The United States Detailed National Report on 

Systematic Observations for Climate:

United States Global Climate Observing System 

(U.S.-GCOS) Program

Submitted to the Conference of the Parties 

to the United Nations Framework Convention on 

Climate Change

Compiled by the 

National Oceanic and Atmospheric 

Administration

on Behalf of the United States Government

August 2001
Compiled on Behalf of the United States Government by the:

United States Department of Commerce

National Oceanic and Atmospheric Administration

National Environmental Satellite, Data, and Information Service

1335 East-West Highway, Room 7214

Silver Spring, Maryland, USA 20910

Howard Diamond, U.S. GCOS Program Coordinator

http://www.eis.noaa.gov/gcos

e-mail contact: howard.diamond@noaa.gov

Department of Commerce

Donald L. Evans, Secretary

National Oceanic and Atmospheric Administration

Scott B. Gudes, Acting Under Secretary / Administrator and Deputy Under Secretary

National Environmental Satellite, Data, and Information Service

Gregory W. Withee, Assistant Administrator
iii

Preface

Long-term, high-quality observations of the global environmental system are essential for 

defining the current state of the Earth’s system, and its past history and variability. This task 

requires both space- and surface-based observation systems. The term “climate observations” can 

encompass a broad range of environmental observations. These include:

(1) Routine weather observations, which, collected over a long enough period, can be used to 

help describe the climatology of a region.

(2) Observations collected as part of research investigations to elucidate chemical, 

dynamical, biological, or radiative processes that contribute to maintaining climate 

patterns or to their variability.

(3) Highly precise, continuous observations of climate system variables collected for the 

express purpose of documenting long-term (decadal to centennial) change.

(4) Observations of climate proxies, collected to extend the instrumental climate record to 

remote regions and back in time to provide information on climate change for millennial 

and longer time scales.

Because this is the first government attempt to document all U.S. contributions to global climate 

observations, a wide net was cast to include information on observations that fall into each of 

these categories.

The sections of the report delineate climate monitoring from five distinct yet integrated areas: 

(1) in-situ atmospheric observations; (2) in-situ oceanographic observations; (3) in-situ terrestrial 

observations; (4) satellite based observations which by their nature cut across the atmospheric, 

oceanographic, and terrestrial domains; and (5) data and information management related to 

systematic observations.

The various federal agencies involved in climate observing, through space-based and groundbased activities, provide many of the required long-term observations. Space-based systems have 

the unique advantage of obtaining global spatial coverage, particularly over the vast expanses of 

the oceans, sparsely populated land areas (e.g., deserts, mountains, forests, and polar regions), 

and the mid and upper troposphere and stratosphere. They provide unique measurements of solar 

output, the Earth’s radiation budget, vegetation cover, ocean biomass productivity, atmospheric 

ozone, stratospheric water vapor and aerosols, greenhouse gas distributions, sea level and ocean 

interior, ocean surface conditions and winds, weather, and tropical precipitation, among others.

Satellite observations alone are not sufficient; they require in-situ measurements for calibration 

and validation. In-situ observations are required for the measurement of parameters that cannot 

be estimated from space platforms (e.g., biodiversity, groundwater, carbon sequestration at the 

root zone, and subsurface ocean parameters). They also provide long time series of observations 

required for the detection and diagnosis of global change, such as surface temperature, 

precipitation and water resources, weather and other natural hazards, the emission or discharge of 

pollutants, and the impacts of multiple stresses on the environment due to human and natural 

causes. To meet the need for the documentation of global changes on a long-term basis, the U.S.

integrates observations from both research and operational systems. The goal of the U.S.’s 

observation and monitoring program is to ensure a long-term, high-quality record of the state of 
iv

the Earth system, its natural variability, and changes that occur. The U.S. will continue to support 

systematic observations in support of climate monitoring, and will provide reports of this nature 

in the future.

Gregory W. Withee, Member of the International GCOS Steering Committee

Assistant Administrator for Satellite and Data Information Services

National Environmental Satellite, Data, and Information Service

National Oceanic and Atmospheric Administration

U.S. Department of Commerce

Silver Spring, Maryland

August 2001
 v

Acknowledgement

Material for this report was developed by a U.S. interagency Global Climate Observing System 

(GCOS) coordination group comprised of representatives from the following federal agencies: 

(1) the U.S. Department of Agriculture’s (USDA) Natural Resources Conservation Service 

(NRCS) and U.S. Forest Service (USFS); (2) three line offices of the U.S. Department of 

Commerce’s National Oceanic and Atmospheric Administration (NOAA); (3) the U.S. 

Department of Energy’s (DOE) Office of Science; (4) the U.S. Environmental Protection Agency 

(EPA); (5) the U.S. Department of the Interior’s U.S. Geological Survey (USGS); (6) the 

National Aeronautics and Space Administration (NASA); (7) the U.S. Department of 

Transportation’s Federal Aviation Administration; (8) the National Science Foundation (NSF); 

(9) the U.S. Naval Oceanographic Office; (10) the U.S. Army Corps of Engineers (USCOE); and 

(11) the U.S. Air Force. The report was coordinated with the U.S. Global Change Research 

Program.

This report was prepared as directed by United Nations Framework Convention on Climate 

Change (UNFCCC) Decision CP/1999/L.3, which requested all Annex I Parties to provide a 

detailed report on systematic observations in accordance with the UNFCCC reporting guidelines 

on global climate change observing systems adopted by UNFCCC Decision CP/1999/L.4. The 

principles of this report are based on climate observing requirements for observing networks, 

practices, and data management as agreed to internationally in "The Plan for the Global Climate 

Observing System (GCOS),” Version 1.0, May 1995 GCOS-14 (WMO/TD-No. 681).

NOAA wishes to express its great appreciation to the large group of individuals from many 

federal agencies for coming together and producing this very detailed and informative report 

characterizing the vital and diverse aspects of the U.S.’s global climate observing effort.

Contributors to the Report

Overall Report Coordinator: Howard Diamond, U.S. GCOS Program Manager

Atmospheric Section Coordinator: Russell Vose, NOAA/National Climatic Data Center

Contributors:

Richard Artz, NOAA/ARL

John Augustine, NOAA/ETL

Carl Bower, NOAA/NWS

John Deluisi, NOAA/ARL

Rainer Dombrowsky, NOAA/NWS

Bruce Hicks, NOAA/ARL

Detlef Matt, NOAA/ARL

Thomas Peterson, NOAA/NCDC

Rick Petty, DOE Office of Science

Marc Pitchford, NOAA/ETL

Steven Pritchett, NOAA/NWS

Russell Schnell, NOAA/CMDL 

Dian Seidel, NOAA/ARL

Bob Thomas, NOAA/NWS

Ed Young, NOAA/NWS
U.S. National Report on Systematic Observations, August 2001

vi

Oceanographic Section Coordinator: Steve Piotrowicz, NOAA Research

Contributors:

John Calder, NOAA/OAR

Muriel Cole, NOAA Office of the Chief Scientist

Elizabeth Horton, Naval Oceanographic Office

Michael Johnson, NOAA/OGP

Paul Moersdorf, NOAA/NWS/NDBC

Rik Wanninkhof, NOAA/AOML

Stan Wilson, NOAA Office of the Chief Scientist

Terrestrial Section Coordinator: David Clark, NOAA/National Geophysical Data Center

Contributors:

Roger Barry, NSIDC

Jerry Brown, IPA

Tom Carroll, NOAA/NWS

Gary Clow, USGS

Mark Eakin, NOAA/NGDC

Florence Fetterer, NSIDC

Michael Jasinski, NASA

Gregory Johnson, USDA/NRCS

John Lyon, EPA

Lawrence Pettinger, USGS

Rick Petty, DOE Office of Science

Al Riebau, USFS

Kernell Ries, USGS

Hal Walker, EPA

David Wingerd, USCOE

Ed Young, NOAA/NWS

Satellite Remote Sensing Section Coordinator: Robert Schiffer, NASA

Contributors:

John Faundeen, USGS/EROS Data Center

Arnold Gruber, NOAA/NESDIS

Herbert Jacobowitz, NOAA/NESDIS

Steve Mango, NOAA/NESDIS

George Ohring, NOAA/NESDIS

Lawrence Pettinger, USGS

Tim Smith, USGS/EROS Data Center

Sushel Unninayar, NASA

Tim Walsh, NOAA/NESDIS

Other Contributors:

Donald Carver, NOAA/OFCM

Billie Cooper, NOAA/NWS

David Goodrich, NOAA/OAR

Reid Harvey, EPA

Linda Moodie, NOAA/NESDIS

Thomas Spence, National Science Foundation

Colonel H.W. Tileston, U.S. Air Force

Robert C. Worrest, U.S. Global Change Research Information Office
U.S. National Report on Systematic Observations, August 2001

vii

Table of Contents

EXECUTIVE SUMMARY.............................................................................................................................1

I. ATMOSPHERIC OBSERVATIONS......................................................................................................1

A. GCOS Networks .................................................................................................................................................1

1. GSN Stations ....................................................................................................................................................1

2. GUAN Stations.................................................................................................................................................1

3. GAW Stations...................................................................................................................................................2

B. Other Surface Networks.....................................................................................................................................2

1. First Order Network..........................................................................................................................................2

2. Cooperative Observing Network ......................................................................................................................4

3. Observing Equipment .......................................................................................................................................5

4. Data Assimilation and Quality Control.............................................................................................................6

5. Metadata ...........................................................................................................................................................6

6. Observation Problems.......................................................................................................................................6

7. Cooperative Network of the Future ..................................................................................................................7

8. Climate Reference Network..............................................................................................................................7

C. Upper Air Network.............................................................................................................................................8

1. Operations.........................................................................................................................................................8

2. Data Quality Assurance ....................................................................................................................................8

3. Metadata ...........................................................................................................................................................8

4. Network Stability..............................................................................................................................................9

5. Network Changes 2000 to 2005........................................................................................................................9

6. Network History ...............................................................................................................................................9

7. Other Upper Air Observation Systems ...........................................................................................................13

a. Next Generation Doppler Weather Radar (NEXRAD)...............................................................................13

b. Tropospheric Wind Profilers......................................................................................................................13

c. Global Positioning System Integrated Precipitable Water (GPS-IPW).......................................................13

d. Automated Aircraft Reporting Systems......................................................................................................14

D. Atmospheric Constituent Networks................................................................................................................14

1. Atmospheric Baseline Measurement Network................................................................................................14

2. Atmospheric Coordinated Observations and Research Network (ACORN)...................................................15

