BRW 29.5 28.4 23 3 15.7 17. I 

Re) kja' ok, Jccl311d 35.6 35.2 39.!i 41 4 36.5 

\\'eslman Is., JcclJnd 

:'-Lice Ile:1d , lrcl.rnd ~8.~ 377 40.8 41.0 43.8 

:\\\"R 44.6 4 5.4 48.7 52.4 47. I 

llermuda 42.9 42.4 52.0 48.0 35.4 

\11.0 40 I 42.7 53 4 60 9 46.8 

11.trhJJos 23.3 23.3 22 !i 19.5 16.4 

S\10 

Sl'O S.3 l!i.O 17.4 21.8 23 .0 

40 

June Jul) Aug. 

19.7 18.6 19.0 

30.9 20.7 24.9 

36.2 27.9 30.9 

47.0 44. I 41.9 

26.6 23.8 24. I 

49.4 38.8 30.6 

16.0 16.6 

31.2 32.3 31.4 

Sep1. 

24.2 

(33.5) 

30.9 

41.5 

27.9 

26.3 

18.2 

27.7 

Oct. 

33.6 

32.9 

39.I 

39.5 

24.3 

Nov. 

39.I 

36. I 

35.8 

34.2 

25.2 

Dec. 

38.6 

30.5 

38.2 

35.9 

28.I 
35 

30 

25 ,..-..., 

E 

_.:::{_ 

..._,, 20 

w 

0 

2 15 

I-

_J 

<!: 

10 

5 

0 

0 

03 

SOUTH POLE STATION 

SPRINGTIME OZONE MINIMA 

2 4 6 8 10 

PARTIAL PRESSURE (mPo) 

f-ig. 3.9. Profile of ozone partial pressure over South Pole on the 

dale nearest 1he minimum in column ozone each year in lhe period 

1986-1992. 

This represents a 60% decline from late Augus1 to midOctober. Twenty years earlier, ozone actually increased 

during this portion of the year [Ol1mans el al., 1993). 

At Hilo and Boulder, ozone profiles have remained 

perturbed late into 1992 from the effects of the Mt. 

Pinatubo eruption 1.5 years earlier (Figure 3.11), This 

perturbation is primarily seen as a displacement of the 

ozone profile with lower ozone amounts in the lower 

stratosphere and enhanced concentrations above the 

maximum. Overall, there has been a decline in the total 

column amounts for the period following the eruption 

[llofmann el al., 1993). In the subtropical (or high 

tropical) latitude and mid-latitude cases represented by 

Hilo and Boulder, the poleward transport of ozone poor air 

in the lower stratosphere and enhanced ozone amounts 

higher in the stratosphere, resulting from the lofting of the 

tropical ozone column following the volcanic eruption, is 

consistent with the pauerns shown in Figure 3.10. The 

lifting of the column results from the heating by absorption 

from the upwelling long-wave radiation and an enhanced 

vertical and horizontal circulat ion in the tropics [Brasseur 

and Granier, 1992). It appears that the persistent nature of 

these anomalies well into 1992 is at least partially related 

to the timing of the eruption relative to the shift in the 

phase of the tropical stratospheric quasi-biennial wind 

oscillation (QBO) from its easterly to westerly regimes 

41 

35 

SOUTH POLE STATION 

1992 OZONE HOLE 

30 

25 ,..-..., 

E 

_.:::{_ 

..._,,20 

w 8/21 0 

2 15 

I-

_J 

<!: 

10 DATE TOTAL 0 3 (DU) 

8/21 259 

9/5 215 

9/20 162 

5 9/26 133 

9/29 117 

10/11 105 

0 

0 5 10 15 20 

03 PARTIAL PRESSURE (mPo) 

f-ig. 3.10. Ozone venical profiles at South Pole from August 21-

Oc1obcr 11, 1992, showing 1he spring decline in s1ra1ospheric 01one. 

[llofmann el al., 1993), although chlorine-catalyLcd OLOnc 

depletion, rcla1ed lo the increase in volcanic aerosol 

particle surface area, is probably also involved. 

3.1.9. STRATOSPH EIUC WATER VAPOR 

In addition to the cont inuing monthly water vapor 

profile measurements carried out at Boulder, upper 

tropospheric and stratospheric measurements were done in 

Hilo, Hawaii; Barstow, California; Lauder, New Zealand; 

McMurdo and South Pole, Antarctica; and Kiruna, Sweden. 

Most of the soundings were carried out as part of the 

UARS correlative measurements program. 

The 12-year record of over 110 water vapor profiles 

obtained in Boulder during 1981-1992 were recently rcanalyLcd. Two kilometer layer averages were calculated 

for the stratosphere and upper troposphere between 10-26 

km (Table 3.9). A linear least-squares trend was computed 

for the time series of approx imately monthly balloon 

soundings (Figure 3.12 and Table 3.9). Significant 

increasing water vapor con-ccntrations were found in the 

lower stratosphere with the largest increase of -1% yr-1 in 

the 18-20 km layer. Since the primary source of water 

vapor in the stratosphere is the oxidation of CH4 [LeTexier 

el al., 1988], the rising concentrations of atmospheric CH4 

[S1eele el al., 1992] are expected to lead to rising 
30 

2:3 20 

:J 

1--

1--

__J 

<( 

10 

' ', 

HILO, HAWAII 

SEP-OCT-NOV 

1985-1990 

±1 SD 

• 1992 

(a) 

0 ~~~-'--'--'--'--'--'--'----'-----'--'--'--'-J.._L.....J--1._J 

30 

10 

0 50 100 1 50 200 

0 3 PARTIAL PRESSURE (nbar) 

. ' ' . 

' ' ' 

. ·, 

' ' 

-' 

BOULDER 

DEC-JAN-FEB 

1985- 1988 

±1 SD 

• 1992-1993 

. 

,' 

(b) 

0 ~~~~~~~~~~~~~~~~~~~ 

0 50 100 150 200 

0 3 PARTIAL PRESSURE (nbar) 

f-ig. 3.11. (a) Autumn 1992 average ozone profile (thick line) 

compared to the 1985 average for this season (thin line) at llilo, Hawaii, 

and (b) winter 1992-1993 ozone profile at Boulder compared to the 

1985-1988 winter average. 

42 

TABLE 3.9. Water Vapor Mixing Ratios Over 

Boulder, Colorado, During 1981-1992 

Level Mean Std. Dev. Number Trend 95% Confidence 

(km) (ppmv) (ppmv) Obs. (% yr-1) Jn1crval (% yr-1) 

10-12 59.15 48.67 113 1.63 3.27 

12-14 12.18 9.02 113 1.01 2.77 

14-16 4.59 1.71 113 .38 I. I I 

16-18 3.83 .65 113 _75• .67 

18-20 3.82 .35 112 I.OS• .49 

20-22 4.08 .31 105 .90• .41 

22-24 4.21 .30 IOI .54• .38 

24-26 4.28 .30 84 .29 .4 1 

The trends are computed for dcseasonalized values. The 95% 

confidence interval is based on sl!Jdents I-distribution. 

•Significant at 95% confidence level. 

stratospheric water vapor concentrations as well. The 

measured increase is somewhat larger than that expected 

from rising CH4 amounts alone. This may indicate another 

source of increasing water vapor in the lower stratosphere 

such as an increase in the troposphere resulting from rising 

tropospheric temperatures. 

3.1.10. SURFACE RADIATION 

Solar and Terrestrial Atmospheric Radiation 

Surface based radiation monitoring projects continue at 

eight CMDL locations: Barrow, Alaska; Erie and Boulder 

(BAO and BLD), Colorado; Bermuda (BRM); Mauna Loa, 

Hawaii; Kwajalein, Marshall Islands (KWJ); American 

Samoa; and the South Pole. 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 irradiancc 

measurement projects are also maintained. The surface 

radiation budget (SRB) is a basic and criti cally important 

climate variable that has long been inadequately observed 

because of insufficient global coverage and inherent 

instrumental limitations. The more extensive observations 

are made at CMDL sites where the measurements are more 

areally representative, especially with respect to land 

surface and cloudiness. In order to make the CMDL data 

more available to the general scientific community, 

irradiances observed at those 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 which exists 

for the past 15 years at four of the sites (BRW, MLO, 

SMO, and SPO). Previous CMDL and GMCC Summary 
> 

:E 

a... 

"' 

"' 

N 

"' 

"' 

a... "' 0 

l-a: ~ 

a:: 

(.!) 

z"' 

x 

:E 

BOULDER CO 

~-~· 

.. !.....J'-~-·-·-·~~>-,J'---~·~-!~·~-~~,,_,,_-~-_.__,-~~~·-~ • • "'••I : \ 

~ . 

. . , 

.. 

2i-26KM 0.29 :!: 0.41 %/yr 

.. . ·- . •' __ ..__.. -·-- L- ..__::.....::...,,,.-="~...;.....--.1--';'·c-#:'•,,-·· ~~~:-· ·......,,~-~'T---~-~-.-::- ---J- ·.. : .. : 

22-2iKM 

. ,• ..... · ..... • ..J>•'.\.- - ·- ·-;--- • •• . ·' . . .. 

20-22KM 

. . ... ,~-.- : ;- - -. -·- .: .. _ 

" 

0.54 :!: 0.38 o/o..') r 

-.. ··• ·, ..! ~~-- --- __ , . : . .. . .. . . 

. · 

0.90 :!: 0.41 %/yr 

' 

.. . ~ ~ -- ·~· .... -'" .!:-.·· 'J . , . .. - - -.. . '· ... ... "' . 

1 B-20KM 1.05 :!: 0.49 %/yr 

N [_~~-'-~"---l.~~~L-~~.J-~~-L~~~"-'~ 

80 

. . . .. -·-. -- -- - - .,, , ... 6-IBK~ 

62 81 

.. ' 

.. . . ~ .. -~_: _:. __ j_:~ 

I 

.. 

. .. . : ' 

86 86 

Yt:FR 

· ... .· 

0.75 : 0.67 °o )T 

90 92 

f-ig. 3. 12. Time series of water vapor mixing ratios in 2-km intervals 

for individual profile measurements at Boulder, Colorado, during 1980. 

1992. The solid line is lhe mean for each 2-km interval. The dashed 

line is the linear fit to lhe dcscasonalized data. 

Reports have discussed the wide ranging and useful 

applications of these data to scientific c;•tcsiions. Recently 

completed projects utilizing the radiation obscrva1ional 

results from the CMDL field sites arc as follows: the 

detection of a long-term decrease in arctic haze [Bodhaine 

and Du11on, 1993); comparison of satellite- and BAOdcrived SRB under clear and cloudy conditions [Cess et al., 

1991, 1993); the effects of snow surfaces on atmospheric 

absorption [Nemesure et al., 1993]; detection of 

in1ermedia1e-1crm !rends in cloudiness related lo radiation 

43 

perturbations [Du11on 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 [Du11on, l 992a]; a surprisingly good 

agreement between modeled and observed thermal infrared 

irradiances over the range of globally extreme conditions 

[Dutton, 1993); and a de.termination of the radiative effects 

of the Mt. Pinatubo volcanic eruption [Dutton and Christy, 

1992; Russell et al., 1993; Du11on et al., 1993). Numerous 

additional requests were made and fulfilled for CMDL 

radiation data for a variety of research applications. 

Figure 3.13 shows updated results on the latc summer 

cloudiness and irradiance trends at SPO reported by Du11on 

et al. (1991]. As suggested by Dutton et al. (1991], the 

previously observed trends during January and February 

unti l 1988, did not project into the fu ture. The current SPO 

irradiance level suggest a return to previous levels . 

The MLO atmospheric transmission record updated 

through 1992, is shown in Figure 3.14. The effects of the 

eruptions of Pinatubo and El Chichon are most obvious and 

are enlarged and compared in the inset of the figure. 

Frequent updates of this data arc submitled 10 the NOAA 

Climate Analysis Center monthly Climate Diagnostic 

Bulleti11. 

Snowmell dale at Barrow, Alaska, is defined as the las! 

date each year that any significant snow remains on the 

ground, but considerable differences between the National 

Weather Service observations within the village of Barrow 

and out on the tundra were noted in Figure 3.15. The 

CMDL albedo data continue to suggest that there has been 

no significant change in the annual date of sprirg snowmclt 

near Barrow since the 1940s. 

Observatory operations continued during the year 

showing only a few significant changes that can be an 

important altribule of a long-term measurement effort. 

Newly available blowers were added to the upward facing 

pyranomeler and pyrgcomcicr al BRW. The new units arc 

very effective in keeping frozen prec1pttation and 

condensation off the filter domes. Additional blower units 

will be acquired as funds allow for implementation al other 

sites. All continuous data logging al all eight si tes now 

have 3-minule-or-bctter resolution recorded and permanently stored. Data sampling times range from 1 10 2 

seconds al all sites except Boulder where it is 10 seconds in 

order lo accommodate a large number, nearly JOO, AID 

channels on one data logger. Many current data loggers 

(BAO, BLD, BRM, and KWJ) have integrating AID 

channels, and all other sites will be converted lo this 

capability in the next couple of years. A critical 

requirement of the radiation project is to make stable and 

accurate micro-volt level measurements to ensure that the 

potential voltage measurement error is small compared 10 

other sources of error. 

Data processing for the three newer sites (KWJ, BAO, 

and BRM) was largely incorporated into the system used to 

process raw data from the other older sites. Incoming data 
410 JAN 230 FEB 80 MAR 

~ 400 ~ 220 ~ 55 

::E 390 ~ 210 :I 50 a: a: ~ 380 UJ 

~ 45 

~ 370 ::; 200 

~ 40 ~ 

~ 360 ~ 190 <( 

35 :i: 

350 180 30 

74 76 78 80 82 84 86 88 90 92 94 74 76 78 90 82 84 86 88 90 92 94 74 78 78 ao ~nr 88 90 92 94 YEAR YEAR 

40 SEP 150 380 

~ 35 ~ 140 ~ 350 

:I 30 ::E a: a: : 340 UJ 25 ~ 130 UJ Q. 

Q. 330 

~ 20 s 120 ~ < 15 ; 320 :i: ;i: 

10 110 310 

74 76 78 80 82 84 86 88 90 92 94 YEAR 74 76 78 80 82 84 86 88 90 92 94 74 76 78 80 82 84 86 88 90 92 94 YEAR YEAR 

460 

~ 450 

:I 440 

a: 430 UJ 

Q. 420 

~ 410 < 

;i: 400 

390 

74 76 78 80 82 84 86 88 90 92 94 YEAR 

f-ig. 3.13. :-Olonlhly mean total (direct plus diffuse) solar irradiance 3t SPO. The ploucd Jines arc for linear least-squares fits for 1976-1987. 

arc presently processed and edited as received from the site 

within 2-4 weeks. Data received from the sites is being 

delayed by as much as 3 weeks as data tapes are filled and 

1ransmi11ed. Final processing is completed about l 

calendar year after the data are first avail able for 

processing. Final assignment of calibration information is 

ongoing as updated radiometer calibration da ta arc made 

available. Data editing, processing, and fi nal storage have 

all been moved to medium-si zed and personal computers 

directly under the control of CMDL, thereby eliminating 

the dependence of outside computer expertise and 

resources. Data processing is evolving towards a system 

where real-time interrogation of the field data is possible, 

and preliminary analysis of the data can be completed in 

the Boulder offices the day after the data are collected. 

Several sites (KWJ, BAO, BLD, and BRM) currently 

operate in that mode. 

Remote Sensing of Aerosol Optical Properties and Water 

Vapor 

Other than clouds, aerosols and water vapor arc the main 

contributors to thermal-infrared and solar r adiation 

44 

vanattons and subsequent radiative climate forcing . The 

potential climate variations rcsulling from such factors are 

extensive and varied. The observed and potential radiative 

variations may be due 10 either anthropogenic causes: 

increased industri al production of aerosols and water vapor 

feedback resulting from increasing greenhouse gases, or 

from natural causes; i.e., volcanic, biogenic, or surface 

wind-generated aerosols and inherently varying water 

vapor. CMDL has a long history of exploratory and 

operational projects relating 10 the remote sensing of 

aerosols and water vapor as related lo climate variations. 

Wide-band spectral observations of direct solar irradiance 

using a filter wheel NIP at BRW, MLO, SMO, and SPO 

were used to in fer aerosol optical depth and column water 

vapor amounts since 1977. These measurements have 

proven to be durable and stable over time, thereby 

extending monitoring efforts 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. Here , several 

narrowband (0.005 μm) sunphotometers are routinely 
z 

0 

en 

en 

:E 

en 

z 

< 

a: 

.... 

0.95 

0.9 

0.85 

0.8 

0.95 

0.9 

0.85 

0.8 

0.75 

0.85 

X-PINATUBO 

0 - EL CHICHON 

0.8 

0 2 3 

YEARS AFTER ERUPTION 

0.75 

YEAR CURRENT THAU 31 DEC t2 

f-ig. 3.14. Monthly mean "apparent" atmospheric transmission as determined from broadband direct solar beam observations at MLO. 

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 Duuon el al. [1993], 

Russell el al. (1993], and in previous CMDL Summary 

Reports. Two additional aerosol optical-depth measurement series were begun in 1992, one uses handheld I-series 

sunphotometers at Sable Island, Nova Scotia. The other at 

., 

u •O c 

·;;:; 

w 

..... 

-<( 20 0 CWOL CURRENT THRU 1'9l 

199l dot• -- U J1,1nt HWS CURA(Hl THRU 1992 

199l dole -- 2~ Wo1 

19~0 1960 1970 

YEAR 1980 1990 

Fig. 3.15. Date of annual spring snowmelt as determined by various 

researchers at different locations in and around Darrow, Alaska. The 

downward trend indicated by the foster (i\"WS) curve is believed to be 

due to "urbanization" in llarrow. 

45 

MLO was a short-term (6-month) comparison of a 

commercially available automatic four-channel sunphotometer (from EKO, Japan) that is operated in the automated 

solar dome. The Sable Island measurement series is a part 

of a new, comprehensive, surface-based CMDL aerosol 

sampling project described elsewhere in this report. 

3.1.11. SOLAR RADIAT ION FACILITY 

An observational broadband radiation plan for the 

Department of Energy Southern Great Plains Clouds and 

Radiation Testbed site (SOP/CART) located near Lamont, 

Oklahoma, was developed during the first half of the year. 

A site plan incorporating measurement capability for solar 

diffuse, direct, and global radiation, plus longwave 

radiation using pyrgeometers, was completed. The solar 

diffuse and IR pyrgeometer incorporated an SRF-designed 

tracking disk system to occult the sun during operation. 

Use of tracking disks has resulted in improved accuracy in 

solar diffuse determination and, in the case of the 

pyrgeometers, minimizes the corrections to data due to 

sensor dome heating effects. A preliminary suite of these 

broadband sensors was prepared and transported to Lamont 

during early June 1992. Personnel from the CMDL Solar 

Radiation Facility (SRF) were on site at SGP/CART to 

erect a temporary measurement array consisting of a 

pyranometer, tracking-disk-equipped pyranometer for 

diffuse sky radiation measurements, tracking-disk-equipped 

pyrgeometer for IR measurements, and a pyrheliometer 

mounted on an automatic solar tracker. A data acquisition 

system for this suite of sensors was also built and 
acqu1slllon software was developed by CMDL personnel. 

This preliminary suite of sensors remained operational until 

!he permanent site plan could be implemented. 

The SRF look delivery of two au1oma1ed absolute cavity 

systems. These units will result in more accurate 

dc1ermina1ions of !he solar beam data used in calibra!ion 

modes and, hence, enable more accurate transfers of the 

absolute scale 10 CMDL field sensors. The units arc also 

capable of all weather operation and thus have the potential 

for becoming an operationally continuous measurement 

system. Continuous measurements have beneficial 

potential for CMDL field sites, particularly MLO, with its 

long history of solar beam measurements that arc the basis 

of the M LO transmission record. The development, 

operation, and performance of 1hc automated cavity system 

is described in l/ickey et al. (1 992, 1993). 

Calibration and characterization activities of the SRF 

continued during the year. During the second half, a 

review of all CMDL field sensors was completed and an 

updated inventory of sensors by serial number, calibration 

history, and deployment history was created using a 

database management program. A total of over 90 different 

sensors were deployed over the past 20 years at the original 

GMCC and now CMDL sites, and the new database 

package will enable better management of this large group 

of sensors. 

During 1he year, standards act1v111cs consisted of 

establishing the relationship of the new automated cavities 

to existing SRF reference units. This was accomplished 

through side-by-side comparisons and computation of 

ratios. Excessive cloudiness during the summer and fall of 

1992 preven ted 1hc collection of as much data as desirable, 

but these activities are a regular part of the SRF operations, 

and eventually comparison histories will be created for 

traceability to historical NOAA SRF reference units. 

Collaboration with other laboratories was also maintained, 

and, in particular, standards comparisons were continued 

with the National Renewable Energy Laboratory in Golden. 

3.1.12. ATMOSPH ERIC TRAJ ECTORY ANALYSIS 

During the past year, the computing environment for the 

trajectory programs has improved since the acquisition of a 

Sun Spare-II workstation, which has provided significantly 

more memory and computing speed than the old Cyber 

computer. The workstation has allowed the use of a "0 

chooser" that automatically picks 0 for a given location, 

time, and elevation or pressure. It has also permitted 

modifications to the isentropic program to make it more 

usable and realistic in the lower atmosphere. 

Input to 0 chooser includes beginning and ending dates, 

destination identifier, destination latitude and longitude, 

limits of the data grid, and either the required pressure or 

elevation for the 0 surface at the destination. The 0 

chooser outputs a line for each date with its calcula1cd 0 

upon arrival. 

46 

Usually 0 chooser can find 0 within several tens of 

meters of the requested elevation. If the 0 surface is 

strongly tilted with respect to the surrounding pressure 

surfaces, and the destination docs not lie on or near a grid 

point, a difference of a few hundreds of meters could occur 

in arrival height of the trajectory versus the requested 

height. The error occurs due to spatial interpolation on the 

isobaric and isentropic surfaces. When the 0 chosen results 

in an elevation that differs from the requested elevation by 

more than 50 m, a 1° adjustment is made to 0, and the 

elevation is recomputed and rechecked against the 

requested elevation. This procedure may have to be 

iterated several times until the actual and the requested 

elevations differ by fewer than 50 m. 

Theta chooser is a tool that is helpful when the potential 

temperature of the trajectory is not known. In the future it 

will also be used to adjust 1he 0 surface as its elevation 

changes in response to synoptic and seasonal variations of 

temperature and pressure. This is important for the 

construction of long-term climatologies because it will 

produce trajectories that arrive at approximately the same 

elevation each day. 

In the past, there were problems associated with using 

the isen tropic model below about 1500 m ms) and over 

mountainous terrain. Trajectories would often "crash" into 

the ground because the 0 surfaces were bumpy or traveled 

through mountains. Although isentropic trajec tories are not 

always suitable in the near-surface layer, air traveling to 

this altitude may encounter significant vt:r1i1.:al motions 

along the way; for example, as a res ult of travel around a 

high-pressure system or transport from colder regions at 

higher latitudes. It is recognized !ha! isobaric trajectories 

used in the past to model air flow at lower altitudes, are not 

the best solution under these conditions because they do not 

take into account the vertical motions !hat transport the air 

parcels to these lower altitudes. Experimental changes to 

the isentropic model are aimed at solving these problems. 

With these changes, trajectories are calculated on a given 

isentropic surface until they come within I 00 m of the 

topography. At this poin t, trajectories are promoted by 

winds averaged in the layer 100-600 m above the ground 

which is assumed 10 be representative o f the mixed 

boundary layer above the friction layer. If 100 m ms! is 

below 1000 hPa, winds at 1000 hPa are us ed as the lower 

limit of the surface layer. It is known that the air docs not 

simply stop when the potential temperature surface 

becomes undefined or when it approaches a mountain 

barrier. By using surface layer winds as an approximation 

of air movement when the isentropic surface becomes 

undefined, the usefulness of the trajectory model can be 

extended. 

Figure 3.16 shows trajectories arriving at BRW on 

January 15, 1985. The plot of vertical motion at the bottom 

indicates that air parcels descended about l km in 5 days as 

they approached BRW. Theta levels of 257.SK for 00 UT 

and 256.2K for 12 UT were selected by the 0 chooser in the 
so• N 

120° E 

140 

160° E 

' . 180° w 140° w E"'k::::16o0 

:.: . w 

;:: - - .-· .. - ::c .. c.:> . 

w 

::r: 0 1 I I 

0 I 2 3 4 5 67 

DAYS FROM BRW 

- 100° w 

I 

8 

SOLID - 00 UT 

DASH - 12 UT 

I I 

g 10 

Fig. 3.16. Hybrid trajectories arriving at BRW on January 15, 1985, al 

500 m elevation (see text). 

previous step so that trajectories arrive at 500 m. Figure 

3.17 depicts trajectories for February 2, 1985. The 8 

surfaces were adjusted to 265.6K for 00 UT and 265.9K for 

12 UT lo be 500 m elevation al BRW. The trajectories 

show flow from the southeast over mountainous terrain (the 

Brooks Range and the Alaskan Range). The European 

Centre for Medium-Range Weather Forecasts suppl ied the 

so• N -' . . . 

120° E 

140 

160° E 

r~·.l40°W 

:I: 0 1 I I 

0 2 3 4 5 6 7 

DAYS FROM BRW 

- 100° w 

I 

8 

SOIJD - 00 UT 

DASH - 12 UT 

I I 

g to 

fig. 3. 17. Hybrid trajectories arriving at 13RW on fcbruary 2, 1985, at 

500 m elevation (see text). 

47 

2.5° gridded data of winds, temperature, and height used in 

the trajectory calculations. Topography is smoothed over a 

2.5° grid. Air traveling in the boundary layer mode rather 

than the isenlropic mode is assigned pressure, temperature, 

and height of the surface, interpolated bilinearly from the 

four surrounding grid points. During transitions of mode, 

some interpolations in space and time may use data from 

both modes. 

These modifications to the trajectory program are still 

considered experimental. If all goes well, after further 

review and refinement, a similar hybrid version of the 

traj ectory program will be used lo construct a near surface 

pseudo-iscntropic flow climatology for BRW. 

3.2. SPECIAL PROJECT - A DECREASE IN ARCTIC 

HAZEATilRW 

Introduction 

The "Arctic haze" as an Arctic-wide phenomenon has 

been the subject of intense interest since the first aerosol 

chemical analyses of Barrow samples by Rahn et al. 

[ 1977]. although the phenomenon was first discussed in the 

literature by Mitchell [ 1957). Excellent reviews of the 

subject were provided by Barrie [1986) and Shaw and 

Khalil [ 1989). 

Continuous aerosol measurements were initiated al BRW 

in May 1976 [Bod/zaine, 1989) with the installation of a CN 

counter for the measurement of the particle number 

concentration and a four-wavelength nephelometer for the 

measurement of aerosol scattering extinction coefficient 

(cr,p). Optical depth (1:) measurements were initiated in 

1976 using wideband spectral pyrheliometers [Dutton and 

Christy, 1992). Surface-based aerosol and 1: measurements 

at BRW were presented by Bod/zaine et al. [1984, 1989) 

and Dutton el al. (1 984, 1989). 

The purpose of this brief report is to show statistically 

significant long-term decreases since 1982 of March-April 

cr,P and 1: measurements. March-April is the time of year 

when the Arctic haze caused by long-range transport is 

most evident in the vicinity of Barrow [Bodlzaine and 

Du/Ion, 1993). 

I 11strume11tatio11 

Aerosol scattering extinction is measured continuously at 

BRW with an MRI four-wavelength nephelometcr similar 

to the design of Ahlquist and Charlson (1969]. A rotating 

filler wheel in front of the photodetector allows continuous 

measurements at 450, 550, 700, and 850 nm. This 

instrument can measure aerosol scatter as low as about I0-7 

m· 1 (about 1 % of Rayleigh scatter by air molecules) at an 

averaging time of about 1 hour. The nephelometer is 

calibrated every 2 months by filling it with C02 gas and 

adjusting the output of the instrument to give the known 

scattering coefficients of C02. The accuracy of 

nephclomcter data is generally accepted to be about ±20%. 

The direct solar beam has been measured at BRW since 

1976 using a F\VNIP with wide-band Schott glass cutoff 
fillers. The 't data for the 0.3-0.69 μm wavelength band 

were derived from the pyrhcliomctric data using the 

spectral one-layer radiative transfer model of Bird and 

Riordan [ 1986]. This wide-band method has proven 

sufficiently stable to provide an excellent 't record 

beginning in 1976. The BRW instrument has been 

calibrated by a comparison with a traveling standard at 

about 2-year intervals. The calibration of the traveling 

standard has been maintained by comparison with an 

absolute cavity laboratory standard in Boulder, Colorado. 

The measurement accuracy for computed o is about ±0.04 

with an overall precision of better than ±0.02. 

Data Analysis 

Monthly means of o,P (550 nm) and 't arc presented in 

Figure 3.18. Both data sets clearly show an annual cycle 

with a maximum in March-April, known as the "Arctic 

haze" phenomenon, which is caused by long-range 

transport from industrial regions in the springtime. Osp and 

't reached monthly mean values as high as about 2 x 10-5 

m·t and 0.3 respectively in March-April, and as low as 10-6 

m·t and 0.05 in the summertime. The 't data set shown here 

was cut off just prior to the stratospheric aerosol innux 

from the Pinatubo eruption in 1991. The 't data in Figure 

3.18 have not been corrected for the effects of volcanic 

eruptions. However, volcanic corrections were included in 

further analyses presented here. 

Because 't is measured over the entire vertical column, 

the data can be significantly inOuenccd by volcanic 

eruptions that inject aerosol into the stratosphere. During 

the time period under study, four eruptions may have 

affected the BRW 't data: (I) Nyamuragira (December 20, 

1981); (2) El Chichon (April 4, 1982); (3) Nevada de! Ruiz 

(November 13, 1985); and (4) Pinatubo (June 14, 1991). 

o~-:1-~---~~-'-~--'~~_._~__.~~_._~__.~~-+-

o.2S 

0.2 

"" 0.15 

0.1 

0.05 

3 

·e 2.5 

b 2 ~ 

~ 1.5 

t::>" 

0.5 

81 

83 87 89 91 

83 85 87 YEAR 89 91 

rig. 3.18. Monthly means of -r (a) and a,P (b) for 1977-1992 at 13arrow, 

Alaska. The effects of El Chichon have not been removed, and the 't 

data have been tcnninated in 1991 to avoid the effects of Pinatubo. 

48 

Corrections for the effects of Nyamuragira and Nevada de! 

Ruiz were made on the basis of balloon measurements near 

Laramie, Wyoming [D. Hofmann, personal communication]. and El Chichon on the basis of Du11on et al. 

[1984]. The Pinatubo contribution was removed by 

assuming that the 1992 data would have been the same as 

in 1991. However, the 1992 't data point was omitted from 

the trend analysis described below because of the 

uncertainty of the Pinatubo contribution. A 1-ycar efolding decay time was assumed for each volcanic pulse . It 

should be noted that in Apri l 1986, aircraft measurements 

gave stratospheric 't values near 0.00 and never larger than 

0.03 [Du11on et al., 1989). 

To investigate the time of year that shows the largest 

long-term decrease, a trend line for Osp during 1982-1992 

was calculated for each 2-day period of the year. The 

March 7-May 5 time period showed downward trends 

significantly larger than the rest of the year. Next, the 2-

day mean data sets were used to calculate a March 7-May 5 

mean and standard deviation for each year. These data are 

plotted in Figure 3.19 where the standard error (S.E.) for 

each data point is shown. A linear regression for 1982-

1992 was calculated where each point was weighted 

inversely by (3 S.E.)2 (99% confidence level) for that 

point. The slope of the trend line is -9.34 x J0-7 ± 1.95 x 

10-7 nrt yr·l, at the 99% confidence level, and with a 

correlation coefficient of r = -0.934, a significant 

downward trend for this data set. 

A similar analysis was performed on the 1982-1991 't 

data set. A linear regression gave a slope of -0.0032 

±0.0029 yr·t , at the 95% con fidence level , with a 

correlation coefficient of r = -0.640. The 't data along with 

the S.E. for each data point are also shown in Figure 3.19. 

The correlation coefficient between the Osp and 't data sets 

for 1977-1991 is r = 0.760 at the 99% confidence level. 

Discussion 

According to Figure 3.19, the Arctic haze reached a peak 

in 1982 and then declined thereafter. A similar long-term 

trend in opti cal depth was shown by Radionov and 

Marshunova [ 1992). It is well known that the primary 

contributors to Arctic haze were Europe and Asia, 

including the former Soviet Union [Rahn and Lowe11thal, 

1984 ; Barrie et al., 1989) . Although the exact percentages 

of contributions may be open to question, Europe and Asia 

are considered to be the primary source regions for the 

BRW si te. 

A decrease by approximately a factor of two in the Arctic 

haze phenomenon during 1982-1992, as shown here in the 

Osp and 't data, implies a decrease in the output of pollution 

aerosol by Europe and the Soviet Union. Since it is known 

that during 1980-1989 the Soviet Union increased the use 

of natural gas and decreased the use of coal and oil, thus 

decreasing S02 and particulate emissions [J. Pacyna, 

personal communication], part of the long-term decrease of 

Osp and 't at BRW may be attributed to this decline. 
0.3 

A) 

0.2 

I0.1 

0 

•> .....-. 

i 

E 

"' I 

0 

-.. t::> 

0 

7 79 •• •l ~ 

YEAR • .. 91 93 

fig. 3.19. Means and slandard errors of 't (A), and cr,P (550 run) (13), 

calculated from 2-d means for :-Vlarch 7-May 5 for each year, and plotted 

as a time series for 1977- 1992. The straight dashed lines show linear 

regressions for 1982-1992 calculated by wcigliting each data point 

inversely by (3 S.E.)i (99% confidence level). The short-dashed line 

shows 1: before volcanic corrections were applied. Details of the 

regression lines arc given in the text. 

Stricter pollution controls in western Europe over this time 

period may have contributed to our long-term decrease in 

O"sp and 'l. 

It is not entirely clear what effect this decrease of Arctic 

haze might have on climate. However, Valero a11d 

Ackerman (1986] suggested heating rates of 0.15-0.25 K d·l 

on the basis of measurements made in the spring of 1983. 

This is almost entirely due to absorption because the effect 

of a scattering aerosol above a bright surface is small. 

Therefore, in the absence of detailed aerosol size and 

chemistry information, and assuming that the single scatter 

albedo remained constant, it is suggested that the decrease 

of the Arcti c haze phenomenon shown here would result in 

a 1992 warming of only about half the 1983 warming 

suggested by \! alero a11d /\ckcrman [ 1986]. 

Co11clusio11 s 

On the basis of the BR \V record of O"sp and 'C obtained 

over the time period 1976-1992, the following conclusions 

may be drawn: (1) The phenomenon known as the Arctic 

haze, as observed at BR\V, reached a maximum in 1982 and 

then decreased over the remainder of the time period 

through 1992. (2) This decrease was most likely due to a 

decrease of pollution aerosols that originated in Europe and 

the Soviet Union. (3) The effect of this decrease on 

climate is uncertain, but would most likely lead to a 

warming effect about half that estimated for Arctic haze for 

1983 by Valero and /\ckerma11 [ 1986]. 

49 

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Hickey, J.R., D.B. Daniels, and D.W. Nelson, Au1oma1ion of cavity 

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Hofmann, D.J., and S.J. Oltmans, Anomalous Antarctic ozone 

during 1992: Evidence for Pinatubo volcanic aeroso l effects, J. 

Geophys. Res., in press, 1993. 

Hofmann, D.J., S.J. Oltmans, J.M. Harris, W.D. Komhyr, J.A. 

Lath rop, T. DcFoor, and D. Kun iyuki, Ozonesonde measurements 

at Hilo, Hawaii, following the eruption of Mt. Pinatubo, Geophys. 

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1985 ozone absorption coefficients for use with Dobson ozone 

specirophotometers, J. Geophys. Res., in press, l 993a. 

50 

Komhyr, W.D., A. Lapworth, and K. Vanicek, Dobson Data Reevaluation Handbook, edited by W.G. Planet and R.D. Bojkov, 

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Washington, DC, I 993b. 

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Oltmans, S.J., and H. Levy II, Surface ozone measurements from a 

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Radionov, V.F., and M.S. Marshunova, Long-term variations in the 

turbidity of the Arctic atmosphere in Russia, Atmos. Ocean, 30, 531-

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209-215, 1957. 
4. Acquisition and Data Management Division 

G. HERBERT (EDITOR), M. BrENIULIS, T. MEFFORD, AND K. T!IAUT 

4.1. CONTINUING PROGRAi\IS 

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, wind speed, station pressure, air and 

dewpoint temperature, and precipitation amount. The 16-year 

station climatologies arc an important record for the 

interpretation of measured values of aerosols, trace gases, and 

climatic change. The sensors currently in use were selected not 

only for high accuracy, but also for ruggedness, to minimize 

failures in the extreme conditions of the polar region (Table 

4.1). To the extent that is practical, WMO siting standards 

were followed. 

On DOY 336, air temperature sensor 291 was moved to a 

height of 20.7 m from a height of 21. m. On DOY 350, the 

primary anemometer 826, was moved to a height of fl0.9 m 

from a height of 11.8 m. There were no changes in the 

instruments at BRW, MLO, or SMO in 1992. At SPO on DOY 

70, thermometer 703 was repl aced with 293 and 704 was 

replaced with 291. Table 4.1 describes the disposition of the 

sensors as of December 31, 1992. 

Barrow 

Descriptions of the BRW station and its climate are given in 

previous CMDL Swnmary Reports [e.g., DeLuisi, 1981]. Wind 

roses of hourly averages resultant wind direction and speed are 

presented in 16 direction classes and 4 speed classes (Figure 

4.1). Winds from the "clean-air" sector, north-northeastsoutheast directions occurred 55.7% of the time as compared to 

62.6% for the 15-year climatology. Wind speeds greater than 

10 m s-1 occurred 14.3% of the time as compared to 11.5% for 

the 15-year climatology. The year's maximum hourly average 

wind speed of 24 m s-1 occurred on December 4, which ties the 

all time record for December. New maximum wind speeds 

were measured during the months of April and June as well. 

The average temperature for 1992 tied the climatological 

average of -12.7°C (Table 4.2). Like 1991, the monthly mean 

pressure was not significantly different from nomrnl. 

MaunaLoa 

In this report, the climatology of /\!LO is regarded as 

consisting of two distinct regimes because the bimodal 

distribution of the wind direction changes with the time of day. 

The night (downslope) period (1800-0600 LST) and the day 

(upslope) period (0600- 1800 LST) define the two regimes. 

The 15-year night and day wind roses illustrate the two distinct 

wind patterns (Figure 4.2). 

Night Regime. The 15-year wind rose (Figure 4.2), 

shows that 92.6% of all the winds observed had a southerly 

component with south-southeast dominating. Storm related 

winds (WS ~ 10 m s-1) with westerly and easterly 

components are evident in both the 1992 and 15-year wind 

rose. The 1992 wind rose (Figure 4.3) shows these winds 

occurred 5.5% of the time as compared to 7 .1 % for the 15-

year climatology. The upslope or northerly component 

winds (north-northwest through east-northeast) about 5% of 

the time, are primarily the results of the daytime, upslope 

flow extending into the evening hours. A new maximum 

TABLE 4.1. CMDL Meteorological Sensor Deployment December 31, 1992 

BRW MLO SMO SPO 

Serial Elevation, Serial Elevation, Serial Elevation, Serial Elevation, 

Sensor No. m No. m No. m :\o. m 

Primary anemometer• 576 16.7 [1 829] 8.5 [883] 14.3 [826) 10.9 

Secondary anemometer• [ 782] 38.5 

Pressure lransducert 2366 9 225 3403 752 30 28 2840 

Mercurial barometer 641 9 278 3403 96 1 30 1215 2840 

Air temperature A:j: 8801 2.5 8805 1.7 8803 9.8 (293+} 2.0 

Air temperature B§:j: 8802 15.3 8809 37.8 8806 2.3 ([291+)] 20.7 

Air temperature C:j: 8 3.1 46 2.0 50 9.8 835+ 2.0 

Dewpoinl temperature hygrometer•• 8 3.1 46 2.0 50 9.8 3720 2.0 

•Aerovane, Bendix, Inc., model no. 141, Baltimore, Maryland 

tPressurc transducer, Rosemount, Inc., model no. 1201 Fl b, Minneapolis, Minnesota. Heights of all pressure sensors arc given with respect to MSL 

:j:Lincarized thermistors, Yellow Springs Inst. Co., model no. 44212, Yellow Springs, Ohio, except al SPO 

+Platinum resistance thermometer, Yellow Springs Inst. Co., model no. RTD-385, Yellow Springs, Ohio 

§Thermometer, positioned at the lop of the local sampling tower lo facilitate an estimation of boundary layer stability 

.. Hygrothermometer, Technical Servi ces Laboratory model no. 1063, Fort Walton Beach, Florida 

[]Instrument put in service in 1991 

{)Instrument put in service in 1992 

51 
BARROW 

1992 

\ 

WltlD SPEED (ll/S) 

-- 5 'YS < 5 

C7l2'Z2ZZZ'd5 ' WS < 10 

WS ~ 10 

Prevailing wind 

direction 

Average wind 

...... 

..... ~ 

WIND ROSE 

' 

\ 

\ \. \ ... 

\ \ 

\ \.,, \ ' 

.'/

;-- ·,) . ··_~;(-

•.. I I ! / t . ; i i I I / ' I I;· / / ... / / 

.< .. I .. ·" ·· ....... 

BARROW 

1977-91 

WltlD SPEED (ll/S) 

·- N: . ·----~:-~: ·: ·,· .. , .. .-··"°· ···· I ··• •.• 

...-.. ---·· ··-·--.. 

.......... ~-. --.. ···- ··· ·· ·~--· .. -·· 

............ ... ______ ·~ ..... ----·· 

··_:-· -- -···-~::.:-...-- WltlO Ftu:Q 

>: 

--5' ws < 5 

~5' W'S< 10 

WS ~ 10 

····--. .. 

Fig. 4.1. Wind rose of surface winds for BRW for 1992 (left} and 1977-1990 (right}. 

TABLE 4.2. BRW 1992 Monthly Climate Summary 

Jan. Feb. March April May June July Aug. Sept. Oct. :\ov. 

E:\E NE E:SE E:\E WSW E:\E E E E:\E ENE E:\E 

7.5 5.5 5.0 6.5 6.8 5.9 5.8 6.6 6.1 6.9 7.2 

17 15 13 19 13 17 13 13 17 17 20 

60 107 80 58 187 238 86 289 254 156 57 

WIND ROSE 

llltlD FREQ 

>: 

Dec. 1992 

NE E:\E 

8.1 6.5 

24 24 

238 238 

speed (m s·t) 

Maximum wind 

speed* (m s·t) 

Direction of max. 

wind* (deg.) 

Average station 

pressure (hPa) 

~laximum pressure• 

(hPa) 

1015.5 1021.5 10 13.5 1021.0 1011.1 1014.1 1015.1 1008.7 1014.7 1008.7 1010.4 1015.0 1014.l 

~1inimum pressure• 

(hPa) 

Average air 

lemperatu re ('C) 

~laximum temperature• 

('C) 

:-.tinimum temperature• 

('C) 

Average dewpoint 

temperature ('C) 

~laximum dewpoint 

temperature ('C) 

inimum dewpoint 

temperature ('C) 

Precipitation (mm) 

1033 

1002 

-28.4 

-18 

-42 

-31.3 

-21 

-45 

0 

1045 1033 

993 988 

-29.2 -23.3 

-8 -11 

-38 -41 

-32.0 -25.8 

-9 -12 

-41 -45 

0 0 

1040 1022 1026 

1002 997 997 

-17.5 -6.7 I.I 

-6 3 11 

-29 -25 -6 

-19.7 -8.6 -0.6 

-8 7 

-3 1 -27 -8 

0 0 

1026 1024 1027 1030 1038 10~4 10~5 

1005 990 995 980 980 982 980 

2.6 2.9 -3.6 -10.4 -1 8.8 -23.2 -12.7 

12 16 4 3 -5 -5 16 

-4 -3 -14 -2 1 -37 -37 -42 

0.9 1.3 -5.5 -12.1 -20.9 -25.5 -14.8 

9 10 3 0 -6 -7 10 

-5 -4 -15 -24 -·10 -41 -45 

0 0 0 0 3 

Instrument heigh1s: wind, 16.7 m; pressure, 9 m (~ISL); air temperature, 2.5 m; de\\ point tcmpera1urc, 3.1 m. Wind and temp<:ra1ure ins1nunents arc 

on tower 25 m nonhcast of the main building. 