3. Integrated Surface Irradiance Study Network (Level 1) .................................................................................16

4. Surface Radiation Network (Level 2).............................................................................................................17

5. Surface Energy Balance Network (Level 3) ...................................................................................................18

6. The CO2 Sequestration Network and AmeriFLUX (Level 4).........................................................................19

7. AIRMoN-dry Network (Level 5)....................................................................................................................19

8. AIRMoN-wet Network (Level 6)....................................................................................................................19

9. National Atmospheric Deposition Program National Trends Network...........................................................20

10. National Atmospheric Deposition Program/Mercury Deposition Network ..................................................21

11. Interagency Monitoring of Protected Visual Environments Network (IMPROVE) .....................................21

12. Atmospheric Radiation Measurement (ARM) Program................................................................................22

12a. ARM Sites...................................................................................................................................................22

12b. ARM Instrumentation .................................................................................................................................23

II. OCEANOGRAPHIC OBSERVATIONS ..............................................................................................33
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viii

A. Recent Developments........................................................................................................................................33

B. Fixed Mooring Observational Programs........................................................................................................34

1. TAO/TRITON ................................................................................................................................................34

2. Pilot Research Moored Array in the Tropical Atlantic ...................................................................................36

3. Eastern Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System....................36

4. Arctic ..............................................................................................................................................................37

C. Marine Observational Network of the National Weather Service ...............................................................39

1. Moored Buoys ................................................................................................................................................39

2. Coastal-Marine Automated Network ..............................................................................................................41

D. Drifting Buoy Program ....................................................................................................................................42

1. Global Lagrangian Drifters.............................................................................................................................42

2. Arctic ..............................................................................................................................................................43

E. Voluntary and Ships of Opportunity ..............................................................................................................44

F. U.S. GOOS VOS Program...............................................................................................................................44

1. Shipboard Environmental (Data) Acquisition System (SEAS).......................................................................45

2. Expendable Bathythermograph Program........................................................................................................45

3. Thermosalinograph (TSG)..............................................................................................................................46

4. Carbon Dioxide...............................................................................................................................................47

5. Automated Shipboard Aerological Program (ASAP).....................................................................................47

6. Improved Meteorology ...................................................................................................................................48

G. Floats..................................................................................................................................................................49

H. In-Situ Sea Level...............................................................................................................................................51

I. Time Series........................................................................................................................................................53

1. Bermuda Atlantic Time Series........................................................................................................................54

2. HOT Series.....................................................................................................................................................55

J. Remote Sensing Systems...................................................................................................................................56

1. Altimetry.........................................................................................................................................................56

2. Sea Surface Winds..........................................................................................................................................57

3. Sea Surface Temperature................................................................................................................................58

4. National Polar orbiting Operational Environmental Satellite System (NPOESS) ..........................................58

5. Ocean Color....................................................................................................................................................59

K. Miscellaneous....................................................................................................................................................60

1. Current Transport from Voltage Measurements .............................................................................................60

2. Coral Reef Observations.................................................................................................................................61

3. Trans-Pacific Profiler Network.......................................................................................................................61

III. TERRESTRIAL OBSERVATIONS .....................................................................................................67

A. Status of the National Terrestrial Portion of the GCOS Program...............................................................67

1. U.S. Component of the Global Terrestrial Network for Permafrost ...............................................................67

2. U.S. Component of the Global Terrestrial Network for Glaciers (GTN-G) ...................................................68

3. U.S. Component of the Global Terrestrial Network for Carbon (FLUXNET - AmeriFlux)...........................68

4. Streamflow and Surface Water Gaging...........................................................................................................69

5. Hydromet System............................................................................................................................................71
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ix

6. Ground Water Monitoring Wells....................................................................................................................72

7. Manual Snow Courses....................................................................................................................................72

8. SNOwpack TELemetry (SNOTEL)................................................................................................................72

9. Airborne, Satellite, and Modeled Snow Cover Data.......................................................................................73

10. Soil Climate Analysis Network (SCAN).......................................................................................................74

11. Paleoclimatology ..........................................................................................................................................75

12. Ecological Observation Networks ................................................................................................................76

a. Fire Inventory and Analysis Program..........................................................................................................76

b. LTER Network ...........................................................................................................................................77

13. Fire Weather Observations Remote Automated Weather Stations ...............................................................78

14. Global, National, and Regional Land Cover Characterization......................................................................78

B. International Data Exchange...........................................................................................................................81

IV. SATELLITE AND REMOTE SENSING OBSERVATIONS.................................................................85

A. Objectives..........................................................................................................................................................85

B. Implementation Status of Satellite Series and Platforms ..............................................................................87

C. Operational U.S. Satellite Observing Systems................................................................................................89

1. Polar Operational Environmental Satellites (POES).......................................................................................89

2. Defense Meteorological Satellite Program .....................................................................................................91

3. NPOESS .........................................................................................................................................................92

4. NPOESS Preparatory Project (NPP) ..............................................................................................................94

5. Geostationary Operational Environmental Satellites (GOES) ........................................................................95

6. Landsat ...........................................................................................................................................................96

D. Research and Experimental Satellites.............................................................................................................97

1. ACRIM-III......................................................................................................................................................97

2. TOMS.............................................................................................................................................................98

3. UARS .............................................................................................................................................................99

4. TOPEX/Poseidon ...........................................................................................................................................99

5. SeaWiFS.......................................................................................................................................................100

E. Recently Launched “Next” Generation Research Satellites and Instruments...........................................100

1. Tropical Rainfall Measuring Mission (TRMM) ...........................................................................................100

2. NASA-Shuttle Radar Topography Mission ..................................................................................................101

3. NASA’s EOS Satellite Series .......................................................................................................................101

F. Specific EOS-Terra Research Instruments ..................................................................................................102

1. EOS-Terra.....................................................................................................................................................102

2. EOS-Terra/CERES .......................................................................................................................................103

3. EOS-Terra/MODIS.......................................................................................................................................104

4. EOS-Terra/ASTER.......................................................................................................................................104

5. EOS-Terra/MISR..........................................................................................................................................105

6. EOS-Terra/MOPITT.....................................................................................................................................106

G. Future (Approved) NASA Research Satellites.............................................................................................106

1. QuiKTOMS ..................................................................................................................................................106

2. Jason-1..........................................................................................................................................................106

3. EOS-Aqua.....................................................................................................................................................106

4. SeaWinds......................................................................................................................................................107

5. EOS-ICESat..................................................................................................................................................107
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6. Solar Radiation and Climate Experiment......................................................................................................107

7. EOS-Aura .....................................................................................................................................................107

H. Future (Approved) Experimental Satellites..................................................................................................108

1. Gravity Recovery and Climate Experiment (GRACE) .................................................................................108

2. CloudSAT.....................................................................................................................................................108

3. Vegetation Canopy Lidar (VCL) ..................................................................................................................108

4. PICASSO-CENA..........................................................................................................................................108

5. Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) ............................109

V. DATA AND INFORMATION MANAGEMENT RELATED TO GCOS ..............................................125

REFERENCES ........................................................................................................................................129

ACRONYMS............................................................................................................................................130

LIST OF TABLES

Table 1. U.S. Participation in the Global Atmospheric Observing Systems .........................................................2

Table 2. U.S. Participation in the Global Oceanographic Observing Systems.....................................................3

Table 3. U.S. Participation in the Global Terrestrial Observing Systems ............................................................4

Table 4. U.S. Environmental Satellite Program......................................................................................................5

Table 5. ARM Climate Measurement Categories.................................................................................................24

Table S1. National Climate Monitoring Systems for Land Surface (Meteorological) Observations................27

Table S2. Available Homogeneous Data Sets for Land Surface (Meteorological) Observations......................28

Table S3. National Climate Monitoring Systems for Upper Air Observations (Meteorological).....................30

Table S4. Available Homogeneous Data Sets For Upper Air Observations (Meteorological)..........................31

Table S5. National Climate Monitoring Systems for Atmospheric Constituents...............................................31

Table S6. Available Homogeneous Data Sets For Atmospheric Constituents....................................................32

Table S7. National Climate Monitoring Systems for Oceanographic Observations..........................................63

Table S8. Available Homogeneous Data Sets for Oceanographic Observations. ...............................................64

Table S9. National Climate Monitoring Systems for Terrestrial Observations.................................................82

Table S10. National Climate Monitoring Systems for Ecological Observations ................................................83

Table S11. Available Homogeneous Data Sets for Sustained Terrestrial and Ecological Observations. .........83

Table 6. Satellite Series/Systems, Responsible Agencies, Data Exchange/Availability, Applications.............110

Table 7. Satellite Series, Observations, Series Duration/Continuity, Compliance with GCOS Principles.....115

Table 8a. Key Observations for Identifying Earth-Climate System Variations and Trends. .........................119

Table 8b. Key Observational Requirements for Determining Primary Forcings on Earth-Climate System.121

Table 8c. Special Observational Requirements for Response and Feedback Process Studies ........................122

Table 8d. Special Observational Requirements for Prediction and Assessments.............................................124
U.S. National Report on Systematic Observations, August 2001

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Executive Summary

Since 1998, Parties to the United Nations Framework Convention on Climate Change 

(UNFCCC) have noted with concern the mounting evidence of a decline in the global observing 

capability and have urged Parties to undertake programs of systematic observations and to 

strengthen their capability in the collection, exchange, and utilization of environmental data and 

information. It has long been recognized that the range of global observations needed to 

understand and monitor Earth processes contributing to climate and to assess the impact of 

human activities cannot be satisfied by a single program, agency, or country. The U.S. supports 

the need to improve global observing systems for climate, and we join other Parties in submitting 

information on national plans and programs that contribute to the global capability. This report 

was prepared as directed by UNFCCC Decision CP/1999/L.3, which requested Annex I Parties to 

provide a detailed report on systematic observations in accordance with the UNFCCC reporting 

guidelines on global climate change observing systems adopted by the UNFCCC Decision 

CP/1999/L.4.

The U.S. actively supports the Global Climate Observing System (GCOS) through its 

participation in and support of the GCOS networks, and through its support of related climate 

observing activities. The U.S. recognizes that international cooperation both in data collection 

and sharing of information is essential to provide the climate information required by the 

UNFCCC.