• :Vla~imum and minimum values are hourly averages. 

52 
MAUNA LOA 

1977- 91 

.•. ~---. 

_?-. 

_ ... -· ...... · 

_ .... . \:__ / 

· . .,(.. -· 

i .. · '··.._.-_,,.. _ ..... - ---· ....... - , ,.... /.· ·....,, ... - //'"· .. . ... 

i ! / ./ ... -· ... / ! / / ,/ /~ 

I ! ( i W\-Y\\\h 

:•. .. --· ·· .... 

).. -.... WIND SPEED (11/ S) ·-...... 

--5,WS<5 

iz=5' WS < 10 

WS ~ 10 

: -·-···--·-1·-- ----... ···-.. 

-·········-·:-----.. ........ _ 

WIND ROSE 

··-... ·· ... ________ _ 

\ 

\ 

\ 

\ 

MAUNA LOA WIND ROSE 

1977-91 .-····· ... ·· .----- -------- ; '···-... 

.... -· _ .. ··• 

. .. -· 

';.{ __ .,..-·· 

. -··· '· .. ..,,..·· 

. l 

/ ..•.•• / / ...... 

: ! ,./ / 

'

{ ! ! / 

: ! f f --'t-t-·-i -----i·-··l··-···!-··-·'----l. i . i \ \ \ 

; 

\,_ \ \ \ \ \. \ \ •. \_ ... .\ \ .. \. \ . \ 

··., .. 

·· ... ..... \. .. 

.. ·· ·.. ·· ....... :··. "· .. 

WIND SPEED (11/ S) 

--5,WS<~ 

=~' WS < 10 

WS i 10 

.......... _ 

····· -·······-~·-·· -. 

-·-······r-···----- · .. _ 

···--. _,~ ·. ··-.... ·-.. _ ··-.,../ ·-. ·-.... _ ··-. 

··-.. ·--.......... ..> .. ~ ... ··-.. 

· ... _ 

\ .. 

\ \ ... 

\ \ 

\. \ ·, \ \. ..... \.. ' \ \ 

........ \._ '\., \. \ \,_ \ . \,, . \ \ \ ~ : 

--;;-;-+tr 

,////// . . ...-"' .. a:. _.-/ ./ j fo· :..<· ... i I 

··· ..... 

·· .... ... ___ r--· ······ ··- ··-~--·---· ··· 

.. ·· -..... /.... / __ ...... · 

__ .. !(;··· ./><" / . .. ~ 

··· ... .... ·· .-· ,/ 

./ 

/ 

..... ··· ·····-······-+···-···· ...... · 

··--------s------- --·- ---···· 

... ·· .··· , ... J'· 

•... ·· lflND f'REQ 

l!; 

Fig. 4.2. Wind roses of the surface winds for MLO for 1977-1991 night (lef1) and day(right). The distribution of re sultant wind direction and 

speed are given in units of percent occurence for the 15-year period. Wind speed is displayed as a function of direc1ion in three speed clases. 

MAUNA LOA 

1992 .-· 

! 

I ! 

I 

/ 

! 

! 

\ 

.. 

/ _ .... -···· 

WIND ROSE WIND ROSE 

·-... 

Fig. 4.3. Wind roses of the surface winds for MLO for 1992 night (left) and day(righ1). The dis1ribution of resultant wind direc1ion and 

speed are given in units of percent occurence for the year. Wind speed is displayed as a function of direction in 1hree speed cla ses. 

53 
TABLE 4.3. MLO 1992 Monthly Climate Swnmary 

Jan. Feb. March 

Prevailing wind SSW SW SSE 

direction 

Average wind 4.6 5.4 3.3 

speed (m s·1) 

Maitimum wind 15 13 9 

speed• (m s"1

) 

Direct.ion of max. 159 204 150 

wind• (deg.) 

Average station 679.4 678.4 680.0 

pressure (hPa) 

Maximum pressure• 683 683 683 

(hPa) 

Minimum pressure• 673 675 677 

(hPa) 

Average air 4.2 3.5 4.0 

temperature ('C) 

Maximum temperature• 10 12 12 

('C) 

Minimum 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

) 

-3 

-13.2 

4 

-28 

11 

NW 

4.1 

-2 -1 

-15.5 -17.2 

4 4 

-29 -33 

0 0 

SW NNE 

5.6 3.5 

'.vlaximum wind 13 14 9 

speed• (m s"1

) 

Direction of max. 157 235 152 

wind• (deg.) 

Average station 679.4 678.4 680.1 

pressure (hPa) 

Maximum pressure• 684 683 682 

(hPa) 

Minimum pressure• 673 675 678 

(hPa) 

Average air 8.5 7.6 9.1 

temperature ('C) 

Max imum temperature• 17 16 15 

('C) 

Minimum temperature• 

('C) 

Average dewpoint 

temperature ('C) 

Maximum dewpoint 

temperature ('C) 

Minimum dewpoint 

temperature ('C) 

Precipitation (mm) 

-3 

-7.0 

8 

-29 

25 

-1 -1 

-10.0 -7.9 

5 7 

-29 -29 

5 0 

April May June July Aug. Sept. Oct. 

Night 

SW SW SSE SSE SSE SSE SSE 

4.4 5.4 5.2 4.2 4.1 3.3 4.7 

13 14 11 13 11 10 16 

222 207 160 159 163 163 149 

679.l 679.6 680.9 680.7 681.7 680.J 680.6 

684 684 684 685 684 685 684 

675 676 678 678 680 677 677 

5.9 6.0 7.5 6.5 6.2 6.1 6.0 

13 12 13 13 13 11 JO 

3 2 2 2 2 3 

-14.4 -10.5 -13.5 -7.4 -3.4 -0.8 -7.J 

JO 7 7 8 9 9 7 

-29 -34 -23 -24 -19 -21 -31 

0 0 0 9 27 14 4 

Day 

NNW WNW NE NNE NNW NW N 

5.1 6.0 4.4 4.0 3.6 3.4 4.3 

15 13 11 11 10 17 12 

234 243 153 98 169 168 137 

679.2 679.8 681.1 680.9 681.8 680.2 680.8 

684 684 684 685 684 684 684 

675 676 678 678 680 678 677 

10.7 11.1 12.7 I 1.0 10.6 10.0 10.3 

18 17 18 18 17 18 16 

2 3 4 4 3 3 3 

-4.9 -3.9 -4.3 0. 1 1.2 3.0 -3.2 

13 II 8 9 9 10 8 

-26 -33 -21 -20 -19 -21 -29 

0 0 0 60 6 1 116 6 

:\ov. Dec. 1992 

SSE SE SSE 

5.1 5.6 4.6 

14 13 16 

153 ISO 149 

679.8 679.l 680.0 

683 684 685 

677 674 673 

5.2 4.0 5.4 

9 9 13 

0 -3 

-8.0 -8.4 -10.0 

7 4 JO 

-30 -26 -34 

51 7 124 

SE SSE NNE 

4.6 5.2 4.5 

14 13 17 

155 139 168 

679.8 679.l 680.0 

683 685 685 

676 674 673 

9.0 7.3 9.8 

IS 14 18 

-3 

-5.7 -5.3 -4.0 

9 8 13 

-30 -26 -33 

58 32 364 

Instrument heights: wind, 8.5 m; pressure, 3403 m (MSL); air temperamre,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. 

54 
TABLE 4.4. SMO 1992 Monthly Climate Summary 

Prevailing wind 

direction 

Average wind 

speed (m s·1) 

'.'vlaximum wind 

speed* (m s"1) 

Direction of max. 

wind• (deg.) 

Average station 

pressure (hPa) 

:>.1aximum 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. 

SSE 

3.7 

10 

149 

998.1 

1003 

991 

27.6 

32 

22 

23.2 

25 

20 

194 

Feb. March 

SE SE 

4.7 3.9 

11 10 

147 105 

999.0 997.3 

1004 1005 

996 987 

27.7 27.6 

32 3 1 

21 24 

24.0 24.4 

26 26 

21 20 

216 222 

April May June July Aug. Sept. Oct. Nov. Dec. 1992 

SE SE SE SE ESE ESE E SE E SE 

4.5 4.2 5.0 4.0 3.0 3.2 2.2 2.6 1.7 3.6 

11 8 9 8 9 7 8 6 4 11 

142 150 128 109 125 132 128 139 100 142 

999.7 1001.1 1001.4 1002.3 1002.3 1001.5 999.8 1000.1 997 .7 I 000.0 

1004 . 1005 1005 1006 1006 1005 1004 1004 1003 1006 

992 996 998 998 998 998 995 995 990 987 

27.6 27.4 27.3 27.3 27.4 27.8 28.2 27.5 28.8 27.7 

31 31 33 34 34 34 36 36 38 38 

21 23 2 1 

24.I 23.8 21.9 22.5 22.8 22.7 22.4 22.4 23.4 23.0 

25 25 26 

22 19 18 17 20 19 16 17 21 16 

509 170 33 60 151 96 166 219 158 2 194 

Instrument heights: wind, 13.7 m; pressure, 30 m (:-.1SL); air temperature, 9 m Wind and temperature instruments are on Lauagae Ridge, l lOm 

northeast of !he main building. Pressure sensors are in the main building. 

•Maximum and minimum values are hourly averages. 

SAMOA 

1977- 91 

WIND SPEED (11/S) 

--5 S WS < 5 

=z!5 'WS < 10 

WS ~ 10 

.... -· -t- . ·-. ····· I ·~-------· ·-········ ..... 

.... :.~~-:_~-· -- ---==-=~~~ 

WIND ROSE 

WIND rREQ 

x 

Fig. 4.4. Wind roses of !he surface winds for SMO fo r 1992 (left) and 1977-1991 (right). The distribution of resultant wind direc1ion and speed are 

given in units of percent occurence for 1he year and 15-year period, respectively. Wind speed is displayed as a function of direction in three speed clases. 

SS 
Prevailing wind 

direction 

Average wind 

speed (m s"1) 

Maximum wind 

speed• (m s"1

) 

Direction of max. 

wind• (deg.) 

Average station 

pressure (hPa) 

Maximum pressure• 

(hPa) 

Minimwn pressure• 

(hPa) 

Average air 

temperature ('C) 

Maximum temperature• 

('C) 

Minimwn temperature• 

('C) 

Average dewpoint 

temperature ("C) 

Maximum dewpoint 

temperature ('C) 

Minimum dewpoint 

temperature ('C) 

Precipitation (mm) 

Jan. 

N 

3.7 

8 

357 

687.2 

698 

679 

-28.0 

-23 

-34 

-29.3 

-25 

-35 

0 

TABLE 4.5. SPO 1992 Monthly Climate Summary 

Feb. March April May June July Aug. Sept. 

ENE ENE E E N:\E E E N 

5.2 5.9 5.8 4.8 7.3 4.7 6.3 7.0 

11 II 14 13 15 11 13 14 

346 107 313 8 7 354 16 2 

687.0 680.1 678.4 683.8 684.3 675.6 671.0 670.0 

696 693 695 697 702 695 686 696 

676 671 664 671 662 658 649 647 

-41.7 -55.7 -52.8 -58.4 -54 .9 -59.7 -60.1 -57.3 

-31 -43 -31 -46 -38 -40 -42 -33 

-54 -64 -68 -68 -71 -71 -74 -77 

-42.5 -55.4 -52. l -57 .7 -54 .0 -58. 1 -59.2 -56.3 

-30 -44 -30 -46 -38 -40 -42 -33 

-54 -63 -66 -66 -66 -67 -69 -70 

0 0 0 0 0 0 0 0 

Oct. Nov. Dec. 1992 

ENE N:\'E E:\'E ENE 

5.3 5.9 3.2 5.4 

12 11 7 15 

306 352 278 7 

678.7 676.7 684.3 679.7 

689 690 690 702 

668 667 677 647 

-46.5 -38.3 -28.4 -48.6 

-30 -31 -22 -22 

-62 -47 -34 -77 

-45.5 -38.7 -30.1 -48.3 

-30 -31 -25 -25 

-60 -46 -36 -70 

0 0 0 0 

Instrument height~: wind, 12.2 m; pressure, 284 1 (MSL); air temperature, 2.2 m. The anemometer and thermometer arc on a tower 100 m grid eastsoutheast of CAF. Pressure measurements are made inside CAF. 

•Maximum and minimwn values are hourly averages. 

WIND ROSE 

WlHO f'REQ 

" 

SOUTH POLE .... 1977-91 .· .. , 

WIND ROSE 

Fig. 4.5. Wind roses of the surface winds for SPO for 1992 (left} and 1977-1991 (right}. The distribution of resultant wind direction and 

speed are given in units of percent occurence for the year. Wind speed is displayed as a function of direction in three speed clases. 

56 
TABLE4.6a. CMDL CAMS Operations Summary, 1992 

Expec1ed No. of Percent Daia Caplure 

Individual CAMS Blocks 1992 BRW MLO SMO SPO 

ASR 8784 98.51% (131] 99.10% (79] 99.09% (80] 94.18%(511) 

C02 8784 98.48% [ 133] 99.87% [I I] 97.29% (238] 96.40% (316] 

M03 4392 99. 16% (37] 99.79% [9] 96.95% (134] 99.95% [2] 

Total 21960 98.72% (301] 99.59% [99) 97.78% (452] 96.84% [829) 

TABLE4.6b CMDL CAMS Operational Summary, 1992 

Expecled No. of Blocks Recorded and [Blocks Missing) 

Block Type Description Blocks 1992 BRW MLO S~lO SPO 

A Hourly aerosol data 2196 2165 (31) 2176 (20] 2176 (20] 2069 (127] 

B Secondary aerosol data Variable 272 824 1244 993 

c Hourly C02 data 8732• 8290 (442] 8404 [328] 8207 (525) 8133 (599] 

D Daily C02 data 366 366 367 363 [3] 354 (12) 

E Hourly C02 calibration data Variablet 361 369 339 335 

F C02 calibration report 52 52 53 49 [3] 53 

H Daily aerosol data 366 366 373 366 343 [23) 

( Meieorological calibration 366 364 [2] 365 [l] 356 [ 10] 366 

M Hourly meleorological data 4392 4355 (37] 4383 [9] 4258 (134] 4390 (2) 

N Surface ozone calibration 52 51 [l] 56 28 (24) 0 

0 Daily surface ozone da1a 366 367 366 364 [2] 366 

s Hourly solar radiation data 8784 8653 (131) 8705 [79] 8704 [80) 8273(511) 

T Daily solar radia1ion data 366 359 [7] 361 [5) 362 (4) 342 [24) 

w Daily mcieorological dala 366 366 366 364 [21 366 

•Nominal block counl equal 10 total hours in year less 52 7-hour calibraiion periods. 

tNominal block count equal to 52 7-hour calibration periods. 

hourly average wind speed of 16 m s·I occurred during the 

month of October. The average air temperature for 1992 

was S.4°C, which is 0.7°C higher than the IS-year average 

while the station pressure was 0.6 mb below the IS-year 

average. 

Day Regime. The lS-year wind rose (Figure 4.2) 

indicates that light wind speeds in the west-northwest 

through east-northeast sectors were observed S8.9% of the 

time. This represents the upslope flow attributed to the 

daytime heating of Mauna Loa. The 1992 wind rose 

(Figure 4.3) compares well with the 1 S-year rose in that 

northerly wind components prevail S8.6% of the time. The 

day wind rose was more uniformly distributed in the light 

wind classes than that of the night wind rose. This was due 

to the occurrence of variable wind directions during the 

transition periods of dawn and dusk, most of which were 

included in this regime. The percent frequency of 

occurrence of wind in the 10 m s· I or greater wind class for 

1992 was only 0.3% less than the IS-year average. 

The 1992 average day-night temperature difference was 

4.4°C and the average dewpoint temperature for 1992 was 

-7.0°C (Table 4.3). The year's maximum temperature of 

18°C occurred on April 20 and again on September 2S. The 

minimum temperature of -3°C occurred on January 16. The 

average station pressure for 1992 was 680.0 mb, which was 

0.6 mb below the 15-year average. Precipitation for 1992 

57 

was below normal with 488 mm as compared to 54S mm for 

the IS-year climatology. The months of March through 

June recorded no precipitation. 

Samoa 

A comparison of SMO's J 992 wind rose (Figure 4.4) with 

that of the 15-year period shows a much higher percentage 

(75.8%) of "clean air" sector winds (north-northwest 

through east-southeast) in 1992 than for the 1977-1991 

period (58.3%). (If air passing over the offshore island of 

Aunu'u is to be avoided, the south-southeast wind sector 

(2S.6%) cannot be considered in the "clean air" sector.) 

The average wind speed of 3.6 m s·I was 1.4 m s·I below 

the 15-year average. 

Station pressure was slightly above normal with an 

average of 1000.0 mb as compared to the IS-year average 

of 999.3 mb (Table 4.4). The tempe ra tures for June tied the 

record high for the month while the rest of the year set new 

monthly records. A temperature of 38°C, which occurred on 

December 24, set the all time record high temperature for 

the station. The precipitation total for the year measured 

2194 mm. which is slightly higher than the average of 2080 

mm. 

South Pole 

The distribution of the surface wind direction in 1992 

(Figure 4.5) shows a lower percentage of winds (90.3%) 
from the "clean air" sector (grid north-northwest through 

east-southeast) than the 15-year average (94 .2%). A higher 

percentage of winds in the ~10 m s·l range (4.8%) was 

observed in 1992 than the Jong term average of 4.0%. The 

average wind speed for 1992 very closely follows that of 

the 15-year average. The maximum hourly average wind 

speed was 15 m s-1 on June 19. 

While the 1992 annual average temperature was slightly 

cooler than normal, the annual average station pressure was 

slightly higher than normal (Table 4.5). During 1992, the 

minimum pressure for August tied the record for the month. 

Also, the maximum temperature for October tied its record 

for the month. The maximum temperature was -22°C while 

the minimum was -77°C. 

4.1.2. DATA MANAGE:\-IENT 

During 1992, the CAMS operated 98.2% of the time. CAMS 

gathers data from sensors that operate continuously at each of 

58 

the four CMDL observatories. The CAMS performance was 

monitored by comparing the number of data files recorded 

against those expected for the year. In CAMS, there are data 

files regularly recorded 12 or 24 times a day. In the summary 

table (Table 4.6a, b), the hourly solar radiation file was used to 

monitor the ASR CAMS. The hourly C02 data files were used 

for the C02 CAMS. The hourly average meteorological data 

file was used for the M03 CAMS. 

Due to the remoteness of the observatories, power outages 

are common and are the main reason for data loss. Hardware 

failure is another reason for data Joss. During 1992, BRW had 

the line conditioner fail, MLO had two boards fail , SMO had 

five RS422 interface boards fail, and SPO had two clock boards 

and the solar radiation preamp board fai led. 

4.2. REFERENCE 

DeLuisi, J.J. (Ed.), Geophysical Monitoring for Climatic Change, 

No. 9: Summary Report 1980, 163 pp., l\OAA Environmental 

Research Laboratories, Boulder, CO, 1981. 
5. Nitrous Oxide and Halocarbons Division 

T.H. SWANSON (EDITOR), J.W. ELKINS, J.H. BUTLER, S.A. MONTZKA, R.C. MYERS, T.M. THOMPSON, T.J. BARING, 

S.0. CUMMINGS, G.S. DUTION, A.H. HAYDEN, J.M. LOBERT, G.A. HOLCOMB, W.T. STURGES, AND T.M. GILPIN 

5.1. CONTINUING PROGRAMS 

5.1.1. FLASK SAMPLES 

Air sample pairs were collected and analyzed for CFC-I I 

(CCl3F), CFC-I2 (CC12F2). and nitrous oxide (N20) on the 

original HP 5710A GC. Both CFCs, particularly CFC-I l , 

show a decrease in growth rate during the past few years 

that is apparent at all flask locations. In 1992 the growth 

rates of CFC-11 and CFC-I2 were about 3 ppt yr·l (Figure 

5.1) and 11 ppt yr·l (Figure 5.2). For a complete discussion 

of the slowdown of the growth rates, refer to Elkins et al., 

[1993). The global slowdowns of the growth rates observed 

after 1989 are also supported by estimates of reduced 

emissions [AFEAS, I993; McFarland and Kaye, 1992) 

made by the CFC producers and are directly attributed to 

the international efforts of the Montreal Protocol [UNEP, 

I987] and voluntary reductions from producers and users to 

reduc;e stratospheric ozone depletion. If the observed 

slowdowns in the growth rates continue at 1990-1992 

levels, global atmospheric CFC-11 and -12 mixing ratios 

would reach a maximum well before the turn of the century, 

and thereafter begin to decline [Elkins et al., 1993). 

The growth rate of N20 in the northern hemisphere has 

dropped significantly in 1992 and the decline may have 

started as soon as June 1991 (Figure 5.3). From 1977 

28 0 

240 

-

Q. 

.9: 

0 20 0 x ...... u.. 0 Pt. a.now <.> 0 Nlwot AldOf 

" lhul\l loe 

0 Am. Sam~ 

180 .. c.p. Ortm 

:r South'°'• 

78 ao 82 84 86 88 90 92 

Year sin ce 1900 

Fig. 5.1. Long-term trend of CFC-I 1 (dry, ppl by mole fraction) at 

the seven flask sites. A color plot of the figure is available from the 

:\'OAII division. Each tick mark on the x-axis is January I st of 

every year. 

59 

to 1985, the growth rate was about 0.5-0.6 ppb yr·l. From 

1986 through mid-1991, the growth rate reached near 1 ppb 

yr·l, with the peak value in 1989. In 1992, the growth rate 

dropped to about 0.5 ppb yr·l. Whether this drop is a longterm feature remains to be seen. The cause of this 

slowdown is unknown because the relative magnitudes of 

the sources of atmospheric NiO are still uncertain. The gap 

in the N20 and CFC-12 data are the result of a GC problem 

that did not affect CFC-11. 

5.1.2. RITS CONTINUOUS GAS CHROMATOGRAPH 

SYSTEMS AT CMDL STATIONS AND NI WOT RIDGE 

In situ measurements of tropospheric air were made at 

the CMDL baseline stations, BRW, MLO, SMO, SPO, and 

at a cooperative site on Niwot Ridge (NWR). CMDL GCs 

made 24 measurements per day at each site. Each in situ 

GC system has three channels to measure different specie3 

of halocarbons; (1) NiO. (2) CFC-12, and (3) CFC-11, 

CFC- 113, CH3CCl3, and CCl4. Each channel is equipped 

with a chromatographic column and an electron capture 

detector (ECO). 

During a scheduled maintenance trip to SPO, a new 

sampling inlet system was installed . This system draws air 

from the meteorological tower in the clean air sector of the 

South Pole station via two sections of 0.9 cm o.d. Dekabon 

5 00 

450 

-

Q. 

.9: 40 0 

N , ~ 0 

~ u.. 3 5 0 <.> 

. 3 00 .,.J1t>A 

N 

... · " ~ 2 5 0 .. ,. 

-

7 8 80 82 84 86 88 90 92 

Year since 1900 

Fig. 5.2. Long-term trend of CFC-12 (dry, ppl by mole fraction) al 

the seven flask sites. A color plot of the figure is available from the 

NOAll division. Each tick mark on the x-axis is January I SI of 

every year. 
312 

:a 308 

~ Q, 

Q, 

-

0 / .. 304 z 

300 

77 79 8 1 83 85 87 89 9 1 93 

Year since 1900 

Fig. 5.3. Nonhem hemispheric mean mixing ratios of N20 (dry, 

ppb by mole fraction) from 1977 through 1992. A loess fit (f - 24 

months) was applied to the data. 

tubing to a continuously operating pump mounted near the 

GC system. A stream select valve allows air to be sampled 

either from one of the two lines or from calibration 

cylinders. The installation of this air sampling system at 

SPO completes the upgrade for the RITS network. At this 

time, all of the RITS systems use this air sampling method. 

During 1992, we found the mixing ratios of CFC-11 and 

CFC-12 indicate a change in trend from increasing or stable 

growth toward decreasing growth in data from SPO 

[Swanson et. al., 1992]. The daily means for NiO. CFC-12, 

CFC-11, and CCl4 from the in situ systems are shown in 

Figures 5.4-5.7, respectively. The long-term trend of 

increasing mixing ratios of the CFC's is apparent in the 

314~~~~~~-.~~ ..... ~ ..... ~~~..-~~~..-~~._...., 

310 . ~ • + • .J... .......... ~~ ......... ·~•++•+++++•i ..... :. .......... +: .......... : : : 

:0300 i i i iBRW i 

Q.314_... ........................................................ M ................. , .............. "1 

CL : : + ++•+++~ ........ 310 : ......... ·~· ......... ·~·· t 

§ 300 jNWR j :; 314-++ ................... ~ ................................... ~ ...................................... ~ 

b 310 l l ; ..... ~ ............ ~ ......... ..., c : :.. . . .. •+¥.+••+++• : : 

Q,) 308 .... ~ ........... ~ • ••• ~ l MLO ~ 

g 314 ......................... ~.~ ............. ~: ................. : ................ : ............ '"'! 

0 310 : : : : +++++++++ (.) : ...:. .. ... ~ ......... •+:t• 308 ... +::... .......... +f' .......... T·+•++•++ ~ SMO ; ~314 ........................................................................................ .++1 

z 310 

300 :+ ••••••• ·..: ++ 

...... .;.. ........ . iSPO 

. ...... .. 302..i...~...;..~~~....;..~~~-'-~~~...;._~~~~~~ ...... 

87 88 89 90 91 92 

Fig. 5.4. Daily average N20 mixing ratios in ppb from the in situ 

GCs. 

60 

300 ....... ~ ..... ~~~-.~~~ ...... ~~~~ ...... ~~~~.~ ..... ~-. 

...-.... 275 : • .;...... • ••• .;+++++++++++~++++++++++1111 ... : + .............. • ++ • : 

a.250 • .;.• ...... ~ l l BRW : 

.9:300 +.-......... _ .... _ .. ·.__ ........ ;----+;----!-;---'"i 

§ 275 ~ ++++++++++~+++++u++++.;++++++++++-M 

:; 250 l l NWR l 

.=300 ' ' ' ' ' 

c: 275 : : : : +++++++++.;.++++++++++, G> : : +++++~+++++++++++:++ : 

<.> 250 ...... ~ •••••••••• ~......... : ; MLO ~ c ++ . ' • ' 0 300~ ........................... - .................................... ~---.:i 

(.) 275 ,... 

,... 250 

: ..... ~ ......... ++;++++++++++ 

..... ••t;t••++••• : SMO : ...: I . ' ' (.)3004-__ .._ ........................................... _...j .................................. '"i 

LL. 275 ' ' CJ : +++++++ ~++++++++++ 

250 . . • ....... ~:· •;:PO :: ~ +++++++ +: + :::> 225-1-~.....:~~~.....:~~~~;.._~~~~·~~~~·~~~_.. 

87 88 89 90 91 92 

Fig. 5.5. Daily average CFC-I I mixing ratios in ppt from the in 

situ GCs. 

graph of the data. Observations seem to indicate that the 

growth rate of CFC's has decreased since 1989. To 

illustrate the change in growth rates of the CFC's, an 

estimate of the growth rates for CFC-11 and CFC-12 was 

calculated by differentiating the mixing ratio data sets. 

Prior to 1989 the growth rate of the CFC's in the 

troposphere at SPO was approximately 11 ppt yrl for CFC 

11and19 ppt yr-I for CFC 12. After 1989 the growth rate 

of CFC's is calculated to be approximately 4 ppl yrl for 

CFC 11and14 ppt yr·l for CFC 12. 

These decreased overall growth rates are encouraging. 

Our laboratory plans to continue to monitor CFC molecules 

to further document their decline and to extend our 

550-.-~ ......... ~~~ ..... ~~~--~~~ ....... ~~~..-~~--:i 

: ~ ~ ~ .......... ~ .......... ~ ;:i"' 500 l •• .;.. ....... ++++;+++++++++++ : : 

Q.450 ••• ..:.......... ~ ~ ~ BRW ~ 

.9:550~ ..................... ...i..--.... ..i...-................. --.-.. ........ ~ 

. . ... .:.. ............ J 5 500 : +++++++++++:++++++++ : 

:; 450 j ! NWR j 

.=550 . 

c 500 ~ . . . +++++~++++++++++ a» : : +++++++ ~+++++++++++;++++++ : 

g 450 .... + ....... •• 0r·· ~ ~ MLO ~ 0 550 -i.--.. _--................................................. - ............. -*:I . . . . . CJ 500 l ~ ~ ~++++++ +-+++;.++-+++++++ ... 

N ' . +· +++++++++.-:· • ,... 450 : +M++++++++++ :++ : SMO : 0 5so~-·~·-·,..~·-··~-·H·~·H·· .... :................ :._. .............. ~~ .............. ~; ............ -;i 

LL soo : +++ ~++++++++++~ 0 450 : 

~ +++++++ + ~ • • •• ... +:+:: ·s··P ... o. . :: : 

400-'-~_.;..~~~-'-~~~...;,_~~~~~~~~~~...-. . ' 

87 88 89 90 91 92 

Fig. 5.6. Daily average CFC-12 mixing ratios in ppt from the in 

situ GCs. 
120 

_ 110 .... 

C..100 Q. 

-c 120 

.2 110 .... e 100 

.... 

c 120 

Q) 

(.) 110 

c 

0 100 

(.) 120 ~ 

(.) 11 0 

(.) 100 

90 

-

-

-

.,.,.,. ,. .. .,. 

,.. . ...,.'\. -

,....... . ~- 4 

... ..,,,~ 

., .. ,. t .. "'" - BRW -

-

NWR -

-

' ~ 

MLO -

- 111111111 .... • .... ,..~.,...,,,,.,.,,..,,,._, 

SMO -

1992 

Fig. 5.7. Daily average CCJ4 mixing ratios in ppt from the in situ 

GCs. 

understanding of the transport of these compounds to the 

atmosphere over Antarctica. 

5.1.3. Low ELECTRON ATTACHMENT POTENTIAL 

SPECIES (LEAPS) 

The LEAPS program was marked by two significant 

developments in 1992. The old GC system was replaced 

with a new system that yields higher precision and better 

accuracy. Also, year-round samples from SPO were 

collected and analyzed for the first time. 

Near the end of the year, the old LEAPS analysis 

system, consisting of a Shimadzu GC-9A and Chrompack 

cryotrap, was replaced with an HP5890 Series II GC and a 

modified Tekmar dual cryo-trapping unit (Figure 5.8). The 

new analysis system yields precisions (1 s.d.) of ±0.02 ppt 

for a single measurement of halon H-1301 and ±0.04 ppt 

for H-1211, which are almost an order of magnitude better 

than with the old system. On the new system, gases of 

interest are first trapped onto a porous adsorbent (Porapak 

Q) at -60°C, separating them from 02 and N2. Sample 

volume is determi11ed accurately by monitoring the 

temperature and pressure of an evacuated bulb downstream 

of the trap. (On the old system, sample volume was 

determined indirectly by ratio to CFC- 12.) Trapped gases 

are then focused onto a megabore (0.53 mm i.d.), 

Al20 3/KC1-lined, capillary trap (Chrompack) at -60°C at 

the head of the column. Gases are injected at l00°C onto a 

wide-bore (30 m x 0.32 mm i.d.) DB- 1 column (J and W) at 

30°C. After 3 minutes, the column is heated at 8°C min-1 

to 100°C, during which most gases are eluted to the ECD's. 

The column is then purged for 5 minutes at 150°C. 

61 

'CIA»Nt. 0 .M c CAYO rRAF • 100 C 

Fig. 5.8. New GC system for analysis of LEAPS gases. 

Most flasks collected during 1992 were analyzed with 

the old system, but those from SPO, which were returned to 

Boulder at the end of the year, were all analyzed with the 

new GC and dual cryotrap. In previous years flask samples 

from SPO have been collected only during summer months. 

In November of 1991, however, flasks were shipped to SPO 

for sampling throughout the year. Most of these flasks 

were 0.85-L electropolished flasks suitable for analysis of 

low-concentration or poorly responding gases. Flasks were 

filled monthly throughout the year and shipped to Boulder 

in November 1992 after SPO opened for the next summer 

season. 

These large flasks were analyzed for H-1301 and H-1211 

on the newly configured LEAPS GC. There was no 

apparent serious degradation or enhancement of either of 

these compounds during storage, as the numerical values 

were similar to those for other sampling sites in the 

southern hemisphere. The growth rate of H-1301 during· 

this sampling period was 7.3% yrl. H-1211 appeared to 

increase at 3.9% yr!, although the growth rate was not 

significantly different from 0 because of larger variability 

in the data (Figures 5.9 and 5.10). These trends are 

consistent with those reported for the other CMDL 

sampling sites during 1992 [Butler et al. , 1992]. 

The absolute values for H-1211 reported here differ from 

those in previous annual reports and from those in Butler et 

al., (1992] because of a calculation error in the calibration 

scale of H-1211. The revised scale will be published in the 

next annual report, as additional re-calibrations are also 

necessary on the new instrument. 

5.1.4. ALTERNATIVE HALOCARBON MEASUREMENTS 

In response to warnings of stratospheric ozone depletion 

and global warming, the production of many industrial 

chlorine-containing compounds will be banned within the 

next few years [UNEP, 1987]. Although the ultimate goal 

of this legislation is to replace chlorinated compounds with 
0 

0 

"' 

O> 

c 

" :::E 

~ 

0 

0 

0 

"' 

O> 

c 

" 

:::E 

~ 

0 

2.2 

2. 1 

2 

1 .9 

1.8 

1. 7 

1.6 

Slope 

res sd 

7.3 +- 1.7 % yr·• 

2. 2 % 

• •• • • -·--------i------1-.. -- . ------------------·-----. 

,.---------- . 

• 

92.1 92.2 92.3 92.4 92.5 92.6 92.7 92.8 92.9 

3.5 

3 

2.5 

2 

Time 

Fig. 5.9. 1992 H-1301 results from SPO. 

Slope = 3.9 +- 4.8 % yr"' 

res s d = 6. 5 X 

• • • ~--------!· ------------------ -1-------------------··--·-l-· I I 

• • 

• • • • • • 

92.1 92.2 92.3 92.4 92.5 92.6 92.7 92.8 92.9 

Time 

Fig. 5.10. 1992 H- 1211 results from SPO. 

non-chlorinated substitutes, such as hydrofluorocarbons 

(HFCs), hydrochlorofluorocarbons (HCFCs) are currently 

being used until suitable non-chlorinated materials are 

developed. HCFCs are viewed as suitable temporary 

replacements for CFCs because current technology for their 

production and use in air-conditioners and refrigeration 

devices is already in place, and because model calculations 

suggest that the adverse effects of HCFCs on the 

atmosphere will be substantially Jess than those of CFCs. 

Accurate and precise measurements of these compounds in 

the atmosphere are essential in order to validate these 

predictions. These measurements also allow for accurate 

predictions of atmospheric impacts of other proposed 

substitute compounds, such as HFCs, because both HFCs 

and HCFCs are destroyed mostly in the troposphere by 

reaction with hydroxyl radical (OH). This is in contrast to 

CFCs, which are decomposed primarily by photolysis in the 

stratosphere. Presently, estimates of global OH are based 

on the atmospheric budget of a single industrial compound, 

1, l, 1-trichloroethane. Because there is considerable error 

62 

in such a limited estimate there is a need for other trace 

species to test model-generated distributions of OH 

[Prather and Spivakovslcy, 1990]. 

It is within this framework that a program for measuring 

alternative ha!ocarbons was begun at CMDL. Measurements of chlorodifluoromethane (HCFC-22) from 

flasks collected in the NOAH flask network were initiated 

in 1991 and continued in 1992. In addition, 1-ch!oro-J,ldifluoroethane (HCFC-142b) and J,l-dichloro-1-fluoroethane 

(HCFC-14lb) were detected and first measured in ambient air 

samples during 1992. 

The measurements were conducted as described by 

Montzka et al. (1992, 1993a,b] from paired air samples that 

were collected on a monthly basis (on average) al BRW, 

MLO, SMO, SPO, and at the three cooperative flask 

sampling locations of ALT, NWR, and CGO. 

Chlorodifluoromethane ( HCFC-22) 

Chlorodifluoromethane is the major HCFC in use today 

and represents a second trace species available for testing 

models that estimate the global tropospheric abundance of 

OH [Midgley and Fisher, 1993; Fraser el al., 1991]. 

Unfortunately, significant discrepancies among measurements of HCFC-22 by different techniques have been 

reported in the past. Mixing ratios determined from 

ground-based chromatographic measurements of northern 

hemispheric air [Khalil and Rasmussen, 1988, 1990, 1991] 

are 10-30% higher than those determined from Jong-path 

absorption measurements within the troposphere and lower 

stratosphere [Rinsland et al., 1989, 1990; Zander et al., 

1992]. and a small set of grab samples obtained in the 

lower troposphere [Pollock et al., 1992]. Furthermore, the 

lifetime of HCFC-22 suggested by a comparison of 

emission estimates and ambient measurements varies from 

13 to 40 years [Midgley and Fisher, 1993]. Lifetime 

estimates that are based on 3-0 models and the reaction 

rate constant between HCFC-22 and hydroxyl radical, 

suggest a lifetime for HCFC-22 of 14-16 years [Prather 

and Spivakovslcy , 1990; Golombek and Prinn, 1989]. 

Our analysis of air collected in flasks during 1992 at the 

four CMDL stations and three cooperative flask sampling 

sites indicates that the latitudinally-weighted, global mean 

mixing ratio of HCFC-22 in 1992 was 102 ppt (Tables 5.1 

and 5.2). These results are plotted as bi-monthly averages 

together with measurements of air from archived samples 

[Montzka el al., 1992, 1993a] and data from previous 

TABLE 5.1. Mean Mixing ratios of HCFC-22 in 1992 (ppt)* 

Global mean 

Northern hemisphere 

Southern hemisphere 

Mi~ in g Ratio 

101.9 

108.4 

95.4 

•All values were weighted by cosine of latitude. Numbers 

believed accurate within ±2.5%. 
TABLE 5.2. Atmospheric Measurements of HCFC-22 

From Flasks in 1992 

Station 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

ALT 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

BRW 

NWR 

NWR 

NWR 

NWR 

NWR 

NWR 

NWR 

NWR 

NWR 

MLO 

MLO 

MLO 

MLO 

MLO 

MLO 

MLO 

MLO 

MLO 

MLO 

MLO 

Date pp! 

1992.052 110.0 

1992.128 109.5 

1992.328 110.5 

1992.385 113.4 

1992.620 111.5 

1992.713 11 2. 1 

1992.907 115.0 

1992.022 112.2 

1992.120 109.1 

1992.268 110.7 

1992.372 111 .2 

1992.459 110.0 

1992.538 · 110.4 

1992.618 111.4 

1992.866 114.5 

1992.940 116.3 

1992.959 115.7 

1992.131 107.3 

1992.265 108.4 

1992.322 112.7 

1992.552 111.5 

1992.571 109.7 

1992.609 111.7 

1992.727 111 .8 

1992.877 108.7 

1992.954 115. l 

1992.033 104.4 

1992.109 101.8 

1992.262 103.7 

1992.281 103.6 

1992.4 73 105 .7 

1992.530 106.1 

1992.596 108.5 

1992.607 104.3 

1992.691 103 .0 

1992.740 109.1 

1992.779 106.3 

Station 

MLO 

MLO 

MLO 

MLO 

SMO 

SMO 

SMO 

SMO 

SMO 

SMO 

SMO 

SMO 

SMO 

SMO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

CGO 

SPO 

SPO 

SPO 

SPO 

SPO 

SPO 

SPO 

SPO 

SPO 

Date pp! 

1992.893 108.4 

1992.913 105.0 

1992. 970 111.6 

1992.989 111.0 

1992.046 93.6 

1992.112 90.4 

1992.262 95.2 

1992.301 95.7 

1992.456 95.5 

1992.530 95.0 

1992.607 96.3 

1992.686 98.2 

1992.784 98.3 

1992.921 97.5 

1992.036 90.3 

1992.115 92.4 

1992.153 92.4 

1992.306 94 .2 

1992.363 95.1 

1992.402 94.8 

1992.555 94.5 

1992.587 96.2 

1992.669 96.3 

1992.705 96.6 

1992.746 96.2 

1992.798 96.0 

1992.951 97.6 

1992.970 98.6 

1992.063 92.1 

1992.079 90.3 

1992.434 93.8 

1992.506 96.9 

1992.590 96.2 

1992.694 96.4 

1992.781 96.8 

1992.817 96.2 

1992.853 97.1 

investigators over a broad time-scale in Figure 5.11. In the 

northern hemisphere, measurements based on the CMDL 

calibration standards agree with long-path absorption 

measurements of HCFC-22 in the troposphere near 30°N 

[Rinsland et al., 1989]. They also agree with the results 

obtained at 30°N and above 12.5 km with the Atmospheric 

Trace Molecule Spectroscopy (ATMOS)-Fourier transform 

spectrometer on board Spacelab 3 [Zander et al., 1992]. 

Although it is difficult to accurately compare ground-based 

measurements directly with measurements at altitudes 

above 12.5 km, a limited number of studies suggest that the 

mixing ratio of HCFC-22 within the troposphere is fairly 

constant, making these comparisons valid [Leifer el al., 

1981; Rasmussen et al., 1982]. 

63 

C\J 

C\J I 

(.) 

12 

10 

90 

80 

70 

60 

50 

a) Northern 

Hemisphere 

/ 

u. 

(.) 

I 40+-~....._-L..-_._-+-_.__.____.__._-+_,___.__, 

/ .... 100 

0. b) Southern /ti / · ·

0¢0 

Hemisphere~- / _." 0 0. 90 

80 

70 

/. / ·" . / .. / / _ .. ,/ / .--~·-

601----'-_...<---l~---4-' ............ --'---_.__-+-__._..___, 

1980 1985 1990 

Fig. 5.11. Measurements of IICFC-22 and results of a 2-box model 

as described in the text for the northern (a) and southern (b) 

hemisphere. Results from flasks collected at the four CMDL 

stations and three cooperative flask sampling sites are bimonthly, 

latitudinally-weighted hemispheric means (0, Montzka et al., 

(1993)). Flasks collected during the SAGA II Cruise(-+-, Montzka 

et al., (1992); 6, Khalil and Rasmussen (1988]) are presented as 

latitudinally-weighted hemispheric means. Archived samples were 

collected at Niwot Ridge (+, Montzka et al. [1992)). Other 

measurements from flasks are from northern mid-latitudes in the 

upper troposphere (0, Pollock et al., [1992)), Mauna Loa, USA (.6, 

Khalil and Rasmussen [1991]. and C. Grim, Australia(•, Fraser et 

al., [ 1988, 1989)). Long path absorption measurements were made_ 

at 12.5 km (0, Zander et al., (1992)), throughout the troposphere 

(•, Rinsland el al., [1989)), and below 15 km (+, Rinsland el al., 

(1990)). Measurements of Rinsland et al. [1989) were increased by 

a factor of 1.28 to account for an updated cross-section estimate 

[Rinsland et al., 1990). Model calculations were performed for 

different lifetimes of HCf-C-22, 10 years (--), 15 years (- - - -), 

20 years(---), and 50 years (- · - · -). Abscissa tic marks 

correspond to the beginning of the year indicated. 