With regard to capacity building, the initial climate report of the George W. Bush Administration 

noted that national and international bodies have “identified the building of a global observing 

system to monitor climate as being crucial to improving our understanding of the science of 

climate change. This system must include developing countries that have limited resources to 

make the necessary measurements.” It further states that the U.S. will Aprovide resources to help 

build climate observation systems in developing countries throughout the world, and call upon 

other developed countries to provide matching funds for such an investment.@

This report delineates climate monitoring in the U.S. in five distinct yet integrated areas: (1) insitu atmospheric observations; (2) in-situ oceanographic observations; (3) in-situ terrestrial 

observations; (4) satellite based observations which by their nature cut across the atmospheric, 

oceanographic and terrestrial domains; and (5) data and information management related to 

systematic observations. The report attempts to include observation systems now known to be 

relevant, but is representative of the larger U.S. effort to observe environmental variables.

The U.S. actively participates in the GCOS Surface Network (GSN), the GCOS Upper Air 

Network (GUAN), and the Global Atmospheric Watch (GAW). The US supports 75 GSN 

stations, 20 GUAN stations, and 4 GAW stations. These stations are distributed geographically 

as prescribed in the GCOS and GAW network designs. The data (metadata and observations) 

from these stations are shared according to GCOS and GAW protocols. The GSN and GUAN 

stations are part of a larger network, which was developed for purposes other than climate 

monitoring. Nonetheless, the stations fully meet the GCOS requirements. In general, the National 

Oceanic and Atmospheric Administration (NOAA) operates most of the U.S. GCOS atmosphererelated networks.
U.S. National Report on Systematic Observations, August 2001

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There is no comprehensive system designed to observe climate change and climate variability in 

the U.S. Basically, sustained observing systems in the U.S., which provide continuing 

observations, provide data principally for non-climatic purposes, such as predicting weather, 

advising the public, and managing resources. In addition, there are research-observing systems 

that collect data for climate purposes, but they are often oriented toward gathering data for 

climate process studies or other research programs rather than climate monitoring. They are 

usually limited in their spatial and temporal extent. Because the U.S. climate record is based 

upon a combination of existing operational and research programs, it may not be “ideal” from a 

long-term climate monitoring perspective. Nevertheless, these observing systems collectively 

provide voluminous and significant information about the spatial and temporal variability of 

climate in the U.S. and contribute to the international climate observing effort as well. The 

detailed atmospheric section in the main body of the report examines in-situ climate monitoring 

involving systems from the surface, upper air, and atmospheric deposition domains.

Table 1. U.S. Participation in the Global Atmospheric Observing Systems

GSN GUAN GAW OTHER

How many stations are the responsibilities of the Party? 75 20 4 See Section I

How many of those are operating now? 75 20 4 See Section I

How many of those are operating to GCOS standards now? 75 20 4 See Section I

How many are expected to be operating in 2005? 75 21 4 See Section I

How many are providing data to international data centres now? 75 20 4 See Section I

The GCOS requirements for ocean observations are the same as the climate requirements for the 

Global Ocean Observing System (GOOS). Both are based on the Ocean Observing System 

Development Panel (OOSDP) Report, (OOSDP, 1995), which can be found at 

http://www-ocean.tamu.edu/OOSDP/FinalRept/t_of_c.html. The GOOS, like GCOS, is based on 

a number of in-situ and space-based observing components. The US contributes to all of these 

components. It supports surface and marine observations through 149 fixed buoys, over 500 

surface drifting buoys, nearly 200 sub-surface floats, and over 1500 volunteer observing ships as 

part of the Integrated Global Ocean Observing System (IGOSS). It provides support for 244 

sea-level tide gauges through the Global Sea Level Observing System (GLOSS). It currently 

provides satellite coverage of the global oceans for sea surface temperatures, surface elevation, 

ocean surface winds, sea ice, ocean color, and other variables of climate relevance. These 

satellite activities are coordinated internationally through the Committee on Earth Observation 

Satellites (CEOS).
U.S. National Report on Systematic Observations, August 2001

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Table 2. U.S. Participation in the Global Oceanographic Observing Systems1

VOS SOOP Tide 

Gauges

Surface 

Drifters

Sub-Surface 

Floats

Moored 

Buoys ASAP

For how many platforms is the 

Party responsible? 1557 51 244 ~540/year 187 149* <1

How many are providing data to 

international data centres? 1470 51 244 ~800 (11⁄2 - 2 year lifetime) 187 149* <1

How many are expected to be 

operating in 2005? 1470 51 244 ~800 ~1,000 ~130* <1

* Includes 5 mooring pairs along the equator in the Pacific, research moorings in the Arctic and Pacific, two 

time series sites, and an international collaborative program in the Atlantic.

• ASAP – Automated Shipboard Aerological Program

• SOOP – Ships of Opportunity

• VOS – Voluntary Observing Ships

Note: For Table 2, contributing to an international data centre is considered to be data available on the 

Global Telecommunications System (GTS) that is available to be downloaded from an ftp or other site 

either directly or via the Distributed Oceanographic Data System (DODS), as well as to world data centres.

For terrestrial observations, the requirements for climate observations were developed jointly 

between GCOS and the Global Terrestrial Observing System (GTOS) through the Terrestrial 

Observations Panel for Climate (TOPC); see GCOS/GTOS Plan for Terrestrial Climate-related 

Observations, version 2.0 June 1997, GCOS-32 (WMO/TD-No. 796). GCOS and GTOS, have 

identified permafrost thermal state and permafrost active layer as key variables for monitoring 

the state of the cyrosphere. GCOS approved the development of a globally comprehensive 

permafrost monitoring network to detect temporal changes in the solid earth component of the 

cryosphere. As such, the Global Terrestrial Network for Permafrost (GTN-P) is quite new and 

still very much in the developmental stage. The International Permafrost Association (IPA) has 

the responsibility for managing and implementing the GTN-P.

In the U.S., contributions to the GTN-P network are provided by the Department of the Interior 

and the NSF, through grants to various universities. All the U.S. GTN-P stations are located in 

Alaska. The active layer thickness is currently being monitored at 27 sites. Forty-eight boreholes 

exist in Alaska where permafrost thermal state can be determined. Of these, 4 are classified as 

Surface (0-10 m) sites, 1 is Shallow (10-25 m), 22 are Intermediate Depth (25-125 m), and 21 are 

Deep Boreholes (>125 m). U.S. contribution to the GTN-P network comes from short-term (3-5 

year) research projects.

The U.S. operates a long-term "benchmark" glacier program to intensively monitor climate, 

glacier motion, glacier mass balance, glacier geometry, and stream runoff at a few select sites. 

The data collected are used to understand glacier-related hydrologic processes and improve the 

quantitative prediction of water resources, glacier-related hazards, and the consequences of 

climate change.

 

1 See also http://ioc.unesco.org/goos/act_pl.htm for details of ocean observation requirements.
U.S. National Report on Systematic Observations, August 2001

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The approach has been to establish long-term mass balance monitoring programs at three widely 

spaced glacier basins in the U.S. that clearly sample different climate-glacier-runoff regimes. The 

three glacier basins are South Cascade Glacier in Washington State, and Gulkana and Wolverine 

Glaciers in Alaska. Mass balance data are available beginning in 1959 for the South Cascade 

Glacier, and beginning in 1966 for the Gulkana and Wolverine Glaciers.

The AmeriFLUX network endeavors to establish an infrastructure for guiding, collecting, 

synthesizing, and disseminating long-term measurements of CO2, water, and energy exchange 

from a variety of ecosystems. Its objectives are to collect critical new information to help define 

the current global CO2 budget, enable improved predictions of future concentrations of 

atmospheric CO2, and enhance the understanding of carbon fluxes, Net Ecosystem Production 

(NEP), and carbon sequestration in the terrestrial biosphere.

The terrestrial section of the report examines in-situ climate monitoring and involves, in addition 

to the GTN-P, GTN-G, and AmeriFLUX programs, streamflow and surface water gaging, ground 

water monitoring, snow and soil monitoring, the U.S. paleoclimatology program, ecological 

observation networks, fire weather observation stations, as well as global, national, and regional 

land cover characterization. The U.S. contributes to all of these components, and supports 77 

GTN-P sites, 3 GTN-G sites, and 52 Fluxnet sites.

Table 3. U.S. Participation in the Global Terrestrial Observing Systems

GTN-P GTN-G

FLUXNET

AmeriFlux Other

How many sites are the responsibilities of the Party? 77 3 52 See Section III

How many of those are operating now? 77 3 47 See Section III

How many are providing data to international data centres now? 77 3 24 See Section III

How many are expected to be operating in 2005? 80 0 50 See Section III

Space-based, remote sensing observations of the atmosphere-ocean-land system have evolved 

substantially since the early 1970’s when the first operational weather satellite systems were 

launched. Over the last decade satellites have proven their observational capabilities to accurately 

monitor nearly all aspects of the total Earth system on a global basis; a capability unmatched by 

ground-based systems that are limited to land areas and cover only about 30% of the planetary 

surface. Currently, satellite systems monitor the evolution and impact of the El-Nino, weather 

phenomena, natural hazards, and extreme events such as floods and droughts, vegetation cycles, 

the ozone hole, solar fluctuations, changes in snow cover, sea ice and ice sheets, ocean surface 

temperatures and biological activity, coastal zones and algae blooms, deforestation, forest fires, 

urban development, volcanic activity, tectonic plate motions, and others. These various 

observations are used extensively in real-time decision-making and the strategic planning and 

management of industrial, economic, and natural resources. Examples include weather and 

climate forecasting, agriculture, transportation, energy and water resources management, urban 

planning, forestry, fisheries, and early warning systems for natural disasters and human health 

impacts.
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Table 4. U.S. Environmental Satellite Program

Polar 

Orbiting 

(Operational)

Geostationary 

(Operational)

Research

(Systematic and Experimental 

Observations)

For how many platforms is the Party 

responsible?

2 – Landsat

2 – POES

2 – DMSP

2 – GOES 21 (See Section IV)

How many of those are operating

now?

2 – Landsat

2 – POES

2 – DMSP

2 – GOES 21 (See Section IV)

How many are providing data to 

international data centres?

2 – Landsat

2 – POES

2- DMSP

2 - GOES 10 (See Section IV)

How many are expected to be 

operating in 2005?

1 – Landsat

1 – POES

2 – DMSP

2 - GOES 14 (See Section IV)

The GCOS planning process addressed satellite requirements for climate. In so doing, GCOS 

identified an extensive suite of variables that should be observed and monitored from space; see 

GCOS Plan for Space-based Observations, GCOS-14 (WMO/TD – No. 681). In addition, GCOS 

plans specified that instrument calibration and validation be performed to ensure that the 

resulting space-based observations meet climate requirements for accuracy, continuity, and low 

bias.

The current generation of U.S. research satellite instruments exceeds the GCOS requirements for 

the absolute calibration of sensors, something that was lacking in the early satellite platforms 

used for real-time operational purposes. Regarding historical satellite data, several of the data 

series from operational satellites have been re-processed using substantially improved retrieval 

algorithms and, therefore, provide good quality global data products for the purposes of GCOS 

and climate system variability and climate change research and applications. Improving the onboard capabilities for calibration on operational satellites will be one of the objectives considered 

in the development of the National Polar-orbiting Operational Environmental Satellite System 

(NPOESS) program. Prior to the launch of NPOESS in 2008, an NPOESS Preparatory Project 

(NPP) satellite will be launched in the 2005 timeframe as a bridge mission between the NASA 

Earth Observing Satellites (EOS) program and NPOESS. The mission of NPP is to demonstrate 

advanced technology for atmospheric sounding, providing ongoing observations about global 

change after EOS-Terra and EOS Aqua. It will supply data on atmospheric and sea surface 

temperatures, humidity soundings, land and ocean biological productivity, and cloud and aerosol 

properties. NPP will contribute to instrument risk reduction by offering early instrument and 

system level testing, lessons learned for design modifications in time to ensure NPOESS launch 

readiness, ground system risk reduction, early user evaluation of NPOESS data products, such as 

algorithms, and instrument verification, and opportunities for instrument calibration.

The satellite observations section of this report details a number of U.S. satellite operational and 

research missions in support of climate monitoring. The instruments on the Geostationary 

Operational Environmental Satellites (GOES) and Polar Operational Environmental Satellites 

(POES), the series of Earth Observing Satellites (EOS), the Landsats 5 and 7, as well as the Total 

Ozone Mapping Spectrometer satellite and TOPEX/Poseidon satellite measuring sea surface 
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height, winds, and waves form the basis of a robust national remote sensing program that fully 

supports the requirements of GCOS. Additional satellite missions in support of GCOS and 

described in the satellite observations section include: (1) the Active Cavity Radiometer 

Irradiance Monitor (ACRIM) for measuring solar irradiance; (2) EOS-Terra; (3) QuickSCAT; (4) 

the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) for studying ocean productivity; (5) the 

Shuttle Radar Topography Mission (SRTM); (6) the Tropical Rainfall Measuring Mission 

(TRMM) for measuring rainfall, clouds, sea surface temperature, radiation, and lightning; and (7)

QuickSCAT. In addition, a number of missions still to be launched are included in this group of 

environmental satellites.

The Defense Meteorological Satellite Program (DMSP) is a Department of Defense (DOD) 

program run by the Air Force Space and Missile Systems Center (SMC). The DMSP program 

designs, builds, launches, and maintains several near-polar orbiting, sun synchronous satellites, 

monitoring the meteorological, oceanographic, and solar-terrestrial physics environments. DMSP 

satellites are in a near-polar, sun synchronous orbit at an altitude of approximately 

830 kilometers (km) above the earth. Each satellite crosses any point on the earth up to two times 

a day and has an orbital period of about 101 minutes, thus providing nearly complete global 

coverage of clouds every six hours.

The U.S. cooperates on an international basis with a number of coordinating bodies, including 

the Integrated Global Observing Strategy (IGOS). IGOS is a strategic planning process, uniting 

the major satellite and surface-based systems for global environmental observations of the 

atmosphere, oceans and land, in a framework for decisions and resource allocations by individual 

funding agencies. Its purview includes observations for climate, and the needs of multiple 

domains—the entirety of which no single Partner is able to address alone. It takes a strategic 

view across all Earth observing requirements, evaluates capabilities of current and planned 

observing systems, and has begun (at least among the space agencies) to obtain commitments for 

addressing the gaps. An IGOS Ocean Theme is in the implementation phase under leadership 

from GOOS. An analysis of requirements, gaps, and recommendations for priority observations 

is underway for integrated global carbon observations as well as integrated global atmospheric 

chemistry observations. Prospectively, similar analyses, recommendations, and commitments 

will likely be undertaken in the areas of the water cycle, geo-hazards, and coral reefs.

Operational weather satellites are internationally coordinated through the Coordination Group for 

Meteorological Satellites (CGMS), of which the World Meteorological Organization is a member 

and major beneficiary. CGMS has six satellite agency members. The primary body for policy and 

technical issues of common interest related to the whole spectrum of Earth observation satellite 

missions is the CEOS. CEOS has 22 space agency members, including both research and 

operational satellite agencies, with funding and program responsibilities for a satellite Earth 

observation program currently operating or in the later stages of system development. CEOS 

encourages compatibility among space-borne Earth observing systems through coordination in 

mission planning, promotion of full and non-discriminatory data access, setting of data product 

standards, and development of data products, services, applications, and policies.

Global environmental concerns are an overriding justification for the unrestricted international 

exchange of GCOS data and products for peaceful, non-commercial, global scientific and 

applications purposes. As such, GCOS developed an overarching data policy that endorses the 

full and open sharing and exchange of GCOS-relevant data and products for all GCOS users as a 
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ES-7

fundamental objective; these data and products should be provided at the lowest possible cost to 

GCOS users. The U.S. recognizes this and subscribes to GCOS’ data policy.

Achieving the goals of the U.S. climate-observing program requires multidisciplinary analysis of 

data and information to an extent never before attempted. This includes the analysis of 

interlinked environmental changes that occur on multiple temporal and spatial scales, which is 

very challenging both technically and intellectually. For example, many types of satellite and 

in-situ observations at multiple scales need to be integrated with models and the results presented 

in understandable ways to all levels of the research community, decision makers, and the public. 

Additionally, very large volumes of data from a wide variety of sources and results from many 

different investigations need to be readily accessible to scientists and other stakeholders in usable 

forms that can be integrated.

Various U.S. agencies have engaged in extensive development of interagency data and 

information processes to address these needs, primarily through fostering better integration 

among U.S. Government data and discipline specific information. The Global Change Data and 

Information System (GCDIS) has been developed in response to this need and to facilitate data 

accessibility. GCDIS currently provides a gateway for discovery and information access among 

more than 70 federally funded sources of data, both governmental and academic. During the last 

decade, significant strides have been made in GCDIS’ seamless connections between diverse 

data sets and sources, as well as its ability to search across the full complement of sources. The 

World Wide Web has facilitated this effort, however, important challenges remain.

The provision of data and information in forms needed for cross-disciplinary analyses and 

projections remain a challenge, even as the increasing focus of the U.S. agencies on investigating 

the impacts and consequences of change heightens the need for multidisciplinary research. 

Physical and biological data needs to be related to data on environmental conditions and 

socioeconomic trends originally compiled for other purposes. This is a particularly important 

challenge in addressing potential regional consequences of multiple stresses and determining the 

vulnerability of different resources and communities.

While a wide net has been cast to include information on each of the observing categories of this 

report, it is the position of the U.S. government (as evidenced by its active support of the 10 

Principles of Climate Observations, and of the U.S. climate research community [National 

Research Council, 1999]), that high standards must be met if a particular set of observations is to 

serve the purpose of monitoring the climate system to detect long-term change. In general, the 

observing programs and resulting datasets described herein do not meet the ten “Climate 

Monitoring Principles” endorsed by the U.S. and UNFCCC. This shortfall stems from two main 

factors: 1) the principles were articulated only within the past decade (Karl et al. 1995), long after 

the initiation of most of our long-term observing systems; and 2) more recent observing programs 

typically do not have climate monitoring as their prime function.

It is hoped that the detailed information contained in this report will aid the GCOS Secretariat in 

the analysis of the state of global climate observing, as charged by the UNFCCC. The inclusion 

of this level of detail and the format of the supplementary tables for each section was developed, 

in concert with the GCOS Secretariat, at an informal meeting of GCOS national coordinators in 

Melbourne, Australia, in August 2000. This additional detail, while voluntary on the part of 

nations, should assist the secretariat in this endeavor. There are a number of overarching science 
U.S. National Report on Systematic Observations, August 2001

ES-8

questions dealing with how the Earth-Climate System is changing and what the consequences are 

for life on Earth. These questions are as follows:

• How is the global Earth-Climate system changing? (Variability-V)

• How are global precipitation, evaporation, and the cycling of water changing?

• How is the global ocean circulation varying on interannual, decadal, and longer time 

scales? 

• How are global ecosystems changing?

• How is stratospheric ozone changing as the abundance of ozone-destroying chemicals 

decreases and new substitutes increases?

• What changes are occurring in the mass of the Earth’s ice cover?

• What are the primary forcings of the Earth-Climate system? (Forcing-F)

• What trends in atmospheric constituents (including aerosols) and solar radiation are

driving global climate?

• What changes are occurring in global land cover and land use, and what are their causes?

• How is the Earth’s surface being transformed and how can such information be used to 

predict future climate changes?

• How does the Earth-Climate system respond to natural and human-induced changes? 

(Response-R)

• What are the effects of clouds and surface hydrologic processes on Earth’s climate?

• How do ecosystems respond to and affect global environmental change and the carbon 

cycle?

• How can climate variations induce changes in the global ocean circulation?

• How do stratospheric trace constituents respond to change in climate and atmospheric 

composition?

• How is global sea level affected by climate change?

• What are the effects of regional pollution on the global atmosphere, and the effects of 

global chemical and climate changes on regional air quality?

• What are the consequences of change in the Earth-Climate system for human civilization? 

(Consequences-C)

• How are variations in local weather, precipitation and water resources related to global 

climate variation?

• What are the consequences of the interaction between climate and land cover and land 

use change in regard to the sustainability of ecosystems and economic productivity?

• What are the consequences of climate and sea level changes and increased human 

activities on coastal regions?
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ES-9

! How well can we predict future changes to the Earth-Climate system? (Prediction-P)

• How well can weather forecast duration and reliability be improved by new in-situ and 

space-based observations, data assimilation, and modeling?

• How well can transient climate variations be understood and predicted?

• How well can long-term climatic trends be assessed or predicted?

• How well can future atmospheric chemical impacts on ozone and climate be predicted?