The results of Pollock et al. [ 1992] were obtained from a 

small set of samples collected in the upper troposphere in 

the northern mid-latitudes and are also in close agreement 

with the results based on the CMDL standards. Their 

results were obtained from GC-MS analysis of air collected 

in flasks. The similarity between the results of Pollock et 

al. [1992] and those reported by Montzka et al. (1992, 

1993a] suggest that these two independent calibration 

scales agree to within 5%. 
The measurements of Khalil and Rasmussen (1988, 

1990, 1991) and Fraser et al. (1989) are -28% higher than 

measurements based on the CMDL calibration standards 

(Figure 5 .11 ). Their measurements were based on a 

calibration scale that was developed in the late 1970s and 

believed accurate to within ±10% on the basis of 

comparisons with another laboratory at that time 

[Rasmussen et al., 1980). The differences between these 

results and those based on the CMDL standards are likely 

the result of different calibration scales for HCFC-22. 

Given that measurements by different techniques are 

converging towards a lower atmospheric burden of HCFC22 than suggested by Khalil and Rasmussen (1988, 1990, 

1991) and Fraser et al. (1989), it is possible that 

calibration standards used for their measurements were 

inaccurate. Overestimation of HCFC-22 by these 

investigators could explain the large discrepancies reported 

in the past between measured atmospheric mixing ratios 

and emission estimates [Khalil and Rasmussen, 1981) and 

between surface-based flask samples and long-path 

absorption measurements [Rinsland et al., 1990]. 

Using the emission estimates of Midgley and Fisher 

(1993), atmospheric mixing ratios of HCFC-22 were 

calculated with a 2-box, finite increment model [Elkins et 

al., 1993]. The factor "f" [Butler et al., 1992] was used to 

account for the vertical distribution of HCFC-22 throughout 

the atmosphere, and was estimated at 1.07 (±0.2) [Zander 

et al., 1992; Leifer et al., 1981; Fabian et al., 1985]. The 

model was initialized with 10 ppt of HCFC-22 in 1970 to 

account for emissions in years before 1970. Emissions 

after the end of 1991 were estimated by a linear 

extrapolation of emissions from 1985 to 1991. 

When compared to mixing ratios calculated with the 

model and data in Midgley and Fisher (1993), 

measurements based on CMDL standards, suggest an 

atmospheric lifetime for HCFC-22 of 13.6 (+1.9, -1.5) 

years (Figure 5.11). A similar lifetime can be estimated 

from the results of Zander et al. [1992), Rinsland et al. 

(1989), and Pollock et al. (1992]. Recent estimates of the 

atmospheric lifetime of HCFC-22 from global 3-D models 

yield values of 14.2-15.5 years, and are based on an 

atmospheric lifetime for CH3CCl3 of 5.7 or 6.3 years 

[Prather and Spivakovsky, 1990, Golombek and Prinn, 

1989]. However, revised estimates of the reaction rate 

constant between OH and CH3CC!3 suggest that HCFC 

lifetimes should be shortened by 15% [Talukdar et al., 

1992]. Given a lifetime for CH3CCl3 of 5.7 yrl [Prinn et 

al., 1992), and rate constant for CH3CC13 loss to the oceans 

of between 1/59 and 1/129 yr-I [Butler et al., 1991], the 

lifetime of HCFC-22 is estimated at 12-14 years. Although 

error estimates for the lifetime of CH3CCl3 and emission of 

HCFC-22 are ±10% and ±12%, respectively, it is clear that 

our measurements agree well with this revised lifetime 

estimate. 

Until measurements of HCFC-22 are extensive enough to 

allow for calculation of lifetime directly (as done by Prinn 

et al., [ 1992] for CH3CC13), estimates of HCFC-22 

64 

lifetime, and most other HCFCs and HFCs, are dependent 

on the accuracy of rate constants and calibration of 

CH3CCl3 and are subject to change as these latter 

parameters are refined. 

Measurements of archived air and air obtained from 

flasks allow for an estimate of the growth rate of HCFC-22 

from 1987 to the present. From the data based on CMDL 

calibration standards shown in Figure 5.11, a linear growth 

rate of 6.3 (±0.3) ppt yrl or compounding growth of 7.3 

(±0.3)% yr·l (in which the mixing ratio (X) since an initial 

time is defined as X = X0 •(1 + GR)l11 , and X0 is the initial 

mixing ratio, GR is the fractional increase per year, and 6t 

is the time elapsed since time 10 ) is obtained for HCFC-22 

between 1987 and December 1992. 

The global distribution of HCFC-22 as defined by flasks 

collected in 1992 (Figure 5.12) can also be used to estimate 

an instantaneous growth rate in the southern hemisphere 

(SH) during this year [Butler et al. 1992]. Given an 

interhemispheric difference of 13 (±1) ppt, an interhemispheric exchange time of 1.1 (±0. l) yr-t, and a 1992 

mean SH mixing ratio of 95.4 (±2) ppt, we estimate a 1992 

SH growth rate for HCFC-22 of 5.0 (±1.6) ppt yrl or 5.2 

(±1.7)% yrl. 

These estimates of growth for HCFC-22 between 1987 

and 1992 agree with predictions from our model calculation 

and that reported by Midgley and Fisher [ 1993]. Previous 

estimates of HCFC-22 growth from ambient air 

measurements suggest that between 1984 and 1989 HCFC22 was increasing at 6 to 8% yr·! [Fraser et al., 1991]. 

Our measurements, when combined with these earlier 

estimates, suggest that the relative growth rate of HCFC-22 

has remained fairly constant (±2%) since 1984 through 

1992. 

HCFC-22 (ppt) 

1992 Station Means 110 

~ Alert 

100 • Pt. Barrow 

* + 0 Niwot Ridge 

A Mauna Loa 

• Am. Samoa 

90 t><l Cape Grim 

x South Pole 

-90 -30 0 30 60 90 

Latitude 

Fig. 5.12. Mean mixing ratios of HCFC-22 in 1992 as detennined 

from air samples collected in flasks at the seven sampling stations. 

Venical bars represent ±1 standard deviation of residuals from a 

linear fit to the data obtained at each station. 
l ,l-Dichloro-1-Fluoroethane (HCFC-142b) 

HCFC-142b was recently incorporated in air 

conditioners and refrigeration devices where mixtures of 

CFC-11 and CFC-12 were formerly used. This compound 

was identified in ambient air collected at all seven stations 

around the globe in 1992. The only other reported 

measurement of this compound from air samples in the 

remote atmosphere was by Pollock et al. (1992). These 

investigators reported an ambient mixing ratio for HCFCl42b of I.I ppt in air collected in 1989 from the upper 

troposphere in the northern hemisphere. These 

investigators reported that the mixing ratio of HCFC-142b 

was increasing over time at a rate of approximately 7% 

yr-1 . 

Measurements of HCFC-142b from air collected as pan 

of the NOAH flask sampling network are summarized in 

Figure 5 .13. The mean global growth rate of this 

compound was estimated using linear regression at 

approximately 1 ppt yr-1 in 1992. Using the methods of 

Butler et al. (1992) the growth rate in the southern 

hemisphere is estimated at 0.9 ppt yr-1 over this period. 

This corresponds to an atmospheric growth of -30% yr-1 

for HCFC-142b in 1992. These numbers are preliminary 

and will be finalized in 1993 after standards are made at 

CMDL. While the scale reported in Figure 5.13 is 

preliminary at this time, the relative rate of growth of 

HCFC-142b indicated by the results in this figure are 

independent of calibration and are robust, assuming that no 

drifts have occurred in reference gases. A growth of 30% 

yr·l for HCFC-142b is largt:- <.:umpared to atmospheric 

growth rates of other CFCs and HCFCs currently being 

used by industry. However, the yearly increase in the 

atmospheric chlorine burden due to HCFC-l42b is small at 

this point in time as the mixing ratio of this compound is 

less than 10 ppt. 

HCFC· 142b from nosk >omples In 1992 

$.0 ll'roolhly OVOIOQ9' 

40 

l 30 

j 

J 2.0 -globol 

- NH 

1.0 

0.0 

199'2 199'2 5 19927$ 1993 

Fig. 5.13. Bimonthly mean mixing ratios of HCFC-142b for both 

hemispheres and the globe in 1992. Stated mixing ratios are 

preliminary and based on a NOAA scale (see text). 

65 

l-dichloro-1,l-difluoroethane ( HCFC-141 b) 

HCFC-14lb is a compound currently in use as a 

substitute for CFCs and is also present as an impurity in 

samples of HCFC-l42b. This compound was identified in 

air samples in the northern hemisphere during 1992. 

Levels in the southern hemisphere were at or below the 

detection limit of the instrument so as to preclude precise 

quantitation. Work in 1993 will focus on developing 

calibration standards and increasing the sensitivity of the 

GC-MS instrument. 

5.1.5. GRAVIMETRIC STANDARDS 

Chlorodifluoromethane (llCFC-22) 

The focus of the standards laboratory was on completing 

the work started in 1991 for developing a primary 

calibration scale for HCFC-22 (chlorodifluoromethane). 

Research was conducted into the stability of the gas 

contained in specially treated aluminum cylinders both as 

single-component and multi-component mixtures ranging 

from 50 parts per trillion to 1 part per thousand using gas 

chromatography/mass spectrometry (GC/MS) techniques 

[Montzka et al., l993b) and by GC using an oxygen-doped 

electron capture detector. The comparison of standards 

prepared in May 1989 to standards prepared recently, 

indicate that stability in Aculife-treated aluminum 

cylinders is maintained. The response curve for 

gravimetric standards containing HCFC-22 by GC using an 

oxygen-doped ECO is shown in Figure 5.14. 

Tu inv1:-stigate the containers and techniques used to 

generate calibration standards for HCFC-22, standards from 

levels as low as 50 ppl to as high as l part per thousand 

(Figure 5.15) were analyzed with GC/MS techniques 

[Montzka et al. 1992, l 993a,b]. Standards at levels below 

15 ppb were analyzed in the same manner as flask air 

10 

9 

II w 

en 

z 7 

2 

en II 

w 

a: 5 

~ 4 

~ 3 

a: 2 

0 

0 !! 10 1!5 20 2!5 30 3!5 40 

HCFC-22 MIXING RATIO (PPB) 

Fig. 5.14. Response curve of HCFC-22 gravimetric standards with 

an oxygen-doped electron capture detector. 
1.10 

1.0 E(-9) 1.0 E(-6) 1.0 E(-3) 

Stated Mixing Ratio 

r:ig. 5.15. The response per stated mixing ratio of IICFC-22 in 

different gravimetric standards from 50 parts per trillion to 1 part 

per thousand. Vertical bars correspond to one standard deviation of 

the results. All standards are plotted relative to the standard at 

489.9 ppb, to which a response per ppt of 1.00 was assigned. 

Standards made from "pure" HCFC-22 are indicated with shaded 

symbols. The parent cylinder of lower level standards is indicated 

by the symbol shape. Standards below 10 ppb were multi-component mixtures containing carbon dioxide, methane, nitrous oxide, 

and numerous chlorofluorocarbons. 

samples, but without the presence of a drying agent. For 

standards above 10 ppb, sample loops of 81.8 and 13.1 μL 

were filled to atmospheric pressure and injected directly 

onto the column. Loop volumes were determined 

gravimetrically to within 1 % with multiple injections of deionized distilled water onto a desiccant. The volume of the 

evacuated chamber (used for cryo-collection of low level 

samples) was determined barometrically by reference to a 

known volume. When two standards of widely varying 

mixing ratios were compared, different loop sizes and cryocollection volumes were used to minimize the difference in 

the amount of HCFC-22 reaching the detector, thereby 

minimizing non-linearity effects. For standards below I 

ppm this difference was always less than a factor of 6 and 

was typically a factor of 2. For standards above 1 ppm, the 

amount of HCFC-22 in standards being compared never 

differed by more than a factor of 20. Linearity has been 

confirmed (within 1 %) over a range of 6.5x for HCFC-22 

by injections of different loop volumes of the same 

standard directly onto the column. For standards 

containing CFC-12 and CFC-11, we have found that the 

detector responds linearly (within 2%) over a range of 

greater than lOOx in the region of interest. With the 

exception of two standards above 100 ppm (Figure 5.15), 

the HCFC-22 standards were referenced to loop injections 

of the standard at 489.9 ppb. The two standards above 100 

ppm were directly compared only to the standard at 56 ppm 

shown in Figure 5.15. 

The response per ppt of our standards is consistent 

within ±2% (±1 s.d.) and these data suggest that the 

integrity of HCFC-22 is maintained in Aculife-treated 

66 

aluminum cylinders even at the 50 ppt level (Figure 5.15). 

In addition, the data demonstrate that ambient levels of 

C02, N20, CH4, or other halocarbons in a sample do not 

affect our analysis for HCFC-22. We feel that the different 

conditions under which these standards were made and the 

lack of impurities found in our starting reagents (none 

above 1 part per thousand) allow us to estimate the 

accuracy of our HCFC-22 scale by the variance among 

these standards. At the 95% confidence level, we believe 

our standards accurate to within ±2.5%. 

Blended Multi-Component Standards 

Research started this year into preparing synthetically 

blended multi-component standards for use as calibration 

standards for our GCs located at our observatory stations 

and in the standards laboratory. Our division was also 

contracted by the Aeronomy Laboratory to provide a suite 

of round-robin standards for worldwide inter-laboratory 

analysis comparisons. Nine single-component gravimetric 

mixtures were prepared from pure reagents in specially 

treated aluminum cylinders using various dilution 

techniques. These parent mixtures were then used to 

prepare single-component gravimetric standards at lower 

concentrations. The standards were then blended together 

into three nine-component mixtures containing CFC-11, 

CFC-12, CFC-113, methyl chloroform (CH3CCl3), carbon 

tetrachloride (CCl4), HCFC-22, N20, CH4, and C02 in 

blended air. These were then used to prepare two cylinders 

each of gases containing concentrations matching real air. 

Each of the three cylinders contained the gases at various 

mixing ratios found in atmospheric air ranging from the 

mid-latitude to the arctic stratosphere. The gases contained 

in all of the cylinders were analyzed over time to insure 

stability. Unfortunately, the six cylinders used for 

preparing the low concentration standards were found to 

readily absorb CH3CCJ3 and CCl4 from the gas mixtures. 

Losses ranging from approximately 10 to 100% were 

observed for CH3CC13 and from approximately 5 to 90% 

for CC14 within 1 week after preparing the standards. The 

cylinders were returned to the vendor and were retreated 

using their proprietary treatment process. The same 

cylinders were then used to remake the standards. The new 

suite of standards were analyzed and were found to be 

acceptable except for one that exhibited CFC-113 

contamination due to a dirty cylinder valve. A standard 

similar to one of the six has been placed online at the NWR 

station for calibrating the GCs. 

Two gravimetric standards containing approximately 100 

ppm of CO in air and two contammg ambient 

concentrations of CH4 in air were prepared for NCAR. The 

standards were used to calibrate a tunable diode laser 

system. 

Three CO in air gravimetric standards were prepared for 

use as supplemental primary standards to the CO reference 

scale maintained by the Carbon Cycle Division. The three 

standards were prepared at nominal concentrations of 50, 

100, and 150 ppb. The intercomparision of these standards 

to the current scale showed no significant bias. 
Several cylinders contammg dilute mixtures of NiO in 

Ni and NiO in air were analyzed for the NASA Ames 

Research Center. The analyses of these cylinders required 

the preparation of six gravimetric standards. Four of the 

primary calibration standards were prepared containing 

NiO in blended air and two were prepared containing NiO 

in Ni. The mixing ratios of the primary standards were 

targeted in order to closely bracket the mixtures to be 

analyzed. This analysis proved interesting in that it 

allowed us to intercompare NOAA NiO in Ni standards to 

NiO in air standards to determine if mixtures containing 

different diluents (e.g., Ni. air) had any effect on ECDs 

and/or presented a problem involving chromatographic 

peak integration. The results of this experiment indicated 

there was a small bias between analyzing NiO-in-Ni 

mixtures using NiO-in-air and NiO-in-Ni standards. The 

calculated value for a NiO in air mixture using NiO in Ni 

standards was approximately 0.8% higher than what was 

calculated using NiO in air standards (Figure 5.16). 

Instrumentation 

Two GCs with ECDs were added to the standards 

laboratory this year. The two were combined with a third 

on hand to create an automated analytical system similar to 

the systems used by the RITS program at the observatory 

stations. Previously, analysis of standards was conducted 

on the flask analysis system. More time can now be 

devoted to both flask analysis and standards analysis with 

the use of two separate systems. The system for standards 

analysis is capable of measuring CFC-11, CFC- 12, CFC113, CH3CCl3, CC14, and NiO. It is also capable of 

measuring HCFC-22 concentrations as low as 1 ppb without 

injecting cryogenically collected samples. This is made 

possible with the use of a Carbopack B column operated at 

-70°C which gives good separation of the HCFC-22 and 

CFC-12 peaks from the air peak and by doping the electron 

capture detector with a 5% mixture of oxygen in Ni. 

UJ 

CJ) 

z 

0 

Cl. 

CJ) 

UJ 

cc 

UJ 

> 3 

w 

cc 

10 

9 

8 

1 

ti 

5 

4 

3 

2 

1 

850 

--+- N20 IN AIR 

_..._ N20 1NN2 

900 950 1,000 1,050 1,100 1,150 1,200 1,250 

NITROUS OXIDE MIXING RATIO (PPB) 

Fig. 5.16. Response curve of N20 in air and N20 in N2 with an 

electron capture detector and 5% CH4 in Ar carrier gas. 

67 

Standards with concentrations lower than 1 ppb are 

measured on the GC/MS by cryogenic collection. 

There were 56 gravimetric standards prepared in the 

standards laboratory for the year of 1992 (Table 5.3). In 

addition, there were seven calibration standards replaced at 

our various observatory stations for the RITS program. To 

reduce vibrations, our gas standard laboratory was 

relocated from the third floor of building RL-3 to the 

ground floor of building RL-6. 

5.2. SPECIAL PROJECTS 

5.2.1. AIRCRAFT MEASUREMENTS OF THE CFCS 

The Airborne Chromatograph for Atmospheric Trace 

Species (ACATS) instrument has had considerable success 

over the past 2 years in measuring CFC-11 and CFC-113 in 

the troposphere and lower stratosphere. ACATS was built 

inside the reactive nitrogen instrument [Fahey et al., 1989) 

and was described in last year's Summary Report [Montzka 

et al., 1992). Since its construction in 1991, ACATS has 

participated in two major projects, NASA's stratospheric 

ozone program and High Speed Research Program (HSRP). 

These projects use CFC measurements as anthropogenic 

tracers to indicate stratospheric ozone loss. Using an 

airborne platform, in this case the ER-2 (a civilian version 

of the U-2), allows ACATS to measure vertical profiles 

extending into the lower stratosphere. Vertical profiles of 

trace species, including CFCs, have become an integral 

component of the NOAH division's research and is NOAA's 

TABLE 5.3. Summary of Gravimetric Standards 

Compounds 

HCFC-22 

CFC-I I, CFC- 12, 

CFC-1 13, CCl4 , 

CH3CCl3, N10, 

HCFC-22 

CFC-II 

CFC- 12 

CFC- 11 3 

CH1CCl1 

CC14 

CH4 

CFC- I I, CFC- 12, 

CFC- I 13, CC14 , 

CH3CCl3, N20, 

HCFC-22, CO, 

CH4 

Quantity 

12 

3 

I 

2 

I 

I 

5 

5 

8 

17 

Concentration 

Range 

ppt, ppm 

ppt, ppb 

ppb 

ppm 

ppb 

ppb 

ppb 

ppm, percent 

ppb, ppm 

ppb, ppm 

ppt, ppm 

Prepared 

For 

NOAH/AL 

ACATS/NOAH 

NOA H/AL 

NOAH/AL 

NOAH/AL 

NOAH/AL 

NOAH/AL 

NOAH/AL/ 

CC/NC AR 

CC/NCAR 

NOAH/U. of 

N.H./CANMET 

NOAH/AL 
key responsibility to the Global Climate Change Program 

[GCRP, 1993). The Airborne Arctic Stratospheric 

Expedition II (AASE II) and the forthcoming Stratospheric 

Photochemistry, Aerosols, and Dynamics Expedition in 

1993 (SPADE, a component of HSRP) missions have used 

and will continue to utilize ACATS CFC measurements. In 

November test flights for SPADE were conducted at NASA 

Ames, Moffitt Field, California. Although the primary goal 

of the November flights was to integrate new and modified 

instruments into the ER-2 payload, ACATS made 

measurements on two 2-hour flights. For the future 1993 

SPADE project, ACATS will have an additional N20-doped 

ECO channel to measure CH4 and CO in collaboration with 

Carbon Cycle Division [Goldan, et al., 1982). 

AASE-II mission 

The AASE-II mission was designed to primarily focus 

on photochemistry of the lower stratosphere and ozone 

destruction or production due to chemical perturbations. 

Addition of these two CFC molecules to the complement of 

species already measured on the ER-2 platform offers new 

science opportunities. Atmospheric CFC-11 and -113 are 

important ozone depleting chemicals, which together 

represent about 30% of the total organic chlorine in the 

atmosphere. The use of high resolution CFC 

measurements along with correlations between different 

tracers generated by dynamic models [Solomon et al., 

1992) permits calculation of the total organic chlorine over 

the complete flight. Since 1989, the growth rates of both 

chemicals, particularly CFC-11 [Elkins et al., 1993), have 

been slowing down in the troposphere. Monitoring the 

slowdown of the growth rates in the troposphere and 

stratosphere, together with accurate tracking of emissions, 

will further aid in the refinement of chemical lifetimes of 

the these species and may provide for a more complete 

understanding of the transport properties of the atmosphere. 

These CFC molecules are excellent tracers of 

stratospheric dynamics. High levels of chlorine monoxide 

(ClO) indicate that 0 3 has been destroyed. The decrease in 

CFC mixing ratios that were observed on the ER-2 aircraft 

flight of January 16, 1992, in a region where ClO mixing 

ratios increased delineates the extent of the polar vortex 

(Figure 5.17). The slow, steady photochemical destruction 

of the CFCs is the source of the chlorine atom for the more 

Polar Vortex: NOAA/ACATS CFC Data and Harvard/UC! CIO 

0 

u 

1 200 

800 

400 

50400 57600 64800 72000 

!Enter Polar Vortex j. ,.!Exit Polar Vortexj 

> 

50400 57600 64800 

GMT After Midnite (seconds) 

- CIO t 

f ..... CFC-113 i 

...... CFC-11 r 

. j 

j 

i 

+ ; 

~ 

! 

i t 

J f 

<.-, _,..-..,,.· . f 

72000 

300 

() 

200 "T1 

<;"> 

0 

... 

. ... 

... 

w 

Fig. 5.17. Altitude in km (top) and mixing ratios of CFC-I I (&)and CFC-113 (+)from A CATS and of CIO (-) in parts-per-trillion (ppt) on 

the ER-2 flight (bottom) of January 16, 1992. The boundaries of the polar vortex are clearly defined by the increase in mixing ratios of CIO 

and by the decrease in CFC levels. Mixing ratios of CIO were measured by methods described by Brune et al., [ 1989] and preliminary values 

from AASE-2 were made available by Toohey et al. [1993]. 

68 
reactive and destructive ClO molecule. It was this flight 

and one on January 20 showing high levels of ClO over the 

United States that convinced President Bush to move up the 

timetable for the complete phaseout of the CFCs from the 

year 2000 to 1996, 4 years ahead of the schedule mandated 

by the Montreal Protocol. All signatory nations agreed to 

this new schedule in the Copenhagen Amendment of 1992 

for the Montreal Protocol. The concern over the timetable 

was the long atmospheric lifetimes of the CFC molecules. 

The lifetime for CFC-11 is about SS years [Elkins et al., 

1993) and for CFC-113 is 110 years [WMO, 1992), whereas 

the chemical lifetimes of ClO plus its dimer are about 1 

month [Salawitch et al., 1993). This diversity in the 

lifetimes of tracers will allow modelers to check theories 

on transport inside the stratosphere. Linear correlations are 

found for molecules with similar lifetimes or at altitudes 

where the local lifetimes are greater than the time scales of 

vertical transport [Plumb and Ko, 1992). Correlation of 

mixing ratios of CFC-1 13 versus CFC-11 (Figure S.18) 

shows a strictly linear relationship for mixing ratios of -SO 

ppt for CFC-11 and considerable curvature at lower values 

where CFC-11 is more rapidly destroyed than CFC-113. 

During previous missions, ozone depletion at a particular 

altitude was calculated relative to the long-lived tracer, 

N10. Additional measurements of the CFCs and their 

correlations with N20 allow other tracers to be used to 

evaluate the effects of ozone depletion. 

SPADE Mission 

ACATS is a versatile instrument that will be utilized in 

the Stratospheric Photochemistry, Aerosols, and Dynamics 

Expedition (SPADE) and future polar missions like 

Airborne Southern Hemispheric Ozone Expedition 

(ASHOE) in 1994. The SPADE mission will provide 

100 

--Q, 

Q, 80 -

C'? 

.... 

.... 60 ' (.) 

u. 

(.) 4 0 

U> 

I-

~ 2 0 (.) 

jAASE-ttl 

~ 

0 

0 100 2 00 300 

ACATS CFC-11 (ppt) 

Fig. 5.18. Mixing ratios of CFC-113 versus CFC-I I in ppt for all 

flights during AASE-2. All data were fit to following equation: 

CFC-113 = 21.8 + 0.186 CFC-I I - 22.8 e·(0.059 CFC·lll using least 

squares techniques. The linea r range covers mixing ratios for CFC-

! I between 50 and 300 ppt, and CFC- I I is destroyed more rapidly 

than Cr:C-113 below mixing ratios of 50 ppt. 

69 

additional measurements for key components of the prior 

AASE I and II missions. This year's SPADE test flights 

and the 1993 SPADE project are components of NASA's 

HSRP that is in charge of assessing the environmental 

impact of a projected fleet of supersonic high-speed civil 

transports. SPADE has two primary scientific objectives: 

(1) To determine the key chemical processes that affect 

ozone levels in the parts of the stratosphere that would be 

most influenced by future stratospheric aircraft. This 

includes free-radical and heterogeneous chemistry. (2) To 

estimate the distribution of exhaust effluent in the 

stratosphere. This involves measurements of a wide range 

of tracers in the lower stratosphere. 

ACATS measured CFC-11 and CFC-113 on two of the 

test flights this November (Figure S.19). Both of these 

flights were during the day, lasted about 2 hours, and 

reached a maximum altitude of 20 km. The flight path on 

November 9 stayed completely over land, south of the San 

Francisco Bay area, while the flight on the 12th was mainly 

over the Pacific coast. The CFC-11 stratospheric mixing 

ratios for these flights are in good agreement with the 

previous AASE II data. Similarly, the tropospheric mixing 

ratios for these flights agree with northern hemispheric 

station measurements. Unfortunately, the CFC-113 

measurements for the flight on November 9 were lost due 

to contamination, but the data on the 12th also agrees with 

AASE II and station measurements. 

5.2.2. OCEAN/ ATMOSPHERE EXCHA:'\GE OF TRACE 

COMPOUNDS 

The Ocean Atmosphere Exchange of Trace Compounds 

(OAXTC) mission was conducted aboard the University of 

Southern California research vessel John V. Vickers 

between August and October 1992. (Figure S.20). The 

main goal of this study was to determine the atmospheric 

mixing ratio of HCFC-22 and its partial pressure in surface 

waters of the West Pacific Ocean to assess the possible 

existence of an oceanic sink for this compound. HCFC-22 

is one of the major halocarbons in use today with a growth 

rate of 7 .3% per year and a global mean of around I 0 J .8 

ppt [Montzka et al., 1993a]. Water column measurements 

of HCFC-22 were carried out to complement air and 

surface water determinations to better illustrate its behavior 

in the ocean. CFC- I I, CFC-12, methyl chloroform 

(CH3CC13) , and carbon tetrachloride (CCl4) were added to 

these measurements for comparison to similar data that 

were obtained during previous cruises [Butler et al., 1991) 

and to data from our network sites. CFC-113 and N20 

were also measured but are not reported here. 

Sampling and Analysis 

Surface water gases were partitioned with an acrylic 

seawater equilibrator as done on previous cruises [Butler et 

al., 1988). Ambient air and equilibrator headspace were 

sampled with a two-channel pumpboard. In addition, 27 

pairs of flask samples, one each for air and equilibrator 

hcadspace, were collected along meridian l 6S0 E for the 
280 

--

§: 26 0 

-

0 240 

+:: 

ca 22 0 er: 

C> 200 

c 

:g 180 ~ 

T'"" 160 T'"" 

I 140 (.) 

u.. 

(.) 120 

- 280 

-

8: 26 0 

-

0 240 ~ 

~ 220 

C> 200 

c 

:g 180 

~ 

T'"" 

T"" 

I 

(.) 

u.. 

(.) 

160 

14 0 

12 0 

Nov 9 

7 8 000 80000 82000 84000 

GMT (seconds) 

i Nov 12 

\I I • 

• I./ ~ 

~I --- CFC-11 

I ...... CFC-113 

i 

72000 7 4000 76000 

GMT (seconds) 

. ::J 

60 <C 

:0 

C> 

:::!: 

0 5 0 

f-ig. 5.19. cr:C- 11 and Cf-C-113 mixing ratios 10 ppt by mole 

fraction for the SPADE test flights on November 9 and November 

12, 1992. 

determination of gases other than the compounds included 

in this report and to compare flask data with those from in 

situ analyses. CFC-12, CFC-11, C H3CCl3, and CCl4 were 

measured with a custom-designed, three-channel GC. New 

technology was adapted from our ACATS aircraft projects 

for the design of this GC to minimize space requirements 

[Montzka et al., 1992]. In addition to this three-channel 

GC, we built a fourth gas chromatographic channel for the 

determination of HCFC-22, using a 35 cm3 sample loop and 

a preconccntration step before analysis with an oxygen 

doped ECD. Most of the data were analyzed with custom 

70 

- - - - - - - - - - - - - :io.-s 

Noumea New Caledonia 22-0ct-92 ·.·.·.·.·.·.·.•:•.-.·.-.·.·.· .... ·.·:·.·:.:: 

Fig. 5.20. Map with OAXTC cruise track and locations of port 

stops. A total distance of about 19000 km was covered during this 

12-week expedition and about 26000 chromatograms were taken 

with one datapoint each for air and surface water at 40- to 48-

minute intervals. 

software NOAHchrom, developed in our division, for both 

integration of chromatograms and advanced database 

analysis. 

CFC-11 and CFC-12 

CFC-11 and CFC-12 are anthropogenic halocarbons that 

have Jong atmospheric lifetimes and are inert in seawater. 

Hence, they are very useful as tracers of physical 

processes. These two halocarbons are also useful in 

evaluating atmospheric circulation and in determining the 

effects of physical processes, such as mixing, heating, 

cooling, and bubble injection, upon air-sea exchange. 

CFC-I I behaved predictively in both the atmosphere and 

the surface water. Apparent large scatter in the latitudinal 

profile between 55°N and 44°N as well as 28°N and 8°N 

can be explained in part by air mass movement and 

temporal variations during the several crossings of these 

latitudes and must be taken as the expected variabil ity in 

the mixing ratios of such compounds. CFC-11 m ixing 

ratios did not drop significantly until 30°N and leveled out 

below 10°S (Figure 5.21). Saturation anomalies were 

highest in the northern hemisphere where the waters had 

been subjected to warming throughout the summer. Below 

J0°S, the saturation anomaly was negat ive for CFC-11. 

From cooling alone, one might expect negative anomalies 

below the equator, but effects of cooling arc offset to some 

degree by air-injection (air bubble dissolution), which 

tends to supersaturate all gases [Kester et al., 1975]. 

CFC-12 data show basically the same effects as 

explained for CFC- I I (Figure 5.22). CFC-12 in seawater is 

affected only by physical processes, as is CFC- I I, so its 
I CFC-11 air I 

290 

a 

CFC-11 air --tit 

flasks 

o stations .s 

- 280 

0 

u.. 

(.) 270 

290 

a 

.s 

- 280 

0 

u.. 

(.) 270 

5 

o~~------~~Dlll!!111111111!111111'.dB 

i 

-·1 ...... T ........ , ........ , .. - -5 0 

u.. 

(.) -10 am CFC-11 SA i 

-20 -10 0 10 20 30 40 50 

Latitude (degrees north) 

60 

Fig. 5.21. Dry mixing ratios of CFC-I I in the air and the 

headspace of the sea water equilibrator. The saturation anomaly 

(SA) is defined as (MRwatcr·MRair)IMRai? IOO, with :-.IR=mixing 

ratio. Solid lines through the data sets (fit) are running means of 51 

to 81 data points, as are all saturation anomalies shown here. 

saturation anomaly should not differ substantially from that 

of CFC-11, and its net saturation anomaly should be near 

zero. The observed values between 0 and -2% represent the 

effects of slightly different behaviors of physically 

controlled gases. 

Atmospheric mixing ratios from the in situ 

measurements of all compounds agreed well with those 

from flask samples collected on the ship and agreed within 

one s.d. with data from NWR, MLO, and SMO. Most flask 

data between 8°N and 30°N were taken on our first of 

several passes across this region where we observed much 

lower mixing ratios in both air and surface water because 

of an innuence of southern hemispheric air. 

l/CFC-22 

As with CFC-11 and CFC-12, the mixing ratio of HCFC22 in the atmosphere decreased with latitude from 30°N 

(108 ppt) to the equator, where it tended to level off at a 

value of 98 ppt with latitude (Figure 5.23). This is 

consistent with recently published results from the CMDL 

nask sampling network [Montzka et al., 1993a]. Data from 

540 l cFC-12 airl ! . 

a ! ......... 1 .... 

.s 

N 520 

0 -

u.. 

(.) CFC-12 air 

500 ----fit 

o stations 

540 

N 520 

0 -

u.. 

(,) 

....... l1 ====-..!.~'!!.~c--_1_2_w_a_t"'_JI .. 

71 

500 

l 5 ·I CFC-12 SA I ! ~·,··· < 0 .... "' N 

. ! u - -5 u.. 

(.) i l-~ .. CFC-12 SA I - 10 ! 

i 

Ne! SA . 

- 15 

-20 -10 0 10 20 30 40 50 60 

Latitude (degrees north) 

Fig 5.22. Dry mixing ratios of CFC-12 in the air and the hcadspace 

of the sea water cquilibrator. The net saturation anomaly :\SA is the 

saturation anomaly SA according to Figure 5.21, minus the 

saturation anomaly of CFC- I I. 

nasks taken during the cruise extend the dataset of in situ 

measurements to about 40°N and show an HCFC-22 

latitudinal profile that is similar to those of the CFCs. The 

observed latitudinal gradient for HCFC-22 was on the order 

of I 2 ppt between 40°N and 22°S, and is consistent with a 

growth rate of about 7% yr-I as reported by Montzka et al. 

[1993a). 

Although differences in physical properties can explain 

the observed CFC-I I and CFC-12 anomalies, they cannot 

explain the differences between HCFC-22 and CFC-11 

anomalies. Both the HCFC-22 and CFC-1 1 anomalies were 

negative through much of the tropics. Warming and 

cooling was minimal in these areas at this time and cannot 

quantitatively explain the observed departures. Dissolution 

of air bubbles only creates positive saturation anomalies, 

and the anomaly for HCFC-22 was negative over a wide 

latitudinal range even before being corrected with CFC-11. 

Finally, there is some latitudinal dependence of the HCFC22 net saturation anomaly, which implies a possible 

temperature-dependent effect. By contrast, the net anomaly 

for CFC-12 is reasonably constant. Thus, it is also likely 
1::! 100 

t) 

u. 

() 

J: 90 

~ 110 

Q. 

.2' 

~ 100 

() 

u. 

() 

J: 90 

l 5 

~ 0 

N 

~ () ·5 u. 

() 

J: -10 

'i ··19'°1:·· . 

· .. ·. ... .. .:-'·'····]········:"(···· 

.J HCFC-22 SAs i .. 

! 

-20 - 10 0 10 

Latitude 

HCFC.22 air 

--lit 

flask data 

• stations 

water 

--lit 

flask data 

1 · .... SA I ..... am NSA 

20 30 40 50 

(degrees north) 

60 

fig. 5.23. Dry mixing ratios of HCfC-22 in the air and the 

hcadspace of the sea wate r equilibrator, and its saturation 

anomali es. 

hydrolysis, reactions with solvatcd ions, or even microbial 

metabolism. The removal rate could be as much as 10 

times the published hydrolysis r ates, but those rates must 

be considered only tentative at this time. The removal rate, 

whatever its cause, corresponds to a partial atmospheric 

lifetime of 700 years. With an atmospheric lifetime of 13.6 

years, this accounts for 2% of all atmospheric losses. 

HCFC-22 depth profiles, although somewhat noisy, were 

similar to those for CFC-11 and CFC-12 (Figure 5.24). At 

this point, differences in the profiles must be considered 

insignificant and do not reveal any hard evidence of subsurface breakdown of HCFC-22. Ratios of surface-water 

concentrations of the CFCs relative to HCFC-22 were very 

close to the predicted values, calculated from Henry's 

solubility law. 

Methyl Chloroform 

The net saturation anomaly for methyl chloroform is 

negative almost everywhere except for the region around 

30°N where we observed sl ightly positive values (Figure 

5.25). Our data show a significant tropical sink centered 

that some in situ process is removing HCFC-22 in tropical 

72 

0 

200 

= Q. 

4> 

0 600 

800 

. . . . , ............ ! ............ r···· .. ·····1·· .. ········ 

........ CFC-12 

- • - CFC·11 __.,_ HCFC-22 

1000~r:J::I::jl..L.L.J.;.;LJL.i.;.±J;.;.i.;.;LL±J~.L!:~ 

0.0 0.2 0.4 0.6 0.8 1.0 

Normalized water concentration 

Fig. 5.24. Deep water profiles of HCFC-22, CFC-I I, and CFC-12 

for a station in the tropics. Water concentrations are normalized to 

their surface value. Error bars indicate an uncertainty of 15% for 

the HCFC-22 measurements. Deep water profiles of CFC-I I and 

CFC- 12 were provided by Bullister et al., NOAA/PMEL (private 

communication, 1993). 

and subtropical surface waters. This process may involve 

the equator where upwelling and oceanic breakdown by 

hydrolysis, and maybe by biological activity, is most 

intense [Butler el al., 1991]. 

Our results show a latitudinal dependence of the 

saturation anomaly for CH3CCl3, but no obvious 

temperature dependence of the calculated flux. The 

temperature/flux-relationship was confounded by a positive 

net saturation anomaly between 30°N and 40°N and a 

negative net anomaly in the higher latitudes. Although 

these variations are not outside the realm of physical 

effects, they represent fairly strong fluxes, especially in the 

higher latitudes, because of the higher wind speeds and 

higher gas solubilities in those regions. The possible 

existence of a biological sink might explain negative fluxes 

at the higher latitudes, but despite their large magnitude, 

they would not be as great a global contribution as the sink 

in the tropics, because the coverage of the ocean at higher 

latitudes is less compared to the ocean in tropical regions. 

Carbon Tetrachloride 

Although CCl4 appears slightly supersaturated at the 

higher north latitudes, its net saturation anomaly is strongly 

negative at all latitudes (Figure 5.26), which is also 

consistent with earlier findings by CMDL [Butler et al., 

1993]. Laboratory hydrolysis data do not support the loss 

rate required to sustain the observed saturation anomaly for 
160 

120 

160 

120 

5 

l 0 

~ -5 

8 cf -10 

-151LL....L..l....L..l....L..l....L..l..L..l..L..l...L.J...L.JU-JU....U....L..1-L..l-L..L.L..L.L..L..U....U....U....L...L-'-.J 

-20 -10 0 10 20 30 40 50 60 

Latitude (degrees north) 

Fig. 5.25. Dry mixing ratios of CH3CCl3 in the air and the 

headspace of the sea water equilibrator, and its saturation 

anomalies. 

CC14. The highest expected rate of hydrolysis could only 

give rise to a net saturation anomaly of -0. l %. However, 

some deep water profiles obtained by investigators on this 

and other expeditions indicate that CC14 is consumed at a 

depth below the thermocline but near the oxygen minimum. 

The flux of CC14 from the atmosphere required to 

sustain the observed saturation anomalies under steadystate conditions represents a partial atmospheric lifetime of 

around 250 years for loss to the ocean. The best estimate 

of the global CCl4 atmospheric lifetime is 40 years, 

meaning that 16% of the atmospheric CC14 is lost to the 

ocean. This number is a little smaller than the range of 

values calculated from our other cruises (15-35%), but not 

outside an expected range of variability. The loss of CC14 

to the ocean is a significant sink, as it means substantially 

less chlorine will be delivered to the stratosphere. 

5.2.3. SOFTWARE DEVELOPMENT 

The NOAH Division has developed a chromatographic 

interpretation and management system, NOAHchrom, and 

proved it in 1992 on three separate field missions (AASE 

73 

110 

a 

.s. 

100 

90 

110 

90 

5 

l 0 

~ 

8 -5 

- 10 

I oo. water' l···· 

-20 -10 0 10 

Latitude 

CCI_. a ir 

--cc1, m flask• 

o stations 

CCI, water 

--cc1, 1;1 

flasks 

·······•···----··--. ~. .. 

20 30 40 50 

(degrees north) 

60 

Fig. 5.26. Dry mixing ratios of CCl4 in the air and the headspace of 

the sea water equilibrator, and its saturation anomalies. 

II, OAXTC, and SPADE). NOAHchrom runs on Apple 

Macintosh computers within a commercially available data 

analysis and presentation application, Igor, by Wavemetrics 

Corporation. Igor is highly extensible (by virtue of 

"external operations and functions" written in the "C" 

programming language, and its own internal programming 

language), and thus proved to be an excellent platform for 

the development of a unique system for the interpretation 

of chromatographic data. 

The NOAHchrom package provides a variety of tools for 

accurate peak integration and subsequent analysis of large 

data sets. NOAHchrom is essentially a simple database 

management system designed specifically for chromatographic data: all peak locations, integration results, 

concentrations, and standard sampling attributes (e.g., 

chromatogram name and injection time), as well as userdcfined (binary) flags and user-defined, quantifiable, 

sampling attributes (e.g., wind direction, equilibrator 

temperature) are accessible through the manager. Database 

searches based on multiple criteria allow the user to define 

an interesting subset of the entire data set for scrutiny or 

reprocessing (e.g., find all chromatograms with CFC-I I 
concentrations greater than 320 ppt and with wind direction 

between 170-190 degrees, and then reintegrate those peaks 

using an exponential fit to the baseline). NOAHchrom 

supports both automatic and manual peak identification and 

detection. After peaks are located, the user has a variety of 

integration options: linear or non-linear curve fit to the 

baseline and an optional curve fit (e.g., Gaussian) to the 

peak itself. Quality data presentation is accomplished 

within the Igor application, and thus within NOAHchrom 

itself, at any stage of data processing. 

5.3. REFERE'.\CES 

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Brune, W. II., J. G. Anderson, and K. R. Chan, In situ observations 

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Butler, J.H., J.W. Elkins, B.D. Hall, S.O. Cummings, and S.A. 

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Butler, J.ll., J.W. Elkins, C.M. Brunson, K.B. Egan, T.M. 

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Elkin s, J. W., T. M. Thompson, T. H. Swanson, J. H. Butler, B. D. 

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data for 1978-1990, J. Geophys. Res., 97, 2445-2461, 1992. 

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CllCIF2 {F-22) in the earth's atmosphere, Geophys. Res. Lett., 7, 

809-812, 1980. 

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Natural and anthropogenic trace gases in the southern 

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for a decline in the atmospheric accumulation rate of CllCIF2 

(CFC-22), Nature, 337, 535-537, 1989. 

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Kosters, D.G. Murcray, N.D. Sze, and S.T. Massie, Long-term 

trends in the concentrations of SF6, CHCIF2, and COF2 in the 

lower stratosphere from analysis of high-resolution infrared solar 

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Arctic polar vortex in the winter of 1991-1992, Science, 261, 

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75 

Solomon, S., M. Mills, LE. Heidt, W.11. Pollack, and A.F. Tuck, On 

the evaluation of ozone depletion potentials, J. Geophys. Res., 

97(01), 825-842, 1992. 