The U.S.-GCOS effort is designed to aid in addressing these scientific questions, and contributes 

to all the international programs mentioned and their respective objectives. Following the 

UNFCCC reporting guidelines, adopted by COP-5, the U.S. contribution to GCOS regarding 

both in-situ and space-based observations are described in this report. Both operational and 

research systems are included in accord with the GCOS coordinators’ guidance, elaborating on 

the UNFCCC guidelines.
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1

I. Atmospheric Observations

The United States actively participates in the Global Climate Observing System (GCOS) Surface 

Network (GSN), the GCOS Upper Air Network (GUAN), and the Global Atmospheric Watch 

(GAW). However, there is not a comprehensive system designed exclusively to observe climate 

variability in the U.S. As with other countries, most U.S. observing systems provide data for nonclimatic purposes, such as predicting weather, advising farmers, and managing resources. The 

systems that collect data for climate purposes are oriented toward gathering data for climate 

process studies rather than climate monitoring, and are limited in their spatial and temporal 

extent. Because the U.S. climate record is based upon these existing operational and research 

programs, it is not “ideal” from a climate monitoring perspective. Nevertheless, these in-situ

observing systems collectively provide tremendous information about the spatial and temporal 

variability of climate in the U.S.

Space-based remote sensing observations have played a critical role in support of atmospheric 

observations. Over the last decade, satellites have proven their observational capabilities to 

accurately monitor nearly all aspects of the total Earth system. This is a capability unmatched by 

surface based systems which are limited to land areas and cover only about 30% of the planetary 

surface. Currently, satellite systems monitor the evolution and impacts of the El Nino, weather 

phenomena, natural hazards, and extreme events such as floods and droughts, vegetation cycles, 

the ozone hole, solar fluctuations, changes in snow cover, sea ice and ice sheets, ocean surface 

temperatures and biological activity, coastal zones and algae blooms, deforestation, forest fires,

urban development, volcanic activity, tectonic plate motions, and others. While this section 

focuses on in-situ observing systems, a full picture of satellite observing can be found in section 

IV of this report.

A. GCOS Networks

1. GSN Stations

The U.S. has 75 GSN stations that collectively represent the temperature and precipitation 

variability of the country and its territories. Given that the U.S. accounts for less than two percent 

of the terrestrial surface, the U.S. component of the GSN is comparatively large (only the 

Russian Federation has more stations). Fifty-four GSN sites are in the conterminous U.S., 14 in 

Alaska, 2 in Hawaii, 2 in Antarctica, 1 in Puerto Rico, 1 in Guam, and 1 in American Samoa. All 

of these stations are currently operating, and should continue to operate through 2005. Ninety 

percent transmit their data in real-time via the Global Telecommunications System (GTS). The 

data and metadata for all stations are quality controlled by and archived at the World Data Center 

A for Meteorology (i.e., the U.S. NOAA National Climatic Data Center [NCDC]).

2. GUAN Stations

The U.S. has 20 GUAN stations that collect standard radiosonde data at standard observation 

times. Six stations are in the conterminous U.S., three in Alaska, one in Hawaii, two in 

Antarctica, one each in Puerto Rico, Guam, and American Samoa, and five others in areas such 

as Ascension Island in the South Atlantic, and Bermuda. All of these stations are currently 

operating and will continue to operate through 2005; the network is operated by NOAA’s 
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2

National Weather Service (NWS). The data and metadata for all stations are quality controlled by 

and archived at NCDC. The possibility exists for an additional GUAN station, in the central part 

of the U.S., to be added to the network by the year 2005.

3. GAW Stations

The U.S. has four GAW stations that collect atmospheric constituent data. The four stations: 

Barrow, Alaska; Mauna Loa, Hawaii; American Samoa; and the South Pole are currently 

operating and will continue to operate through 2005. The data and metadata for all stations are 

quality controlled by and archived at NOAA’s Climate Monitoring and Diagnostics Laboratory 

(CMDL).

B. Other Surface Networks

According to the 1999 National Research Council (NRC) report entitled, “Adequacy of Climate 

Observing Systems,” the surface networks of the U.S. are only partially capable of delivering 

data suitable for detecting climate variations and changes on multi-decadal time scales. Surface 

temperature is adequate with respect to half of the 10 climate monitoring principles (data 

continuity/quality, integrated environmental assessment, complementary data, continuity of 

purpose, and data/metadata access). Snow cover and snow depth are adequate with regard to 

three of the principles (integrated environmental assessment, complementary data, and 

data/metadata access). Precipitation, wind, water vapor, and sea level pressure are adequate only 

in terms of one of the principles (continuity of purpose).

The two largest national-scale surface observing networks in the U.S. are the First Order 

Network and the Cooperative Observing Network. Many other networks exist at the regional, 

state, and local scale (e.g., the Oklahoma Mesonet), but are too numerous to discuss in this 

report.

1. First Order Network

The civilian surface observation network in the U.S. has undergone equipment modernization 

and management transition over the past ten years. The network of approximately 2100 

observing locations, located mainly at airports, has been expanded in spatial and temporal density 

from previous decades. The network is comprised primarily of modernized automated weather 

observing systems. About 60 percent of the automated systems receive human augmentation or 

backup to enhance the data provided by the automated system.

Two major types of automated observing 

systems are deployed today: the 

Automated Surface Observing System 

(ASOS) (http://www.nws.noaa.gov/asos/) 

and the Automated Weather Observing 

System (AWOS). The sensor 

performance standards for both systems 

are identical, although the systems have 

varying degrees of difficulty in 

maintaining those standards. NOAA and 

the Federal Aviation Administration 

ASOS Site in Haines, Alaska
U.S. National Report on Systematic Observations, August 2001

3

(FAA) manage these automated civilian surface observation networks through a cooperative 

agreement.

The system’s software algorithms and sensors are from different manufacturers. There are about 

900 ASOS, 400 AWOS, and 650 non-federally owned AWOS comprising the surface-observing 

network. There are another 200 manually derived surface aviation observation stations at airports 

providing full-time 24 hour per day coverage or part time coverage observations. The network 

provides dissemination of data on at least an hourly basis for the following elements: 2-minute 

average wind speeds, sky condition (clouds to 12,000 feet and amount of coverage in octants), 

visibility to 10 statue miles, ambient air temperature, dew point temperature, pressure, and 

present weather (lightning data at a minimum). The ASOS also provides hourly precipitation 

accumulation amounts and a range of present weather elements. Some of the AWOS sites 

provide present weather and precipitation accumulation information. The staffed automated 

systems provide more detailed pressure, precipitation, present weather, and operationally 

significant remarks. While the network is located at airports to support the safe movement of 

aircraft, the data from the automated systems support climatological and meteorological 

applications for forecasts and warnings, modeling, research, and retrospective analysis.

The NWS currently has responsibility for certification of civilian weather observers in the U.S. 

and performs quality assurance routines on observations received through the NWS 

communications systems. The quality assurance of the observations is the responsibility of 

various NOAA groups, including the NWS Weather Forecast Offices (WFO), the National 

Center for Environmental Prediction (NCEP) and NCDC. NWS quality assurance includes 

regular maintenance and repairs by NWS electronics technicians for ASOS. FAA performs 

maintenance on the AWOS. Non-federal AWOS quality assurance is very limited.

The NOAA/NCDC is responsible for archiving the data for the surface observation network. 

NCDC archives the hourly and higher-resolution data from the ASOS stations and observational 

data from the AWOS stations that transmit data into the national communications networks. 

NCDC ensures the metadata received from network locations are made available digitally to 

customers. The NWS currently collects metadata from ASOS locations and relays the data to 

NCDC. NWS and NCDC are collaborating in an effort to modernize the digital reporting of 

metadata and station history files directly from the WFOs to NCDC. NWS is working to ensure 

metadata complies with national Federal Geographic Data Committee (FGDC) standards.

The surface observing network of 315 stations (formerly called First Order, or A stations, by the 

NWS) now possess ASOS. All of the stations have 30-year climate records, and approximately 

two-thirds of them contain some climatic elements extending back more than 50 years. Those 

stations have undergone minor relocations and several major equipment changes during the life 

of the stations. Documentation accompanies all of the equipment changes, and data continuity 

studies have been conducted to determine the effect of these changes on the temperature record. 

The results of those studies are also included in the station documentation. One of the data 

quality issues identified after the introduction of ASOS was in the area of precipitation 

measurement. The ASOS precipitation gauge routinely under-reports accumulations during 

freezing/frozen precipitation events. Initiatives are underway to deploy an all-weather 

precipitation gauge for the ASOS. Inadequate cloud cover measurements also impact the 

accuracy of ASOS records. The ASOS ceilometer reports only to 12,000 feet and in an automated 

mode reports clear skies if no clouds are reported below 12,000 feet. The NWS is working to 
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4

improve the sensor and algorithm performance of the ASOS. In the next few years, the following 

sensor improvements for the ASOS are planned: an all-weather precipitation gauge, an improved 

dewpoint sensor, an ice-free wind sensor, an enhanced precipitation identifier, and a new central 

processing unit necessary to accommodate the sensor enhancements.

There will be continuing activities to field automated observing systems by the federal 

government, private industry, and local governments. The proliferation of these systems presents 

problems in the future for management and quality control. As the requests for access to the 

systems increase, the connectivity to national communication systems will increase. 

The NWS has developed a climatic elements observation network comprising the 121 WFOs 

within the NWS to supplement the surface observing network. This network provides six hourly 

supplementary climatological data reports of the following elements: total cloud cover and 

synoptic cloud types, snowfall, water equivalency of snow on the ground, depth of snow on the 

ground, duration of sunshine (limited number of locations), six hourly precipitation accumulation 

amounts, and precipitation types and intensities. This is a new network located at newly built 

WFOs. As more experience with ASOS climate records is obtained, the quality and reliability of 

the data should increase with time, and long-term climatological records will begin to be 

established at these sites.

2. Cooperative Observing Network

The Cooperative Observing Network (Coop Network) is a nationwide weather and climatemonitoring network (http://www.nws.noaa.gov/om/coop/index.htm) that observes and reports 

weather information on a regular basis. It is an important component of the NWS data collection 

process and is vital to the national observing capability for monitoring temperature, precipitation, 

snowfall, and other significant weather events across the U.S.

The network was initially established at the end of the 19th century to serve agricultural needs, 

but due to the expansion of data applications over the past decades, the network data are now 

used across many disciplines ranging from management of water resources, and design and 

maintenance of infrastructure to predictions of crop yield and local weather forecasting. The data 

provided through this network are used for a myriad of important political and economic 

decisions by both government and the private sector. Because of its stability over time and the 

geographic density of its observations, the network is particularly well suited for monitoring and 

detecting local, regional, and nationwide climate variations and changes.