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Butler, and J3.D. Hall, Decline in the accumulation rates of 

atmospheric chlorofluorocarbons 11 and 12 al the South Pole, 

Ant. J. U.S., 27, 1992. 

Talukdar, R.K., A. Mellouki, A. Schmoltner, T. Watson, S.A. 

Montzka, and A.R. Ravishankara, Kinetics of the OH reaction 

with methyl chloroform and its atmospheric implications, 

Science, 257, 227-230, 1992. 

Toohey, D.W., LM. Avallone, LR. Lail, P.A :\ewman, M.R. 

Schoeberl, D.W. Fahey, E.L Woodbridge, and J.G. Anderson, 

The seasonal evolution of reactive chlorine in the northern 

hemisphere stratosphere, Science, 261, 1134-1136, 1993. 

UNEP (United Nations Environmental Programme), Montreal 

Protocol to reduce substances that deplete the ozone layer report, 

Final Report, UNEP, 15 pp., New York, 1987. 

WMO (World Meteorological Organization), Scientific Assessment 

of Ozone Depletion, 1991, 25 pp., Geneva, 1992. 

Zander, R., M.R. Gunson, C.B. Farmer, C.P. Rinsland, F.W. Irion, 

and E. Mahieu, The 1985 chlorine and fluorine inventories in the 

stratosphere based on ATMOS observations al 30°N latitude, J. 

Atmos. Chem., 15, 171-186, 1992. 
6. Director's Office 

STRATOSPHERIC AEROSOL AND RADIATION MEASUREMENTS IN THE ALASKAN 

ARCTIC DURING AGASP-IV/LEADEX, APRIL 1992 

P.J. SHERIDAN Al\D R.S. STONE 

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 

6.1. INTRODUCTION 

The Fourth Arctic Gas and Aerosol Sampling Program 

(AGASP-IV), a component of the Arctic Leads Experiment 

(LEADEX), was conducted over the Beaufort Sea during 

late March and April 1992. The NOAA WP-30 (P-3) Orion 

research aircraft was the primary measurement platform for 

AGASP-IV and was one of several airborne laboratories 

used for atmospheric measurements in LEADEX. The 

NOAA P-3 was instrumented to measure atmospheric gas 

and aerosol species, radiation parameters at multiple 

wavelengths, and meteorological state variables. The 

purpose of these airborne measurements in LEADEX was 

to complement and compare with concurrent baseline 

station, ice camp, ice buoy, and submarine measurement 

programs. 

The NOAA P-3 flew a total of nine research missions in 

the Beaufort Sea area (- 90 research hours), operating at 

altitudes between -10 and 10,500 m above the surface 

[Herbert el al., 1993). The major objectives of AGASP-IV 

were to ( 1) measure the concentration and composition of 

gaseous and particulate constituents of springtime Arctic 

haze in the Alaskan Arctic, (2) determine components of 

the atmospheric (especially the marine) sulfur cycle, 

through measurements of OMS, MSA, S02, OCS, and so4 

in the inversion layer over lead-filled pack ice, and (3) 

determine whether significant amounts of volcanic aerosols 

from Mount Pinatubo were present in the atmosphere over 

Alaska and the Beaufort Sea. In this report, we focus on 

the analysis of stratospheric aerosol and radiation 

measurements that show severe perturbations from 

"normal" or background values. 

In the polar regions it is especially difficult to observe 

and quantify the effects of volcanic forcing because natural 

climate fluctuations are anomalously large there. In particular, efforts to estimate the radiation balance for the polar 

regions using satellite data are hampered by problems 

associated with the remote sensing of atmospheric 

properties over bright, cold surfaces [Key and Barry, 1989). 

Thus, there is a critical need for "ground truth" measurements to validate and improve operational algorithms that 

use satellite data to monitor polar climate variables. Our 

aircraft data include nearly 1300 discrete spectral measurements of solar irradiance using handheld sunphotometers, 

and in situ measurements of aerosol light scattering, 

number concentration, and particle size distribution. Our 

76 

measurements reveal elevated aerosol concentrations and 

significant numbers of large (supermicrometer) particles in 

the lower Arctic stratosphere and upper troposphere, 

indicating the presence of considerable amounts of Mount 

Pinatubo volcanic debris. These data corroborate and 

should be useful for quantifying polar-orbiting satellite 

observations of greatly enhanced aerosol optical depths at 

high northern latitudes in the spring of 1992 [long and 

Stowe, 1993]. 

6.2. METHODS 

The primary optical depth data are derived from spectral 

measurements made during AGASP-IV flight segments flown 

above the Arctic tropopause. These observations were made 

using handheld, dual-channel sunphotometers that sense 

directly-transmitted solar irradiance at 380 and 500 nm, and at 

778 and 862 nm, respectively. Each channel has a nominal 

half-band width of 5 nm and a field-of-view of 2.4' [Reddy el 

al., 1990]. Only data collected during cloud-free periods were 

analyzed. Ancillary surface-based measurements of optical 

depth used in support of aircraft analyses and to evaluate the 

decay rate of Mount Pinatubo aerosols in the Arctic are 

discussed in Stone el al. [1993]. 

Airborne measurements were made whenever viewing 

was possible within ±30' of the solar azimuth angle 

through optical glass windows fitted on either side of the 

aircraft (Du11on et al., 1989). The sunphotometers were 

carefully calibrated at high altitude sites before and after 

AGASP-IV in accordance with recommended procedures 

using the Langley plot method [Shaw, 1983]. Each 

instrument was determined to be stable with precision of 

-0.002. All optical depth values reported in this paper 

account for Rayleigh scattering, ozone absorption at 500 

nm, and changes in relative airmass as a function of time 

and location. A correction due to attenuation by the optical 

glass was also performed. Thus, from total slant path 

irradiance measurements, columnar aerosol optical depths 

were computed. Estimated uncertainties due to all sources 

are <10% of typical values reported here. 

The optical depth data are supported by several other 

types of aerosol measurements. An automated threewavelength integrating nephelometer [Bodhaine et al., 

1991] made continuous aerosol light scattering (B5p) 

measurements. This instrument performs continuous 

checks of operating parameters and corrects for Rayleigh 
scatter and instrument background in real time. A 

condensation nucleus (CN) counter [Schnell et al., 1989) 

monitored stratospheric particle number concentrations. 

Two aerosol spectrometer probes permitted optical particle 

sizing measurements for calculation of particle nurnberand volume-size distributions [Sievering et al., 1989). 

Cascade impactor samples of stratospheric particulate 

material were also collected and later analyzed using 

standard analytical electron microscopy techniques 

[Sheridan, 1989). 

6.3. RESULTS 

6.3.1. STRATOSPHERIC AEROSOL OPTICAL DEPTH 

The locations and dates corresponding to the various 

sunphotometer measurement periods are shown in Figure 6.1. 

The curved arrows are isentropic 36-hour back-trajectories 

representing stratospheric winds prior to each flight. Only 

direct measurements made above the tropopause were selected 

for analysis. Bridgman el al. [1993) give case-by-case analyses 

of eight AGASP-IV flights including discussions of a variety of 

tropospheric measurements. Tropopause heights for each flight 

were determined on the basis of analyses performed by Herbert 

el al. [1993); these range from approximately 7 km to 10 km 

depending on geographic location and synoptic conditions. 

Figure 6.2 shows the mean spectral optical depths derived 

for the corresponding times and locations shown in Figure 6.1. 

Several features of Figure 6.2 are notable. First and most 

important, the values derived for all times and locations are 

one to two orders of magnitude greater than stratospheric 

background levels which range between 0.002 and 0.006 for 

visible wavelengths [Toon and Pollack, 1976). These 

... ~ 

~ ··· ········· ············~··· 

Fig. 6.1. Distribution of sunphotometer measurements made during 

AG ASP-IV /LEAD EX stratospheric flight segments. Curved vectors 

represent stratospheric winds as described in the text. 

77 

:z: 

.. ... 

w 

0 

..J 

~ 

>= 

... 

0 

s 

"' 0 

a: 

w 

q: 

02.2 .... 

02 ~ 

0 ,, -

0.16 1 

0 14 --1 

J 

0 12 -1 

01 : 

••• I 

•• , f ········· .. J 4 0 3 .......... " 

••• 

WAVELENGTH (nm) 

Fig. 6.2. Stratospheric spectral optical depths derived for the flight 

segments shown in Figure 6. I. Slight offsets are used to clearly 

indicate values at plus and minus one standard deviation (vertical 

bars) of the means. 

values also exceed similar measurements made in the 

Arctic approximately a year after El Chichon erupted 

[Dutton el al., 1984; Spinhirne and King, 1985]. Second, 

the optical depths are rather flat spectrally in the visible 

range but show a marked decrease in the near infrared. 

Third, three of the flights (nos. 403, 406, and 407) show a 

high degree of homogeneity in time and space as evidenced 

by their small standard deviations, similar magnitudes, and 

spectral dependencies. Finally, the values for flight no. 

402 are about 60% lower than those measured during flight 

no. 407 despite their having similar flight tracks and 

altitudes relative to the tropopause. These similarities and 

differences are discussed below. 

Based on the data presented in Figure 6.2, effective aerosol 

size distributions were inferred using the constrained linear 

inversion algorithm of King el al. (1978). The maximum 

radius sensitivity (rmin ~ r ~ rmax) [Spinhirne and King, 1985) 

determined for our particular set of measurements was within 

the range rmin = 0.10 ± 0.02 μm and rmax = 1.10 ± 0.10 μm. 

We assumed an index of refraction of 1.45-0.0i based on earlier 

in situ observations of the Mount Pinatubo aerosol layers 

[Deshler el al., 1992). The inversion results are presented in 

Figure 6.3. Each curve shows the total number concentration 

dN (cm-2 μm-1) for seven radius increments (dlog( r)). The 

vertical bars indicate the range of number density determined 

by inverting the mean spectral optical depth data ±lcr presented 

in Figure 6.2. The inferred size distributions are bimodal 

having a large particle mode centered at -0.S μm and a small 

mode of higher concentration peaking below 0.18 μm radius. 

6.3.2. STRATOSPHERIC AEROSOL MEASUREMENTS 

Several sets of aerosol measurements taken during the 

AGASP-IV flights strongly support the optical depth 
...... 

'C' 

-en 

0 

'.§_ 

z 

~ 

" 0 

..J 

9 

8 

7 

6 

5 

4 

0.05 0.1 0.5 

RADIUS (MICRONS} 

407 

406 

402 

1.0 2.0 

Fig. 6.3. Effective aerosol size distributions showing the range of 

number concentrations dN at each radius interval (dlog(r)) inferred 

from the optical depth data shown in Figure. 6.2. 

observations discussed previously. This corroboration is 

particularly evident in data collected during flight nos. 406 

and 407. On both of these flights, and on flight nos. 402, 

404, and 405, the tropopause was penetrated over Alaska 

during the inbound ferry to Anchorage, and substantial time 

was spent in stratospheric air [Herbert et al., 1993). In 

contrast to this scenario, the aircraft experienced an engine 

failure on flight no. 401 that prevented it from climbing 

into the stratosphere, and during flight no. 403, 

stratospheric air was only briefly encountered [Herbert el 

al., 1993]. No sunphotometer measurements were taken on 

flight no. 408. 

Stratospheric aerosol data from flight nos. 404 through 

407 exhibit consistently high aerosol light scattering 

coefficients and particle number concentrations. As an 

example, Figure 6.4 (from Bridgman et al. [1993)) clearly 

shows the flight no. 406 stratospheric sampling period with 

enhanced CN and Bsp levels. During this flight segment, 

some of the highest optical depth measurements of the 

entire AGASP-IV program were observed (see Figure 6.2). 

The aerosol spectrometer probes typically showed 

bimodal particle size distributions that display a largeparticle number peak in the 1-2 μm diameter range, with 

the volume distribution secondary peak at slightly larger 

particle sizes than the number peak [Bridgman et al., 

1993]. Figure 6.5 (also from Bridgman el al. [1993)) 

shows the number-size and volume-size distributions for 

flight no. 405, which was chosen as a typical example and 

closely resembles those from other flights in the 404-407 

78 

sequence. These data confirm the size distributions inferred 

from the sunphotometer measurements (Figure 6.3), which 

display a large number peak at <0.18 μm radius and a 

secondary large-particle peak centered at -0.5 μm radius. 

Cascade impactor samples were also collected during 

AGASP-IV flights 402-407. Electron microscope analyses of 

these aerosol samples revealed heavy particulate loadings for 

stratospheric samples collected during flight nos. 404, 405, 

406, and 407. Figure 6.6 is a photomicrograph of stratospheric 

aerosol particles collected during flight no. 406. The smaller 

(mostly < 0.5 μm diameter) particles are nearly all composed 

of sulfate. The larger particles are one to several micrometers 

in size and are usually either sulfates or solid particles rich in 

Si or Na and CJ (suggesting terrestrial or marine origin, 

respectively). The types, sizes, and relative loadings of 

particles were similar for all stratospheric samples collected 

250 

'E 200 a. 

s 

~ 150 

~ 100 

50 

250 

:0 200 a. 

.!:!; 

~ 150 

0 

N 

0 100 

FLT 406 STRATOSPHERE 

03, Bsp, PA, 0121 TO 0310 UTC 

1.81 2.25 2.53 2.81 3.09 

TIME (hour) 

03 vs CN, 0121 TO 0310 UTC 

11 

10 e 

e 

9 :i 

8 < 

UJ 

a: 7 ::> 

6 g'l 

UJ 

a: 5 0.. 

• ~ 3 ~ 2 ~ 

lil' 

CD 

0 

6000 

5000 

Fig. 6.4. Plots of atmospheric parameters measured by aircraft instruments during a portion of flight no. 406. The stratospheric 

flight segment is denoted by the period of high 0 3, decreasing 

temperature and the highest pressure altitudes. During this time, 

CN counts and B,P were significantly elevated over upper 

tropospheric levels. 
M' 1000 

E 

~ 

0 100 (!) 

g 

~ 10 'Q 

a: 

UJ 

ID 

::; 

::::> 

z 

...J 

g 0.1 

0 

a: 

ASASP 405 PMS dN/dLOGd 

O 137 -0316, 0455-0513 UTC 

UJ 

< O.Dl .l---.,.--...,,-.,.-r-r-rrr1r---r--..--r-,-,--r...-r;i10 

0.1 

DIAMETER (um) 

Fig. 6.5. Particle size dislribu lions derived from the ASASP 

aerosol spectrometer probe data. This bimodal distribution was 

lypical of stratospheric aerosols sampled during flight nos. 404-407. 

during flights 404-407. High altitude impactor samples 

from flights 402 and 403 showed very light particulate 

loadings. For flight 403, this is probably because little 

time was spent in stratospheric air. The aerosol data from 

flight no. 402 suggest that the aircraft flew well into the 

stratosphere, but showed no significant elevation in aerosol 

concentrations (as was observed on the later flights). 

Possible explanations for these observations are discussed 

in section 6.4. 

Fig. 6.6. Analytical electron micrograph of particles collected 

during the stratospheric flight segment of AGASP-IV flight 406. 

Aerosol optical depths and concentrations measured during this 

period were consislently among the highest observed in this study. 

Parlicles exhi biled a roughly bimodal size distribution peaking al 

< 0.5 μm and several micrometers in diameter. 

79 

6.4. DISCUSSION 

It appears from Figure 6.2 that some temporal and/or 

spatial variations in stratospheric aerosols occurred over 

the period and region represented by our data. The 

relatively lower stratospheric aerosol concentrations and 

opacity noted for flight no. 402 can be explained by 

differences in synoptic conditions during the respective 

flight periods [Herbert et al., 1993). During flight no. 402 

strong northerly winds transported polar air into the region 

whereas weaker southerly flow generally characterized the 

later flights. An analysis of isentropic back-trajectories 

[Harris and Bodhaine, 1983) based on the ECMWF 2.5" 

gridded data supports the synoptic analyses. Figure 6.1 

shows 36-hour backward air mass trajectories representing 

the flow at altitudes ranging from -14.5 km to 15.8 km 

referenced to the respective mid-flight segments. This 

analysis suggests that relatively clean Arctic air displaced 

or mixed with lower latitude air effectively reducing the 

stratosphere's opacity prior to flight no. 402. The 

formation of the polar vortex during the previous 

autumn/winter probably prevented high concentrations of 

Mount Pinatubo aerosols from penetrating the central 

Arctic. Similar gradients related to the position, size and 

shape of the polar vortex were observed several months 

after El Chichon erupted [McCormick et al., 1983). 

The relatively large 380 nm optical depths measured 

during flight no. 402 (Figure 6.2) suggest fundamental 

differences in the aerosols' microphysical properties 

compared with the results of the other flights. Increased 

attenuation at shorter wavelengths can be explained by the 

presence of higher concentrations of small particles (Figure 

6.3) that have greater extinction efficiencies as the ratio of 

size-to-wavelength (r/"A.) increases (van de Hulst, 1981). 

The sharp decreases evident at the large particle end of the 

inferred size spectra are probably due to diminishing 

opacity as wavelength increases [Spinhirne and King, 

1985). 

In situ aerosol measurements (CN counts and B5p) made 

during flight no. 402 [Bridgman et al., 1993) indicate no 

enhanced small particle mode similar to those observed on 

flight nos. 404-407. This is the only case in which the 

aircraft aerosol measurements do not directly support the 

results derived from sunphotometer measurements. Figure 

6.3 suggests a small-particle enhancement and largeparticle depletion in the inferred size distribution relative 

to the other flights. It is conceivable that Mount Pinatubo 

sulfate aerosols were in the optical path above the aircraft 

flight level, but were not present in high concentrations at 

the altitude the aircraft reached on flight no. 402. This is 

consistent with the notion of low settling velocities for very 

small (i.e., few-tenth micrometer) particles. 

The high degree of consistency between our optical depth 

measurements (including their inferred size distributions) 

and the in situ aerosol data lends confidence lo our 

measurements that strongly support recent ground-based 

[Stone et al., 1993) and satellite [Long and Stowe, 1993) 

observations of large aerosol optical depths in the Arctic in 
spring 1992. Further, these data are being used in multipleycar studies that begin to address potential climate impacts 

of the volcanic aerosols by documenting their longevity 

(i.e., decay rate) in the atmosphere [Stone el al., 1993]. 

Preliminary data from these studies suggest a significantly 

longer aerosol residence (e-folding) time in the arctic 

atmosphere compared with that observed for past volcanic 

episodes (e.g., El Chichon). 

Acknowledgments. Thanks are due 10 G. Herbert, H. Bridgman, and 

E. Dutton for access to ancillary data; to J. Harris for kindly 

providing the isentropic trajectories; lo J. Key for mak ing 

sunpholometer measurements during several of the AGASP flights; 

and to the NOAA P-3 crew. 

6.5. REFERE!liCES 

Dodhaine, B.A., N.C. Ahlquist, and R.C. Schnell, Three-wavelength 

nephelometer suitable for aircraft measurement of background 

aerosol scattering coefficient, Atmos. Environ. 25A, 2267-2276, 

1991. 

Bridgman, H.A., P.J. Sheridan, R.S. Stone, P. McCaslin, B.A. 

Bodhaine, and R.C. Schnell, The analysis of haz.e distribution, 

aerosol chemistry, and optical depths for the Fourth Arctic Gas 

and Aerosol Sampling Program (AGASP IV), March-April 1992, 

NOAA CMDL Technical Memorandum, NOAA Environmental 

Research Laboratories, Boulder, CO, (in preparation) 1993. 

Deshler, T., D.J. Hofmann, B.J. Johnson, and W.R. Rozier, 

Balloonbome measurements of the Pinatubo aerosol size 

distribution and volatility at Laramie, Wyoming during the 

summer of 1991. Geophys. Res. Leu., 19, 199-202, 1992. 

Dutton, E.G., J.J. DeLuisi , and B.A. Bodhaine, Features of aerosol 

optical depth observed at Barrow, March 10-20, 1983, Geophys. 

Res. Lei/., 11, 385-388, 1984. 

Dutton, E.G., J.J. DeLuisi, and G. Herbert, Shortwave aerosol optical 

depth of Arctic haze measured on board the NOAA WP-3D during 

AGASP-11, April 1986,J. Atmos. Chem., 9, 71-79, 1989. 

Harris, J.M. , and B.A. Bodhaine (Eds.), Geophysical Monitoring for 

Climatic Change No. 11: Summary Report 1982, 160 pp., NOAA 

Air Resources Laboratory, Boulder, CO, 1983. 

Herbert, G.A., P.J. Sheridan, R.C. Schnell, M.Z. Bieniulis, B.A. 

Bodhaine, and S.J. Oltmans, Analysis of meteorological 

80 

conditions during AGASP-IV: March 30-April 23, 1992, NOAA 

Technical Memorandum ERL CMDL-5, NOAA Environmental 

Research Laboratories, Boulder, CO, April 1993. 

Key, J.R., and R.G. Barry, Cloud cover analysis with Arctic 

AVHRR, part I: Cloud detection, J. Geophys. Res., 94(D15), 

18,521-18,535, 1989. 

King, M.D .. D.M. Byrne, B.M. Herman, and J.A. Reagan, 

Aerosol size distribu tions obtained by inversion of spectral 

optical depth measurements, J. Atmos. Sci., 35, 2153-2167, 

1978. 

Long, C., and L. Stowe, Using the NOAA A VIIRR to study 

stratospheric aerosol optical thickness following the Mount 

Pinatubo eruption, Geophys. Res. lell. (in review) 1993. 

McCormick, M.P., C.R. Trepte, and G.S. Kent, Spatial changes in 

the stratospheric aerosol associated with the north polar vortex, 

Geophys. Res. lell., 10, 94 1-944, 1983. 

Reddy, P.J., F.W. Kreiner, J.J. DeLuisi, and Y. Kim, Aerosol optical 

depths over the Atlantic derived from shipboard sunphotometer 

observations during the 1988 global change expedition, Glob. 

Biogeochem. Cycl., 4, (3), 225-240, 1990. 

Schnell, R.C., T.B. Watson, and B.A. Bodhaine, NOAA WP-30 

instrumentation and flight operations on AGASP-11, J. Atmos. 

Chem., 9, 3-16, 1989. 

Shaw, G.E., Sunphotometry, Bull. Amer. Meteorol. Soc., 64, 4-10, 

1983. 

Sheridan, P.J., Characterization of siz.e segregated particles 

collected over Alaska and the Canadian high Arctic, AGASP-11 

flights 204-206, Atmos. Environ., 23, 2371-2386, 1989. 

Sievering, H., P.J. Sheridan, and R.C. Schnell, Siz.e distribution of 

large aerosol particles during AGASP-11: Absence of St. 

Augustine eruptive particles in the Alaskan Arctic. Atmos. 

Environ., 23, 2495-2499, 1989. 

Spinhime, J.D., and M.D. King, Latitudinal variation of spectral 

optica l thickness and columnar size distribution of the El 

Chichon stratospheric aerosol layer, J. Geophys. Res., 90(D6), 

10,607-10,619, 1985. 

Stone, R.S., J.R. Key, and E.G. Dutton, Enhanced opacity of the 

Arctic stratosphere after the 1991 eruptions of Mount Pinatubo, 

Geophys. Res. Lei/., (in press) 1993. 

Toon, O.B., and J.B. Pollack, A global average model of 

atmospheric aerosols for radiative transfer calculations, J. Appl. 

Meteorol., 15, 225-246, 1976. 

van de Hulst, H.C., Light Scallering By Small Particles, 410 pp., 

Dover Publications, Inc., New York, 1981. 
7. Cooperative Programs 

Antarctic Ultraviolet Spectroradiometer Monitoring Program: 

South Pole and Barrow Contrasts in UV Irradiance 

C.R. BOOTH, T .B. LUCAS, J.R. TUSSON IV, J.H. MORROW, AND T. MESTECHKINA 

Biospherical Instruments Inc., San Diego, California 92110-2621 

1. INTRODUCTION 

The Antarctic Ultraviolet spectroradiometer monitoring 

network was established by the United States 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 placed in strategic locations in 

Antarctica and the Arctic (Table 1), and a new operational 

site in San Diego that is also used for training and testing. 

The network makes essential measurements of UV spectral 

irradiance and provides a variety of biological dosage 

calculations of UV exposure. Under contract to Antarctica 

Support Associates (ASA), directed by NSF, Biospherical 

Instruments Inc., is responsible for operating and 

maintaining the network and distributing data to the 

scientific community. 

The spectroradiometer system contains an irradiance 

diffuser, double holographic grating monochromator, 

photomultiplier tube (PMT), and calibration lamps. 

Tungsten-halogen and mercury vapor lamps are used for 

automatic internal calibration of the optical pathway. The 

monochromator and PMT are located m individual 

temperature controlled subassemblies. The entire instrument is operated under computer control, including regular 

calibration cycles, several times each day. Details may be 

found in Booth et al., (1992). 

2. UV RADIATION CLIMATEATTHEAMUNDSEN·SCOTI 

SOUTH POLE STATION AND BARROW, ALASKA 

The South Pole and Barrow, Alaska, installations are in 

locations that also have CMDL installations, and 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 generally thin when it does occur. The very small 

hourly change in the solar-zenith angle 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 significant change in surface albedo occurs 

both due to the springtime snowmelt [Dutton and Endres, 

1991) and changes in sea ice coverage. Significant changes 

in incident irradiance also occur due to Arctic storms. The 

contrast between Barrow and the South Pole can be seen in 

Figure lb, where the integrated noontime irradiance over the 

UV-A (320-400 nm) for 1992 is plotted. 

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 I a, a substantial drop is 

seen in the 300 nm irradiance around December 6. Data 

from Total Ozone Mapping Spectrometer (TOMS) report 

that the ozone column over the South Pole rose from 193 

DU on December 5 lo 292 DU on December 7, 1992. TOMS 

update on CD-ROM is available from the National Space 

Science Data Center, Goddard Space Flight Center. 

Strong springtime depletion in ozone over the Pole, both 

in the spring and approaching mid-summer, compared with 

higher ozone levels in the fall, allow careful estimates of the 

impact of changes in ozone on UV irradiance with most 

other conditions (cloud cover, albedo, and solar zenith 

angle) being equal. Figure 2 shows the DNA dose weighted 

TABLE 1. Installation Sites 

Site Latitude Longitude 

McMurdo 77"5l'S 166"40'E 

Palmer 64"46'S 64"03'W 

South Pole 9o·oo·s o· 

Ushuaia, Argentina 54·59·s 68"W 

Barrow, Alaska 71"18'N 156" 47'\V 

San Diego, California 32"47'N 117"14'\V 

*CADIC: Centro Austral de lnvestigaciones Cicntificas, Argentina 

tUkpcagvik Inupiat Corporation-1\ational Arctic Research Laboratory 

81 

Established 

March 1988 

May 1988 

February 1988 

November 1988 

December 1990 

October 1992 

Location 

Arrival heights 

Clean air building 

Clear air building 

CAD IC• 

UIC-NARLt 

Biospherical Instruments Inc. 
Ql8 

Ql6 

Ql4 

Ql2 

N § QI 

~ Qa! =I, 

QQ) 

QC» 

Q02 

O+---._;;_~--~t4-~-+-~~i--~..:+i..i;:;"""""'~~----

l-Jan :D-Hi> 10..Ap- D-Miy 19-hl 7-Sq> 71-01 16-Dx: 

lNA 

4500 

400) 

35aJ 

no 

a 25(X) u 

~mi =I, 

1500 

laD 

~ 

0 

1-Jai :D.Rb 10..Ap- D-Miy 19-Jul 7-Sq> 71-01. 16-Dx: 

Fig. I. The noontime irradiance is shown al Barrow (fine line) and the 

South Pole (heavy line) during 1992. Panel (a) shows the irradiance al 

300 nm and is contrasted with panel (b) which shows the integrated UV-A 

(320-400 nm) irradiance. The higher values al Barrow are due lo the 

higher sun elevation. The irradiances al Barrow peak in June, while the 

irradiance al the South Pole normally peaks in December. 

Radiation Amplification Factor of 2.2 

600% 

500% 

:; 400% 

.5 300% 

:ii 

8 200% 

~ 100% 

0%. 

-100% 

-60% -50% -40o/o -30% -20% -10% 0% 

Decrease in Ozone 

Fig. 2. Radiation amplification factor computed for South Pole data set 

covering 1991-1992. Points referto equal solar zenith angles (± 0.3"). 

irradiance (after Set/ow, 1974; see Booth et al., 1992 for 

details) change measured for a series of day pairs when 

different amounts of ozone depletion were encountered. 

One scan per day was selected closest in time to the 

overpass of the TOMS satellite. A random mixture of l 

year against another, or spring against fall observations, was 

used covering ozone concentrations ranging from 111 DU to 

408 DU. Figure 2 shows the observed relationship between 

ozone depletion expressed in percentage, versus doseweighted irradiance enhancement, also in percentage. No 

scans were included when a time mismatch of greater than 5 

hours occurred. Only data where the sun was higher than 

80' (zenith angle) were considered. In all, 277 spectra were 

included in the analysis. 

Two lines are shown in Figure 2: the straight line 

expresses a simple formulation of the effect of ozone 

depletion to amplify UV irradiance and is a linear 

extrapolation of a rule of" l % decrease in ozone will bring a 

2.2% increase in UV," while the curved line expresses a 

power-based formulation of this rule as suggested by 

M adronich [ 1993]. This allows us to determine the 

"amplification" of UV irradiance caused by ozone depletion. 

82 

3. SUMMARY 

High spectral resolution scanning UV spectroradiometers 

have been established at several high latitude sites and are 

successfully providing multiyear data sets. Resulting data 

have been used to test radiative transfer models (Lubin and 

Frederick, 1990, 1991, 1992); Lubin el al .. (1989); Smith et 

al., (1991, 1992a), derive ozone concentrations (Stamnes et 

al., 1990, 1991, 1992), and examine the biological impact of 

enhanced UV [Lubin et al .. 1993; Cullen et al., 1992; Smith 

et al., 1991, 1992b). The data are available on CD-ROM to 

a broad segment of the scientific community . Please contact 

the authors for more information. 

The data from the NSF UV Spectroradiometer Network is 

available to all qualified researchers. The data shown in 

this report is available on CD-ROM, ISO 9660 format. NSF 

grantees have priority access to these data. For more 

information, please contact: C. R. Booth at Biospherical 

Instruments Inc., 5340 Riley St., San Diego, CA 92110 (Fax 

619 686-1887, or BOOTH@SSURF.UCSD.EDU). 

Acknowledgments. This research and monitoring activity was 

funded by contract A IT-Ml 743 from Antarctic Support 

Associates under direction of Polly Penhale at NSF, Office of 

Pola r Programs. B. Mendonca of CMDL assisted in providing 

operators and support for the installations at the South Pole and 

Barrow. R. McPeters of NASA/GSFC provided TOMS total 

ozone data for compa rison purposes. Barrow operators include 

D. Norton (Arctic Sivumnun llisagvik College); D. Endres and 

Brad Ha lter (CMDL). The Ukpeagvik Jnupial Corporation of 

Barrow prov ided assistance in the installation. Operators at 

Palmer and McMurdo have been provided by ASA. Special 

thanks go to John Gress of ASA who has been invaluable in the 

ope ration of the network. 
4. REFERE1'CES 

l3001h, C.R., T. Lucas, T. Meslechkina, J. Tusson, 0. Neuschuler, and 

J. Morrow, NSF polar programs UV spec1roradiome1er network 

1991-1992 operations report, Bio. Instr. Tech. Rep. 92-1, 145 pp., 

Biospherical Instruments Inc., San Diego, CA, 1992. 

Cullen, J.C., P.J. Neale, and M.P. Lesser, Biological weighting 

function for the inhibition of phytoplankton photosynthesis by 

ultraviolet radiation, Science, 258, 646-650, 1992. 

Dutton, E.G., and DJ . End res, 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, 0., and J.E. Prederick, The ultraviolet radiation environment 

of the Antarctic Peninsula: the ro les of ozone and c loud cover, J. 

Appl. Meteorol., 30, 478-493, 1991 . 

Lubin, 0., and J.E. Frederick, Observations of ozone and cloud properties 

from NSF ultraviolet monitor measurements at Palmer Station, 

Antarctica, Ant. J. U.S., 1989 Review, 25(5), 241-242, 1992. 

Lubin, 0., J.E. Frederick, C.R. Booth, T.B. Lucas, and D.A. 

Neuschuler, Measurements of enhancaed springtime ultraviolet 

radiation al Palmer Station, Antarctica, Geophys. Res. Lett., 16(8), 

783-785, 1989. 

Lubin, 0., Mitchell, B.G., J.E. Frederick, A.O. Alberts, C.R. Booth, 

T. Lucas, D. Neuschuler, A contribution toward understanding the 

biospherical signifi cance of Antarctic ozone depletion, J. 

Geophys. Res., 97, 78 17-7828, 1993. 

Madronich, S., UV Radiation in the Natu ral and Perturbed 

Atmosphere, in UV-8 Radiation and Ozone Depletion, edited by 

M. Tevini, pp. 28-29, Lewis Publishers, Boca Raton, FL, 1993. 

Setlow, R. B. The wavelengths in sunlight effective in producing 

sk in cancer: a theoretical analysis, Proc., Nat. Acad. Sci., 71(9), 

3363-3366, 1974. 

Smith, R., K. Baker, 0. Menzies, and K. Waters, Biooptical 

measurements from the Ice Colors '90 cruise 5 October-21 

November 1990, SIO Reference 91-13, 121 pp., Scripps 

Institution of Oceanography, San Diego, CA, 1991. 

Smith, R., B.B. Prezelin, R.R. Bidigare, 0. Karentz, and S. 

Macintyre, Ice Colors '90: Ultraviolet radiation and phytoplankton 

biology in Antarctic waters, Ant. J. U.S., in press, 1993. 

Smith, R. C., Z. Wan, and K. S. Baker, Ozone depletion in 

Antarctica: Satellite and ground measurements, and modeling 

under clear-sky conditions, J. Geophys. Res., 97, 7383-7397, 

1992a. 

Smith, R. C., B. B. Prezelin, K. S. Baker, R. R. Bidigare, N. P. 

Boucher, T. Coley, D. Karentz, S. Macintyre, H. A. Matlick, D. 

Menzies, M. Ondrusek, Z. Wan, and K. J. Waters, Ozone 

depletion: Ultraviolet radiation and phytoplankton biology in 

Antarctic waters, Science, 256, 952-959, l 992b. 

Stamnes, K., J. Slusser, and M. Boden, Derivation of total ozone 

abundance and cloud effects from spectral irradiance 

measurements, J. Appl. Optics, 30, 4418-4426, 1991. 

Stamnes, K., J. Z. Jin, J. Slusser, C. Booth, and T. Lucas, Severalfold enhancement of biologically effective ultraviolet radiation 

levels al McMurdo Station, Antarctica, during the 1990 ozone 

hole, Geophys. Res. lellers, 19, 1013-1017, 1992. 

Stamnes, K., J. Slusser, M. Bowen, C. Booth, and T. Lucas, 

Biologically effective ultraviolet rad iation, total ozone abundance, 

and cloud optical depth at McMurdo Station, Antarctica, 

September 15, 1988, through April 15, 1989, Geophys. Res. 

Lellers, 17, 2181-2184, 1990. 

83 
Lidar Observations of Volcanic Aerosol Layers and Polar Stratospheric 

Clouds at South Pole, 1990, 1991, and 1992 

M. CACCIANI, P. DI GIROLAMO, A. DI SARRA, G. FIOCCO, D. FuA, P. COLAGRANDE, AND G. PANEGROSSI 

Universita "la Sapienza ", Physics Department, 00185 Roma, lta/y 

11'TRODUCTION 

The Physics Department of the University of Rome "La 

Sapienza" has maintained a lidar at SPO since December 

1987, mainly to study polar stratospheric clouds (PSCs) 

and aerosols in the antarctic stratosphere. The system is 

run by winterover personnel of NOAA and NSF. 

During 1991 the eruptions of Mt. Pinatubo in the 

Philippines and of Mt. Hudson in Chile produced a 

substantial increase of the aerosol load in the polar 

stratosphere. Two well-separated layers could be identified 

in the lidar echoes: the lower layer, L, around 10 km and 

with a vertical extent of about 3 km; and the upper layer, 

U, characterized by a lower value of the backscattering 

coefficient between 17 -26 km [Deshler et al., 1992). 

The height and time of appearance of layer L support its 

attribution to the eruptions of Mt. Hudson. Layer U can be 

attributed to the aerosol cloud generated by the eruptions of 

Mt. Pinatubo, although the identification of the arrival time 

of the layer is difficult because of the poor performa."lce of 

the lidar during the critical period of the vortex break-up. 

Analyses of the integrated backscatter suggest that the 

Pinatubo cloud first reached the Antarctic stratosphere at 

altitudes higher than 17 km, and at lower altitudes only 

later. After that time, approaching winter, the total 

integrated backscatter, IB, remained approximately 

constant at all levels. An example of the vertical profiles 

of the aerosol-to-molecules backscattering ratio in 1991 is 

given in Figure 1 distinctly showing the two layers: the 

lower one centered around 10 km and the higher one 

extending between 16 and 28 km. 

The change in the characteristic features of lidar echoes, 

particularly as a function of the atmospheric temperature, 

has been studied with the aim of identifying the formation 

30000 

-

lSOOO ~ 

:! 20000 

,;; 

.. ?-- ~ ISOOO ::c 

~ 10000 v--- sooo 

B1eluu1trrin& ,.,lo 

Fig. I. The backscattering ratio profile for December 8, 1991. 

84 

of PSCs, type I (NAT) and type II (ice) when, during 

winter, the conditions leading to the condensation of either 

HN03 or H20 are reached. 

MASS LOAD AND SEDIMENTATION OF 

PINATUBO AEROSOL 

Under the assumption that the particles are homogeneous 

spheres, the backscattering efficiency, Qbs, has been 

approximated by a linear function of the size parameter 

[Pinnick et al., 1980) and used to relate the mass content 

per unit volume, M, to the backscattering coefficient 

regardless of its dependence on the particle-size 

distribution. 

The aerosol mass load was computed combining the 

known values of the composition of sulfuric acid aerosol 

[Steele and Hamill, 1988), water vapor profiles measured in 

Antarctica [Rosen et al., 1991). and the temperature 

profiles at South Pole. In a similar way the sulfuric acid 

content of the particles was estimated [Cacciani et al., 

1993). 

The columnar aerosol mass evolution follows the total IB 

trend, increasing to a maximum value around 80 mg m-2 

comparable to those reported by other authors at low- and 

mid-latitudes [Valero and Pilewski, 1992; Winker and 

Osborn, 1992; Gobbi et al., 1992). 

To establish if sedimentation of the particles takes place 

in the stratosphere, the height of the center of the mass of 

the sulfuric acid contained in the aerosol was compared to 

the height of the 100 mb and 50 mb surfaces during the 

period January-early June. An estimate of the height 

decrease of the air mass due to the diabatic cooling is given 

by the altitude of the 100 mb isobar; the descent is about 1 

km between January and June. In fact, the center of mass 

is decreasing at a faster rate than the isobaric altitude 

during January and February, when changes in the aerosol 

vertical distribution occur that are attributable to the arrival 

of aerosol-rich air in the lowest layers. 

POLAR STRATOSPHERIC CLOUDS 

Analyses of PSC observations have been carried out for 

the winters of 1990 and 1992. The comparison shows 

differences attributable to the large amount of sulfuric acid 

aerosol of volcanic origin present in the polar stratosphere 

during 1992 and its effect on nucleation. 

The evolution of the backscattering in the two cases 

shows a different character: larger echoes attributable to 

PS Cs were recorded in 1992 com pared to 1990. The 

differences in the intensity of the echoes is being 
interpreted as due to a large number of smaller particles 

present in PSCs in 1992 compared to those present in 1990. 

An example of the vertical profile of the backscattering 

coefficient obtained in July is given in Figure 2 for 1990 

and in Figure 3 for 1992. 

Criteria to distinguish the echoes from PSCs from those 

due to the sulfuric acid aerosol and those due to type I 

PSCs from those due to type II, are being applied to the 

present set of data. 

The sensitivity of the backscattering to temperature 

changes near the base of a PSC is amenable to a relatively 

30000 

25000 

! 10000 ~ ~ 

.li 

·r 

:: 15000 

~ 

10000 ~ 

- 5000 

0.0[+00 5.0E-ot I.OE-GI 1.5[...0I 

81cluulluin1 codllclrol {<111·1 lr·I) 

Fig. 2. The backscattering coefficient profile for July 3, 1990. 

JOOOO 

25000 

! 10000 

,;; 

.. ·; 15000 

= 

sooo~::;=;;:;:;=f=r~...,..,,j ...... ~.,.....j.~.......-...-+~.......-...-+-.-.,...,...~I 

0.0[+00 5.01:-ot 1.01:-U l.SE-01 2.0£.01 2.5£.0I 3.0£.0a 

Bacluu1tui11 <0<1'1\cltat (<m·I 1r-I) 

Fig. 3. The backscauering coefficient profile for July 17, 1992. 

85 

simple calculation [Fiocco et al., 1991, 1992; Fua et al., 

1992], in which this quantity can be related to the 

difference between the partial pressure of the condensing 

species. A more elaborate criterion is based on the use of a 

more complex model for aerosol formation. 

REFERENCES 

Cacciani, M., P. Di Girolamo, A. di Sarra, G. Fiocco, and D. Fua, 

Volcanic aerosol layers observed by lidar at South Pole, 

September 1991 -June 1992, Geophys. Res. Lei/., 20, 807-810, 

1993. 

Deshler, T., A. Adriani, G.P. Gobbi, DJ. Hofman, G. Di 

Donfrancesco, and EU. Johnson, Volcanic aerosol and ozone 

depletion within the antarctic polar vortex during the austral 

spring of 1991, Geophys. Res. Lett., 19, 1819-1822, 1992. 

Fiocco, G., D. Fua, M. Cacciani, P. Di Girolamo, J. DeLuisi, On the 

temperature dependence of polar stratospheric clouds, Geophys. 

Res. Lei/., 97, 5939-5946, 1991. 

Fiocco, G., M. Cacciani, P. Di Girolamo, D. Fua, and J. DeLuisi, 

Stratospheric clouds at South Pole during 1988: I. Results of lidar 

observations and their relationship to temperature, Geophys. Res. 

Lei/., 97, 5939-5946, 1992. 

Fua, D., M. Cacciani, P. Di Girolamo, G. Fiocco, A. di Sarra, 

Stratospheric clouds at South Pole during 1988: II. Their 

evolution in relation to atmospheric structure and composition, J. 

Geophys. Res., 97, 5947-5952, 1992. 

Gobbi, G.P., F. Congeduti, and A. Adriani, Early stratospheric 

effects of the Pinatubo eruption, Geophys. Res. Lei/., 19, 997-

1000, 1992. 

Pinnick, R.G., S.G. Jennings, and P. Chylek, Relationship between 

extinction, absorption, backscattering, and mass content of 

sulfuric acid aerosols, J. Geophys. Res .. 85, 4059-4066, 1980. 

Rosen, J.M., N.T. Kjome, and SJ. Oltmans, Balloon borne 

observations of backscauer, frost point, and ozone in polar 

stratospheric clouds at the South Pole, Geophys. Res. Le11 .. 18, 

17 1-174, 1991. 

Steele, H.M., and P. Hamill, Effects of temperature and humidity on 

the growth and optical properties of sulfuric acid-water droplets 

in the stratosphere,J.Aeroso/ Sci., 12, 517-528, 198 1. 

Valero, F.P., and P. Pilewskie, Latitudinal survey of spectral depths 

of the Pinatubo volcanic cloud-derived particle sizes, columnar 

mass loading, and effects on planetary albedo, Geophys. Res. 

Lett., 19, 163-166, 1992. 

Winker, D.M., and M.T. Osborn, Airborn lidar observation of the 

Pinatubo volcanic plume, Geophys. Res. Lett., 19, 167-170, 1992. 
Fine Sulfur Concentrations at the Mauna Loa Observatory 

and Other Hawaiian Sites 

THOMAS A. CAHILL 

Air Quality Group, Crocker Nuclear l..Aboratory and Department of !..And, Air, and \Vat er Resources, University of California, Davis 95616 

Fine aerosol mass and its components, including sulfur 

(= sulfate) aerosols, have been collected (Wednesday, 

Saturday) and analyzed at the Kiluaea site of Hawaii 

Volcanoes National Park since fall 1986. This was a 

component of the National Park Service's fine aerosol 

network concerned with visibility degradation at national 

parks and monuments. In 1988 this formed the foundation 

of the Interagency Monitoring of Protected Visual 

Environments (IMPROVE) program, with the same mission 

but expanded scope, now operating at 57 sites in the United 

States. In 1990 sites were added at Haleakala National 

Park on Maui and at the Mauna Loa Observatory (MLO) on 

Hawaii, partly to better understand the effect of the 

continuously erupting volcano on the Hawaii Volcanoes 

data set. The data have also given a rare opportunity for a 

statistically significant fine aerosol data set in a mid ocean 

site as a function of elevation above sea level, with 

potential use in the aerosol forcing term of global climate 

models. 

The aerosols arc collected for a 24-hour period each 

Wednesday and Saturday at Hawaii Volcanoes and 

Haleakala parks at elevations of 1240 m and 1150 m above 

sea level, respectively. The samples from MLO (3380 m) 

are also collected twice a week, but the samplers operate on 

different time schedules. One operates continuously giving 

3-day (Monday-Thursday) and 4-day (Thursday-Monday) 

samples (MALO!), while the other operates in the same 

manner but only for hours bet\Ueen 2200 and 0600, thus 

generally dominated by downslope winds (MAL02). Each 

sampler is the standard 22-L min·l. IMPROVE 2.5 μm D(p) 

cyclone sampler with no pre-treatment of the air stream. 

Particles are collected on stretched Teflon filters with 

supporting plastic rings. In addition, at Hawaii Volcanoes 

and Haleakala National Park, the full IMPROVE array is 

present including a nylon filter following an acidic 

gas/vapor denuder [Eldred et al., 1988]. The nylon filter is 

analyzed by ion chromatography for sulfates, nitrates, and 

chlorides, while the Teflon filters are analyzed for fine 

mass, hydrogen for organic, Na and heavier by PIXE and 

PESA [Cahill et al. 1990]. Sensitivity for transition metals 

is roughly 0.02 ng m-3, while for heavy metals it rises to 

roughly 0.06 ng m·3 [Cahill et al., 1992]. 

While all collection and analysis protocols adhere to 

published quality control procedures, the IMPROVE 

network is designed to exploit ways to ensure knowledge of 

both precision and accuracy through our concept of 

"integral redundancy." In this concept, most major species 

are measured by two independent methods on two fully 

independent samplers operating side by side, with analysis 

on different substrates at different laboratories. For the 

86 

situation of sulfur, we can make measurements of sulfur by 

PIXE on Teflon in channel A which, when multiplied by 

3.0, should equal the results of sulfate analyses by ion 

chromatography on nylon filters in channel B. Figure 1 

shows this comparison for all western U.S. sites, excepting 

those in California but including all three Hawaiian sites, 

for summer 1992. The excellent agreement is not only 

proof that all samplers are operating properly, including 

flow rates, timing, etc., but that the sulfur present is 

consistent with sulfate. Similar redundancies are done for 

gravimetric fine mass versus the sum of all species, and 

organic matter by two very different techniques, from 

carbon analysis off quartz filters by combustion in channel 

C versus hydrogen by PESA from Teflon in channel A 

[Cahill et al., 1990]. However, note that only channel A 

was operated at MLO so that quality assurance tests such as 

these at lower elevations must be extrapolated to this site. 

An example of the type of data generated quarterly (and 

available to any user) is shown in Tables 1, 2, and 3 for the 

MLO downwind sampler. All values are in ng m·3 except 

mass which is in μg m-3. The term "KNON" means 

II 

.q0 

(/) 

H • 46) 

R • 0 99~ 

v . 1 01eo•x - 11 •eaa o0 • 0 009~ ob• tO 144 4 

7000. 

0. 

0. 

53 

i - 106~ Jt o;- lJ 77 o.- 726 68 

j • 1013. 09 oy J4 JS o

1 - 739 69 

7000. 

Fig. I. Sulfur (from PIXE) versus sulfate (from ion 

chromotography) from IMPROVE western sites, summer 1992. 

IMPROVE sites in California have been deleted from this 

comparison, but all Hawaiian sites are included. 
00 

-J 

TABLE 1. 24-Hour Concentrations (ng m·3) of Major Elements, and Tracer Elements from the IMPROVE Paniculate Network, 

June 1, 1993-August 31, 1992, at 0000 LST 

Date H 

June 03 26.9 

June 06 33.0 

June 10 19.8 

June 13 32.6 

June 17 19.4 

June 20 30.4 

June 24 25.0 

June 27 17.2 

July 01 17.6 

July 04 40.0 

July 08 28.7 

July 11 28.0 

July 15 40.0 

July 18 28.4 

July 22 29.4 

July 25 19.5 

July 29 35.5 

Aug. 01 16.6 

Aug. 05 25.8 

Aug. 08 56.3 

Aug. 12 15.4 

Aug. 15 17.0 

Aug. 19 25.9 

Aug. 22 29.2 

Aug. 26 16.8 

Aug. 29 5l.l 

s 

60.9 

76.7 

48.6 

70.0 

61.0 

54.2 

59.6 

47.5 

36.6 

73.2 

73.1 

77.8 

105.0 

63.7 

103.0 

51.1 

115.0 

68.2 

76.7 

219.0 

43.1 

47.0 

86.0 

80.1 

56.5 

152.0 

Masst 

0.79 

0.73 

0.58 

0.68 

0.75 

0.85 

0.82 

0.44 

0.41 

0.63 

0.78 

0.51 

0.95 

0.32 

0.72 

0.76 

0.94 

l.12 

0.72 

1.13 

0.44 

0.29 

0.56 

0.51 

0.59 

1.16 

SI 

35.2 

61.9 

13.5 

39.4 

27.4 

44.5 

41.5 

13.8 

9.8 

12.3 

11.8 

9.9 

35.5 

7.8 

4.6 

11.0 

18.5 

17.1 

6.6 

6.0 

2.6 

4.4 

5.0 

4.6 

3.3 

9.3 

•Analytical minimum detectable limit (mdl). 

tMass in micrograms m·3 

K 

7.5 

12.5 

3.9 

7.1 

5.8 

9.8 

8.5 

2.8 

2.1 

2.1 

3.0 

2.2 

9.6 

2.2 

1.9 

3.4 

4.6 

4.9 

1.6 

1.4 

2.5 

2.2 

2.0 

1.5 

2.8 

2.9 

Soil Elements 

CA 

11.4 

20.6 

4.0 

11.2 

9.3 

17.5 

14.9 

3.1 

3.3 

2.5 

3.3 

2.6 

9.1 

2.7 

0.7 

3.0 

5.5 

6.6 

l.l 

I.I 

0.4 

1.4 

0.3 

1.0 

0.8 

2.1 

TI 

0.8 

1.8 

•o.3 

1.0 

0.5 

1.1 

1.0 

0.6 

0.6 

0.4 

0.3 

0.6 

0.6 

0.6 

0.3 

0.6 

0.4 

1.0 

0.2 

0.4 

0.5 

•0.4 

0.5 

•o.3 

1.3 

0.4 

MN 

*0.2 

0.6 

•0.2 

0.9 

0.2 

•0.2 

0.3 

0.5 

0.2 

•0.2 

•0.1 

•0.2 

0.5 

•0.2 

0.2 

•0.2 

•0.2 

0.4 

0.2 

•0.2 

•0.2 

•0.2 

0.3 

0.3 

0.4 

0.2 

FE 

10.0 

16.8 

3.5 

10.4 

8.2 

14.3 

12.4 

2.9 

2.5 

2.6 

3.9 

2.5 

11.2 

1.6 

0.9 

3.2 

5.3 

5.0 

1.2 

0.5 

0.6 

1.0 

1.7 

0.8 

1.3 

2.7 

Smoke Marine 

KNON 

1.5 

2.4 

1.8 

0.9 

0.9 

1.3 

1.0 

1.1 

0.5 

0.6 

0.7 

0.7 

2.9 

1.2 

1.3 

1.5 

1.4 

1.9 

0.9 

1.1 

2.2 

1.6 

1.0 

1.0 

2.0 

1.3 

NA 

*6.84 

•9.43 

48.90 

74.90 

•6.42 

34.50 

22.60 

45.20 

•5.47 

58.00 

•4.67 

31.70 

61.50 

87.10 

53.20 

54.50 

48.20 

88.80 

29.90 

54.40 

48.70 

69.80 

60.60 

72.90 

71.50 

66.90 

v 

•0.26 

•o.35 

•0.27 

0.37 

•0.24 

•0.31 

•0.22 

0.52 

•0.22 

•0.28 

0.28 

•0.26 

•0.25 

•0.29 

0.53 

•0.28 

*0.24 

0.51 

*0.19 

0.31 

0.32 

0.55 

0.42 

0.43 

•0.23 

•0.26 

NI 

•0.03 

•o.04 

•0.03 

•o.04 

•0.03 

•o.04 

•O.Q3 

•o.04 

•0.03 

•o.04 

•0.02 

•o.04 

•O.Q3 

•o.04 

•om 

•o.04 

•0.03 

•o.04 

*0.03 

•o.04 

*0.03 

•o.04 

0.12 

•o.04 

•0.03 

•0.04 

cu 

0.17 

•o.04 

•0.03 

0.33 

0.22 

0.06 

•0.03 

•o.04 

•0.03 

•o.04 

•0.03 

0.13 

0.39 

0.22 

•om 

0.06 

0.19 

0.12 

0.08 

0.31 

•0.03 

•o.04 

•0.03 

0.06 

•0.03 

•o.04 

Metallic Tracers 

ZN 

0.34 

0.32 

0.11 

0.30 

0.29 

0.25 

0.19 

0.20 

0.17 

0.25 

0.18 

0.51 

0.56 

0.26 

0.12 

0.24 

0.15 

0.18 

0.25 

0.29 

0.04 

0.23 

0.12 

0.16 

0.18 

0.23 

AS 

*0.02 

•0.02 

•0.02 

•0.02 

0.03 

•o.D2 

•0.02 

•0.02 

•0.02 

•0.02 

•0.02 

•0.02 

•0.02 

•0.02 

•0.02 

•0.02 

0.07 

•0.02 

0.05 

•0.02 

•0.02 

•0.02 

•o.D2 

•0.02 

•0.02 

•0.02 

SE 

0.03 

0.03 

•0.02 

0.05 

0.03 

•0.02 

0.03 

0.04 

*0.02 

0.04 

0.03 

•0.02 

0.04 

•0.02 

0.05 

0.04 

0.06 

•0.02 

0.03 

0.08 

0.02 

0.04 

0.04 

•0.02 

0.03 

•0.02 

BR 

0.23 

0.25 

0.09 

0.13 

0.11 

0.14 

0.17 

0.07 

0.07 

0.13 

0.12 

0.11 

0.14 

0.11 

0.07 

0.13 

0.09 

0.14 

0.10 

0.09 

0.03 

0.06 

0.09 

0.13 

0.14 

0.18 

PB 

0.12 

0.19 

0.06 

0.25 

0.09 

0.14 

0.12 

0.08 

0.07 

0.11 

0.08 

0.10 

0.32 

0.09 

0.07 

0.11 

•0.07 

0.08 

•0.07 

0.06 

0.09 

0.05 

0.09 

0.06 

0.07 

0.12 
TABLE2. Distribution of Concentrations (ng m·3) From the IMPROVE Particulate Network, June 1, 1992-August 31, 1992 

%ofCases Arithmetic Maximum 

Cases Significant Mean Minimum Median Maximum Occurs 

H 26 100% 27.90 15.40 27.50 56.30 Aug. 08 

s 26 100% 77.10 36.60 69.10 219.00 Aug. 08 

SI 26 100% 17.60 2.57 11.40 61.90 June 06 

K 26 100% 4.26 1.45 2.84 12.50 June 06 

CA 26 100% 5.36 0.30 3.04 20.60 June 06 

TI 26 88% 0.62 0.20 0.54 1.78 June 06 

MN 26 53% 0.267 0.13 0.247 0.90 June 13 

FE 26 100% 4.89 0.52 2.79 16.80 June 06 

KNON 26 73% 1.32 0.54 1.25 2.91 July 15 

NA 26 80% 46.20 4.67 51.10 88.80 Aug. 01 

v 26 38% 0.247 0.19 0.287 0.55 Aug. 15 

NI 26 3% 0.027 0.02 0.047 0.12 Aug. 19 

cu 26 50% 0.107 O.D3 0.05? 0.39 July 15 

ZN 26 100% 0.23 0.04 0.23 0.56 July 15 

AS 26 11% 0.017 0.02 0.02? O.D7 July 29 

SE 26 69% O.D3 0.02 0.03 0.08 Aug. 08 

BR 26 100% 0.12 O.D3 0.11 0.25 June 06 

PB 26 92% 0.10 0.05 0.09 0.32 July 15 

A significant value is greater than 2 times the uncertainty of that value. 

? =The percentage of significant values is less than 65% 

KNON is nonsoil potassium, a qualitative smoke tracer, K - 0.6 Fe 

TABLE 3. Distribution of Concentrations (μg m·3) and Percent of Fine Mass From the Improve Particulate Network, 

June 1, 1992- August 31, 1992 

%ofCases Arithmetic 

Cases Significant Mean 

MASS 26 100% 0.70 

RCMA 26 100% 0.66 

NIISO 26 100% 0.32 

NIISO% 26 100% 47% 

OM!! 26 69% 0.12 

OMJ!% 26 61% 19%? 

SOIL 26 100% 0.08 

SOIL% 26 100% 11% 

BABS 26 73% 0.61 

A significant value is greater than 2 times the uncertainty of that value. 

? =The percentage of significant values is less than 65% 

Maximum 

Minimum Median Maximum Occurs 

0.29 0.72 1.16 Aug. 29 

0.33 0.61 1.16 Aug. 08 

0.15 0.28 0.90 Aug. 08 

25% 43% 83% July 18 

-0.01 0.11 0.30 July 04 

0% 17%? 54% July 18 

0.01 0.05 0.28 June 06 

2% 8% 39% June 06 

0.16 0.56 1.51 Aug. 08 

NHSO 

SOIL 

OMII 

RCMA 

ammonium sulfate, (NH.JzS02 

soil 

organic mass by hydrogen 

reconstructed mass 

standard fonn of sulfate, sulfur times 4.125 

sum of Al, Si, K, CA, Ti, Fe and oxides 

13.75 (H · S/4) 

sulfate+soil+OMH+BABS/2, but not nitrate 

potassium not associated with soil, an excellent tracer of 

smoke from biomass. These values are very low, almost all 

within the uncertainty, showing essentially no smoke 

impact on the down-slope winds. The "all hours" sampler 

at the site, MALO!, occasionally shows heavy smoke 

impacts that could well reflect agricultural burning on the 

island. Formulas for the derived quantities (NHSO = 

88 

ammonium sulfate, OMH = organic matter from hydrogen, 

etc.) are explained on the bottom of Table 3. BABS is 

b(absorption) from the integrating plate method, in units of 

1 o-6 m· l. The most important of these is RCMA, 

reconstructed mass as the sum of all measured species. 

This should be close to, but somewhat less than, MASS, the 

gravimetric fine mass from weighing the Teflon filter. The 
difference appears to be overwhelmingly water, since the 

filters are weighed in air but the analyses are done in hard 

vacuum, thus drying the filters. 

In the analyses that follow, the median value was used 

as opposed to the mean, due to the extremely non-log 

normal distributions seen at Hawaii Volcanoes National 

Park. This is due to the occasional arrival of the plume of 

the ongoing eruption, which gives sharp spikes to the data 

not only for sulfur but selenium and other volcanic trace 

elements. At the Mauna Loa sites, this is not a problem 

and the median is close to the mean (0.70 versus 0.72 μg 

m-3, summer 1992). 

Figures 2a, b, c, and d show the seasonal trends for 

sulfur (= sulfate) at all four sites for the period of record. 

No statistically significant trends can be seen in the annual 

values, but clear seasonal shifts are seen in the MAL02 

(downwind) data. Since this is so, the last two years were 

'E 

' i 

~ 

'9 

' I 8 r 

'' 

'6 

I 5 

1 4 

l .l 

I 2 

11 

09 

08 

07 

06 

0 5 

0 4 

O.l 

01 

01 

0 

I 9 

I 8 

17 

I 6 

I 5 

1 4 

1 .l 

1 2 

11 

0 9 

0 8 

0' 

0 6 

0 5 

0 4 

0 .l 

02 

0 1 

1986 

1986 

-:c eoka1c ·,clonal t='cr~ 

1988 1990 

1987 1989 1991 

Ytor end Seasons - Spr.n9 ( .l<I 5 ). etc 

Hawaii Volcanoes Notional Pork 

A.,,mon11om SuHott ( from S ) 

1987 1989 199 1 

Yeor ord Seo501'11 - Sor"''9 ( } .4 ,5 ).tit 

--, 

(al 

(b) 

Fig. 2. Ammonium sulfate (from PIXES times 4.125) at Haleaka la 

National Park (a), and from Hawaii Volacnoes (b). 

89 

}v ouno Loo Observatory - 10 Plvl lo 6 AM AmmQn•.om $.,•tote ( lrom $ ) 

·= (c) 

09 

08 

01 

06 

05 

0 4 

0 .l 

02 

0 I 

1986 1988 

1987 1989 1991 

Ytor O"CI Seo'O"S - Spr.r•9 ( .l.4.5 ) etc 

Mouno Loo Observatory - All nour s Ammon•"'m S,.,.fo\t ( from S ) 12.--~~~~~ ~~ ~~~~~~~~~~~~~, 

11 

09 

"' E o s 

~ 07 E 

• 0 6 

~ 0 > 

't 0" 

E o .l 

0' 

0 1 

(d) 

1986 1988 

198 7 1989 1991 

Yeor crd S t osont. - SP"""9 ( J, 4.5 ).et c 

Fig. 2. Continued - Ammonium sulfate (from PIXE S times 4.125) 

at Mauna Loa Obcrvatory - downwind (c), and a ll hours (d). 

aggregated and provide the data for Table 4. There is a 

good deal of information in Table 4 that is going to require 

further analysis before it is fully understood. But the first 

point is the similarity between Hawaii Volcanoes and 

Haleakala National Parks. This was not expected due to the 

volcanic activity at Hawaii Volcanoes, but a closer 

inspection of the records show that there were few plume 

impacts on the site and thus did not influence the median 

for these two seasons. The situation was very different in 

winter when Hawaii volcanoes had numerous plume 

impacts and well elevated levels of sulfur, selenium, and 

other elements. 

Thus we can use the summer and fall data to obtain a 

measurement of the vertical gradient of sulfur. This can be 

enhanced by deriving the "upslope" sulfur value at MALOl 

by subtracting the data of MAL02 (Table 5). One can then 

assign an approximate "altitude" for the source of these 

aerosols almost all of which lie at elevations below that of 

MLO. The surprising consistency of the two NPS sites and 

the "upslope" MALOl values gives us some confidence 

that an average value could represent the aerosol column 

from sea level to 3380 m. There then appears to be a sharp 

discontinui ty to the MAL02 "downslope" aerosols with a 

ratio near 2.24 ± 0.02 spring and summer and 5.0 ± 0.6 fall 

and winter. Thus at this site, clear summer/winter 
TABLE 4. Fine Arnmoniwn Sulfate(S x 4.125) Winter 1990 to Fall 1992 

Hawaii Volcanoes Haleakala Mauna Loa Mauna Loa 

National Park National Park All hours 2200 to 0600 

(elev. 1240 m) (elev.1150m) (elev. 3380 m) (elev. 3380 m) 

Cone. Cone. Cone. Cone. 

(μg m3) % Mass (μg m3) % Mass (μg m3) % Mass (μg m3) % Mass 

Spring 1.13 ± 0.33 43.5 ± 6.5 0.795 ± 0.23 26.0 ± 2.0 0.635 ± 0.27 38.5 ± 7.5 0.400 ± 0.01 23.5 ± 0.5 

Summer 0.70 ± 0.17 35.0 ± 2.0 0.65 ± 0.03 24.5 ± 4.5 0.51 ± 0.09 52.5 ± 3.5 0.29 ± 0.05 30.0 ± 11.0 

Fall 0.94 ± 0.10 46.5 ± 1.5 0.88 ± 0.09 32.5 ± 4.5 0.44 ±0.07 51.5 ± 0.5 0.18 ± 0.02 34.3 ± 10.2 

Winter 2.78 ± 1.61 50.5 ± 2.5 0.85 ± 0.02 28.5 ± 0.5 0.25 ±0.02 40.5 ± 7.5 0.13 ± 0.02 22.0 ± 5.0 

Spring 1.31 ± 0.38 0.91 ±0.29 0.99 ± 0.52 0.77 ±0.02 

Summer 0.81±0.20 0.80 ±0.03 0.80 ± 0.17 0.56 ±0.09 

Fall 1.17 ± 0.12 1.08 ±0.11 0.85 ± 0.14 0.34 ±0.05 

Winter 3.22± 2.01 1.05 ±0.02 0.49 ± 0.05 0.25 ±0.05 

The top half of the table presents the data as μg m-3 at altitude, the standard IMPROVE protocol for visibility correlation s. The bottom half 

of the table presents the data corrected for the pressure differential to sea level (i.e., NTP). 

Spring= March, April, and May 

Summer= June, July, and August 

Fall =September, October, and November 

Winter= December, January, and February 

TABLES. Vertical Profiles of Ammonium Sulfate Aerosols (Hawaiian Site s Winter 1990 to Fall 1992) 

Mauna Loa Mauna Loa 

Season Hawa ii Volcanoes Haleakala National Park (Up) Average (Down) Ratio 

Spring 1.13 0.80 0.75 0.89 ± 0.17 0.40 2.23 

Summer 0.70 0.65 0.62 0.66 ± 0.03 0.29 2.26 

Fall 0.94 0.88 0.56 0.79 ± 0.17 0.18 4.41 

Winter 2.78• 0.85 0.62 0.73±0.12 0.13 5.60 

Spring 1.31 0.91 1.17 1.13 ± 0.17 0.77 1.47 

Summer 0.81 0.80 0.97 0.86 ± 0.08 0.56 1.54 

Fall 1.1 7 1.08 1.08 I.I I± 0.04 0.34 3.26 

Winter 3.22• I.OS 1.24 1.14±0.09 0.25 4.56 

The top half of the table presents the data as μg m·3 at altitude, the standard IMPROVE protocol for visibility correlations. The bottom half 

of the table presents the data corrected for the pressure differential to sea level (i.e., NTP). 

• Note: Deleted winter, Hawaii Volcanoes, in averaging 

Spring= March, April, and May 

Summer= June, July, and August 

Fall= September, October, and November 

Winter= December, January, and February 

differences appear due mainly to changes in the upper 

tropospheric aerosols, not the boundary layer aerosols. 

In summary, we are beginning to obtain a 

statistically signifi cant data set at MLO to match the 

data sets at unpolluted (at least, not anthropogenic 

pollution) sites at lower elevations. Based on the strong 

trade winds at the Hawaii Volcanoes and Haleakala 

90 

sites, these sites are sampling aerosols characteristic of 

the planetary boundary layer and, as such, represent all 

elevations from 0 to about 3380 m. Since the sites are 

well removed from the coast and since coarse parti cles 

are removed in sampling, these data then give an 

estimate of the sulfate column in the atmosphere on and 

over the Pacific Ocean. 
Acknowledgments. I wish to thank the operators at the Mauna Loa 

and Park Service sites for excellent reliability and data quality that 

makes analysis and interpretation easy. I also wish to thank all 

members of the Air Quality Group for outstanding support in filter 

analysis and data handling. 

REFERENCES 

Cahill, T.A., R.A. Eldred, K. Wilkinson, W.C. Malm, M. Pitchford, 

and R. Fisher, Spatial and temporal trends of fine particles on a 

continental scale: First results of the U.S. IMPROVE network, 

91 

Aerosols, Procudings of the third International Aerosol 

Conference, Kyoto, Japan, September 24-27, S. Masuda and K. 

Takahashi, (eds.), Vol. 2, 1105-1108, 1990. 

Cahill, T.A., K. Wilkinson, and R. Schnell, Composition analyses of 

size-resolved aerosol samples taken from aircraft downwind of 

Kuwait, Spring, 1991, J. Geophys.I Res., 97(Dl3), 14,513-

14,520, 1992. 

Eldred, R.A., T.A. Cahill, M. Pitchford, and W.C. Malm, 

IMPROVE--a new remote area particulate monitoring system for 

visibility studies, Proceedings of the Air Pollution Control 

Association 8lst Annual Muting, Dallas, TX, June 19-24, 1988. 
Artificial Windshielding of Precipitation Gauges in the Arctic 

GEORGE P. CLAGETT 

Soil Conservation Service, Anchorage, Alaska 99508 

1. INTRODUCTION 

Precipitation gauges can provide good measurements of 

the water equivalent of snow precipitation, provided the 

gauge is protected or shielded from wind effects. 

Unfortunately, there are no standards 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 

efficiency. Also, the various studies of artificial shields in 

the United States and Canada have produced a wide range 

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. 

2. METHODS 

A study of the windshield alternatives, under the unique 

conditions of Alaska's Arctic coastal region, was set up at the 

CMDL facility at BRW 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 [Hanson, 1988). Two of the 

new gauges were shielded----one with a Nipher shield 

[Goodison et al., 1983) and the other with an Alter shield 

[Alter, 1937}-and two were unshielded. One of the 

unshielded 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 naturally 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-shielded gauge 

is 30.5 cm in diameter x 2 m tall, and is equipped with a 

Leupold-Stevens water-level recorder. 

92 

3. RESULTS 

Provisional results from the September 1, 1992, to 

June 2, 1993, winter season indicate that the Wyomingshielded gauge provided 13.0 cm of snowfall waterequivalent catch. The Nipher-shielded gauge caught 

exactly the same amount over the same period. The Altershielded gauge caught 5.2 cm or 40% of the Wyomingshielded gauge. The unshielded but serviced gauge caught 

only 1.8 cm of water-equivalent snowfall which was barely 

over 14% of that of the Wyoming-shielded gauge. The 

unshielded and non-serviced gauge did slightly better, 

catching 2.3 cm water-equivalent, or nearly 18% of the 

snowfall caught by the Wyoming-shielded gauge. 

These results are right in the ballpark of expectations: 

the Wyoming and Nipher shields are expected to have very 

similar catches; the Alter-shielded catch drops off 

substantially; and a non-shielded gauge catch should drop 

off even substantially more at exposed and windy locations 

during snowfall events. 

Acknowledgment. Appreciation is expressed to D. Endres. Station 

Chief, BRW, who serviced the precipitation gauges and collected 

the snow samples. 

4. REFERENCES 

Alter, S.C., Shield storage precipitation gauges, Mon. Weather Rev., 

65, 262-265, 1937. 

Goodison, B.E., V.R. Turner, and J.E. Metcalfe, A nipher-type 

shield for recording precipitation gauges, Proceedings, 5th 

Symposium on Meteorological Observations and 

Instrumentation, Toronto, Ontario, Canada, pp. 2-126, American 

Meteorological Society, Boston, 1983. 

Hanson, C.L., Precipitation measured by gages protected by the 

Wyoming shield and the dual-gauge system, Proceedings, 56th 

Western Snow Conference, Kalispell, Montana, pp. 174-177, 

Colorado State University, Fort Collins, CO, 1988. 
A Comparison of Aerosol Size Distributions and Nephelometer 

Measurements at Mauna Loa Observatory 

ANTONY CLARKE 

University of Hawaii, Department of Oceanography, Honolulu, Hawaii 96822 

BARRY BODHAINE 

NOAA CMDL, Boulder, Colorado 80303 

1. INTRODUCTION 

Mauna Loa Observatory (MLO) has maintained a Jong 

term and near continuous record of aerosol light scattering 

since 1974 [Bodhaine, 1983; Massey el al., 1987]. The 

existing four-wavelength instrument allows for assessment 

of both the scattering coefficient, Osp• at four wavelengths 

and some inference of the aerosol size distribution through 

the parameter alpha [05 p(A) = K/A.-cx]. This data has been 

valuable in providing information on aerosol properties in 

the remote troposphere and their optical effects [Clarke and 

Charlson, 1985; Bodhaine et al.; 1992]. Because of this 

record and the accessibility of remote tropospheric air at 

MLO, this site was selected for aerosol measurements in 

support of the NASA Laser Atmospheric Wind Sounder 

program. One objective of this program was the 

assessment of the relationship of lidar backscatter to 

measured aerosol size distributions [Clarke and Porter, 

1991]. A second objective was to examine the relationship 

of aerosol size distributions to the nephelometer record in 

order to see if the latter could be used as a surrogate 

measurement of the aerosol size distribution. If so, the 

long nephelometer record at MLO could be used to infer an 

aerosol climatology for the Pacific mid-troposphere. More 

recently, questions regarding the link of aerosol sulfate to 

scattering extinction in the atmosphere [Charlson el al., 

1991] prompted us to examine the relationship of the 

aerosol size distribution and o,P al MLO in order to assess 

the mass scattering efficiency for sulfate in the free 

troposphere. 

Here, we report the results of these comparisons. One 

key observation is that changes in aerosol concentration of 

1 to 2 orders of magnitude between upslope and downslope 

flow coupled with the Jong averaging time used for the 

nephelometer (about 1 hour) can prevent o,P from 

achieving the minimum representative downslope values. 

This often results in both hourly and mean nightly 

downslope Osp values that are several times greater than 

they should be and thereby posing a difficulty for direct 

comparison of Osp with other MLO data sets. 

2. OBSERVATIONS 

Aerosol heated to 40, 150, and 3oo·c and sized with a 

laser optical particle counter (OPC) was used to assess the 

size distribution (0.15-7.0 μm) of sulfuric acid, ammonium 

93 

sulfate and refractory (dust) components of the aerosol at 

MLO during January-March 1988 [Clarke and Porter, 

1991]. During the downslope conditions of interest here 

the fine volume with diameters below 1 μm were primarily 

sulfate while the coarse volume tended to be refractory 

aerosol (remaining at 300'C) and probably dust. The few 

periods of high relative humidity were deleted in order to 

avoid o,P values that might reflect growth through water 

uptake rather than changes in aerosol sulfate. The 

refractory component remaining at 3oo·c was present at all 

sizes but was a small component of the total, and dust 

present in the submicrometer fraction appeared to be 

heavily coated with a sulfate shell. 

Figure 1 shows the fine, coarse, and total volumes 

plotted against the corresponding nephelometer data during 

downslope conditions. These data usually represent the 

two cleanest 3-hour averages during each night and these 

generally occurred between 2200 and 0800 LST. The 

strongest relationship is evident between the fine aerosol 

cli' 

§ 0.1 

1 

(» 

E 

::s 

0 

> 

~ 0.01 

~ 

• 

0. 001 +----.---..--..-.-,.......,r-TT"--.---.-"T"-.--.-~ 

1E-07 1E-06 1E-05 

• FM D 

a,P (m-1) 

Coarse a Total 

Fig. 1. A plot of fine (0.14<Dp<0.6 μm), coarse (0.6<Dp<7.0 μm) 

and total aerosol volume versus cr,P for 3-hour nightly downslope 

minimum periods for DOY 16-86 1988. 
volume and Osp as evidenced by the least scatter of the data 

points for this fraction. Similar behavior was also evident 

for upslope data (not shown). This measurement period 

includes times of episodic transport from Asia and it is 

common to observe three orders of magnitude change in 

both volume and scattering during this period. It is 

significant to note that during periods of highest Osp both 

fine particle sulfate and coarse particles are high. This is 

consistent with prior evidence for an anthropogenic source 

of pollutant aerosol that is coincident with periods of dust 

transport to MLO [Clarke and Charlson, 1985]. 

Examination of Figure 1 indicates that a measured fine 

(or total) particle volume may be associated with several 

values of Osp· Coincident 3-hour averages were plotted for 

Osp and the fine, coarse, and total volumes in order to make 

a direct comparison of these data. An example of several 

consecutive days are shown in Figure 2. A clear 

upslope/downslope signal is evident in both data but closer 

examination reveals that the transition to low aerosol 

volume occurs in the OPC data shortly after downslope 

flow has begun while the light scattering values decrease 

only gradually during the night to reach minimum values 

just before upslope recurs. 

This delayed response is a consequence of the above 

mentioned long averaging time of the nephelometer and the 

large dynamic range often present between upslope and 

downslope flow. This is clearly evident for the case shown 

in Figure 3 where DOY 80 having moderate upslope 

aerosol is followed by DOY 81 with weak upslope aerosol. 

Here the optical particle counter (OPC) data reveals that 

downslope aerosol concentration for both nights are similar 

while the corresponding Osp values (see circled pairs) differ 

by a factor of about 5. In fact, the slope of the Osp data 

does not approach the slope in the aerosol volume data 

until about 1800 hr (GMT) on DOY 81, about 36 hours 

after the upslope peak on DOY 80. (The Osp value just 

before DOY 82 is a zero test.) This reveals that an 

10 

"' 8 ~ (') 

], 6 CD 

E 

:I 

0 

> 

4 

(.) 

a.. 

0 2 

050 

c::J C.:::> C=:J C::J c:::J 

= 

51 52 

== = = 

unbiased comparison of Osp with the aerosol mass from 

which the cr.P signal is derived is only possible for about 3 

hours out of the 48 shown. Moreover, this is only possible 

because the upslope aerosol on DOY 81 was little enhanced 

above free troposphere values. 

The above observations have significant impact upon 

attempts to relate the optical scattering of the aerosol to 

aerosol properties at MLO. This is illustrated through our 

attempt to establish the specific scattering coefficient for 

sulfate (scattering coefficient divided by the mass 

concentration - 0 5p/M) in the clean free troposphere since 

this is a quantity of some significance to the assessment of 

sulfur emissions upon climate [Charlson et al., 1991). 

Here we will examine data during the "clean" part of the 

year at MLO during the Mauna Loa Aerosol Backscatter 

Intercomparison Experiment (MABIE) carried out in 

November of 1988. As indicated in Figure 1, fine particle 

sulfate is the major contributor to Ow However, because 

of the concerns mentioned above, we used only edited time 

periods when the nephelometer was stable and unperturbed 

by significant previous upslope aerosol. The result is 

shown in Figure 4a. In order to convert the predominantly 

sulfuric acid aerosol volume to mass, we have used our 

laboratory derived diameter correction (division by 1.1) 

due to the uptake of water at the typical downslope OPC 

relative humidity of 10% at MLO and employed a density 

of 1.8 g cm-3 to the resulting volume. A strong correlation 

(r2 = 0.9) is evident between fine particle sulfate and Osp at 

550 nm although the intercept does not go through zero. 

This is because some aerosol mass is present below the 

lower limit of detection of the OPC at 0.15 μm resulting in 

some scattering extinction due to fine particle mass not 

observed by the OPC. Because 0 5 p/M decreases rapidly for 

decreasing size below 0.3 μm and because the mass mean 

diameter tends to increase with concentration, the relative 

contribution to Osp from these smaller aerosol decreases 

rapidly as concentrations increase. Moreover, the slope of 

= = 

= 

53 

== == == 

2 

1.5 iO 

w 

0 

.... 

8l 

E 

E. 

tU 

.c 

a. 

< 

ea 

1: 

"' 

~ ... 

b 

DAY Of YEAR (GMT) 

-- Fine vol. -+- Coarse Vol. -- a,P @ 550 nm = Alpha 

Fig. 2. Time series of 3-hour averaged values for fine and coarse aerosol volume, a,P at 550 nm and alpha for period with moderate daily 

upslope flow. Note slow decay of a,P signal and alpha compared to fine particle mass. 

94 
5 1.SE-05 

Note: Different a1p for similar aerosol volume. 

Unless daydme upslope aerosol Is low, 

4 

cli 

a true low for downslope asp Is not reached. 

~ 1E-05 

"' 

~ 3 ~ 

~ i 

E Q. 

:> i; 0 2 

> SE-06 () 

0.. 

0 

o1-.~~~~~~~;E3:~;:::1o 80 81 82 

Day of Year (GMT) 

Pine vol. ......... Coarse Vol. -- a,P @ 550 nm 

Fig. 3. Time series for DOY 81-82 as per Figure 2 showing the 

gradual decay of Osp values over a 2·day period when the 

intervening upslope perturbation is weak. 

the regression line can be used to determine the 0 5p/M for 

the aerosol resulting in a value of about 5.6 m2/g. Given 

the 20% estimated uncertainty in the OPC measurement, 

this tends to support the value of 5.0 m2/g recently 

suggested [Charlson et al., 1991) for the remote 

troposphere. 

In contrast to the above edited data, Figure 4b shows the 

data for downslope conditions between about 2200 and 

0600 LST, similar to times often used for filter sampling 

for aerosol chemistry (e.g., sulfate). Note that the "best 

fit" regression line from Figure 4a falls along the upper 

boundary of this data set and that these downslope values 

show far greater scatter. The resulting cr,p/M that might be 

derived from the 4b data would be both higher by about a 

factor of two and more uncertain than Figure 4a. The 

result of including both upslope and downslope data is 

shown in Figure 4c. In spite of increased scatter, this plot 

is more similar to the data in Fig 4b than 4a. This supports 

the point made earlier that "downslope" O"sp values often 

retain the inOuence of prior "upslope" values due to the 

long averaging time. 

3. CONCLUSION 

These observations have important consequences for the 

use and interpretation of MLO O"sp data. First, the common 

occurrence of significantly enhanced upslope aerosol means 

that for many nights a true minimum 0"5p value 

corresponding to the actual clean free tropospheric aerosol 

present at MLO will not be reached. Second, even for 

those nights when the prior upslope aerosol concentration 

was low, the decay to minimum O"sp may not occur until the 

3-hour period just before the onset of upslope flow. This 

may persist even though aerosol volume at MLO could 

95 

[ 

<D 0.8 

~ Q. 

0 

v 

I() 0.6 

ci 

~ 

"' bi 

.;!: 0.4 

~ 111 

E 

g 0.2 ~ :; 

() "' 

0.. 0 0 0 

[ 

<D 

~ 0.8 a. 

0 

v 

I() 

ci 0.6 

M' 

bi 

.;!: 

~ 111 

0.4 

E 

g 

~ 

:; 

0.2 

"' () 

0.. 

0 00 

[ 

<D 

~ 0.8 a. 

0 

v 

I() 

ci 0.6 

M' 

~ 0.4 ~ 111 

E 

g 

~ 0.2 

:; 

"' () 

0.. 0 0 0 

MABIE88 · EDITED • 

• A = 0.90 

a,p M - 5.6 m2/g 

2 3 

crap (10-$ m·1) 

MABIE88 - DOWNSLOPE b 

BEST FITTO EDITED DATA 

MABIE88 c 

BEST FIT FOR EDITED ~TA 

• ~ ..... . ,,/ /./ . / . /~" • 

,,.!~ • ,,..,,.. I • ...... ,,. .. ........ ~ . ti-'4: • 

• 

• 

•• 

3 

Fig. 4. (a) Fine sulfate mass versus cr,P at 550nm for periods when 

both had a similar slope indicative of stabilized conditions and 

appropriate cr,P values. (b) Fine sulfate mass versus cr,P for all 

nightly periods characterized by downslope flow. (c) Fine sulfate 

mass versus cr,P for all periods with cr,P less than 4 xIQ·6 m·t. 
have been low for over 12 hours. Third, these effects will 

tend to make estimates of clean tropospheric scattering 

values based upon MLO data systematically higher than is 

warranted for the aerosol actually present. Fourth, 

averages of other nightly downslope measurements (e.g., 

filter samples) that are frequently compared to averaged 

downslope Osp will include a scatter in the relationship that 

may be appreciably influenced by the above effects. 

This error in downslope values will be largest for periods 

when the previous day's upslope aerosol scattering is 

greatest. As a result, a careful evaluation of nephelometer 

data is required if it is to be used or compared reliably with 

other data representative of the clean free troposphere. 

Recognition of this bias and its nature can make it possible 

to stratify the Osp data in order to seek out times when the 

Osp values are most representative of the actual aerosol 

present. Comparing data with simply the minimum Osp on 

nights following a mild upslope aerosol influence is an 

obvious possibility. Even after stronger upslope, the 

evaluation of the slope of the Osp signal just before the 

downslope mm1mum might provide a means of 

extrapolating to the real 0 1p value. 

96 

Aclcnowledgrrumts. We wish 10 thank Elmer Robinson and the CMDL 

staff at MLO for their help and assistance and David Bowdle of NASA 

MSFC for his encouragemenL This work was supported by NASA 

Headquarters through Ramesh Kakar under NASA NAG8-634. 

4. REFERENCES 

Bodhaine, B. A., Aerosol measurements at four background si1es, J. 

Geophys. Res., 88, 10,753-10,768, 1983 

Bodhaine, B.A., J.M. Harris, J.A. Ogren, and DJ. Hofmann, Aerosol 

optical properties at Mauna Loa Observatory: Long Range Transporl 

from Kuwait?, Geophys. Res. Ult., 19, 581-584, 1992. 

Charlson, R.J., J. Langner, H. Rhode, C.B. Leovy, and S.G. Warren, 

Perturbations to the northern hemisphere radiative balance by backscatlering from atmospheric aerosols, Tel/us, 43AB, 152-163, 1991. 

Clarke, A.D., and RJ. Charlson, Radiative properties of the background 

aerosol: absorption component of extinction, Science, 229, 263-265, 

1985. 

Clarke, A.D., and J. N. Porter, Aerosol siz.e distribution, composition, and 

C02 backscatter at Mauna Loa Observatory, J. Geophys. Res., 5237-

5248, 1991. 

Massey, D.M., T.K. Quackenbush, and B.A. Bodhaine, Condensation 

nuclei and aerosol scattering extinction measurements at Mauna Loa 

Observatory: 1974-1985, NOAA Data Rep., ERL ARL-14, Air 

Resources Laboratory, Silver Spring, MD, 174 pp., 1987. 
Improved MFOV Performance at Mauna Loa 

PAULF. HEIN, JOHN M. DAVIS, AND STEPHEN K. Cox 

Colorado Stalt University, DtpartmLnl of Atmospheric Scienct, Fort Collins, Colorado 80523 

1. INTRODUCTION AND BACKGROUND 

The Multiple Field of View (MFOV) sunphotometer at 

Mauna Loa Observatory was replaced in November 1992 in 

order to improve the data quality. The instrument, which 

basically consists of five coaligned silicon photodiodes, 

each with a different field of view (fov), was originally 

designed to infer the optical depth of clouds by utilizing 

the information contained in the amount of scattering of 

solar radiation into the different fov's. The instrument was 

modified by using a different set of fovs and introducing a 

slope angle into the design of the collimating tubes. 

Additionally, the solar tracker was replaced. Results from 

the new configuration are encouraging. Data analysis 

algorithms are being improved with anticipation of adding 

the ability to infer some information concerning the cloud 

particle size. 

The original approach is described in Hein el al., 

[ 1990]. wherein the transmittance from a particular fov 

T(fov) was described as resulting from attenuation of the 

incident solar radiation by an atmosphere of optical 

thickness 't • and enhancement of the measured signal by 

scattering from the same atmosphere into the fov, a process 

which is assigned an optical thickness for scattering 't1 . 

Or; 

T(fov) = ( 't -'t1 (fov )]. 