The Coop Network consists of thousands of volunteer citizens and institutions. Participants are 

provided with a set of simple weather instruments and observing instructions by the NWS, which 

manages the network under the Cooperative Observer Program (Coop Program). The observers 

provide basic weather data for their locations, usually on a daily basis. Within the Coop Network 

there are several types of stations. At the heart of the network are about 5,000 full 

“climatological” stations that measure daily maximum and minimum temperature, precipitation, 

snowfall, and temperature and snow depth. Many observers provide supplemental information, 

such as time of day when precipitation fell and other weather conditions, such as fog, freezing 

rain, thunder, hail, and damaging winds. These stations are called A stations by the NWS.

Over time, other types of stations have been added to the network. The Bureau of Reclamation 

and the U.S. Army Corps of Engineers (USCOE), which designs, builds, and operates many 
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5

major water storage, river navigation, and flood control projects requires hydrologic data. As a 

result, a large number of “hydrologic” stations (also known as B stations) were added to the 

Coop Network, mostly during the 1940’s and 1950’s, many of which report only precipitation 

and/or river stages. Some stations are equipped with rain gauges to collect and record 

information on the intensity and duration of precipitation. The Coop Network also includes a 

small number of AC stations, which serve a variety of special purposes, such as research on, and 

forecasts of, frost in fruit growing areas and measurements of precipitation in remote areas. The 

total number of cooperative observer stations managed and maintained by the NWS is around 

11,700. Of these stations, over 3,000 have been operational for 30 years or more. Currently the 

Coop Network is not participating in the GCOS Network due to the nature of the observation 

processes described. The U.S. has developed a list of recommended sites that will join the GCOS 

Network following station upgrades. These sites were identified for their length of service and 

quality of data. A Climate Reference Network (CRN) of 250 stations is being developed to aid in 

this area.

3. Observing Equipment

With a few exceptions, the instruments used by the cooperative observers have not changed 

significantly over the past century. Snowfall and snow depth are measured manually with rulers 

or stakes. Liquid precipitation is measured with two types of rain gauges:

• Non-recording gauges are standard 8-inch rain gauges that require the observer to go 

outside, take a visual measurement (using a dipstick) of the water level in the magnifier 

tube, and record the information on a paper form. About 90 percent of the stations that 

report precipitation use non-recording gauges.

• Recording gauges can be one of two types: the Belfort Fischer-Porter type or the Belfort 

Universal type. Recording gauges automatically weigh and record precipitation, using 

either a paper punch tape or paper analog chart. The Belfort Fischer-Porter gauges 

represent 1960’s technology.

Two basic types of instruments are used to measure temperature:

• Liquid-in-glass maximum/minimum thermometers require the observer to go outside to 

the radiation shelter (know as the cotton region shelter) that houses the thermometers, 

manually read the thermometer, record the observation on the appropriate paper form, and 

reset the thermometer. This type of thermometer is used at about 40 percent of the nearly 

5,000 AA stations.

• Maximum-minimum temperature systems (MMTS) consist of electric thermistors in 

pole-mounted plastic radiation shelters and remote display units inside the observer’s 

home or workplace. MMTSs are powered by observer-provided electricity. Observations 

are recorded manually on paper.

Many observers at hydrological stations phone in their observations shortly after taking daily 

readings. Transmission of daily observations is mainly by voice. Observers at climatological 

stations make and record observations of significant weather events, which are recorded 

manually on official forms but are not routinely included in daily transmissions.
U.S. National Report on Systematic Observations, August 2001

6

4. Data Assimilation and Quality Control

NCDC has the primary responsibility for processing and interpreting coop data and disseminating 

it to users. NCDC typically receives the data forms and paper tapes from NWS forecast offices 

two to four weeks after the end of the calendar month. Because these forms are sent by mail from 

121 NWS forecast offices, NCDC does not receive them all at the same time. After varying 

amounts of review and preliminary quality control, NCDC prepares the forms and paper tapes for 

entry into an electronic database. More intensive quality control of the Coop data is performed 

after keying. Once all data have undergone full quality control processing, NCDC prepares 

various data products.

5. Metadata

The NWS has been modernizing the Coop Network metadata support, upgrading from the 

traditional and laborious process of entering data manually on complicated forms. The recently 

completed support software will provide much-improved access and quality control of the data. 

Many field offices have been equipped with hand-held global positioning system (GPS) receivers 

and digital cameras, important improvements to the management and oversight of the Coop 

Network.

6. Observation Problems

Time shifting – Monthly average temperatures in the U.S. are calculated using daily maximum 

and minimum temperatures for climatological purposes. The preferred measurement period is 

midnight-to-midnight. However, because readings by human observers at midnight are not 

feasible for a “volunteer” network, the vast majority of cooperative observers operate on a 

“climatological day” that does not correspond to the standard midnight-to-midnight calendar day. 

Since the end of the observation day varies from station to station, a non-climate time-ofobservation bias is introduced into the calculated mean temperatures. Therefore, when a station 

changes its time of observation, an “apparent” climate change is introduced into the data set. 

Random changes have been made in the preferred observation time. For personal convenience, 

observers sometimes switch from a sunset-to-sunrise climatological day to a sunrise-to-sunrise 

schedule or the reverse. 

Date shifting – A related problem is “date shifting,” the practice of entering data for a date other 

than when the observation was made, or combining daily totals. Some cooperative observers do 

not measure precipitation during the weekend. Instead, they include weekend precipitation in 

their Monday observation. This problem is difficult to identify because the monthly totals are 

consistent with those of nearby stations. Date shifting skews daily totals and can influence 

statistics on extreme events.

Missing observations – Another problem is dropped or missing observations. Sometimes 

observers get sick, take vacations, leave home for a weekend or longer, use improperly trained 

substitutes, forget to take an observation, record observations illegibly, or are too busy to take 

observations. Problems also occur frequently at institutional sites. Although these sites have 

around-the-clock staffing, their observers often have high turnover rates, and because of 

inadequate training, motivation, or management, they may not be dedicated to taking consistent 

observations.
U.S. National Report on Systematic Observations, August 2001

7

7. Cooperative Network of the Future

The Coop Network will continue to rely on volunteer observers and will incorporate strategic 

upgrades that are feasible with current technology. The growing demand for accurate and timely 

cooperative data will determine the requirements for the modernization. In the design process the 

following questions are being considered: How many sites will be required? What other 

networks, if any should be incorporated? What variables should be measured? Which 

components should be automated? How often should data be sampled? How rapidly should data 

be made available to users? What tradeoffs of costs against quality and performance should be 

made? On what schedule should system design or redesign be implemented?

In addition to the 250-station CRN, NOAA proposes to embark on a coop modernization

initiative for the larger population of cooperative stations beginning in the 2002 time frame. In 

preparation for this modernization and restructuring, the NWS has contracted for a spatial density 

study to determine an appropriate size for the Coop Network.

8. Climate Reference Network

The CRN (http://www.ncdc.noaa.gov/ol/climate/research/crn/index.html) will provide the nation 

a benchmark climate reference network and fulfill the nation=s need for long-term high quality 

climate observations and records with minimal time-dependent biases affecting the interpretation 

of decadal to centennial climate variability and change. The full network will be limited to about 

250 geographic locations (500 paired instrument suites, a primary site and a backup site) 

strategically selected to capture the representative climate regions of the nation. The number of 

quality observing instruments is limited and focused on a few climate significant parameters, 

specifically air temperature, precipitation, and humidity.

The primary goal of the CRN is to provide future long-term (50-100 years) high quality 

homogeneous observations of surface air temperature and precipitation that can be coupled to 

past long-term observations for the detection and attribution of present and future climate 

change. Fifty years from now the CRN will provide the requisite level of long-term high quality 

data that will, with the highest degree of confidence possible, support the answer to the question: 

How has the U.S. climate varied and changed over the past 50 years?

The U.S. CRN program complements the Coop Network and many 

other existing and proposed observing networks operated by NOAA and 

other federal, state, and local agencies, as well as private industry. The 

CRN Program has initiated contact with many other agencies (e.g., 

Drought Monitoring Program, USGS, USDA, USCOE, USGS, BLM, 

NWS, OFCM, DoD, DOE, and State networks) in coordinating 

additional “instruments of opportunity” and site selection to make an 

“optimal fit” with other network sites. There is a strong commitment to 

direct participation and involvement by the Regional Climate Centers 

(RCC) and State Climatologists (SC). Universities have already 

contacted the program and expressed interest in hosting CRN 

instrument sites and participating in related climate research activities.
U.S. National Report on Systematic Observations, August 2001

8

C. Upper Air Network

The U.S. and other World Meteorological Organization (WMO) member countries maintain and 

manage an agreed-to network of observing locations that cumulatively form part of the Global 

Observing System of the World Weather Watch network. The synoptic rawinsonde observing 

programs of the U.S. and the other WMO member countries are designed to meet real-time 

operational needs for weather analysis and forecasting. These observations also provide a 

national and international data base of upper air observations for research and climatological 

purposes. From the standpoint of the 10 climate monitoring principles, the upper air network is 

probably adequate in only one respect: integrated environmental assessment.

1. Operations

The NOAA NWS, as the primary provider of upper air data for national and international data 

exchange, operates or supports the operation of a network of upper air weather observing stations 

in the contiguous U.S., Alaska, the Pacific Islands, and the Caribbean. At each station, a balloonborne instrument called a radiosonde is sent aloft twice daily, at 0000 hours Universal 

Coordinated Time (UTC) and 1200 hours UTC, to measure atmospheric profiles of the 

temperature, moisture, pressure, and winds. The U.S. network of stations contributes more than 

ten percent of the global rawinsonde network. The primary responsibility for maintaining this 

network rests with the NWS. The network is augmented by observations made at military, 

National Aeronautics and Space Administration (NASA), DOE, and other installations. The 

NWS operated and supported network consists of 102 sites (Table S3). Ten of these sites in the 

Caribbean comprise the Cooperative Hurricane Upper Air Stations network. These sites are 

supported by the NWS through bi-lateral agreements with other nations.

The primary atmospheric variables collected from each rawinsonde location are pressure, 

temperature, relative humidity, wind speed, and wind direction. These variables are collected 

from surface to as high as 35 km and ranges out to 250 km from launch site to burst site.

2. Data Quality Assurance

Data quality assurance is carried out at several levels. At the station, the operator responds to data 

messages on data that are computer flagged. Data profiles are also reviewed and necessary 

editing accomplished before message generation and transmission over the GTS. NCEP performs 

the next level of quality control during the data ingest process and in comparisons with first 

guess fields. Data that are inconsistent with surrounding stations and/or the first guess field may 

be rejected. Data rejections can entail individual thermodynamic elements or wind elements in a 

sounding, for part or all of a sounding. Climatological data archives in a designated format are 

provided to NCDC. NCDC performs data quality checks on the climatic data set. Each archive 

data file has metadata information for the sounding, including location, time, date, latitude, 

longitude, radiosonde type, and balloon type. Data quality checks are adequate at the station level 

but could be improved through automation and the use of artificial intelligence.

3. Metadata

NCDC maintains extensive files of digital metadata, including station history information. The 

NWS archive data submitted monthly to NCDC have metadata information as a part of each data 

record. NWS supports the WMO with updates to the WMO Catalogue of Radiosondes and 
U.S. National Report on Systematic Observations, August 2001

9

Upper-Air Wind-Finding Systems in use for each site in the network. These data are also 

supplied to the national meteorological centers in the U.S., as well as to various international 

meteorological centers. NWS maintains current metadata on all stations.

4. Network Stability

The total number of stations in the NWS radiosonde network in the contiguous U.S. has 

remained relatively constant since the mid-1960’s. However, from 1988 to 2000, 35 upper air 

sites were relocated as a part of the NWS modernization. In the late 1980’s, the NWS changed 

from a single provider of radiosondes with a given sensor pack to multiple providers using 

different sensor packs. These changes have created discontinuities in the climatological records 

at sites employing different radiosondes.

5. Network Changes 2000 to 2005

Changes are not anticipated in the number of reporting stations by 2005. However, studies have 

been conducted with an eye toward reducing the radiosonde network and using aircraft 

measurements in areas where high volume aircraft traffic with sensor suites can enable provision 

of ascent, enroute, and descent temperature and relative humidity values. Over the period 2002 

through 2005, the existing radiosonde network is scheduled for replacement with a new 1680 

MHz-based ground system and the implementation of GPS radiosondes at all sites. The current 

vendors for the radiosondes will introduce new sensors that will in turn introduce data continuity 

issues.

6. Network History

The inability of kite and aircraft meteorographs to achieve high altitudes, operate in all weather, 

and provide data in real-time helped foster the development for the radio transmission of upper 

air data. In the late 1920’s, scientists from many nations began suspending crude radio 

transmitters from free balloons and by the early 1930’s the first radio-meteorographs or 

“radiosondes” were being flown. In 1937, the U.S. Weather Bureau established a domestic 

network of radiosonde stations that has continued to the present day.

World War II increased the need for upper air data and accelerated the development of 

radiosonde components and the growth of observational networks. Furthermore, advances were 

made in radio-direction finding or radio-theodolite technology that allowed the radiosonde to be 

tracked in flight so winds aloft could be obtained. Such observations became known as 

“rawinsonde” observations. Initially, radio-theodolites were adjusted by hand to track the 

in-flight radiosonde, but by the 1950’s automated radiotheodolites (ART) were implemented, 

which are still used today. The early rawinsonde stations lacked computerized data processing 

systems, which resulted in a significant amount of manual labor and time needed to process and 

disseminate the upper air data. The observation process was generally a two-person effort. 

However, a third person was frequently involved for quality control, general oversight of 

procedures, and assistance during periods of difficult weather, ground system, or data analysis 

conditions.
U.S. National Report on Systematic Observations, August 2001

10

A chronology of major observing/sensor changes in the U.S. rawinsonde network from 1943 to 

1960 follows:

1943 Lithium chloride humidity element replaced hair hygrometer.

1943 Ceramic temperature element, operating on resistance principle, replaced glass 

tubes with electrolytic temperature elements.

1948 Began computing all relative humidity using saturation values with respect to 

water. Prior computations involved saturation with respect to ice for temperature 

below freezing.

1949 Smaller ceramic temperature element introduced to decrease instrument response 

time.

1950 Introduced correction to temperature data between 400 and 10 hPa for daytime 

soundings whenever solar elevation angle was equal to or greater than -2.5 

degrees. Such corrections, which adjusted for radiation effects on the instrument, 

were discontinued with the introduction of white thermistors.

1957 Observation time changed from 0300 and 1500 UTC to 0000 and 1200 UTC.

1960 Introduced white-coated temperature elements.

To ease the workload required for taking a rawinsonde sounding, development of computerized 

reduction of rawinsonde data began during the late 1960’s and early 1970’s. By the 1980’s, 

technological advances in telemetry and computers made rawinsonde observations more 

automated. This significantly reduced manual involvement in taking rawinsonde observations. In 

the mid-1980’s the NWS made significant progress in automation. Through the use of station 

mini-computers and interfaces to automatically acquire flight data, data computations, coded 

message generation, and data transfer and storage functions could all be performed with minimal 

human intervention. The rawinsonde observation had become a one-person operation, with the 

time required for processing data reduced to less than one staff hour with improved data quality.

Parallel with the advances in computerized data processing came new techniques for determining 

winds aloft. Rawinsonde systems were developed to take advantage of radio-navigation aids 

(NAVAID) such as LORAN and Omega (note: Omega was discontinued in October 1997). 

NAVAID radiosondes contain electronics that receive radio signals from fixed, ground-based 

transmitter stations. The radiosonde then either retransmits the received signal to the ground 

subsystem or processes the received signals into velocity or position information and then 

transmits. Winds aloft are contained in or derived from this information. A chronology of major 

observing/sensor changes in the U.S. Rawinsonde Network for the period 1960 through 1986 is 

outlined below:

1960 Outrigger thermistor designed and implemented.
U.S. National Report on Systematic Observations, August 2001

11

1965 Introduced carbon element relative humidity sensor. Began reporting low relative 

humidity (RH) measurements. Earlier practice with the lithium chloride sensor 

was not to report low values.

1969 Changed from completely manual system to a time-share computer system for 

calculating upper air data.

1972 Redesigned carbon hygristor ducts introduced to reduce insolation effects on 

instruments that were responsible for low biases in RH measurements for some 

daytime soundings.

1973 Introduced the current practice of considering measuring RH less than 20 percent 

and reporting all lower RH values as 19 percent.

1974 Introduced semi-automatic minicomputer-based system.

1980 New carbon hygristors introduced. RH transfer equation changed for the new 

sensor.

1985 Introduced fully automatic minicomputer-based system.

1986 GMD-5 System built by Space Data Division (SDD) introduced at five synoptic 

Air Force stations. The radiosonde was also changed to one built by SDD similar 

to the MSS radiosonde, which did not employ a pressure sensor to acquire 

pressure/heights but instead utilized a transponder.

In the 1990’s, rawinsonde technology development continued through improved radiosonde 

sensors, data processing, and NAVAID systems. A primary advancement was the development of 

rawinsonde systems that use the GPS to determine winds aloft. Like other NAVAID systems, 

GPS radiosondes are equipped with a GPS receiver and associated electronics that transmit the 

GPS position information to the ground receiver from which winds are derived. NWS began the 

effort to replace the current ART ground systems and associated radiosondes with GPS-based 

systems.

Other advances in upper air observing technology included the development of operational 

remote observing systems such as wind profilers and the placement of temperature and water 

vapor sensors on commercial jet aircraft. Compared to rawinsondes, these systems are capable of 

providing more frequent upper air data, but with reduced vertical coverage and data resolution.

A chronology of major observing/sensor changes for 1988 through 1999 is outlined below:

1988-1989 MRS installed on 42 Navy ships and at six synoptic stations supported by 

the Navy. All use the Vaisala RS80 radiosonde.

1988-1990 SDD radiosonde introduced at 17 sites in the southwest U.S. and in 

Alaska. VIZ Type-B radiosonde introduced at remaining NWS supported 
U.S. National Report on Systematic Observations, August 2001

12

sites. Last use of VIZ Type-A radiosonde which had been in use for 30 or 

more years.

1989-1990 MicroART system phased into network replacing the MiniART System. 

Algorithms and level selection methods were not changed in this system 

during the phase over to minimize problems with data continuity.

1989 First use of transponders to compute winds in NWS network in 12 years.

1990 Software modified to include the 925 hPa mandatory level per WMO 

request. Additional modifications pursued to eliminate relative humidity 

20 percent, temperature -40 degree Celsius cutoffs, and changing the 

gravity constant per WMO recommendation.

1994-1995 SDD radiosondes phased out and replaced by Vaisala RS80-56H 

radiosondes at 17 sites in the southwest U.S. and in Alaska.

1997 On June 1, the NWS switched from the VIZ-B to the VIZ-B2 radiosonde 

at 57 upper air sites, in the conterminous U.S.

1998 On June 1, 1998, the NWS began use of the Vaisala RS80-57H radiosonde 

at 35 upper air stations. Use of VIZ radiosondes at these sites will be 

discontinued. Radiation corrections are applied to Vaisala temperature at 

the field site. The NWS uses the Vaisala radiation correction algorithm 

RSN93 for applying these corrections. The policy of not correcting data 

transmitted from the remaining VIZ radiosonde upper air sites will 

continue.

1999 On Microcomputer Automatic Radiotheodolite (MicroART) system 

software upgrades implemented at all upper air stations February 1. 

Features included:

• Automated addition of a WMO 41414 cloud data group to the upper 

air coded message.

• Allow for the recording of radiosonde temperatures colder than -90OC.

• NWS upper air stations using the Sippican, Incorporated VIZ-B2 

radiosonde implemented additional coefficients in the RH algorithm. 

NWS-supported stations in the Caribbean using this radiosonde also 

implemented these coefficients. The new coefficients improve the 

accuracy of RH measurements at high and low RH. Starting about 

October 15, 1999, NWS stations using the VIZ-B2 radiosonde began 

phasing over to radiosondes with the new coefficients. This activity 

was completed by December 1, 1999. 
U.S. National Report on Systematic Observations, August 2001

13

7. Other Upper Air Observation Systems

a. Next Generation Doppler Weather Radar (NEXRAD)

A U.S. national network of 158 NEXRADs (also known as the WSR-88D) 

provides essential information on the existence, location, and intensity of 

severe weather and precipitation (http://weather.noaa.gov/radar/national.html). 

NEXRAD makes conventional reflectivity observations and uses the “Doppler 

effect” to measure the motion of clear air and atmospheric phenomena within 

storms. The maximum range of NEXRAD is 230 km (125 nautical miles). 