Monte Carlo modeling results for a Rayleigh atmosphere 

indicate almost no enhancement by scattering into the 

larger fields of view as shown in Table 1, which is also 

being presented as a correction to a similar table presented 

in the I 991 summary CMDL report. The previous year's 

T ABI.:E 1. Modeled transmittances for solar zenith angles 

of 0°, 15°, 30°, 45°, and 60° and optical depths derived 

from the Langley method, for fields of view of 

11.4°, 6.4°, 4.1°, 2.3°, and 2.0° 

and direct measurements 

11.4° 6.40 4.10 2.3° 2.0° Direct 

oo 0.9327 0.9325 0.9324 0.9324 0.9324 0.9324 

15° 0.9304 0.9303 0.9302 0.9302 0.9302 0.9302 

30° 0.9227 0.9225 0.9224 0.9224 0.9224 0.9224 

45° 0.9066 0.9063 0.9062 0.9062 0.9062 0.9062 

60° 0.8710 0.8707 0.8705 0.8705 0.8705 0.8704 

't'Jang 0.0684 0.0686 0.0687 0.0687 0.0687 0.0688 

97 

discrepancy resulted from a coding error. The table shows 

modeled transmittances for a Rayleigh sky with a specified 

optical thickness of 0.07, for solar zenith angles of 0, 15, 

30, 45 and 60 degrees. The last row shows optical 

thicknesses which are derived from the Langley method 

using the modeled data. By taking ratios of modeled 

(Monte Carlo) cloud transmittances, using the largest fov in 

the denominator, it was found that a parameter a('t) could 

be established such that; 

T(fov) [ ( )) T(max) =exp -a('t) emu -0rov ' 

and that a('t) was nearly linear in 't up to an optical 

thickness of 10, at least for a stratocumulus base droplet 

distribution. In theory, this provided a method to find the 

optical depth from measured transmittances; however, in 

practice such determinations were uncertain due to poor 

solar tracking performance. 

2. RECENTIMPROVEMENTS 

The new instrument design appears to have improved its 

performance. For example, Figure 1 displays 

transmittances measured on a clear morning using the 

signal of each detector. The Langley method was used to 

determine "top of the atmosphere" values for the detector 

voltages V 0(fov), and the transmittances were calculated as 

the simple ratio V(fov)/V 0(fov), where V(fov) is the 

instantaneous voltage from the detector. The divergence of 

the traces after 0900 LST may have resulted from thin 

clouds, slight tracking misalignment, or changing detector 

sensitivities; however, the spread in the transmittances 

reaches a maximum of about 0.02 at local noon, and 

scattering even by thin cloud cover is expected to produce 

differences in the transmittances exceeding that value. 

The MFOV was not designed to measure clear sky 

scattering characteristics; however, typical clear sk~ optical 

depths derived by the Langley method for the Spring of 

1992 were 0.18. The standard deviation of the optical 

thicknesses derived from the individual detectors on a 

typical clear sky morning was 0.006. This degree of 

stability is judged adequate for inference of thin cloud 

optical thicknesses. 

3. DATA ANALYSIS 

The current method of inferring cloud optical thickness 

differs somewhat from what is described above and 

consists of the following procedure. First, curves of the 
0.85 

0.80 

Cl> 

() 

c 0.75 0 

-+J 

-+J 

E 

(/) 

c 0.70 

0 

'- I0.65 

0.60 

7 8 

Julian Day 148 

9 

Field of View 

11.42 

6.36 

4.09 

2.29 

1.96 

1 0 11 

Hours (Local Time) 

1 2 

Fig. I. Transmittances detennined from each fov for the morning of 

Julian day 148. 

natural Jog of the ratios of theoretically determined 

transmittances are plotted as a function of the difference in 

the detector fields of view for various optical thicknesses 

using an assumed microphysical distribution. Figure 2 

shows such a plot for a C.6 ice sphere distribution 

characterized by a 20 μm modal radius. The smallest 

optical depth corresponds to clear-sky conditions with a 

moderate volcanic aerosol in the stratosphere. 

Next, the natural log of the transmittance ratios from 

the data are plotted in a similar manner, and an optical 

thickness is inferred for each microphysical distribution 

using the theoretical slopes associated each optical 

thickness. Finally, the derived optical thicknesses are 

plotted against the corresponding optical thicknesses 

determined from the transmittance as measured by the 

smallest fov. An example is shown in Figure 3 for three 

distributions using the data of Julian day 144, during a time 

for which the data indicated thin cloud conditions. Three 

droplet distributions have been used; the third distribution 

is a modified C.6 for which the modal radius has been 

adjusted from 20 to 30 

μm. From this plot one would conclude that the cloud's 

optical thickness varied between 0.2 and 2.0 and that it 

consists of particles with an equivalent sphere modal radius 

between 6 and 20 μm. Of course, as a rule it would be 

advisable to apply the information from additional 

distributions. 

The advantage of this method of data analysis is that it 

appears to allow simultaneous determination of both the 

optical depth and some indication of an equivalent sphere 

modal radius for the cloud. 

98 

C6(20μm) Ice 

0.07 

Zenith=O.O T= l.174 

0.06 ,..-..... 

,..-..... 

..q- T=0.974 0.05 

....__, 

I- 0.04 ............ 

,..-..... 

> 

0 0.03 ....__, 

-I- 0.02 ....__, 

c 

0.01 T=0.174 

0.00 ~".'.:]_J.....J......L..JW-J.....J....J._J_i._L..L...l.-L..J....JL_.L_.L.-L-'-'_,_, 

0.00 0.05 0.10 0.15 0.20 0.25 

11 .4-fov (in radians) 

Fig. 2. Theoretically derived curves of the natural logarithm of 

transmittance ratios used in the MFOV data analysis. 

Julian Day 144 0900-1550 LT 

3.0 

C5(6μm) (/) 

0 2.5 • C6(20μm -+J 

0 v C6(30μm) 0::: • 

2.0 v 

E 

0 

'-

'+- • 1.5 0 

..c 

-+J 

0 

a.. 1.0 

0 

() 

-+J 

Q. 0.5 0 

0.0 

0.0 0.5 1.0 1.5 2.0 2.5 3 .0 

Optical Poth from 2 FOV 

Fig. 3. Optical thicknesses derived from transmittance ratios versus 

those derived from extinction as measured by the smallest fov for three 

microphysical distributions. 
4. FUTURE DEVELOPMENT 

Perhaps the most interesting feature of the current data 

analysis is that the optical depth on the vertical axis is 

derived solely from scattering information (since the 

extinction optical depth subtracts out in the ratio), while 

the optical depth displayed on the hori zontal axis is derived 

primarily from extinction information (this is the fov that 

is least affected by reentry from multiple scattering). This 

suggests that a more refined treatment may hold the 

promise of also utilizing the single particle scattering 

albedo as an upper limit constraint, which according to 

ongoing analysis, would be given directly by the slope of 

the line of best fit in a plot similar to Figure 3. Thus on 

such a plot, the C.6 and modified C.6 lines would be 

99 

eliminated since they would infer a single particle 

scattering albedo greater than unity. 

Acknowledgments. We are sincerely grateful to lhe personnel at 

MLO who have monitored the tracking mechanism for the MFOV 

and forwarded data to Colorado State University. Funding for 

modification of the MFOV instrument was provided by the National 

Aeronautics and Space Administration Grant NAG 1-1146. 

5. REFERENCE 

Hein, P.F., J.M. Davis, and S.K. Cox, A new look at optical depth 

retrieval with the multiple field of view sunphotometcr, in 

Climate Monitoring and Diagnostics Laboratory, No. 18: 

Summary Report 1989, edited W.D. Komhyr, 105-106., NOAA 

Environmental Research Laboratories, Boulder, CO, 1990. 
Atmospheric Methane at Cape Meares, Oregon 

M.A.K. KHALIL AND R.A. RASMUSSEN 

Global Change Research Center, Department of Environmental Science and Engineering 

Oregon Graduate Institute , Beaverton, Oregon 97006 

1. INTRODUCTION 

At Cape Meares, on the Oregon coast, we have taken 

measurements of CH4 for nearly 15 years starting in the 

middle of 1978 and continuing at present. Numerous 

experiments have been conducted at this station because it 

is close to our laboratory and because it represents 

background air of the middle northern latitudes. In these 

latitudes, human activities have the greatest influence on 

atmospheric composition which eventually spreads to all 

parts of the world carried by the winds and atmospheric 

turbulence. 

Three major experiments have been conducted on CH4 

at Cape Meares. The most elaborate is an automated highfrequency measurement of atmospheric CH4 concentrations. This experiment has produced more than 120,000 

individual measurements of CH4. The early portion of data 

first established the increasing concentration of CH4 

[Rasmussen and Khalil, 1981). The other two experiments 

are to measure CH4 in flask samples that are collected 

every week at the site. One set of flasks is for our 

research, which includes the analysis of more than 20 trace 

gases in which the Cape Meares site is one of six globally 

distributed locations. The other set of flask samples is 

collected for the NOAA/CMDL program for the analysis of 

CH4, C02. and CO. 

Here we describe briefly the continuous Cape Meares 

data and how readers may obtain them for their own 

research and, perhaps more important, to compare the 

broader features of the trend found in the available CMDL 

data with the results from the continuous measurements. 

The details of the nature, interpretation, and environmental 

implications of the continuous data set are discussed in our 

recent papers [Khalil et al., 1993; Khalil and Rasmussen, 

1993). 

2. THE SALIENT RESULTS FROM CONTINUOUS 

MEASUREMENTS 

(a) The data provide detailed observed concentration of 

CH4 in the middle latitudes of the northern hemisphere as 

shown in Figure 1. Pronounced seasonal variations are 

apparent, as is the trend and decrease of the trend. (b) The 

cycle amplitude increased during the course of 

measurements (1979-1993). This finding is equivalent to 

the fact that CH4 increased most rapidly in winter and least 

in late summer and fall. (c) The rate of increase of CH4 

declined in recent years. The rate during the most recent 

years is about half as large as in the early years of the 

measurements. See also Khalil and Rasmussen (1993 and 

100 

18:>0 

"> D 

~ c 1700 0 '! 

5 

l! 

8 1600 

1500 '---'-~~-'--~--'~~---'-~~-'--~~-'--~--' 

80 82 84 86 88 90 92 

Year 

Fig. 1. High frequency measurements of CH4 at Cape Meares, 

Oregon, between 1979 and 1993. 

elsewhere) and for the CMDL data, see Steele el al. (1992). 

(d) There are yet other variabilities that are not fully 

understood at present. These include diurnal cycles during 

fall and sub-monthly variabilities that may reflect seasonal 

long distance transport. 

The data provide definitive information on the sources 

of CH4 in this region. De-convolutions of 1he 

measurements to calculate emissions show that 1here are 

significant seasonal variations. The observed seasonal 

cycle of CH4 is therefore caused not only by the cycles of 

OH that remove CH4 from the atmosphere but also the 

seasonal cycles of emissions. 

3. THE TRENDS AND DECLll'E IN THE 

ACCUMULATION RATES 

To verify the trends seen in the continuous data, we 

constructed an independent data set. It consists of two 

other primary data sets. The first is the flask sampling data 

of the CMDL from Cape Meares, Oregon, which is one of 

the 20 or so sites in their network. The other set is from 

the analysis of air stored in large 36-L stainless steel tanks. 

We recently analyzed 217 such air tanks over a 6-week 

period referenced against a single standard (NBS-982). It 

has been shown in numerous experiments that CH4 

concentrations remain stable in such tanks for decades [see 

Khalil et al, 1993, for recent results]. The time series 

obtained from this instantaneous analyses we believe 

accurately represents the trends of the past. 

There was a good distribution of air before 1984, and 

some air was also available for more recent times. But for 
the crucial period of 1985-1989 when major changes of 

trends took place, there was almost no stored air. 

Fortunately the CMDL flask sample data were avail able for 

this period. Therefore, the two data sets that separately 

were not sufficient for comparisons with the long timeseries of continuous measurements, together become most 

useful in verifying the trends in the continuous data. These 

comparisons are shown in Figures 2 (concentrations) and 3 

(running slopes over 3-year periods). The continuous data 

1800 

1750 l 

-. 

> 

.D 1700 Q, 

Q, 

"" 

"<t' 

::c 

u 

1650 Continuous 

+ NOAA/CMDL 1600 Flask 

• Stored Air 

1550 

78 80 82 84 86 88 90 92 

Time (months) 

f-ig. 2. Monthly average concentrations of the continuous 

measurements and the composite independent data described in the 

text. The composite data are taken at much lower frequency than 

the continuous data. 

....... ... 

24 

~ 18 

> 

.c 

Q, 

Q, 

.._, 

.. 

'O u 12 

'O 

6 

80 82 

-0- Continuous 

--+- · Stored & 

NOAA 

84 86 88 

Time 

90 

f-ig. 3. Trends of methane over 3-year overlapping periods of time. 

The graph shows the slowdown of methane trend during the course 

of the experiment. 

101 

and the composite data (CMDL and stored air) agree very 

well, showing that CH4 has probably decreased from about 

20 ppbv yr· 1 down to 10 ppbv yr-I . The somewhat abrupt 

timing of this change is also supported by both data sets. 

These results lend support to the accuracy of the continuous 

data from Cape Meares, which are, as mentioned earlier, 

extremely detailed and contain much more information than 

the composite data or the flask sampling data in general. 

4 . HOW TO GET THE DATA 

The data are archived at the Carbon Dioxide 

Information and Assessment Center (CDIAC) and may be 

obtained from CDIAC, Oak Ridge National Laboratory. 

Oak Ridge, TN 37831-9984. The data at CDIAC are in 

three tables that can be directly retrieved into the computer. 

Table 1 contains time and continuous data in ASCII format. 

Table 2 contains the time, daily average concentration, 

standard deviations (of daily concentrations), number of 

data during each day, and a column with interpolated data. 

The interpolation is used to fill gaps when samples were 

not collected. Table 3 contains monthly average data. The 

primary references for this data set are Khalil and 

Rasmussen [1993) and Khalil et al. [1993). 

Acknowledgments. We thank D. Pierotti, D. Joseph, S. Crawford, J . 

Mohan, D. Steams, and R. Dalluge for experimental work and D. 

Joseph, P. Turner, and M. Shearer for data management. There has 

been no continuous or systematic financial support for this project. 

During some periods grants have provided either full o r partial 

financial support to the CH• measurements program at Cape Meares 

Station. These grants were: National Science Foundation (ATM8109047), National Aeronautics and Space Administration (':\AGW1348, NAG-1-35, NAG-1-160), and Department of Enerey (DEFG06-85ER6031 ). Some recent work was supported by the 

Environmental Protection Agency through a contract to Andarz 

Company for modeling and data analysis (contract no. 

1 D3216NASA). Additional support was provided by the resources 

of the Biospherics Research Corporation and the Andarz Co. 

5. REFERElliCES 

Khalil, M.A.K., and R.A. Rasmussen, Decreasing trend of methane: 

Unpredictability of future concentrations, Chemosphere, 27, 803-

814, 1993. 

Khalil, M.A.K., R.A. Rasmussen, and F. Moraes, Atmospheric 

methane at Cape Yleares: Analysis of a high resolution data base 

and its environmental implications, J. Geophys. Res., in press, 

1993. 

Khalil, M.A.K., and R.A. Rasmussen, Atmospheric methane, carbon 

monoxide and carbon dioxide at Cape Meares, Oregon: Data 

analysis, interpretation and experimental design, U.S. EPA, 

Research Triangle Park North Carolina, in press, 1993. 

Rasmussen, R.A., and M.A.K. Khalil, Atmospheric methane: Trends 

and seasonal cycles, J. Geophys. Res .. 86, 9826-9832, 1981. 

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

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

atmospheric methane during the 1980s, Nature, 358, 313-316, 

1992. 
Radioactivity in the Surface Air at BRW, MLO, SMO, and SPO During 1992 

R ICHARD J. LARSEN AND COLIN G. SANDERSON 

Environmental Measurements laboratory, U.S. Department of Energy, New York, New York 10014-3621 

1. INTRODUCTION 

Hi-volume air filter samples are routinely collected by 

CMDL personnel 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 radionuclides in the lower troposphere. Of the 

radionucl ides that are analyzed by gamma-ray 

spectrometry, only the naturally occurring radioisotopes 

7Be and 2I0Pb are still readily measured in most of the 

filter samples. Beryllium-7 (T112 = 53.2d) is produced by 

cosmic-ray interactions in the upper troposphere and the 

stratosphere and 2I0Pb (T112 = 22.3 years) is a decay 

product of 222Rn, a noble gas that diffuses from soils. 

Because of their distinctly different source regions, these 

radioisotopes may serve as excellent tracers for air masses 

of upper and lower tropospheric origin. Therefore, they are 

quite useful in studies of atmospheric transport processes. 

2. MATERIAL AND METHODS 

Weekly air filter samples are continuously collected 

using Dynaweb fi lter material. The air samplers move 

-1700 m3 of air per day through a 20.3-cm diameter filter. 

The weekly filter samples collected at BRW and MLO are 

TABLE l. Monthly Surface Air Concentrations of Radionuclides at BRW, MLO, SMO, and SPO During 1992 

Site 

BRW 

MLO 

SMO 

SPO 

BRW 

MLO 

SMO 

SPO 

BRW 

~1LO 

SMO 

SPO 

BRW 

~1LO 

S~10 

SPO 

BRW 

MLO 

SMO 

SPO 

BRW 

MLO 

SMO 

SPO 

*No da1a 

Nuclide 

Gamma (cpm m·3) 

Gamma (cpm m·3) 

Gamma (cpm m·3) 

Gamma (cpm m·3) 

7Be (ml3q m·3) 

7Be (m l3q m·3) 

7Bc (ml3q m·3) 

7[3e (ml3q m·3) 

95Zr (μBq m·3) 

95Zr (μBq m·3) 

95zr (μBq m·3) 

95Zr (μBq m·3) 

mes (μBq m·3) 

mes (μBq m·3) 

mes (μBq m·3) 

mes (μBq m·3) 

t44Cc (μBq m·3) 

t44Cc (μBq m·3) 

144Ce (μBq m·3) 

144Ce (μBq m·3) 

210Pb (mBq m·3) 

210Pb (mBq m·3) 

210Pb (mBq m·3) 

210Pb (mBq m·3) 

Uncertainty is <20% except: 

Jan. 

<0.01 

<0.01 

<0.01 

2.0 

5.8 

• 

5.5 

<4.5 

<20. 

• 

<100. 

< 1.2 

<2.9 

• 

<3.7 

<5.2 

<12. 

• 

<24. 

0.78 

0.31 

• 

0.05t 

Feb. 

<0.01 

<0.01 

<0.01 

<0.01 

2.2 

6.6 

I .4t 

4.2t 

<7.0 

<9.4 

<38. 

<100. 

<I.I 

<2.1 

<3.0 

<1.3 

<5.5 

<I I. 

<17. 

<8.0 

1.07 

0.36:j: 

0.04:j: 

0.02t 

tt.;ncertainty is between 20% and 50% 

:j:Uncertainty is between 50% and 100% 

§Uncertainty is greater than 100% 

March 

<0.01 

<0.01 

<0.01 

<0.01 

2.0 

7.3 

1.5 

2.5 

<8.9 

< I I. 

<I I. 

<100. 

<1.2 

<1.0 

<2.3 

<2.4 

<6. 1 

<4.0 

<I I. 

<18. 

0.78 

0.56 

0.02:j: 

O.Olt 

April 

<0.01 

<0.0 1 

<0.0 1 

<0.0 1 

2.3 

9.2 

1.2 

2.0 t 

<20. 

< 16. 

< 13. 

<75. 

<1.5 

<2.3 

<1.5 

<1.8 

<8.2 

<13. 

<5. 1 

<9.6 

0.48 

0.63 

0.04 

O.Ol:j: 

May 

<0.01 

<0.01 

<0.01 

<0.01 

1.7 

5.8 

2.6 

3.3 

<8.4 

<14. 

<13. 

<87. 

<I.I 

<2.4 

<i.3 

<1.8 

<5.4 

< 12. 

<5.4 

<13. 

0.27t 

0.43 

0.07 

0.03t 

102 

June 

<0.01 

<0.01 

<0.01 

<0.01 

<0.4 

8.3 

2.7 

2.4 

<30. 

<13. 

<28. 

<69. 

<2.5 

<2.1 

< 1.7 

<2.7 

<13. 

<I I. 

<10. 

<18. 

0.08t 

0.48 

0.09t 

0.03:j: 

July 

<0.01 

<0.01 

<0.01 

<0.01 

0.8 

6.8 

2.2 

1.9 

<8.6 

<7.0 

<7.0 

<40. 

<0.7 

<1.4 

<0.8 

< 1.9 

<3.9 

<5.3 

<3.9 

<12. 

O.D7t 

0.39 

0.04t 

0.02:j: 

Aug. 

<0.01 

<0.01 

<0.01 

<0.01 

0.7 

4.0 

1.8 

1.8 

<3.4 

<15. 

<24. 

<20. 

<0.6 

<2.2 

< 1.4 

< 1.2 

<2.7 

< I r. 

<8.2 

<5.5 

0.06t 

0.16 

0.06 

O.O l:j: 

Sept. 

<0.0 1 

<0.0 1 

<0.01 

<0.01 

0.7 

3.3 

2.8 

2.0 

< 19. 

<18. 

< 18. 

< 15. 

<2. 1 

<3.0 

<2.3 

<1.2 

<11. 

<12. 

<12. 

<5.1 

0.08t 

0.20 

0.09t 

0.0l:j: 

Oct. 

<0.01 

<0.01 

<0.01 

<0.01 

1.0 

4. 1 

3. 1 

2.6 

<19. 

<59. 

<14. 

<12 

< I. I 

<3.8 

<1.4 

< 1.8 

<5.6 

<23. 

<7.5 

<8.5 

0.29 

0. 15 

0.1 1 

0.0 1§ 

Nov. 

<0.01 

<0.0 1 

<0.01 

<0.01 

1.2 

4.8 

1.8 

3.5 

<8.0 

<76. 

<2.9 

< 10. 

<0.7 

<5.7 

<0.6 

<2.0 

<3.3 

<30. 

<2. 1 

<9.2 

0.38 

0.19 

0.06 

0.01§ 

Dec. 

<0.0 1 

<0.01 

<0.01 

<U.U I 

2.2 

4.3 

1.6 

4.7 

<12. 

<20. 

<9.1 

<6.1 

<1.5 

<4.2 

<2.8 

<1.7 

<7.7 

<18. 

<I I. 

<7.9 

1.27 

0.13t 

0.05t 

0.03t 
analyzed by gamma-ray spectrometry using a high-purity 

germanium (HPGe) detector with a 1.5 cm diameter well. 

The individual weekly samples from SMO and SPO are not 

routinely analyzed. A monthly composite sample for each 

site was formed by adding together one half of each of the 

weekly filter samples. These monthly composite samples 

are compressed into 45-cm3 plastic planchets and are 

routinely analyzed for several gamma-ray emitting 

radionuclides using either n-type low-energy coaxial, highpurity germanium (HPGe) detectors or p-type coaxial highresolution, germanium lithium or HPGe detectors. Detailed 

information on SASP is periodically published [Larsen and 

Sanderson, 1991]. 

3. 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 1992 are 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 7Be and 

2t0Pb are reported in millibecquerels (mBq) per standard 

cubic meter of air, and 95Zr, 137Cs, and 144Ce are reported 

in microbecquerels (μBq) per cubic meter of air referenced 

103 

to 15°C and l Atm. The concentrations are reported as 

corrected for radioactive decay to the midpoint of the 

month of collection. The results of the analyses on the 

weekly samples from BRW and MLO are presently being 

prepared for publication as an EML report. 

4. DISCUSSION 

There were no reported significant releases of radioactive 

materials into the atmosphere during 1992, and the 

concentrations of fission products such as 95Zr, 137Cs, and 

144Ce were at or below the lower limits of detection for the 

analytical and sampling techniques that we currently use to 

measure them. The seasonal cycles of 7Be and 210pb 

continue to follow those observed in previous years. 

Acknowledgment. We wish lo 1hank the NOAA CMDL staff at 

BRW, MLO, SMO, and SPO for the collection of air filter samples 

for the SASP. 

5. REFERENCE 

Larsen, R.J., and C.G. Sanderson, EML surface air sampling 

program, 1989 da1a, August 1991, U.S. DOE Rep. EMl-541, U.S. 

Dept. of Energy, Environmenial Measurement Laboratories, New 

York, 1991. 
Tomsk-7 Debris at BRW: Detection and Transport 

H. N. LEE, R. J. LARSEN, AND C. G. SANDERSON 

Environmental Measurements Laboratory, U.S. Department of Energy, New York, New York 10014-3621 

1. INTRODUCTION 

On April 6, 1993, radioactivity was accidently released 

into the atmosphere during an explosion and fire at a 

reprocessing plant in the Tomsk-7 military nuclear complex 

located 16 km north of the Siberian city of Tomsk. About 

40 Ci (19.9 TBq) of beta-gamma radionuclidcs were 

released into the atmosphere. The isotopic composition of 

the beta-gamma radionuclidcs at the time of the accident 

was reported by the IAEA (1993) to be 43.2% 95Nb, 35.3% 

106Ru, 18.7% 95Zr, 2.7% t03Ru, <0.1% 137Cs, with traces 

of 90Sr. 

2. MATERIAL A:'\D METHODS 

Week-long, high-volume air filter samples are routinely 

collectc.d by CMDL personnel at BRW, MLO, SMO, and 

SPO for EML's Surface Air Sampling Program. The 

primary purpose of this program is to study the temporal 

and spatial distribution of specific natural and 

anthropogenic radionuclides in the surface air. Following 

notification of the accident, air filter samples collected at 

BRW were express mailed to EML and were immediately 

analyzed for gamma-ray emitting isotopes. The samples 

were collected on Dynawcb filters, which have an effective 

exposure area of about 266 cm2, at a now rate of -1.5 m3 

min·l. A 65.3 cm2 section of each filter was removed and 

compressed into a 1-2 cm3 cylinder and analyzed by 

gamma-ray spectrometry using a 320 cm3 high-purity 

germanium well detector. 

3. RESCLTS A:'\D DISCt.:SSION 

The fission products 95Nb and 106Ru were first detected 

in the BRW sample collected from April 15-21. The 

surface air concentrations of these isotopes inferred from 

this sample were 2.2 and 15 μBq m-3, respectively, at the 

midpoint of collection. In the sample collected from April 

21-30, 95Zr and 103Ru were detected in addition to 95Nb 

and 106Ru. The surface air concentrations of 95Zr, 103Ru, 

95Nb, and 106Ru inferred from this sample were 1.2, 0.8, 

2.8 , and 16 μBq m·3, respectively, with counting 

uncertainties at 1 sigma, between 10% and 30%. No 

fission products were detec ted in the sample collected from 

April 30-May 8. These results have been submitted for 

publication [Larsen et al., 1993). 

To understand the global transport of these isotopes, a 

three-dimensional trajectory model was developed to 

calculate the transport paths of the radionuclidcs released 

104 

during the accident. The trajectories were calculated based 

on the wind forecast generated by the global model 

operated at the National Meteorological Center, Camp 

Springs, Maryland. The 12-hr analysis wind data at grid 

intervals of 2.5 degrees for the 1000-, 850-, 700- and 500-

mb in the northern hemisphere were used in this study. 

Figure 1 presents two trajectories, computed at each 3-hr 

interval, showing the transport paths, from April 6-30, for 

radionuclide particles released near the Tomsk-7 site on 

April 6. The computations start at 875-mb (solid line) and 

835-mb (dotted line). This figure shows that the debris 

initially moved in a northeastern direction. Then, the 

debris meandered around at 80 degree latitude above the 

Arctic Ocean before finally moving southward, passing 

near the sampling station at BRW. The estimated arrival 

times for these trajectories at BRW, April 17 (835-mb) and 

April 27 (875-mb) are consistent with the arrival times 

estimated from the measurements. The debris followed 

different trajectories, depending on the initial time and 

location assumed for the released radionuclide particles. 

Fig. I Trajectories of radionuclides released at the Tomsk-7 site. 

The release heights arc 875-and 835-mb for solid and dolled lines, 

respectively. The star represents th e sampling site at Barrow, 

Alaska. 
We have computed additional trajectories showing the 

transport of the Tomsk-7 debris to Greenland and to central 

and eastern Canada, where we also have detected traces of 

Tomsk-7 debris. 

The concentrations of these fission products are 

extremely low and are of no dosimetric significance to the 

residents of Barrow. For example, we estimate the 

maximum increase in the daily external radiation exposure 

rate resulting from these fission products was less than 

1/1 OOth of a percent. 

105 

Acknowledgmenl. We wish to thank Dan Endres for coordinating 

the collection and mailing air filter samples to EML. 

REFERENCES 

IAEA, Tomsk-7 caused minimal radiation hazards, Nuclear Waste 

News, 13, 157, 1993. 

Larsen, R.J., C.G. Sanderson, H.N. Lee, K.M. Decker, and H.L. 

Beck, Fission products detected in Alaska following the Tomsk7 accident, submitted, J. Environ. Radioactivity, 1993. 
Ultrahigh Resolution Infrared Solar Spectra from Mauna Loa Observatory 

FRANK J. MURCRAY, SllELLE J. DAVID, RONALD D. BLATllERWICK, AARON GOLDMAN, A\'D DAVID G. MURCRAY 

University of Denver, Department of Physics, Denver, Co/oardo 80208 

1. INTRODUCTION 

An ultrahigh resolution (0.0035 cm·l) FTIR system was 

installed al the Mauna Loa Observatory (MLO) in May 

199 I. It was run routinely once per week by the MLO staff 

since November 1991. This instrument is serving as a 

prototype for the solar absorption FTIR instrument that will 

be used in the Network for Detection of Stratospheric 

Change. The instrument and analysis procedure were 

described in last year's Summary Report (Ferguson and 

Rosson, 1992). 

During 1992, University of Denver (DU) personnel 

operated and adjusted the equipment during a I-week period in 

January. In May and June, the quality of the data slowly 

degraded until it was not usable. DU personnel returned !I) 

MLO and found that a set screw holding the solar tracker in 

position had became loose. The screw was tightened and the 

system ran fine. In October, one of the instmment's power 

supplies failed. A new power supply was installed in 

December. Throughout the rest of the year when everything 

was running properly, MLO staff operated the instrument on a 

once-per-week basis (usually Wednesdays), weather 

pcrmiuing. 

This instrument currently measures the spectrum in the 750 

to 1250 cm·l (8 to 13 micron) band and the 2500 to 3100 cm·l 

(3 to 4 micron) band. Total column amounts of HCl, HN03, 

0 3 and N20 arc currently processed routinely. Retrieval 

software for many of the other gases are under development. 

Last year we presented results pertaining to HCl and HN03. 

This year we will focus on our 03 and N10 results. 

2. ANALYSIS 

The procedure for analyzing data is the same as 

described last year. A small section of a MLO spectrum 

filled to a calculated spectrum, around 1163 cm·l, is shown 

in Figure 1. The ozone spectral lines were chosen to be 

isolated and only weakly temperature dependent. The 

filled spectral region includes two prominent ozone 

absorptions and a strong line due to N10. The difference 

between the observed and calculaled spectra is shown 

below the spectra on an expanded scale. The residuals 

appear to be random, indicating that the fit is good down to 

the noise level of the instrument. The initial profile used in 

filling the ozone was based on an average of the ozone 

sonde data provided by S. Oltmans (personal 

communication). 

106 

1.00 

.. 

g 

2 

~ 0 .50 ., 

c 

~ 

0.00 -+---~--~--~--~--~--~-

1162.85 

0 .10 Wavenumber {cm"1

) 

1163.45 

-0.1 0 ---~--~--~--~- --~-

1162.85 1163.45 

Wavenumber (cm"1

) 

f.ig. 1. The top panel shows a portion of the spectrum in the 750 to 

1250 cm·t band, which is analyzed for 0 3 and N20. The N20 line 

is the broader line near the center of the region, sharper 03 lines are 

on either side. The observed spectrum is the dotted line, the best fit 

calcu lated spectrum is the solid line. The bottom panel shows the 

difference between the observed and calculated on an expanded 

scale. 

3. DISSCUSSION 

Figure 2 shows the total column ozone measured by FTIR 

and by the Dobson for January 1992-January 1993. Except 

when the instrument was down. there is FTIR data for almost 

every week. The data are ploued to show the natural 

variability as well as to compare the FTIR and Dobson results. 

Using only the days where measurements were made using 

both techniques (29 days), the mean total ozone column 

determined by the FTIR is 4.6% lower than the Dobson. After 

raising the FTIR results by 4.6%, the RMS difference between 

FTIR and Dobson is 2.7%. Considering the two techniques 

differ widely in instrumentation, analysis and spectroscopy, the 

agreement between them is extremely good. 
Ozone Vertical Column 

9 

6 0 

0 + 

?ti +<'J •c!>+ Ill 7 + Ill 

0 IP 0~111 0 0 

Ffi° 0 l!l J + 

6 

Ill 

ii 

Ui 5 ~ + Dobson 

.. 

.. 

E o FTIR 

E. 

3 

2 

0-1--~~~~~~~--.~~~~..--~-,--~-.--~-.-~--.-~--; 

10/15 12/15 02/14 04/15 06/15 08/15 

1991-1992 

Fig. 2. Total column ozone on days with both FTIR and Dobson 

measurements (Dobson data are taken from the WMO Wo rld Ozo ne 

Data Center). 

Figure 3 shows the total column of N20 measured by 

FTIR. We have not yet carried out a detailed study of the 

error budget in this analysis; however, retrievals of NiO 

are consistent within about 2.5% (RMS). 

We are still trying Lo understand the remaining 

differences between the Dobson and FTIR, even though the 

agreement is already very good. Possible systematic 

differences include different response to tropospheric 

ozone. 

5.0 

4.5 . 4.0 

. ,,. . 

. .. 

Column over Mauna Loa Jari"92 .Jan'93 

. .. 

co 3.5 

iii 

~ 3.0- ~ 

c 

E 

:i 

2.5 

8 2.0 

0 

N 

z 1.5 

107 

1.0 

0.5 

o.: 

01/01 03/02 05/02 07/02 09/01 11/01 01/01 

Fig. 3. Total column N20 as mea sured by the FTIR. There is a 

slight indication of a possible seasonal effect, possibly related to the 

tropopause height. 

Acknowledgments. We wish to thank the staff of MLO for the ir kind 

support. Russell Schne ll has been very helpful. We a re panicularly 

indebted to Bob Uchida for collecting most of the data every week 

and IClling us know when problems arise with the instrument. 

4. REFERE\'CE 

Ferguson, E.E., and R.~. Rosson (Eds.), Climate Monitoring and 

Diagnostics laboratory No. 20: Swnmary Report 1991, pp. 115- 116, 

NOAA Environmental Research Laboratories, Boulder, CO, 1992. 
Advanced Global Atmospheric Gases Experiment (AGAGE) 

R.G. PRINN 

Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 

R.F. WEISS 

Scripps Institution of Oceanography, University of California, LA Jolla, California 92093 

F .N. AL YEA AND D.M. CU~NOLD 

Georgia Institute of Technology, Atmospheric Sciences, Atlanta, Georgia 30332 

P.J. FRASER AND L.P. STEELE 

CS/RO, Division of Atmospheric Research, Victoria, Australia 3195 

P.G. SI'.\1MONDS 

University of Bristol, School of Chemistry, Bristol, United Kingdom BS8 ITS 

1. INTRODUCTION 

In this global network program, continuous highfrequency gas chromatographic measurements of two 

biogenic/anthropogenic gases (CH4, N20) and five 

anthropogenic gases (CFCl3, CF2Cl2, CH3CCl3, 

CF2CICFCl2, CCl4) are 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 program that 

started in 1978 is conveniently divided into three parts 

associated with three changes in instrumentation: the 

Atmospheric Lifetime Experiment (ALE) that utilized 

Hewlett-Packard HP5840 gas chromatographs, the Global 

Atmospheric Gases Experiment (GAGE) that utilizes 

HP5880 gas chromatographs, and the Advanced (AGAGE) 

phase that has recently started 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. 

The current station locations are 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, 10°W). Stations also previously 

existed at Cape Meares, Oregon (45°N, 124°W) and 

Adrigole, Ireland (52°N, 10°W). The current Mace Head 

station replaced the Adrigole station, and a station is 

planned at Trinidad Head, California, (41°N, 124°W) to 

replace Cape Meares. 

2. 1992-1993 UPDATE 

The data for the seven long-lived gases measured in 

GAGE during 1992-1993 continue to generally be of good 

quality. Two publications have appeared or are about to 

appear describing and analyzing the data. First, 

measurements made between 1978 and 1990 of the 

anthropogenic chemical compound l, l, 1-trichloroethane 

(methyl chloroform, CH3CCl3) show it increasing at a 

108 

global average rate of 4.4 ± 0.2% per year (lcr) over this 

later time period. The measured trends combined with 

industrial emission estimates, are used in an optimal 

estimation inversion scheme to deduce a globally averaged 

CH3CCJ3 tropospheric (and total atmospheric) lifetime of 

5.7 (+0.7, -0.6) years (lcr) and a weighted global average 

tropospheric hydroxyl radical (OH) concentration of 8.7 

±1.0 x l 05 radical cm-3 (lcr). Inclusion of a small loss rate 

to the ocean for CH3CCJ3 of 1/85 year-I docs not affect the 

stated lifetime but lowers the stated OH concentration to 

8.1±0.9 x 105 radical cm-3 (lcr). The rate of change of the 

weighted global average OH concentration over this time 

period is determined to be 1.0 ± 0.8% per year (lcr) which 

has major implications for the oxidation capacity of the 

atmosphere and more specifically for methane (CH4 ), 

which like CH3CCl3 is destroyed primarily by OH radicals. 

The CH3CCl3 measurements at Samoa show remarkable 

sensitivity to the El Nino-Southern Oscillation (ENSO) that 

is attributable to modulation of cross-equatorial transport 

during the northern hemisphere winter by the interannually 

varying upper tropospheric zonal winds in the equatorial 

Pacific. Thus measurements of this chemical compound 

have led to the discovery of a previously unappreciated 

aspect of tropical atmospheric tracer transport [Prinn et al., 

1992). 

Second, 13 years of ALE/GAGE CCl3F and CCl2F2 

measurements have also been analyzed. Comparisons are 

made against shipboard measurements by the SIO group 

and archived air samples collected at Cape Grim, 

Tasmania, since 1978. CC13F in the lower troposphere was 

increasing at an average rate of 9. l ppt yr· I over the period 

July 1978 to June 1988. CCl2F2 was increasing at an 

average 17.4 ppt year· I in the lower troposphere over the 

same period. However, between July 1988 and June 1991 

the increases of CCl3F and CCl2F2 in this region have 

averaged just 6.9 ppt year·! and 15.7 ppt year-I 

respectfully. The rate of increase has been decreasing 2.4 

ppl year-2 and 2.9 ppt year-2 over this 3-year period. On 

the basis of recent scenarios of the worldwide releases of 
these compounds and using the calibration scale SIO 1986, 

the equilibrium lifetimes are estimated to be 49~~ years 

and 150~5j0 years for CC!3F and CC12F2 respectively. 

Using these lifetime estimates and a two-dimensional 

model, it is estimated that global releases of these two 

chlorofluorocarbons in 1990 were 242 ± 20 x 106 kg for 

CCl3F and 367 ± 29 x 106 kg for CCl2F2. It is also 

estimated that combined releases of these 

chlorofluorocarbons in 1990 were 21 ± 4% less than those 

in 1986. Slightly different estimates of lifetimes and 

emissions are obtained using new SIO 1993 calibrations 

[Cunnold et al., 1993]. 

Operations at the American Samoa CMDL Observatory 

will soon make the transition from the GAGE instrument to 

the new AGAGE system. During 1992 the GAGE HP5880 

continued to be operated by the CMDL station personnel in 

collaboration with the SIO group. Operations were 

generally smooth and uneventful except for two significant 

problem periods. In the aftermath of Hurricane Val 

(December 1991), the island electrical power was 

extremely unreliable and the station's generating system 

was severely taxed. Although the GAGE instrument 

operates on an uninterruptible power supply, the island 

power is so unreliable that we have decided not to risk 

uncontrolled shutdowns by operating the GAGE instrument 

when the station generator is not working . Station 

generator problems resulted in the suspension of operations 

for 11 days in early January and again for 9 days at the end 

of January. The second major problem was the erratic 

performance of the GAGE air sampling system between 

August and October. During this period there were several 

problems with failures of the metal bellows air sampling 

pump that were ultimately traced to a clogged inlet fil ter 

and approximately 2 months of data were lost. 

The new instrument 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 

injection system and a single gas standard. All channels of 

109 

the instrument are fitted with precolumns to avoid column 

contamination by late-eluting gases, and as a result the 

frequency of measurement was increased three-fold versus 

GAGE. Precision is also greatly improved over the GAGE 

instruments, with 1 o relative precisions on the order of 

0.05% for the rapidly eluting gases CH4, CCl2F2. NiO. and 

CC!3F. The system works interactively with its 

uninterruptible power supply so that controlled shutdown 

and startup of the entire instrument and sampling system 

are assured when there are extended power outages. The 

first AGAGE field instrument is now in operation at Cape 

Grim, and the instruments for Samoa and the other stations 

will be installed during the coming year. 

3. DATA ACCESS 

The ALE/GAGE/AGAGE data are archived at the 

Georgia Institute of Technology and are available to 

interested scientists. Potential users of the data should 

contact Fred Alyea (Internet: alyea@eas.gatech.edu, 

telephone: 404-894-3815). Generally, monthly means and 

standard deviations can be immediately transferred 

electronically. Transmission of the full data set (4-12 

measurements day· I for each compound at each station for 

all years beginning 1978) will require consultation. 

Acknowledgments. The AGAGE is supported by NASA Grants 

NAGW-732 and NAGW-2034, NOAA Contract NA85-RAC05103, 

CSlRO, Australian Bureau of Meteorology, and the U.K. 

Department of Environment. We thank the NOAA staff at Samoa 

for their continued excellent local support for ou r instrumentation 

there. 

4. R EFERENCES 

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

B.R. Miller, F.N. Alyea, and A.J. Crawford, Global trends and 

annual releases of CC13F and CC12F2 estimated from ALE/GAGE 

and other measurements from July 1978 to June 199 1, J. 

Geophys. Res., in press, 1993. 

Prinn, R., D. Cunnold, P. Simmonds, F. Alyea, R. Boldi, A. 

Crawford, P. Fraser, D. Gutzler, D. Hartley, R. Rosen, and R. 

Rasmussen, Global average concentration and trend for hydroxyl 

radicals deduced from ALE/GAGE trichloroethane (methyl 

chloroform) data, Geophys. Res. Lett .. 97, 2445-246 1, 1992. 
The 13C/12C of Atmospheric Methane 

PAUL QUAY, JOHN STUTSMAN AND DAVID WILBUR 

School of Oceanography, University of Washington, Seal/le, Washington 98195 

1. 11'TRODUCTION 

For the past 5 years we have been measuring the 13C/12C 

of atmospheric CH4 on air samples collected at three 

CMDL sites (BRW at 71 'N 156' W, MLO at 19'N 155'W, 

and SMO at 14'S 170'W) and on the Washington coast at 

48'N 126'W. 

The t3C/12C of atmospheric CH4 is a tracer that can 

distinguish between CH4 input from bacterial and nonbacterial CH4 sources. Bacterial CH4 is microbially 

produced in anoxic 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 ot3C 

of about -60°/oo (versus PDB) whereas the ot3C of natural 

gas and CH4 produced from biomass burning are about -40 

and -27°/oo, respectively [Quay et al., 1991]. 

The spatial and temporal variations in the 13C/12C of 

atmospheric CH4 depend on the variations in the relative 

strength and t3C/12C of the CH4 sources and sinks. Over 

interannual time scales, the change in the 13C/12C of 

atmospheric CH4 indicates changes in the source 

composition, i.e., the relative strength of bacterial versus 

non-bacterial CH4 sources. Because CH4 will likely 

contribute about 15% of 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 

slow down in the rate of CH4 increase in the atmosphere 

[Steele et al., 1992] 

2. METHODS 

The air samples are collected, at approximately 2-week 

intervals, using pre-evacuated stainless-steel fl asks either 

15 or 30 Lin volume. The CH4 is extracted from air in our 

laboratory using the procedure developed by Stevens and 

Rust (1 982]. 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, 1205 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 standards, is JOO ± 2% (n = 114). The 

13C/12C of the C02 derived from CH4 is measured on a 

Finnigan MAT 25 1 gas ratio isotope mass spectrometer. 

The overall measurement precision is about ±0. l 0 /oo. We 

obtain a ot3C of -41.73°/oo (versus PDB) for NBS-16. 

3. RESULTS AND DISCUSSION 

The seasonal cycle in the ot3C of CH4 is greatest at 71 ' N 

(BRW), with an amplitude of -0.6°/oo and decreases 

southward to 14 • S (SMO) where we measure no significant 

seasonal trend, i.e., <0.1°/oo (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 ot3C 

values occur at these two sites in September-October of 

each year. Generally at the northern hemisphere sites the 

lowest o13C values occur in the fall and the highest values 

occur in the summer. This trend toward enriched 

summertime o13C values is expected if CH4 oxid ation by 

OH primarily controls the seasonal cycle because the 12CH4 

molecules react at a slightly faster rate (1.005x) than the 

13CH4 molecules [Cantrell et al., 1990]. The annual mean 

l)13C values increase southward from about -47 .8°/oo at 

7 l 'N to -47.3°/oo at 14'S. 

We calculate a global average o13C of CH4 of about 

-47.5°/oo. The mean global ol3C value, when combined 

with the 14C content of atmospheric CH4, yields an 

estimate of the proportion of bacterial versus non-bacterial 

CH4 source strengths [Quay et 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 ot3C dominates the time 

series measurements, there is evidence for a slight 

interannual trend. Measurements at all four time series 

locations indicate an increase in o13C, and when combined, 

yield an average rate of approximately 0.04 ± 0.02°/oo per 

year. Measuring the interannual change in the ot 3C of 

atmospheric CH4 over the longer term will be a useful 

indicator of changes in the proportion of bacterial and nonbacterial CH4 inputs. 

4. REFERENCES 

Cantrell, C.A., R.E. Shetter, A.II. McDaniel, J.G Calvert, J.A. 

Davidson, D.C. Lowe, S.C. Tyler, R.J. Cicerone and J.P. Greenberg, 

Carbon kinetic isotope effect in the oxidation of methane by the 

hydroxyl radical, J. Geophys. Res., 95, 22455-22462, 1990. 

Quay, P.D., S.L. King, J. Stutsman, D.O. Wilbur, L.P. Steele, I. Fung, 

R.H. Gammon, T.A. Brown, G.W. Farwell, P.M. Grootes, and F.H. 

Schmidt, Carbon isotopic composition of atmospheric methane: 

110 

Fossil and biomass burning source strengths, Global Biogeochem. 

Cycles, 5, 25-47, 199 1. 
Steele, L.P., E.J. Dlugokencky, P.M. Lang, P.P. Tans, R.C. Martin, 

and K.A. Maserie, Slowing down of the global accumulation 

and atmosphe ri c methane during the 1980s, Nature, 358, 313-

316, 1992. 

PT. BARROW 

(71 •N 1 56•W) 

-47.2~----.-----.----...----r-----. 

-47.4 

-47.6 

-47.8 

-48.0 

-48.2 

- 48.4 

-48.6 

- 48.8 

-49.0 

- 49·2 ......,_1_9B_B_..._1_9_B_9 __ ....._1_9_9_0__..__1_9_91-~-1-99-2-~ 

OLYMPIC PENINSULA 

( 48•N 1 26•W) 

-47.1 ..---~---~----.-----~--~ 

-47.2 

-47.3 

~ -47.4 a.. 

~ -47.5 

~ - 47.6 

-47.7 

-47.8 

-47.9 

-48.0 

1988 1989 1990 1991 1992 

Stevens, C.M., and F.E. Rust, The carbon isotopic compositi on of 

atmospheric methane, J. Geophys. Res., 87, 4879-4882, 1982. 

Wigley, T.M.L., and S.C.B. Raper, Implications for climate and sea 

level of revised IPCC emission scenarios, Nature, 357, 293-300, 1992. 

-47.0 

-47.1 

ID -ft7.2 0 

a.. 

~ 

-47.3 

~ -47.4 

-47.5 

-47.6 

-47.7 

-47.8 

MAUNA LOA 

(1 9°N 1 55°W) 

-47.9 ......., ___ ....._ ___ ..._ ___ .___ __ _._ ___ ... 

1988 1989 1990 1991 1992 

SAMOA 

(1 40S 1 700W) 

- 47.0 ,...----,-----,..----,----,..-----. 

-47.1 

-47.2 ........ 

~ -47.3 a.. 

~ -47.4 

~ -47.5 

~ -47.6 

1i -47.7 .., -47.8 

-47.9 

-48.0 ....._ __ ......_ ___ .___ __ ...._ ___ .___ __ _, 

1988 1989 1990 1991 1992 

Fig. I. The time series of the l)l3C of atmospheric CH4 measured at Pt. Barrow, Alaska; Olympic Peninsula, Washington; Mauna Loa, 

Hawaii; and American Samoa since 1988. 

I 11 
Non Seasalt Sulfate to Methanesulfonate Ratios at American Samoa 

DENNIS L. SAVOIE AND JOSEPH M. PROSPERO 

University of Miami, Rosenstiel School of Marine and Atmospheric Sciences 

Division of Marine and Atmospheric Chemistry, Miami, Florida 33149-1098 

1. INTRODUCTION 

A major goal of our cooperative work at SMO is to more 

rigorously define the sources, atmospheric transport 

pathways, and fluxes of particulate nitrogen and sulfur 

species in the remote marine atmosphere. As a major 

component of aerosols, non seasalt (nss) S04 is believed 

to play an important role in the radiation balance of the 

atmosphere as well as in the acidity of atmospheric 

particles and precipitation. Estimates of the absolute 

and/or relative contributions of the marine and continental 

sources to the total nss so4 concentration require an 

independent estimate of the amount of nss S04 derived 

from at least one of these two sources. Methanesulfonate 

(MSA) has frequently been used as a tracer for the marine 

biogenic component because its dominant source over the 

ocean is believed to be the oxidation of dimethylsulfide 

(CH3SCH3, DMS). However, there has been some concern 

that the (DMS) derived nss SO;\/MSA ratio may vary 

significantly in both time and space. The best locations to 

assess the variation in the OMS-derived nss SO;\/MSA ratio 

are those in regions that are minimally impacted by 

continentally-derived material either anthropogenic or 

natural; SMO appears to be one such location. In this 

report, we use the results from 149 more recent samples in 

addition to the original 22 of Saltzman et al. [ 1985) to 

assess the variations in the relative concentrations of MSA 

and nss S04 at SMO. The more recent data are from 96 

weekly samples collected from January 3, 1990, through 

May 6, 1992, and from 53 daily samples collected in 

conjunction with the NASA GLOBE aircraft missi.ons of 

November 1989 and May 10 to June 10, 1990. 

The aerosol samples were collected by drawing air 

through 20 x 25-cm Whatman-41 filters at a nominal flow 

rate of 1.1 m3 min-1. The sampling pumps are controlled 

by wind sensors that activate the pumps only when the 

wind is off the ocean at speeds greater than 1 m s· 1. MilliQ water extracts of quarter-sections of the filters were 

analyzed for SO;\ and MSA (lo uncertainties = 5%) using 

suppressed ion chromatography and for N; (lo uncertainty = 

2%) using flame atomic absorption. Nss so4 is the 

difference between total so4 and seas alt so4' the latter 

being calculated as total N; times 0.2516, the S04/N! 

mass ratio in bulk seawater. The results from an intensive 

study of concurrent samples collected on Barbados indicate 

that the uncertainties in a given interspecies ratio are about 

2-5% and are attributable almost exclusively to the 

imprecisions in the chemical analyses. 

112 

2. RESULTS 

The mean concentrations of nss so4 and MSA for a 

variety of periods are presented in Table l. A similar mean 

nss S04 concentration, 0.36 μg m·3, was reported by 

Savoie et al. [1989a,b) for 2 15 samples. Even the 

comparatively small data set (n = 22) used by Saltzman et 

al. [1985) provided comparable means: 0.41 μg m·3 for nss 

SO;\ and 26 ng m-3 for MSA. The seasonal cycles of nss 

S04 and MSA are indicated by the seasonal averages listed 

in Table l. The nss so4 seasonal cycle is virtually 

identical to that which was based on the 1983 through 1987 

samples [Savoie et al., 1989b]. Perhaps partially as a 

consequence of the more limited data set, there is no 

clearly coherent pattern in either the monthly or the 

seasonal averages for MSA. 

The coefficients of determination (r2) between MSA and 

nss so4 are clearly significant: 0.66 for all of the weekly 

averages; 0.64 for November 1989 daily samples; and 0.83 

for May-June 1990 daily samples. Using a least-squares 

regression technique that takes into account the errors in 

both variables, the 127 weekly averages for nss so4 and 

MSA yield the following equation: 

nss so4 = 15.6 (±3.5) MSA + 0.047 (±0.089) (1) 

where all concentrations are in μg m·3 and ± indicates the 

95% confidence intervals. Excluding the intercept (which 

is not significantly different from zero) yields the 

following relationship: 

nss so4 = 17.9 (±2.7) MSA (2) 

For the 127 weekly averages, the geometric mean (GM) 

ratio (18.1 ± 0.9) is virtually identical to the MSA 

regression coefficient in eq. (2) and to the results obtained 

if all of the daily samples are considered separately rather 

than combined into weekly averages. The results from the 

composited seasonal data sets clearly indicate that there is 

no consistent seasonal variation in the nss S04 /MSA ratio. 

Moreover, the GM ratio for all of the 53 daily samples 

considered collectively (GM = 17.4; standard geometric 

deviation (SGD) = 1.346; median = 17.3) does not differ 

significantly from those for the overall or seasonal data 

sets even though there appear to be differences between the 

two daily sets. 

The overall variance in the measured nss S04 /MSA ratio 

includes two principal components: (1) the variance due to 
TABLE I. Mean Concentrations (Standard Deviation, N) of Nonsea-Sall (nss) S04 and MSA and Statistics 

of the nss S04/MSA Ratio at American Samoa for Various Time Periods. 

NSS so4 MSA NSS so4~1sA Ratio 

Data Set μg m·3 ng m·3 N GM SGD 

All weeky averages 0.37 1 (0.160, 393) 22.9 (10.6, 128) 127 18.07 1.328 

All individual samples, 171 18.06 1.373 

1983-1992 

Seasonal Using Weekly Averages 

Dec., Jan., Feb. 0.41 1 (0.174, 78) 22.9 ( 8.0, 21) 21 17.46 1.230 

March, April, May 0.340 (0.165, 99) 21.9 (I 1.6, 36) 36 18.14 1.306 

June, July, Aug. 0.320 (0.133, 107) 22.8 (12.1, 33) 32 17.50 1.382 

Sept., Oct., Nov. 0.421 (0.148, I 09) 23.8 (9.9, 38) 38 18.84 1.354 

Daily Samples 

Nov. 1989 0.366 (0.177, 25) 17.7 (8.0, 25) 25 20.13 1.373 

May-June 1990 0.444 (0.227, 28) 29.9 (16.5, 28) 28 15.25 1.229 

N = Number of data, GM= geometric mean, SGD =standard geometric deviation 

the random errors in the measured concentrations of S04 , 

N; , and MSA; and (2) the variance in the actual nss 

S04 /MSA ratio in the atmosphere. Because the frequency 

distribution of the ratio is lognormal, we assess the 

variance in the natural logarithm of the ratio (In R) which 

exhibits a normal distribution. In this case, the appropriate 

equation is: 

lnR = Jn (nss S04) - In (MSA) (3) 

and propagation of errors yields the following estimate for 

the variance in lnR that arises solely as a consequence of 

the analytical variance (a) of so4, N;, and MSA: 

o2[JnR,a] = o2[Jn (nss so4), a] + o2[in (MSA), a] (4) 

which can be calculated from the following: 

o2[Jn(MSA), a] = o2[(MSA), a]/(MSA)2 = 

(5) 

(0.05*MSA)2/ (MSA)2 = 0.0025 

o2[in(nss so4). a] = o2[(nss so4). a]/(nss so4)2 (6) 

o2[(nss S04), a)= (0.05*S04) 2 + (0.02*0.2516*N;)2 (7) 

where the constants 0.05 and 0.02 represent the analytical 

uncertainties for MSA, so4, and N;, respectively. 

For all sample sets that were examined, the variance of 

the measured lnR is comparable to the variance that would 

be expected from the uncertainties in the measured 

atmospheric concentrations alone. For the 171 individual 

113 

samples, o2[inR,m) was 0 .085 which is virtually identical 

to the estimated analytical variance, o2[JnR,a] = 0.083. For 

all 127 weekly averages, o2[JnR,m] is similar, 0.080, and 

only 10% higher than o2[inR,a]. 0.073. For all 53 daily 

averages, o2[1nR,m], 0.090, is 14% lower than o2[JnR,a]. 

0.104. Even for the May-June 1990 daily samples for 

which the geometric mean rat io was statistically 

significantly different from that in the other sets, 

o2[inR,m] and o2[inR,a] were within 14% of one another 

(0.073 and 0.063, respectively). The largest difference 

between the two variances was for the November 1989 

daily samples for which o 2[inR,m]. 0.112, was about 28% 

less than would have been predicted from the uncertainties 

in the concentrations, o2[inR,a] = 0.155. 

3. CO:-ICLUSIONS 

Several fundamental conclusions can be drawn from the 

results of this research. A nss S04/MSA ratio of 18.1 (±0.9) 

appears to be applicable al Samoa throughout the year. This 

value is only 7% higher than the GM ratio of 16.9 (±1.1) in the 

much smaller data set used by Salrzman et al. [1985). Since 

the observed variances from this value can be attributed solely 

to the random errors in the measurements, there is no evidence 

that this ratio varies to any significant extent. Hence 

measurement uncertainties would have to be reduced 

substantially in order to observe any variations that could be 

attributed to actual changes in the ambient atmosphere. The 

ratio at Samoa is consistent with the biogenic nss S04/MSA 

ratios that were estimated for Bermuda and Barbados from the 

results of multiple variable regression analyses, 19.6 (±2.1) and 

18.8 (±2.2), respectively [Savoie el al., 1993). 
AcknowledgmenJs. We thank T. Snowdon, F. Huang, T. Huang, M. 

Izaguirre, and L. Custals (University of Miami) for their technical 

assislllnce; B. Mendonca and CMDL Boulder for their continued 

cooperation; and C. Farmer and M. Winey (SMO) for mainlllining and 

operating our sampling systems. The research was supported by NSF 

grants ATM8703411 and ATM9013 125, and NASA contracts NAG8-

621 and NAGS-841. 

4. REFERENCF.S 

Saltzman, E.S., D.L. Savoie, J.M. Prospero, and R.G. Zika, Atmospheric 

methanesulfonic acid and non-seasall sulfate al Fanning and 

American Samoa, Geophys. Res. utt., 12, 437-440, 1985. 

114 

Savoie, D.L., J.M. Prospero, and E.S. Saltzman, Nitrate, non-seasalt 

sulfate and melhanesulfonate over the Pacific Ocean, in Chemical 

Oceanography, Vol. JO, SEAREX: The Sea/Air Exchange 

Program, pp. 219-250, edited by J.P. Riley, R. Chester, and R. 

A. Duce, Academic, San Diego, CA, l 989a. 

Savoie, D.L., J.M. Prospero, J.T. Merrill, and M. Uematsu, Nitrate in 

the atmospheric boundary layer of the tropical South Pacific: 

Implications regarding rources and transport, J. Atmos. Chem., 8, 

391-415, 1989b. 

Savoie, D.L., R. Arimoto, J.M. Prospero, R.A. Duce, W.C. 

Grau stein, K.K. Turekian, J.N. Galloway, and W.C. Keene, 

Oceanic and anthropogenic contributions to non-seasalt sulfate in 

the marine boundary layer over the North Atlantic Ocean, J. 

Geophys. Res., submiued, 1993. 
USGS Barrow Observatory 

JACK TOWKSHEND 

U.S. Geological Survey, College Observatory, Fairbanks, Alaska 99775-5160 

The USGS Barrow Observatory is the northernmost of 

this agency's 13 continuously recording, 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 at 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 observatory is operated 

from the USGS College Observatory at the University of 

Alaska in Fairbanks as a satellite station. Staff scientists 

from the College Observatory visit the site bimonthly to 

make absolute observations, perform routine equipment 

maintenance, and retrieve data on magnetic tape. Staff 

personnel from NOAA CMDL make weekly visits to the 

site to check equipment operation and occasionally 

115 

perform emergency service when there is a problem and a 

College Observatory staff person is not available to make 

repairs. 

The primary equipment used to acquire the magnetic 

data is an EDA FM-100-BR Triaxial Ouxgate magnetometer, an EDA PPM-I 05 proton free-precession 

magnetometer, an observatory magnetometer interface 

system, and several pier-mounted instruments for absolute 

control observations. Data arc retrieved by telephone 

periodically through a computer modem by the USGS 

office in Golden, Colorado. A seismograph is operated on 

site in a vault located 6.1 m beneath the ground surface. 

The present seismic program is operated in cooperation 

with the Geophysical Institute at the University of Alaska, 

Fairbanks. 

The USGS Barrow Observatory has been in continuous 

operation since 1949. 
Separation of Local From Distant Pollution at MLO Using Pb-212 

S. WmrrLESTONE 

Australian Nuclear Sciences&. Technology Organisation, Menai, N.S.W. 2234, Australia 

S.D. SCHERY A~D Y ANXIA LI 

New Mexico Tech., Socorro, New Mexico 87801 

1. INTRODUCTION 

At MLO there are several means of deciding whether an 

air mass can be considered "baseline." Wind direction, dew 

point, CN, and radon are the most important parameters on 

which 10 base selection of baseline samples. Combined, 

they can be used with a high success rate to select air 

samples that represent a large volume of the atmosphere 

and are free from recent pollution [Gras el al., 1992]. They 

cannot, however, be used lo distinguish between local and 

distant sources. 

Some observers need to know if the air parcel has been in 

contact with Hawaiian soil. Asian contact a few days 

before is nol always important. Some short-lived gases 

such as isoprene have shown that it is possible lo have 

entrainment of Hawaiian air into the down-slope flow. But 

isoprene has complex generation and transport, and a more 

quantitative, or at least a complementary indicator of local 

influence is needed. 

Pb-212 has the potential to fulfill this role. It is the 

decay product of thoron gas (radon 220) that is emitted 

from all soils along with radon-222. Thoron has a 55-

second half life and that of Pb 212 is 10.6 hours. After 4 

days, only 0.2% of the original Pb-212 remains, which 

means that it has virtually disappeared from the fastest 

Asian air flows. However it lasts long enough to be present 

in 1-day scale circulation. Pb-212 has been used by others 

for indication of close land contact [Heimann el al., 1990]). 

I/utter el al., (1990] have measured Pb-212 at MLO, and 

shown the expected result that Pb-212 lends lo be present in 

up-slope air, bul not in downslope. 

This report describes a 5-week study of Pb-212 

concentration at MLO to assess its potential for detecting 

local land influence on air samples. The measurements 

were carried out at the invitation of NCAR in July-August 

1992 to coincide with the last phase of MLOPEX II. Brief 

mention is made of some measurements of Pb-212 and 

thoron emanation from Java in April 1993 because the 

preliminary results clarify the MLOPEX measurements. 

2. EXPERIME1'TAL METHOD 

The method employed to measure the concentration of 

Pb-212 required three steps. First, air was drawn from a 

mast 3 m above ground at a rate of 250 L min-I through a 

filter (Gelman versipore, 1.2 micron pore size) with 

diameter 115 mm. This stage lasted 2 hours, and was 

synchronized with even hours local time. Next, the filter 

116 

was left for 4 hours; Jong enough to allow any radon-222 

decay products to decay . Finally, the filter was exposed lo 

a screen coated with zinc sulfide, the scintillation's of 

which were detected by a photomultiplier. 

This process was fully automated and permilled 

measurement of Pb-212 averaged over precisely defined 2-

hour periods. Extraction of the Pb-212 concentration was 

simple in principle, requmng only subtraction of 

background events from the raw count and multiplication 

by a calibration factor. 

3. RESULTS 

At MLO influence of Hawaiian land is most strongly fell 

during the day when the synoptic winds arc light and there 

is no heavy cloud above the mountain. Under these 

conditions convective northerly upslope winds become 

established. At night the same cloud and wind conditions 

lead to southerly downslope winds that are subject to the 

least island contact. Synoptic flows and clouds result in 

more complex sampling conditions. 

The week starting July 16 (Figure 1) was so variable that 

most conditions of interest occurred. On July 16, CN, 

water, Pb-212, and radon concentrations varied as expected 

for upslope and downslope conditions: concentrations 

elevated in upslope winds compared to concentrations in 

downslope winds. On other days most possible 

combinations of tracer concentrations occurred: high CN 

0 

0 

......... ~ (/) 

w - I- 0 

-ct E 

3:1 0 

Qi 

a. 

0 

0 

......... ~ (/) 

w 0 

~ E 

3: I 

0 

Qi 

a. 

300 0 

200 8. NON-UP-SLOPE WINDS 

0 

100 

O--+-.~~~~~~~~~~~~~~~ ~~----< 

300 Rnf ~ ~i o g g g9 __ o_ __ o_ - o- -

615~~ Oo ---

15@<2> g ?- - - - - - -A. UP-SLOPE WINDS 

200 

100 

-o 

0 100 200 

Pb-212 (atoms m-3) 

Fig. I. Pb-212 versus water concentration. 
and water with low Pb-212 and radon on July 20, low CN 

and water with high Pb-212 and radon on July 18, and so 

on. It is of particular note that elevated Pb-212 does occur 

in dry downslope winds when land contact should be a 

minimum. 

The data for 5 weeks were sorted into groups in which 

the wind had persisted in the upslope (315° through north to 

67°) and non-upslope sectors for 2 hours. Upslope 

conditions arc easiest to understand. A high proportion of 

radon in upslope wind is from Hawaii, rather than from 

remote land, and correlation analysis indicated that the 

correlation of Pb-212 with radon is quite high (0.76). The 

sources of Pb-212 and CN tend to be differently distributed 

on the island, so this correlation is modest (0.48). In the 

case of water, the data arc stronger than would appear from 

the modest correlation coefficient of 0.45. This is 

illustrated in Figure la. It is not unusual to have moist 

boundary layer air transported to the observatory with a 

minimal contact with Pb-21 2 producing land, so there will 

be times when Pb-212 is low but water concentration high: 

at low Pb-212 concentrations it is possible to have a wide 

range of water concentrations. However, if the Pb-212 

concentration is high, the air path must have been close to 

land and therefore, from the moist boundary layer. Pb-212 

thus provides clear discrimination of moist air into parcels 

with and without contact with Hawaiian soil. 

In non-upslope winds, the proportions of non-Hawaiian 

radon and CN are higher and the correlations with Pb-212 

weaker as expected. The relationship between Pb-212 and 

water (Figure l b) was markedly different from that in the 

upslope sector and the correlation coefficient was slightly 

negative (-0.2). This suggests that some of the down-slope 

Pb-212 may not have come from the moist boundary layer. 

The origin of non-upslope Pb-212 was investigated in a 

number of ways. First, correlations were carried out for 

data from a wind sector close to directly downslope. These 

winds tend to occur when the skies are clear and the 

synoptic winds light and should accentuate any direct 

effects of the mountain above MLO. Table 1 shows 

correlations of Pb-212 with radon, CN, water, wind speed, 

and differential temperature. The number of events in this 

sector was only 20, 17% of all non-upslope, so not too 

much weight should be given to the correlations. 

TABLE 1. Correlations between Pb-212 and wind speed, 

radon, CN, and water concentrations, for winds 

persisting in the downslope sector, south ±16°, 

for at least 2 hours at more than 2 ms·l 

PB-212 Radon CN Water Wind Speed 

Radon 0.81 

CN 0.82 0.90 

Water O.Q3 0.17 0.27 

Wind speed -0.47 -0.44 -0.66 -0.52 

DP -0.64 -0.36 0.34 0.38 0.25 

*DT- Differential temperature 2-40 m. 

117 

The correlations in the downslope sector are very much 

stronger than in the broader non-upslope sector. Taking 

them at face value , it would seem that Pb-212 is higher 

when wind speed is less and the differential temperature is 

more negative: conditions favoring a smaller mixing depth 

and a larger contribution from the lava above MLO. There 

are also strong correlations, not seen in the rest of the nonupslope sector between Pb-212 and species that can be 

imagined to come from •:olcanic vents: CN and radon. It is 

somewhat confusing that the correlation of differential 

temperature is weakly positive with CN but moderately 

negative with Pb-212. 

A second approach to assessing the origin of non-upslope Pb-212 was to compare the average concentrations in 

the three wind sectors. From Table 2 it is evident that Pb2 12 responds more strongly to Hawaiian land contact than 

the other species: the ratio of non-upslope to upslope is 0.2. 

This proportion is small enough for it to be reasonable to 

attribute it to either lava above MLO or re-circulated air 

from below MLO. Data in Table 2 support the indication 

above that a significant proportion of non-upslope radon is 

from above MLO: the Pb-212 concentration in the broad 

non-upslope sector is only half that in the downslope 

sector. 

Thirdly, Pb-212 was compared to another natural tracer, 

isoprene. Both the source distributions and evolution with 

time of these species are somewhat different. Even so, 

there is close correlation between the means of groups 

selected on the basis of Pb-212 concentration ranges as 

shown in Figure 2. lsoprene has no source above MLO or 

distant from Hawaii. Figure 2 therefore supports the 

evidence from wind sector averages that most Pb-212 

comes from below MLO. 

The final evidence for location of Pb-212 sources comes 

from a set of measurements specifically designed to set 

limits on the amount from above MLO. From preliminary 

analysis of this experiment three conclusions are suggested: 

(1) The thoron emanation from lava above MLO is 

sufficient to produce Pb-212 concentrations of the order of 

those observed in downslope winds with reasonable mixing 

depths. (2) In ideal downslope winds, Pb-212 

concentrations close to the top of Mauna Loa, directly 

upwind of MLO have been observed to be close to the limit 

TABLE 2. Ratios between concentrations of PB-212, radon, 

CN, water, and wind speed in three wind sectors. The nonupslope sector excludes the downslope, south ±16°, sector. 

Ratio 

Wind Sectors PB-212 Radon CN Water Wind Speed 

Non-upslope 0.21 0.67 0.54 0.66 1.58 

Upslope 

Non upslope 0.50 1.14 0.94 1.02 1.07 

Downslope 
-> 

.J:J 

~20 

-

L.J 

z 

L.J 

g: 10 

0 

Vl 

0-+--'-~~+-~..---.~~~-+~~~.....--~~__. 

0 10 20 30 40 50 

Pb-212 (atoms m-3) 

Fig. 2. Average isoprene concentration in each Pb-212 

concentration range. Bars are errors on the means. 

of detection (2 atoms m-3) while the level at MLO was up 

to 17 atoms m-3 This may have come from the Java in the 

path of the air flow. (3) When a moderate southeasterly 

synoptic wind de-coupled the boundary layer from MLO, 

the Pb-212 concentration in the saddle below MLO was 

lower than the concentration at MLO. This is strong 

evidence for a Pb-212 source above the saddle where the 

terrain is similar to that above MLO. 

4. CONCLUSIONS 

Continuous measurements of Pb-212 with 2-hour time 

resolution have established that levels at MLO over a wide 

range of conditions could be made by a relatively simple 

instrument with sufficient sensitivity at 1-hour time 

resolution. 

118 

The presence of Pb-212 is unequivocal evidence of 

passage of an air parcel close to the Hawaiian land, and it is 

feasible to detect concentrations as small as 2% of the 

highest levels observed in upslope winds. Pb-212 is, 

therefore, an excellent supplement to radon, which detects 

land contact, but not necessarily with Hawaii. 

Interpretative difficulties arise because some Pb-212 

enters air from even ti vely recent Java above MLO. 

The total amount of Pb-212 in non-upslope winds is 

generally small compared with that in upslope winds, being 

Jess by a factor of 5 on average. Most of the Pb-212 in a 

narrow downslope sector appears to come from the lava 

above MLO. Further analysis is required to decide whether 

there is any Pb-212 recirculated from below MLO to the 

broad non-upslope sector. 

Acknowledgments. CMDL provided some equipment and 

preliminary meteorological data. The practical assistance of S. 

Ryan was most valuable. J. Greenburg of NCAR supplied 

preliminary isoprene data. The automatic Pb-2 12 detector was built 

by B. Stenhouse of ANSTO. S. Schery's and Y. Li's research is 

funded in part by the U.S. D.0.E. 

5. REFERENCES 

Gras, J.L., and S. Whittlestone, Radon and CN: Complementary tracers of 

polluted air masses al coastal and island sites, J. Radioanalytical and 

Nuclear Chem., 161, 293-306, 1992. 

Heimann, M., P. Monfray, and G. Polian, Modeling the long-range 

transport of 222Rn to subantarctic and antarctic areas, Tel/us, 428, 83-

99, 1990. 

Huller, A.R., A.C. George, M.L. Maiello, J.M. Fisenne, R.J. Larsen, J-1.L. 

Beck, and F.C. Wilson, 222Rn, 222Rn progeny and 220Rn progeny as 

atmospheric tracers of air masses at the Mauna Loa Observatory, 

EMI...-522., 26 pp., Environmental Measurements Laboratory, U.S. 

Dept. of Energy, New York, 1990. 
Recent Interannual Variations in C02 in Both Hemispheres 

T. P. WHORF, C. D. KEELl:\G, AND D M. WAHLEN 

Scripps Institution of Oceanography, La Jolla, California 92093-0220 

1. INTRODUCTION 

Cooperative programs of C02 measurements between the 

Scripps Institution of Oceanography (SIO) and CMDL 

continued through 1992 at Point Barrow, Alaska (PTB), 

Mauna Loa Observatory (MLO), Cape Kumakahi (KUM), 

Samoa (SAM), and the South Pole (SPO). Air samples 

were collected in 5-L glass flasks several times per month 

since the 1950s at MLO and SPO, and since the mid 1970s 

to early 1980s at the other three stations. SIO also collects 

flask samples at a few other stations, including La Jolla 

(LJO) since 1969. In addition, SIO continues to monitor 

atmospheric C02 concentrations at MLO on a continuous 

basis using the non-dispersive infrared (NDIR) gas analyzer 

installed on site in 1958. Furthermore, since 1978 al some 

stations the 13C/12C isotopic ratio of atmospheric C02 was 

determined from samples collected in flasks. Measurements before 1992 were made at the laboratory of Willem 

Mook at Groningen University [Keeling et al., 1989, and 

unpublished data]. Subsequent measurements were made al 

SIO. Recent data indicate that the persistent rise in 

atmospheric C02 has anomalously slowed since 1989 on a 

global basis. The anomalous departures at MLO and SPO 

are the largest ever seen at these stations in over 30 years 

of record. Nevertheless, as with previously observed 

anomalies in atmospheric C02. this anomaly appears Lo be 

associated with an El Nino event. It may also be related to 

the eruption of the Pinatubo volcano. In either case, the 

anomaly is expected to be transient and not an ir}<lication 

that the global carbon cycle has become more efficient in 

sequestering C02 produced by the combustion of fossil 

fuels. 

2. DATA Al'iD ANALYSIS 

All flask samples were analyzed for their C02 

concentration with an NDIR gas analyzer of the same 

design as that installed at MLO. Calibrations have 

continued with reference gases similar to those used al 

MLO [Keeling et al., 1986]. Air samples were rejected if 

pairs did not agree within 0.40 ppm (0.60 ppm for Point 

Barrow), i.e., singlets were rejected also, or if found Lo be 

outliers having a residual greater than three standard 

deviations from a smooth curve fit describing the seasonal 

and interannual variations. The function chosen in the 

fitting process uses a sum of four harmonics Lo describe the 

seasonal variations, and a cubic spline [Reinsch, 1967] to 

describe the interannual variations. A gain factor is used to 

model an approximately linearly increasing seasonal 

amplitude variation [Keeling et al., 1989, pp. 167, 176]. 

This simple model of increasing annual C02 cycles was 

119 

introduced when it became clear in our longer C02 records 

that there were significant increases in the seasonal 

amplitude of C02 concentration. 

Figure 1 shows the results of such fits made to the C02 

observations selected from a subset of the stations where 

we sample air. Point Barrow data were augmented Lo 

include continuous C02 data measurements made by Kelley 

[Kelley, 1969] during the period 1961-1967. Data at five 

additional sites are shown in the figure: La Jolla, California 

(33"N, 117"\V), MLO (19"N, 15S"W), Christmas Island 

(2"N, 157"W), SMO (14"S, 171"W) and SPO (90"S). A 

cooperative program at Alert between SIO and the 

Atmospheric Environment Service of Canada has existed 

since 1985. The Alert C02 record is, however, relatively 

Cl.OBA.I. STATION DATA 

36S ,_.._,.....,-----.----,....,...---------~ 365 

PTB 

71°1' 

uo 

JJ•N 

MLO 

20°N 

CHR 

2°N 

SAM 

15"S 

SPO 

go•s 

Fig. I. Monthly average C02 conce ntratio n (in ppm) at six SlO 

stations spanning the globe and fit by the function prescribed in the 

text. Early Point Darrow data are from Kelley [ 1969) and Mauna 

Loa data from the continuous data record. 
short and thus in this analysis provides only supporting 

evidence 10 the resulls from the longer stations. The 

Christmas Island data record shown in Figure 1 was 

extended back from 1976 10 1972 by using data from 

nearby Fanning Island in the computation of C02 

anomalies discussed in the next section. 

3. RESULTS 

Plots of C02 anomalies were prepared from seasonallyadjusted monthly average C02 data at each station by 

subtracting a constant fraction of the C02 produced by 

industrial processes, as described by Keeling et al., [ 1989, 

p. 179-180]. This airborne fraction (58 .6%) was chosen so 

that the anomaly is zero on January 1, 1959, and 1986 for 

MLO in the northern hemisphere and for SPO in the 

southern hemisphere. Figures 2 and 3 show the results for 

selected northern and southern hemisphere stations, 

respectively. A strong negative anomaly is seen 10 have 

developed al all stations in 1992. At many of the stations it 

began immediately following the eruption of Mt. Pinatubo 

in the Philippine Islands. It is more pronounced in the 

northern hemisphere, but is global in scope. 

To determine the cause of this anomaly, we have 

computed global terrestrial vegetative and oceanic fluxes of 

C02 that explain the recent trends in both atmospheric C02 

q,o ....... 'l"'""T""'1"TI"l~1'"'"l""''"T"m'Tf~l""'"l""''"T"m'Tf~l""'"l""''"T"m"'f"'"'Tl" I 1 1 I 11 'I 11 I 'l'".,l'""l""'l'""P""l'""l""'l"'"l"'"l'll"l""'I 111111111 I "'I"" 

>: 

CL 

CL 

z 

0 

3.5 

3.0 

2.5 

2.0 

I. 5 

58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 

YEAR 

f-ig. 2. C02 anomalies for northern hemisphere stations obtained by seasonally adjusting the data and then subtracting a constant airborne 

fraction of the C02 released to the atmosphere by industrial processes, calculated to agree with the Mauna Loa C02 record (58.58%). The 

latitude of each station is indicated: Alert 82°N, Pt. Barrow 7 l 0N, La Jolla 33°N, Mauna Loa 20°N, Christmas Island 2°N. 

~.o 

3.5 

3.0 >: 

CL 2.5 CL 

2.0 

z I. 5 0 

t-- 1.0 a: 

:= . 5 

~ 0 u 

~ -.5 

u - 1.0 N 8 - 1. 5 

-2.0 

-2.5 

" \ 

,.,...., \ 

' 

-3. 0 ............................ ~ .................... u.W.~ .......................................................................... ~ ...................................................................... ~ ...... ~ ............. ~ ...... ~ ............. ~ ........................... ........ 

58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 

YEAR 

f-ig. 3. C02 anomalies for southern hemisphere stations obtained as in f-igure 2, except that the constant airborne fraction is calculated fo r 

the South Pole (55.94%). Stations ploned are Samoa 14°S , Kennadec 29°S, New Zealand 41 °S, and South Pole 90°S. Christmas Island is 

repeated from Figure 2 but with the airborne fraction calculated for the South Pole. 

120 
concentration and its 13C/12C ratio. First we combined data 

for MLO and SPO to obtain estimates of the global trends 

in both the concentration and 13C/12C ratio. Then with a 

one-dimensional model of the oceanic carbon cycle 

[Siegenthaler, 1983) we estimated the rate at which the 

oceans have absorbed C02 injec ted into the atmosphere by 

industrial processes. 

The calculated rate is a function of the rate of industrial 

emissions [Marland, 1991 and personal communication] 

and of the observed atmospheric concentration variation 

since preindustrial times. The concentration variation used 

in the calculation, as described by Keeling et al., [ 1989, pp. 

186) combines estimates of C02 concentration from air 

trapped in ice cores with the C02 data from MLO and SPO. 

We then calculated the variations in C02 concentration not 

accounted for by oceanic absorption of industrial C02. For 

the period commencing with the isotopic record in 1978, 

these anomalous variations were further partitioned into 

oceanic and terrestrial components consistent with the 

observed 13C/12C ratio of atmospheric C02. This 

computation was done by a "double deconvolution" as 

described by Keeling et al., (1989, pp 229-230). The 

oceanic and terrestrial fluxes implied by this double 

deconvolution are plotted in Figures 4 and 5, respectively. 

Fluxes in gigatons of carbon (GtC) are shown as integrals 

over intervals defined by episodes of persistently positive 

and negative oceanic anomalies. The anomalies are 

expressed with respect to the average trend in each flux 

from the beginning of 1978 until May 1991, when the most 

recent negative anomaly began. Since May 1991, the 

oceans are computed to have taken up 0.7 GtC, in addition 

to 4.5 GtC absorbed primarily in response to the increase in 

atmospheric C02 from industrial emissions, but partially 

owing to long-term changes in the carbon cycle reflected in 

the average trend in each anomalous flux component from 

~ 

~ 

! 0 

l!; 

§ -2 

a: 

.., 

0 -1 

-1. 5 -6 

-8 1978 1900 1962 1981 1986 1988 1990 1992 

J[AR 

Fig. 4. Time trend of the anomalous release of C02 by the oceans 

shown as a solid curve in units of GtC yT'I. Vertical lines separate 

persistently positive and negative anomalies with amounts 

integrated over each interval expressed in GtC. A da shed curve 

indicates the long-term trend evaluated as the mean of the anomaly 

over the isotopic record period up to May 1991 (0.08 GtC yr-t ). 

121 

-l -

-1.8 

~ -l.6 -J.O 

-5.0 

-6 

-8 L_, _ l _ ..L- j_ 

1978 1980 1967 1981 1986 1968 1990 1992 

l[AR 

Fig. 5. Same as Figure 4 except showing the time trend of the net 

release of C02 by the biosphere. The vertical lines are those used in 

Figure 4, and the mean of the anomaly over the isotopic record up 

to Y!ay 1991 is -0.08 GtC yr-t. 

1978 to 1991. During the same time period, the terrestrial 

vegetation is computed to have anomalously taken up 1.8 

Gtc. These two estimated amounts are, however, more 

uncertain than those for previous periods of persistent 

anomalies, because the isotopic measurements of the final 

period were made on a different mass spectrometer, not yet 

fully calibrated. 

The computations, if correct, indicate that the oceanic 

and terrestrial flux components, since May 1992, have both 

involved withdrawals of C02 from the air, contrary to all 

previously documented episodes shown in Figures 4 and 5, 

in which the fluxes were in opposite directions with respect 

to the atmosphere. Thus they have evidently produced a 

prominent anomaly in C02 concentration, even though they 

are not particularly striking when viewed separately. We 

caution that these conclusions could be altered if the 

isotopic calibrations tum out later to need adjustment. 

In our calculations, we have taken into account the 

influence of temperature at the sea surface on the air-sea 

flux. The oceans cooled since May 1991 by about 0.5°C as 

judged from a cooling trend in global air temperature 

[Dutton and Christy, 1992). According to calculations 

using the one-dimensional model as cited previously, this 

cooling accounts for an additional absorption of only about 

01 GtC C02 by the oceans. Thus the principal cause of the 

anomalous oceanic sink of 0.7 GtC is evidently an increase 

in photosynthesis of marine plants that decreased the 

pressure of C02 gas dissolved in the water by converting 

inorganic carbon to organic carbon. 

4. COi\'CLUDli\'G RE:\IARKS 

Until the present event terminates with a return to a 

positive C02 concentration anomaly, it is difficult to assess 

the extent to which this anomaly is actually synchronous 

with the climatic impacts of the Mt. Pinatubo eruption. 

The El Nino event that began in 1991 in the eastern half of 

the equatorial Pacific, then waned in late 1992, and had a 
short re-emergence in early 1993 [Climatic Analysis 

Center, 1993), is a further complicating factor in deciding 

the cause of the anomaly. Before carrying the 

interpretation any further, the question of the isotopic 

calibration needs to be resolved. Improvements in 

modeling the isotopic aspects of the carbon cycle would 

also add confidence to our tentative findings. 

Acknowledgments. This work was supported by Grants AT:-191-

21986 and DPP9 l-96095 of the National Science Foundation, Grant 

DE-f-G03-90ER60940 of the U.S. Department of Energy and Grants 

NAGW-2542 and NAGW-2987 of the U.S. National Aeronautics 

and Space Administration. In addition NOAA , through Contract 

50RA:\R 100090, provided for the cost of maintaining our primary 

standard reference gases used to maintain accuracy in our 

measurements of atmospheric C02. We are grateful to CMDL for 

providing assistance in our sampling program and for maintenance 

of our continuous recording instrument at MLO. 

5. REFERE~CES 

Climate Analysis Center, Climate Diagnostics Bulletin, NOAA, 

National Meteorological Center, Camp Springs, MD, 5-9, August 

1993. 

Dutton, E.G., and J.R. Christy , Solar Radiative Forcing at Selected 

Locations and Evidence for Global Lower Tropospheric Cooling 

122 

Following the Eruptions of El Chichon and Pinatubo, Geophys. 

Res. Lett., 19, 2313-2316, 1992. 

Keeling, C.D., P.R. Guenther, and D.J. Moss, Scripps reference gas 

calibration system for carbon dioxide-in-air standards: Revision 

of 1985, Report No. 4 of the Environmental Monitoring 

Programme of the \Vor/d Meteorological Organization, Geneva, 

34 pp. and Addendum, 43 pp., 1992. 

Keeling, C.D., R.B. Ilacastow, A.F. Carter, S.C. Piper, T.P. Whorf, 

M. Heimann, W.G. Mook, and H. Roeloff2en, A threedimensional model of atmospheric C02 transport based on 

observed winds: I. Analysis of observational data, in Aspects of 

Clima te Variability in the Pacific and the Western Americas, 

edited by D.H. Peterson, Geophysical Monograph, American 

Geophysical Union, 165-236, Washington, D.C., 1989. 

Kelley, J.J., Jr., An analysis of carbon dioxide in the arctic 

atmosphere near Barrow, Alaska 1961 to 1967, Contract N00014-

67-A-0103-0007 NR, 307-252, 172 pp., Scientific Report of the 

United States Office of Naval Research, 1969. 

Marland, G., Global C02 Emissions, in Trends '91: A Compendium 

of data on global change, ORNUCDIAC-46, T.A. Boden, J.R. 

Sepanski, and F.W. Stoss, (Eds.), Carbon Dioxide Information 

Analysis Center, Oak Ridge National Laboratory, Oak Ridge, TN, 

pp. 389, 1991. 

Reinsch, C.H., Smoothing by spline functions, Numerische 

Mathematik, JO, 177-183, 1967. 

Siegenthaler, U., Uptake of excess C02 by an outcrop-diffusion 

model of the ocean, J. Geophys. Res., 88, 3599-3608, 1983. 
8. International Activities, 1992 

In September-October, E. Ferguson visited the University 

of Paris-South to interact with fonner colleagues in the 

Physical Chemistry Department to discuss current research 

there. He attended the NATO Advanced Study Institute 

program on The Role of the Stratosphere in Global Change 

where he lectured on the subject of "Stratospheric 

Homogeneous Chemistry." Also during this visit he 

participated in a round-table discussion regarding 

collaborations on sampling at the Centre des Faibles 

Radioactivities, and he presented a lecture in the Atomic 

and Molecular Physics Laboratory at Orsay on "Chemistry 

of Stratospheric Ozone and the Ozone Hole." 

E. Ferguson was in Germany in December to attend the 

World Meteorological Organization (WMO) Global 

Atmospheric Watch (GAW) Quality Assurance Program 

meeting that involved experts on global atmospheric 

monitoring. The purpose of the meeting was to devise 

procedures and protocols for assuring high-quality data 

acquisition at the present and contemplated WMO/GA W 

global sites. During this time, he also presented a seminar 

on recent CMDL results at the Max Planck Institute for 

Chemistry. 

J. Peterson traveled to Toronto, Canada, in February to 

participate in a WMO/GA W meeting on the developing 

Chinese baseline stations in Qinghai Province. The 

meeting focused on potential Canadian, Australian, and 

United States cooperative support with the Chinese to 

further development of their baseline station. 

R.C. Schnell traveled to Siberia from Nome, Alaska, in 

April to assist in initiating the Bennett Island Project and to 

recover samples. The Bennett Island ?roject was a Joint 

NOAA/Russia Academy of Sciences airborne project (using 

a Russian AN-26) to sample the Bennett Island plume. 

These plumes periodically originate from an isolated, 

uninhabited island in the New Siberian chain and can last 

for l 0-36 hours. It was thought the plumes may be 

produced by releases of methane from ocean floor clathrate 

decomposition. The sampling showed the plumes to be 

natural, post-frontal orographic clouds. 

The 5th International Symposium on Arctic Air 

Chemistry, Copenhagen, Denmark, September 8-10, 1992. 

was attended by P.J. Sheridan, I. Sokolik, and R.C. Schnell, 

AGASP members. Seven of the twenty-four core papers 

presented at the conference were authored by AGASP 

scientists. 

R.C. Schnell attended the Cape Grim Baseline Station 

annual meeting, Aspendale, Australia, November 25-27, 

1992, and visited a number of CSIRO and university 

facilities both prior to and subsequent to the meeting. Each 

year CMDL and the Australian Bureau of Meteorology host 

one scientist from the other's institution at their respective 

baseline station's annual meeting. 

In January, B. Mendonca was a participant and organizer 

of the first planning meeting for the establishment of a 

GAW station in Algeria, sponsored by the WMO. In Paris 

123 

and Geneva, he met with the research specialists from 

France and Algeria to define and plan for the GAW station 

in Algeria. A location for the station and a measurement 

and instrumentation list was decided on and a time 

schedule for the initiation of the program was established 

and agreed upon. 

Munich, Germany, was the site of the second Programs 

and Technical Advisory Group (PTAG) for the 

Hannonization of Environmental Measurement (HEM) 

program in May. B. Mendonca was an invited member to 

review this United Nations Environment Programme 

(UNEP). As a member of the advisory group, the past 

year's work and accomplishments were reviewed, and the 

future direction and goals of the program were formulated 

and agreed upon . 

The University of La Laguna (Tencrifc, Spain) sponsored 

a course on global climate and its relationship with the subtropical region of the globe. B. Mendonca participated as 

an invited guest lecturer. The course was structured for 

graduate students and offered advanced study m 

environmental issues. The lecture was based on the 

monitoring and research effort in CMDL and with the 

GAW stations and their programs. A full course brochure 

was prepared and distributed as a course aid for the 

students. 

In February, L. Haszpra, Institute for Atmospheric 

Physics, Budapest, Hungary, came to Boulder for 2 weeks. 

The purpose of the visit was to compare C02 data from the 

Hungarian site at K-Puszta and the CMDL flask network. 

Discussions were held regarding NOAA-provided gas 

standards to the Hungarian program and for possible 

collaboration with CMDL on-tower and aircraft 

measurements. These discussions lead directly to the 

preparation and delivery of four carbon dioxide/methane 

standards and plans for setting up a NOAA flask sampling 

network site in Hungary. 

From March 10 to 13, Pieter Tans presented a paper and 

participated in the Workshop for Trace Gas Measurement 

in Both Hemispheres that was held at Aspendale, Australia. 

The conference was sponsored by the Center for Global 

Environment Research, National Inst itute for 

Environmental Studies (Japan). 

The program to bring flask-sampling network personnel 

to Boulder was continued. In preparation for establ ishing a 

sampling site at Sal, Cape Verde, E. Fernando from the 

Servico Mcteorol6gico Nacional visited Boulder between 

May 6 and 13. Following training in the use of the MAKS 

and discussions on methodology and logistics, he handcarried a MAKS unit back to Sal. 

In August 1992, L. Waterman traveled to Warsaw and 

Gdynia, Poland, to initiate twice-weekly sampling on the 

Balanga Queen, a Baltic Sea ferry operating between 

Poland and Sweden. Arrangements were made al the U.S. 

Embassy to receive boxes of flasks sent from Boulder and 

to dispatch boxes of samples sent from Gdynia by way of 
diplomatic post. Arrangements were made with the Morski 

Instytut Rybacki (MIR) [Sea Fisheries Institute] to operate 

the sampling program from Gdynia. Samples are collected 

by the deck officers of the Balanga Queen on scheduled 

voyages between Gdynia and Karlskrona, Sweden. The 

initial Poland-to-Sweden voyage for the CMDL sampling 

network site was made on August 31 by L. Waterman and 

M. Pustuszak (MIR). The Master and several mates were 

briefed on the program, demonstrations were given, and 

practice samples collected. Three days later (September 3) 

on the return voyage to Poland, the second crew was 

briefed and trained to collect samples. While in 

Karlskrona, meetings were held with G. Sellerberg and L. 

Lundahl of the Fiskeriverket Ostersjolaboratoriet, the 

Swedish counterpart of Poland's MIR. 

Following completion of the Baltic work, L. Waterman 

traveled to Oslo and Kristiansund, Norway. Meetings were 

held with A. Grammelvendt, Director, Det Norske 

Meteorologiske Institutt, University of Oslo, and other staff 

members. It was learned that the meteorological institute 

has reasonably secure funding to operate the WIS 

Polarfront (STM) for at least 2 years (1993-1994). 

Logistics were discussed and the institute will continue 

paying some costs associated with the domestic transfer of 

sample boxes. 

L. Waterman visited the WIS Polarfront on September 8 

and presented the crew with a plaque commemorating 10 

years of collecting samples for the CMDL Worldwide Flask 

Sampling Network. Discussions were held with both 

sample collectors, and the sample flushing apparatus (P3) 

was inspected. 

On September 10 and 11, L. Waterman visited Blue Star 

Ship Management Ltd . (London) and the British Antarctic 

Survey (Cambridge). The reorganization of the Blue Star 

Line in the Pacific and the plan to replace both the 

Southland Star and the Wellington Star were discussed. At 

the British Antarctic Survey, a meeting was he ld with the 

liaison with CMDL for Halley Bay and Bird Island , South 

Georgia. 

On September 12 to 14, L. Waterman visited the 

AEROCE Mace Head Station at Carna, County Galway, 

Ireland, and met with G. Spain, Station Manager. A new 

flask sampling procedure using a Dekabon line attached to 

the AEROCE tower was initiated. 

On September 15, L. Waterman traveled to Reykjavik, 

Iceland, to ini tiate a new flask sampling site at Storhofdi 

Lighthouse, Heimaey, Westman Islands, including sending 

flask boxes to and from Icel and by diplomatic post. 

Regular sampling began on October 2. 

In September, P. Tans visited the Chinese Academy of 

Meteorological Sciences (CAMS) in Beijing. The purpose 

of the trip was to inspect the Mt. Waliguan baseline station 

that is a part of the CMDL air sampling network, and to 

investigate the possibilities for a cooperative effort to 

monitor trace gas flu xes in China's agricultural heartland. 

Talks were presented at CAMS on the CMDL global 

methane monitoring program and on the carbon dioxide 

program. A talk on global climate change was also given 

124 

at the State Oceanographic Administration. Hubei Province 

was visited to inspect radio transmission towers in the 

vicinity of Jingzhou. The highest towers are about 125 m 

and not tall enough for the type of concentration 

measurements currently being made in North Carolina. It 

would be useful to obtain experimental data on regional 

greenhouse gas fluxes in this region of China. Discussions 

were held on setting up such an experiment with focus on 

communication, maintenance, and training. The realization 

of this program depends on finding new funding sources, 

however. Qinghai Province was visited with a group 

driving to the Mt. Waliguan baseline station. The site and 

conditions appear to be excellent for atmospheric 

background monitoring activi ties, and when fully equipped 

and staffed as currently envisioned, this observatory can 

become a first-class facility. 

From September 21 to 28, P. Bakwin visited Laszlo 

Haszpra, Hungari an Meteorological Service, to determine 

the feasibility of using an existing te levision transmitter 

tower as a platform for trace gas monitoring. The trip was 

sponsored by the U.S. Hungarian Joint Fund. Three towers 

were considered and inspected: Tokaj in northwest 

Hungary, Komadi in western Hungary near the Romanian 

border, and Hegyhatsal, 7 km southwest of Kormend. 

In October, E. Dlugokencky visited Prof. Y.S. Chung at 

the Korean National University of Education (KNUE) and 

the CMDL flask sampling network site at Tae-ahn 

Peninsula, Korea. Seminars were given at KNUE and for 

the Department of Oceanography, College of Natural 

Sciences, Seoul National University. Discussions were 

held with Prof. Chung on joint publication results of 

collaborative air sampling. 

Two sets of three cylinders each containing C02 

standard gases (341 , 348, 375 ppm) were provided by NIST 

for international "round robin" intercomparisons. Both sets 

were analyzed by NIST and the CMDL Carbon Cycle 

Division prior to starting the circuits. Set A was circulated 

among European laboratories in Germany, France, Spain 

(Canary Islands), Italy, and Hungary. Set B was sent to the 

U.S. (SIO), Canada, Japan, New Zealand , and Australia. 

Altogether, 16 laboratories in IO countries participated. J. 

Peterson ac ted as referee for the experiment. 

E. Dlugokencky and P. Lang conducted comparisons 

with two laboratories in 1992. A standard prepared at 

Niwot Ridge, Colorado, in 1988 and calibrated periodically 

in Boulder, was used for both experiments. During July 

and August, the cylinder was sent to the Geochemical 

Research Laboratory, Meteorological Research Institute 

(Japan), and in September, to the Atmospheric 

Environment Service (Canada). 

P. Novelli conducted intercomparisons of standards 

with the Fraunhofer Institute, Garmisch, Germany. Six 

mixtures in the 50-200 ppb range made in Boulder by the 

NOAH Division [Novelli , et al., 1991] were used. The 

results of five calibrations agreed to within 3%; the sixth 

standard agreed to within 5%. This project was carried out 

over a 2-year period. An experiment involving eight 

laboratories will be next in this series. 
In January, D. Hofmann and F. Polacek III, conducted 

correlative water vapor and aerosol balloon flights in 

support of the NASA UARS program at Lauder, New 

Zealand. The aerosol and water-vapor measurement data 

from these balloon flights were presented at a meeting 

(June 27-July 3) in Aix-en Provence, France, sponsored by 

the NASA Upper Atmosphere Research Satellite (UARS) 

Correlative Measurement program. S. Oltmans and D. 

Hofmann attended the Aix-en-Provence meeting, where S. 

Oltmans presented a paper and participated in the 

Investigators Workshop and Science Team Meeting. D. 

Hofmann presented the aerosol data. After the meeting, D. 

Hofmann participated in cooperative atmospheric research 

involving the effects on the stratosphere of the Mt. 

Pinatubo eruption with colleagues at the Institute for 

Atmospheric Environmental Research in Garmisch, Federal 

Republic of Germany. 

D. Hofmann returned to Lauder in May to participate in 

a joint meeting with scientists from the NOAA Aeronomy 

Laboratory and six other research groups in an international 

intercomparison of nitrogen dioxide measurement 

instruments. Again in November, D. Hofmann traveled to 

Lauder, New Zealand, to conduct water vapor and aerosol 

balloon flights in support of the NASA UARS program. 

B. Bodhaine, J. Ogren, and J. Wendell spent 2 weeks in 

August setting up an aerosol monitoring station at the 

Canadian Atmosphere Environment Services station on 

Sable Island, Nova Scotia. Sable Island is a remote site 

and all the instrumentation that was installed had to be 

shipped by boat and unloaded to a beach without a dock on 

motorized rubber rafts. The measurements recorded so far 

at Sable Island reveal it to be an excellent site for obtaining 

data of aerosols affected by polluted areas. J. Ogren 

traveled to Montreal, Canada, to attend the 1 lth 

International Conference on Clouds and Precipitation to 

present a paper. At that time, he also participated in the 

meeting of the executive committee of the International 

Commission on Clouds and Precipitation. 

In January, J. Ogren was invited to the University of 

Stockholm where he presented a seminar "Measurements of 

the size-dependence of the scavenging efficiency of aerosol 

125 

particles by fog droplets." He also worked on evaluation of 

aerosol and cloud chemical and microphysical 

measurements obtained during a 1990 field experiment in 

Germany. 

In August, S. Oltmans was invited to Wolfville, Canada, 

by the NATO Scientific Affairs Division to attend the 

NATO Advanced Research Workshop on Tropospheric 

Chemistry of Ozone in the Polar Regions where he 

presented a paper. In September, he traveled to Heimaey 

on the Westman Islands of Iceland to set up an ozone 

monitor. Further, he serviced and calibrated the ozone 

monitor at Reykjavik, Iceland. 

J. Easson of the Australian Bureau of Meteorology and 

T. Uebuko of the Japanese Aerological Observatory visited 

Boulder in June and July to calibrate their respective 

country's secondary standard Dobson spectrophotometers 

relative to World Primary Standard Dobson Instrument 83. 

During the summer of 1992, an Argentine Dobson 

instrument was received in Boulder for repair and 

calibration. 

A program to check on the calibration status of Dobson 

spectrophotometers throughout the world by means of 

traveling calibrated standard lamps was continued. This is 

the third such international activity conducted since the 

program was first implemented in 1981. 

To use CFC tracers to determine the ocean circulation 

and age of water mass, J.M. Lobert, J.H. Butler, and T.J. 

Baring participated in the World Ocean Circulation 

Experiment (WOCE-16) starting from Long Beach, 

California, on August 4 and ending at Noumea, New 

Caledonia, on October 22 (see Figure 5.20). 

J.W. Elkins, T.J. Baring, G.A. Holcomb, T.M. Gilpin, 

J.H. Butler, T.M. Thompson, and W.T. Sturges participated 

on the continuation in 1992 of the NASA Airborne Arctic 

Statospheric Expedition II (AASE II) based out of Bangor, 

Maine. The purpose of the participation was to continue to 

measure CFC-I I and -113 using the ACATS instrument_ 

aboard the NASA ER-2 aircraft for the January through 

March polar mission. The science investigators included 

scientists from Canada, United Kingdom, Australia, New 

Zealand and Iceland. 
9. Publications and Presentations by CMDL Staff, 1992 

Barrie, L.A., B.A. Bodhaine, R.C. Schnell, G.A. Shaw, and J.K. 

McKie, Symposium on the Tropospheric Chemistry of the 

Antarctic Region, Tel/us, 448, 250-251, 1992. 

Bodhaine, B.A., and J.M. Harris, Aerosol measurements at the South 

Pole during 1987, NOAA DR ERL CMDL-9, 120 pp., 1992. 

Bodhaine, B.A., J.M. Harris, J.A. Ogren, and D.J. Hofmann, Aerosol 

optical properties al Mauna Loa Observatory: Long-range transport 

from Kuwait? Geophys. Res. lell., 19(6), 581-584, 1992. 

Butler, J.H., Calculation of air-sea transfer velocity from anthropogenic 

halocarbon distributions in the surface oceans, paper presented at 

Biogeochemical Ocean-Atmosphere Transfer, NATO Advanced 

Research Workshop, Bennuda, January 27-3 I, 1992. 

Butler, J.H., The ocean as a source of atmospheric N20, paper 

presented al the American Society for Limnology and 

Oceanography Aquatic Sciences Meeting, Santa Fe, NM, 

February 9-14, 1992. 

Butler, J.H., J.W. Elkins, B.D. Hall, S.0. Cummings, and S.A. 

Montzka, A decrease in the growth rates of atmospheric halon 

concentrations, Nature, 359, 403-405, 1992. 

Cahill, T.A. K. Wilkinson, and R.C. Schnell, Compositional 

analyses of size-resolved aerosol samples taken from aircraft 

down wind of Kuwait, Spring 1991, J. Geophys. Res., 97(D13), 

14,513-14,520, 1992. 

Cantrell, C.A., J.A. Lind, R.E. Shetter, J.G. Calvert, P.O. Goldan, W. 

Kuster, F.C. Fehsenfeld, S.A. Montzka, D.D. Parish, E.J. 

Williams, M.P. Buhr, H.H. Westberg, G. Allwine, and R. Martin, 

Peroxy radicals in the ROSE experiment: measurement and 

theory, J. Geophys. Res .. 97(018), 20,671-20,686, 1992. 

Charlson, R.J., S.E. Schwartz, J.M. Hale, R.D. Cess, J.A. Coakley, 

Jr., J.E. Hansen, and D.J. Hofmann, Climate forcing by 

anthropogenic aerosols, Science, 255, 423-430, 1992. 

DeFoor, T.E., S. Ryan, J.J. DeLuisi, E. Oullon, D.J. Hofmann, P.B. 

Russell, and J.M. Livingston, A comparison of El Chichon and Mt. 

Pinatubo stratospheric aerosols as measured at Mauna Loa 

Observatory, paper presented at the AGU Chapman Conference on 

Climate Volcanism and Global Change, Hilo, Hawaii, March 1992. 

DeFoor, T.E., E. Robinson, and S. Ryan, Early lidar observations of 

the June 1991 Pinatubo eruption plume at Mauna Loa 

Observatory, Hawaii, Geophys. Res. Lei/., 19(2), 187-190, 1992. 

DeLuisi, J.J., J. Wendell, and F. Kreiner, An examination of the 

spectral response characteristics of seven Robertson-Berger 

meters after long-tenn field use, Photochem. Photobio., 56(1 ), 

115-122, 1992. 

Deshler, T., and D.J. Hofmann, Measurements of unusual aerosol 

layers in the upper troposphere over Laramie, Wyoming, in the 

spring of 1991: Evidence for long-range transport from the oil 

fires in Kuwait, Geophys. Res. Lei/., 19(4 }, 385-388, 1992. 

Deshler, T., DJ. Hofmann , B.J. Johnson, and W.R. Rozier, 

Balloonbome measurements of the Pinatubo aerosol size 

distribution and volatility at Laramie, Wyoming during the 

summer of 1991, Geophys. Res. Lei/., 19(2), 199-202, 1992. 

Deshler, T., A. Adriani, G.P. Gobbi, DJ. Hofmann, G. 

DiDonfrancesco, and B.J. Johnson, Volcanic aerosol and ozone 

depletion within the Antarctic polar vortex during the austral 

spring of 1991, Geophys. Res. lell., 19(18), 1819-1822, 1992. 

DeLuisi, J.J., K. Dehne, R. Vogt, T. Konzelmann, and A. Ohmura, 

First results of the Baseline Surface Radiation Network (BSRN) 

broadband infrared radiometer intercomparison at Fire II, in lRS 

'92, S. Keevallik and 0. Kamer (Eds.), Deepak, Ilampton, VA, 

559-564. 1992. 

126 

Dlugokencky, E.J., and A.R. Ravishankara, Laboratory measurements of direct ozone loss on ice and doped-ice surfaces, 

Geophys. Res. Le11., 19(A), 41-44, 1992. 

Oullon, E.G., and J.R. Christy, Solar radiative forcing at selected 

locations and evidence for global lower tropospheric cooling 

following the eruptions of El Chichon and Pinatubo, Geophys. 

Res. Lell., 19(23), 2313-1216, 1992. 

Elkins, J.W., Flying high into the Arctic stratosphere: CFC 

measurements from a spy plane, after dinner speech at the CMDL 

Annual Meeting, Boulder, CO, March 4, 1993. 

Elkins, J.W., Slowdown of the atmospheric growth rates of CFC-I I 

and CFC-12: The result of the Montreal Protocol, paper presented 

at the Center for Analytical Chemistry Seminar, NIST, 

Gaithersburg, MD, June 4, I 992. 

Elkins, J.W., Distributions of two chlorofluorocarbons in the polar 

and mid-latitude stratosphere from August I 991 through March 

1992, invited ulk for the NOAA Aeronomy Laboratory Seminar, 

Boulder, CO, October 21, 1992. 

Elkins, J.W., Slowdown of the atmospheric growth rates of CFC-I I 

and CFC-12: The result of the Montreal Protocol, paper presented 

at the Center for Analytical Chemistry Seminar, NIST, 

Gaithersburg, MD, June 4, 1992. 

Elkins, J.W., J.H. Butler, S.A. Monlzka, J.M. Lobert, and W.T. 

Sturges, The impact of the ocean on atmospheric methyl 

bromide, paper presented at the Methyl Bromide Workshop 

sponsored by the Methyl Bromide Global Coalition, Arlington, 

VA, June 2-3, I 992. 

Elkins, J.W., D.W. Fahey, T.M. Gilpin, M.11. Proff1t1, S. Solomon, 

M. Loewenstein, C.R. Webster, and K.R. Chan, Fast response 

CFC-I I and CFC-113 measurements from the NASA ER-2 

aircraft during AASE-II, paper presented al the NASA HighSpeed Research Project (HSRP) Meeting, Virginia Beach, VA, 

May I 8-22, I 992. 

Elkins, J.W., D.W. Fahey, S. Solomon, W.11. Pollock, L.E. Heidt, 

T.M. Gilpin, C.R. Webster, R.D. May, M. Loewenstein, A. 

Weaver, J.R. Podolske, K.R. Chan, S.C. Wofsy, and R.J. 

Salawitch, The evolution of the total organic and inorganic 

chlorine in the Arctic polar stratospheric vortex, poster 

presentation at the Fall American Geophysical Union Meeting, 

San Francisco, CA, December I 0, 1992. 

Facchini, M.C., S. Fuzzi, M. Kessel, W. Wobrock, W. Jaeschke, 

B.G. Arends, J.J. Mots, A. Bemer, I. Solly, C. Kruisz, G. Reischl, 

S. Pahl, A. Hallberg, J.A. Ogren, H. Fierlinger-Oberlinninger, A. 

Marzorati, and 0. Schell, The chemistry of >Ulfur and nitrogen 

species in a fog system-a multiphase approach, Tel/us, 448, 

505-521, 1992. 

Fahey, D., J.W. Elkins, T.M. Thompson, R.C. Myers, J.H. Butler, 

W.C. Kuster, T.L. Thompson, R.H. Winkler, S.A. '.vlontzka, T.M. 

Gilpin, T.J. Baring, G.A. Holcomb, W.T. Sturges, J.M. Lobert, 

and B.D. Hall, The distribution of CFC-I I and CFC-113 in the 

Arctic polar stratospheric vortex, poster presentation at the Fall 

American Geophysical Union Meeting, San Francisco, December 

9, 1992. 

Ferguson, E.E., A personal history of the early development of the 

flowing afterglow technique for ion-molecule reaction studies, J. 

Am. Soc. Mass Spectrom., 3, 479-486, 1992. 

Ferguson, E.E., and R.M. Rosson (eds.), Climate Monitoring and 

Diagnostics Laboratory No. 20 Summary Report 1991, 131 pp., 

NOAA Environmental Research Laboratories, Boulder, CO, 

1992. 
r-crguson, E.E., J.~I. Van Doren, A.A. Viggiano, R.A. Morris, J.F 

Paulson, J.D. Stewa rt, L.S. Sunderlin, and P.O. Armcnlrou~. 

Internal and translational energy effect on the charge-transfer 

reaction of COi with 0 2, Int. J. Mass Spectrom. Ion Proc., 117, 

261-282, 1992. 

r-iocco, G., M. Cacciani, P. DiGirolamo, D. r-ua, and J. DcLuisi, 

Stratospheric clouds at South Pole during 1988, I, Results of 

lidar observations and their relationship to temperature, J. 

Geophys. Res., 97(05), 5939-5946, 1992. 

r-ostcr, J.L., J.W. Winchester, and E.G. Duuon, The date of snow 

disappearance on the Arctic tundra as determined from satellite, 

meteorological station and radiometric in situ observations,/£££ 

Transactions on Geoscience and Remote Sensing, 30(4), 793-

798, 1992. 

r-uzzi, S., C. r-acchini, G. Orsi, J.A. Lind, W. Wobrock, '.I.I. Kcscl, R. 

,'.\laser, W. Jaeschke, 13.G. Arends, J\. 13crner, I. Solly, C. Kruisz, 

G. Reischl, li. Kaminski, P. Winkler, J.i\. Ogren, J\. Hallberg, 11. 

r-ierlingcr-Obcrlinningcr, II. Puxbaum, A. ,'.\larzorati, H.-C. 

Hansson, J\. Wicdcnsohlcr, 1.13. Svcnningsson, 13.G. Martinsson, 

D. Schell, and 11.W. Gcorgii, The Po Valley fog experiment 

1989: an overview, Tel/us, 448, 448-468, 1992. 

Hahn, C.J., J.T. l\lcrrill, and 13.G. Mendonca, Meteorological 

influences during MLOPEX, J. Geophys. Res., 97(010), 10,291-

10,309, 1992. 

Hallberg, A., J.A. Ogren, K.J. :'\oone, J. Hcintzenberg, A. 13emer, I. 

Solly, C. Kruisz, G. Rceischl, S. Fuzzi, C. Facchini, H.-C. 

Hansson, A. Wiedcnsohler, and 1.13. Svenningsson, Phase 

partitioning for different aerosol species in fog , Tel/us, 448, 545-

555, 1992. 

Ilanscn, i\.D.i\., R.C. Schnell, i\.V. Polissar, and G.S. Golitsyn, 

Aerosol measurements over the East Siberian Sea, paper 

presented al the 51/i Symposium on Arctic Air Ch~mistry, 

Copenhagen, Denmark, September 8-10, 1992. 

Harris, J.'.1.1., i\n analysis of 5-day midtropospheric flow paucms for 

the South Pole: 1985- 1989, Tel/us, 448, 409-421, 1992. 

Harris, J.M., P.P. Tans, E.J. Dlugokencky, K.i\. Masarie, P.M. Lang, 

S. Whiulcstonc, and L.P. Steele, Variations in the atmospheric 

methane at l\launa Loa Observatory related to long -range 

transport, J . G eophys. Res., 97(05), 6003-60 I 0, 1992. 

Harriss, R.C., G.W. Sachse, G.r-. llill, L. Wade, K.O. 13artlcn, J.E. 

Collins, L.P. Steele, and P.C. Novelli, Carbon monoxide and methane 

in the l\orth American Arctic and subarctic troposphere: July-August 

1988,J. Geopltys. Res., 97(015}, 16,589-16,599, 1992. 

Hofmarm, D.J., and S.J. Oltmans, The effect of stratospheric water vapor 

on the heterogeneous reaction rate of CI0:'\02 and H20 for sulfuric 

acid aerosol, Gcophys. Res. Lett .. 19(22), 2211-2214, 1992. 

Ilofrnann, D.J., E.r-. Ferguson, J>.V. Johnston, and W.i\. l\lauhews, 

Tropospheric ozone variation in the Arctic during January 1990, 

Planet. Space Sci., 40, 203-210, 1992. 

Hofmann, D.J., S.J. Oltmans, J.~I. Harris, S. Solomon, T. Deshler, 

and 13.J. Johnson, Observation and possible causes of new ozone 

depiction in Antarctica in 1991, Nature, 359, 283-287, 1992. 

Hubler, G., D.D. ,'.\lontzka R.13. :'\orion, P.C Murphy, F.C. 

FehscnfclJ, S.C. Liu, 13.i\. Ridley, J.G. Walega, E. Atlas, r-.E. 

Grahck, L.E. Heidt, J. l\lcrrill, 13.J. llucbcrt, and 13.A. 13odhaine, 

Total reactive oxidized nitrogen (l\Oy) in the remote Pacific 

troposphere and its correlation with 0 3 and CO: Mauna Loa 

Observatory Photochemistry Experiment 1988, J. Geophys. Res., 

97, 10,427-10,447, 1992. 

Kahl, J.D., :'>l.C. Serrczc, and R.C. Schnell, Tropospheric low-level 

lcrnperalurc inversions in the Canadian Arctic, Atmos.-Ocean, 

39(4). 51 1-529, 1992. 

127 

Kah l, J.D., M.C. Scrreze, S. Shiotani, S.M. Skony, and R.C. Schnell, 

In situ meteorological sounding archives for Arctic studies, Bull. 

Am. Meteorol. Soc., 73(11), 1824-1830, 1992. 

Kahl, J.D., D.J. Charlevoix, R.C. Schnell, and N.A. Zaitscva, Lower 

tropospheric temperature trends over the Arctic Ocean: 1950-

1990, Preprints, Third Conference on Polar Meteorology and 

Oceanography, Portland, OR, September 29-0ctober 2, 1992, 

pp.141-144, American Meteorological Society, Boston, 1992. 

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

and E.J. Dlugokencky, NOJ\i\/C:'>IDL atmospheric methane da ta 

for the period 1983- 1990 from shipboard flask sampling, NOAA 

TM ERL CMOL-4, 88 pp., 1992. 

Luria, M., J.F. Boatman, J.M. llarris, J. Ray, T. Straube, J. Chin, 

R.L. Gunter, G. llcrbcrt, T.M. Gerlach, and C.C. Van Valin, 

Atmospheric sulfur dioxide at ~1auna Loa, Hawaii, J. Geophys. 

Res., 97(05), 6011-6022, 1992. 

Mateer, C.L., and J.J. DcLuisi, J\ new Umkehr inversion algorithm, 

J. Atmos. Terr. Phys., 54(5), 537-556, 1992. 

Marlinsson, 13.G., E. Swictlicki, 11.-C. llansson, A. Wiedensohlcr, 

K.J. Noone, J.A. Ogren, and J\. Hallberg, Elemental composition 

of fog interstitial particle size fractions and hydrophobic 

fractions related to fog droplet nucleation scavenging, Tel/us, 

448, 593-603, 1992. 

l'\oone, K.J., J.A. Ogren, A. Hallberg, H.-C. Hansson, A. 

Wicdensohler, and E. Swietlicki, A statistical examination of the 

chemical differences between interstitial and scavenged aerosol, 

Tel/us, 448, 581-592, 1992. 

Noone, K.J., J.A. Ogren, A. llallbcrg, J. lleintzenberg, J. Strom, H.-

C. llansson, 0. Svenningsson, A. Widensoh ler, S. Fuzzi, M.C. 

Facchini, B.G. Arends, A. Bemer, Changes in aerosol size- and 

phase-distributions due to physical and chemical processes in 

fog, Tel/us, 4411, 489-504, 1992. 

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

monoxide in the troposphere, J. Geophys. Res., 97(018), 20,731-

20,750, 1992. 

Ogren, J ., Size-dependent scavenging efficiencies of areosol 

particles in a polluted fog, paper presented at the 11th 

International Conference on Clouds and Precipitation, Montreal, 

Canada, August 1992. 

Ogren, J.A., and R.J. Charlson, Implications for models and 

measurements of chemical inhomogeneities among cloucf 

droplets, Tel/us, 448, 208-225, 1992. 

Ogren, J.A., K.J. Noone, A. Hallberg, J. Heintzenberg, D. Schell, A. 

Bemer, I. Solly, C. Kruisz, G. Reischl, B.G. Arends, and W. 

Wobrock, Measurements of the size dependence of the 

concentration of non-volatile material in fog droplets, Tel/us, 

448, 570-580, 1992. 

Oltmans, S.J., 13alloon water vapor correlative measurements for 

UARS, paper presented at a meeting sponsored by the !\ASA 

Upper Atmosphere Research Satellite (UARS) Correlative 

Measurement Program, in Aix-cn Provence, France, June 27-July 

3, 1992. 

Oltmans, S.J., Climatology of Arctic and Antarctic tropospheric ozone, 

paper presented at the Ni\ TO Advanced Research Workshop on 

Tropospheric Ozone, Wolf ville, Canada, August 1992. 

Oltmans, S.J., and II. Levy, II, Seasonal cycle of surface ozone 

over the western North i\tlantic, Nature, 358, 392-394 , 1992. 

Parungo, F., 13. Kopcewi cz, C. Nagamoto, R. Schnell, P. Sheridan, 

Z. Zhu, and J. Harris, Aerosol particles in the Kuwait oil fire 

plumes: Their morphology, size distribution, chemical 

composition, tran sport, and potential effect on climate, J. 

Geophys. Res. 97(014 }, 15,867-15,882, 1992. 
Ridley, rl.A., and E. Robinson, The Mauna Loa Observato ry 

photochemistry experiment, J. Geophys. Res., 97(D10), 10,285-

10,290, 1992. 

Rosen, J., 13.A. rlodhaine, J.F. rloatman, J.J. DeLuisi, M.J. Post, Y. 

Kim, R.C. Schnell, P.J. Sheridan, and D.M. Garvey, Measured 

and calculated optical property profiles in the mixed layer and 

free troposphere,J. Geophys. Res., 97, 12,837-12,850, 1992. 

Russell, P.13., R.r:. Pueschel, S.A. Kinne, J.~1. Livingston, E. Dutton, 

T. Dcfooor, J. Reagan, and M. 13ox, Pinatubo optical depth 

spectra; temporal and spatial evolution of inferred particle size, 

areas and backscatter, with radiative implications, paper 

presented at the foall American Geophysical Union Meeting, San 

Francisco, CA, December 7-11, 1992. 

Ryan, S., and J.F.S. Chin, Quiescent C02 outgassing of Mauna Loa 

volcano, paper presented at the Fall American Geophysical 

Union Meeting, San foran cisco, CA, December 7-11, 1992. 

Savoie, D.L., J.M Prospero, S.J. Oltmans, W.C. Graustein, K.K. 

Turckian, J.T. ~lerrill, and II. Levy II, Sources of nitrate and 

ozone in the marine boundary layer of the tropica l North 

Atlantic, J. Geophys. Res., 97(D11 ), 11,575-11,589, 1992. 

Schnell, R.C., G.A. Allen, and A.D.A. Hansen, 131ack carbon aerosol 

output from a photocopier, Proceedings, 85 Annual Meeting and 

Exhibition, June 21-26, Kansas City, Kansas, 9 pp., Air and 

Waste Management Association, Pittsburgh, PA, 1992. 

Schnell, R.C., E. Dlugokencky, T.J. Conway, A. Polissar, and G.S. 

Golitsyn, Airborne investigation of the Dennett Island plume, 

Proceedings, 5th Symposium on Arctic Air Chemistry, 

Copenhagen, Denmark, September 8-10, 1992. 

Serreze, M.C., J.A. Maslanik, R.S. Stone, and R.C. Schnell, 

Predicted heights of buoyant convection above leads in the 

winter Arctic pack ice cover, Preprints, Third Conference on 

Polar Meteorology and Oceanography, Portland, OR, September 

29-0ctober 2, 1992, pp. J45-J48, American Meteorological 

Society, rloston, 1992. 

Sheridan, P.J., R.C. Schnell, D.J. Hofmann, and T. Deshler, Electron 

microscope studies of Mt. Pinatubo aerosol layers over Laramie, 

Wyoming during summer 199 1, Geophys. Res. Lett., 19(2), 203-

206, 1992. 

Sheridan, P.J., R.C. Schnell, and J.D. Kahl, Individual particle 

analysis of the springtime Arctic aerosol, 1983-1989, 

Proceedings, International Conference on the Role of the Polar 

Regions in Global Change, June 11 -15, 1990, University of 

Alaska, foairbanks, edited by G. Well, C.L. Wilson, and rl.A.13. 

Severin, pp. 708-715, Geophysical Institute, Univ. of Alaska 

foairbanks and Center for Global Change and Arctic System 

Research, 1992. 

128 

Sheridan, P.J., R.C. Schnell, D.J. Hofmann, J. M. Harris, and T. 

Deshler, Electron mic roscope studies of aerosol layers with likely 

Kuwaiti origins over Laramie, Wyoming during spring 1991, 

Geophys. Res. Lett, 19(4), 389-392, 1992. 

Sokolik, l.N., and R. Schnell, Comparison of data on physical 

properties of Arctic aerosols, Proceedings, 5th Symposium on 

Arctic Air Chemistry, Copenhagen, Denmark, September 8-10, 

1992, National Environmental Research Institute, Copenhagen, 

1992. 

Steele, L.P., E.J. Dlugokencky, 1'.i'.!. Lang, P.P. Tans, R.C. Martin, 

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

atmospheric methane during the 1980s, Nature, 358, 313-316, 

1992. 

Stone, R.S., J.D. Kahl, M.C. Serreze, and R.C. Schnell, Trend 

analyses of tropospheric temperatures in the Arctic-ls there 

evidence of greenhouse warming?, Preprints, Third Conference 

on Polar Meteorology, Portland, OR, September 29-0ctober 20, 

1992, American Meteorology Society, rloston, 137-140, 1992. 

Strom, J., J. llcintzcnberg, K.J. Noone, K.Il. Noone, J .A. Ogren, r:. 

Albers, and M. Quante, CVI measurements on small crystals in 

cirrus clouds, Proceedings, 11th International Conference on 

Clouds and Precipitation, Montreal, Canada, 1992, International 

Commission on Clouds and Precipitation, International Assoc. of 

Met. and Atmos. Physics, Innsbruck, Austria, 471-472, 1992. 

Sturges, W.T., G.F. Cota, and P.T. I3ucklcy, rlromoform emission from 

Arctic ice algae, Nature, 358, 660-662, 1992. 

Svenningsson, l.rl., 11.-C. llansson, A. Wiedensohler, J.A. Ogren, K.J. 

Noone, and A. llallberg, llygroscopic growth of aerosol panicles in 

the Po Valley, Tel/us, 4413, 556-569, l 992. 

Tans, P., U.S. baseline station network, paper presented at the Workshop 

for Trace Gas Measurements in I3oth I Icmispheres, Aspendale, 

Australia, March 10-13, 1992. 

Walega, J.G., 13.A. Ridley, S. Madronich, FE. Grahek, J.D. Shetter, T.D. 

Sauvain, C.J. llahn, J.T. Merrill, 13.A. [lodhaine, and E. Robinson, 

Observations of pcroxyacetyl nitrate, pcroxypropionyl nitrate, methyl 

nitrate, and ozone during the Mauna Loa Observatory photochemistry 

experiment. J. Geophys. Res., 97(D10), 10,311 -10,330, 1992. 

Whiulestone, S., E. Robinson, and S. Ryan, Radon at the ~1auna Loa 

Observatory: Transport from distant continents, Atmos. Environ. 

26A(2), 251-260, 1992. 

Yamato, M., Y. lwasaka, R.C. Schnell, P.J. Sheridan, M. Nishikawa, T. 

Mizoguchi, and N. Nakai, Chemical composition and physical 

characteristics of aerosols in the smoke plume from the Kuwaiti oil 

fires, Proceedings, Japan Meteorological Society, Annual Meeting, 

Tokyo, Japan, October 23-25, 1991, Japan Met. Soc., Tokyo, 121-122, 

1992. 
AASE 

ACATS 

AEROCE 

AEC 

AES 

A GASP 

AGL 

AL 

ALE/GAGE 

AMIE 

ANS TO 

AOML 

ARL 

ARM 

ASA 

AS ASP 

ASCII 

ASL 

ASR 

ATS 

ATMOS 

BAO 

BC 

BSRN 

BRW 

CAF 

CAMS 

CART 

CFC 

CFC-I I 

CFC-12 

coo 

CI RES 

CMDL 

CN 

CNC 

CSIRO/DAR 

CSU 

DB 

DEW 

OMS 

DOE 

DOY 

DU 

ECC 

ECO 

EC-GC 

ECMWF 

EML 

ENSO 

EPA 

10. Acronyms and Abbreviations 

Airborne Arctic stratospheric Expedition 

Airborne Chromatograph for Atmospheric Trace Species 

Atmosphere/Ocean Chemistry Experiment 

Atomic Energy Commision 

Atmospheric Environment Service, Canada 

Arctic Gas and Aerosol Sampling Program 

above ground level 

Aeronomy Laboratory, Boulder, Colorado (ERL) 

Atmospheric Lifetime Experiment/Global Atmospheric Gases Experiment 

Automated Methane Instrument Evaluation 

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 

American Standard Code For Informat ion Interc hange 

above sea level 

aerosol solar radiation 

Application Technoloy Satellite 

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 

chlorofluorcarbon 

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 

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 Protection Agency 

129 
ERL 

FID 

FPO 

FR LAB 

FSSP 

FTIR 

FW 

GAGE 

GC 

GCRP 

G.E. 

GMT 

GONG 

GR 

GSA 

HAO 

HCFC 

HFC 

HP 

HST 

INSTAAR 

IR 

ISWS 

LAN 

LEAD EX 

LEAPS 

LES 

LPM 

LST 

MAKS 

MASC 

MLO 

MLOPEX 

MRI 

MS 

MSL 

NADP 

NARL 

NASA 

NAVSWC 

NCAR 

NDSC 

NDIR 

NIP 

NOAA 

NOAH 

NSF 

NWR 

NWS 

OAXTC 

OGIST 

OH 

PBL 

PC 

Environmental Research Laboratories, Boulder, Colorado (NOAA) 

flame ionization detector 

flame photometric detector 

Front Range Lidar, Aircraft, and Balloon experiment 

Forward Scattering Spectrometer Probe 

Fourier transform infrared (spectroscopy) 

filter wheel 

Global Atmospheric Gases Experiment 

gas chromatograph 

Global Climate Change Program 

General Electric 

Greenwich Mean Time 

Global Oscillation Network Group 

growth rate 

General Services Administration 

High Altitude Observatory 

hydrochloroflurocarbon 

hydroflurocarbon 

Hewlett-Packard 

Hawaii standard time 

Institute for Arctic and Alpine Research, University of Colorado, Boulder 

infrared 

Illinois State Water Survey 

local area network 

Leads Experiment 

Low Electron Attachment Potential Species 

Lincoln Experimental Satellite 

liters per minute 

local standard time 

Martin and Kitzis Sampler (portable air sampler) 

Mountain Administration Support Center (NOAA) 

Mauna Loa Observatory, Hawaii (CMDL) 

MLO Photochemical Experiment 

Meteorology Research, Inc. 

mass spectrometer 

mean sea level 

National Atmospheric Deposition Program 

National Arctic Research Laboratory, Barrow, Alaska 

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 

Niwot Ridge, Colorado 

National Weather Service 

Ocean Atmosphere Exchange of Trace Compounds 

Oregon Graduate Institute of Science and Technology 

hydroxyl radical 

planetary boundary layer 

personal computer 

130 
PMEL 

PMOD 

QBO 

RITS 

ROA 

RSD 

SBUV 

scs 

s.d. 

SEA REX 

SEASPAN 

SIO 

SMO 

SOI 

SPADE 

SPO 

SRB 

SRF 

SRF 

SST 

STP 

TOMS 

TSI 

UARS 

UCI 

UIC 

UPS 

URAS 

URI 

USDA 

USGS 

UT 

UV 

UVB 

WHO! 

WMO 

Pacific Marine Environmental Laboratory (ERL) 

Physikalisch-Meteorologisches Observatorium Davos (World Radiation Center) 

quasi-biennial oscillation 

Radiatively Important Trace Species 

reduction gas analyzer 

residual standard deviation 

solar backscattered ultraviolet (satellite ozone instrument) 

Soil Conservation Service, Anchorage , Alaska 

standard deviation 

Sea-Air Exchange 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 1 atm) 

Total Ozone Mapping Spectrometer 

Thermo Systems Incorporated 

Upper Atmosphere Research Satellite 

University of California, Irvine 

Ukpeaguik Inupiat Corporation 

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 

Woods Hole Oceanographic Institute 

World Meteorological Organization 

*U. S. GOVERN~IBNT PRINTING OFFICE : l994-573-013/89070 

131