Although NEXRAD is land-based, there is some radar coverage offshore, and 

the greatest offshore coverage is along the U.S. Atlantic and Gulf coasts. Doppler technology 

permits observation of the motion field of the air inside and around clouds. When sufficient 

reflectivity exists, the Doppler capability of the NEXRAD can be used to generate radial wind 

estimates at a limited number of altitudes within the atmospheric boundary layer. While these 

observations are limited to certain meteorological situations, they can, nonetheless enhance the 

composite wind set available for numerical weather processing over the continental U.S. 

However, there are potentially many other climate-related uses for NEXRAD data that involve 

more extensive study of precipitating weather systems and cloud-precipitation processes.

b. Tropospheric Wind Profilers

The NOAA Profiler Network (http://www-dd.fsl.noaa.gov/) is 

fully deployed at 31 locations throughout the central U.S. It 

provides hourly vertical profiles of the horizontal winds from 

.5 km to 16.4 km above ground level. Wind profilers are 

specifically designed to measure vertical profiles of horizontal 

wind speed and direction from near the surface to above the tropopause. The quality and value of 

these observations have been assessed and found to be important for a variety of meteorological 

uses. Radio-Acoustic Sounding Systems (RASS) operate with wind profilers at a dozen 

locations. These systems measure virtual temperature profiles in the lower atmosphere to about 

12,000 feet.

c. Global Positioning System Integrated Precipitable Water (GPS-IPW)

GPS satellite radio signals are slowed as they pass through layers of the 

Earth’s atmosphere, the ionosphere, and the neutral atmosphere. This 

slowing delays the arrival time of the transmitted signal from that 

expected if there were no intervening media. It is possible to correct for 

the ionospheric delay, which is frequency dependent, by using dualfrequency GPS receivers. The delays due to the neutral atmosphere, 

however, are not frequency dependent. They depend on the constituents of 

the atmosphere, which are a mixture of dry gasses and water vapor.

The purpose of NOAA’s ground-based GPS-IPW project is to: (1) evaluate the engineering and 

scientific bases of surface-based GPS meteorology; (2) demonstrate the feasibility and utility of 

using surface-based GPS observations for improved weather forecasting, climate monitoring, and 

satellite sensor calibration/validation; and (3) transfer this observing system technology to 

operational use. The GPS-IPW demonstration network (http://oak.fsl.noaa.gov/gps.html) 
U.S. National Report on Systematic Observations, August 2001

14

currently consists of 72 sites, grouped into three categories: NOAA wind profilers (35 sites), 

other NOAA sites (9 sites), and other agency sites (28 sites). Water vapor is one of the most 

significant constituents of the atmosphere since it is the means by which moisture and latent heat 

are transported to cause weather. Water vapor is also a greenhouse gas that plays a critical role in 

the global climate system. This role is not restricted to absorbing and radiating energy from the 

sun, but also includes the effect it has on the formation of clouds and aerosols, and the chemistry 

of the lower atmosphere. Despite its importance to atmospheric processes over a wide range of 

spatial and temporal scales, water vapor is one of the least understood and most poorly described 

components of the Earth’s atmosphere.

d. Automated Aircraft Reporting Systems

A growing number of wind and temperature measurements from commercial aircraft are made 

available by several air carriers through the Aircraft Communications, Addressing and Reporting 

System (ACARS). These are provided, on a volunteer basis, to the Aircraft-to Satellite Data 

Relay (ASDAR). Currently, just over 50,000 observations are received each day, 46,000 of which 

are over the continental U.S. (http://acweb.fsl.noaa.gov/demo_java/). These data come from 

more than 500 aircraft. There are more data during the daytime than at night, but due to increased 

participation by some parcel-carrying airlines, nighttime coverage is substantial. For instance, 

over 16,000 observations are received between 0500 and 1400 hours UTC. About 20 ASDARequipped aircraft are operating globally, taking hundreds of en route observations per day.

D. Atmospheric Constituent Networks

1. Atmospheric Baseline Measurement Network

NOAA’s CMDL monitors a broad range of atmospheric constituents capable of forcing change 

in the climate of the earth through modification of the atmospheric radiative environment and 

those that may cause depletion of the global ozone layer. Measurements are conducted in 20 

states and 37 countries at facilities ranging from four manned, continuously operating CMDL 

Baseline Observatories (Barrow, Alaska; Mauna Loa, Hawaii; American Samoa; and South Pole) 

to a weekly collection of air samples in flasks at remote surface locations around the world (see 

map on Page 26). At the baseline observatories up to 250 different measurements (continuous-toweekly) may be conducted. These include trace gas concentrations of carbon cycle and 

chlorofluorocarbon (CFC) species, aerosol physical and optical properties, ozone concentrations 

and profiles, solar radiation parameters, and meteorology. Mauna Loa Observatory is a Network 

for the Detection of Stratospheric Change (NDSC) site with a wide range of remote sensing 

instruments monitoring the status of the stratospheric ozone layer.

Continuous records of CO2 concentrations from Mauna Loa and South Pole dating from 1957, 

and continuous solar radiation at Mauna Loa beginning in 1957, are available. Other continuous 

records start in the 1960’s, and the Barrow and Samoa records date from the establishment of 

these stations in 1973. CMDL maintains the world standard for Dobson total column ozone 

measurements and the WMO standards for CO2 and CO atmospheric trace gas measurements. 

CMDL prepares primary gas standards for CFC gas measurements and provides these to other 

global measurement programs. The radiation group of CMDL maintains the WMO Region Four 

solar beam reference standard. All other basic CMDL baseline measurements are traceable to 
U.S. National Report on Systematic Observations, August 2001

15

primary or secondary standards. All regular CMDL data are available either through the CMDL 

home page http://www.cmdl.noaa.gov/ and/or at the relevant World Data Centers for the species 

of interest.

It is expected all the CMDL sampling programs and sites will be in operation for the next five 

years and the following list of planned expansions to the network will be implemented:

1. A baseline station on the West Coast of the U.S. to monitor the trans-Pacific flux of air 

pollution from Asia

2. UV radiation monitoring station in eastern Russia

3. Two new flask and aircraft profile monitoring sites in equatorial Africa

4. Three additional aircraft profile monitoring sites in the U.S.

5. Expanded shipborne atmospheric measurements off the east coast of Asia

2. Atmospheric Coordinated Observations and Research Network (ACORN)

NOAA’s Air Resources Laboratory (ARL) is a long-time leading advocate of the principles of 

coordinated observations and research. This research philosophy is known by some as “integrated 

monitoring.” ACORN represents a new approach to environmental research and prediction, in 

which measurements are not limited to tracking changes in the characteristics of some 

environmental systems, but are also matched with the requirements for specifically designed 

scientific studies of factors that lead to more sound explanations of the causes of those changes. 

From the aspect of climate and weather forecasting research, its objective is to improve forecasts 

by advancing our knowledge of the surface/atmospheric energy input and dissipation processes in 

the models. Coordinated observations and research implies a more focused coupling of 

measurements with theory to enhance the analysis and prediction research efforts being 

conducted by NOAA in compliance with its Strategic Plan. This in turn requires an effort to 

further utilize NOAA’s long-term observing programs along the lines of a traditional scientific 

approach. It is through coordinated sets of observations, coupled with analytical investigations of 

cause-and-effect, that understanding can be improved at a more rapid pace, ultimately leading to 

more accurate prediction of future changes. The observations reveal the details of the true 

behavior of atmospheric phenomena and also provide for research on a continuous or nearly 

continuous basis, involving both NOAA’s surface networks and satellites. The suite of NOAA 

observations constitutes a complementary subset of other national observational programs, such 

as those led by NASA, National Science Foundation (NSF), USDA, and DOE. However, the 

ARL surface networks are unique in that they cover much of the U.S. and obtain continuous data. 

It is the analysis and prediction aspects of the ACORN approach that constitute the heart of 

ongoing research. It is this aspect that differentiates ACORN from classical monitoring of status 

and trends.

Over the last two decades, ARL has organized a number of collaborative and interconnected 

monitoring networks, which together constitute an organized measurement and analysis approach 

to predict future changes in the coupling of the atmosphere-terrestrial biosphere system. This 

assembly of networks and research makes up the ACORN integrated monitoring network.

The components of ACORN start with the Integrated Surface Irradiance Study B (ISIS B) and 

end with the Atmospheric Integrated Research Monitoring Network (AIRMoN B). There are 

several sub-components of these arrays, such as (the ISIS level 2) the SURface RADiation 
U.S. National Report on Systematic Observations, August 2001

16

network (SURFRAD B), but together the ARL monitoring system constitutes the nation’s only 

truly integrated measurement system for permanent recording of past changes in the atmosphereterrestrial system and for extrapolating the future trends. NOAA’s satellite observations supply 

broader spatial coverage from the top of the atmosphere, but with less fine detail than the surface 

measurements. The two systems are complementary, each filling in scientific information voids 

where the other cannot.

The theme underlying ARL’s network operations is the coupling of the earth’s surface and the 

atmosphere. The magnitude and process of this coupling are quantified in terms of fluxes–rates 

of exchange of specific quantities such as heat, water, and various trace quantities like CO2 and 

air pollutants. The driving force of the earth as a dynamic, life-supporting planet is radiation 

received from the sun. ARL’s network operations therefore start with measurements of solar 

radiation received at the earth’s surface.

There are four fundamental reasons the ACORN array is constructed in its present form. First, a 

basic tenet of integrated observing concepts is not all stations need to make every measurement 

with the sampling protocols necessary for every purpose. To do so would be prohibitively 

expensive. Therefore, ISIS (and all ARL network operations) is constructed as a nested network, 

with some stations using more advanced systems than others, but with a common set of 

fundamental observations shared by all. Second, the next generation of prognostic models will 

require observational data on the surface fluxes of heat, moisture, and momentum to benchmark 

the air-surface exchange formulations on which they rely and to serve as a basis for diagnosing 

model performance related to precipitation, evaporation, humidity, etc. Third, ARL scientists 

concur whole-heartedly with the current belief that satellites offer promise yet to be fully 

realized, but further believe in order to extend satellite observations, ground truth is critical. This 

attitude comes from direct experience with the use of ground-based observations to verify 

satellite observations of surface shortwave and ultraviolet (UV) irradiance, and just as 

importantly, the development of inversion algorithms to retrieve information on atmospheric 

properties. Moreover, the World Climate Research Program, in recognition of the importance of 

surface radiation for atmospheric research, has strongly emphasized the need for long term 

surface irradiance observations to validate satellite determinations of these quantities. ISIS and 

SURFRAD in particular offer a unique set of surface radiation observations for checking the 

calibrations and performance characteristics of satellite sensors. Fourth, and in some contexts 

most important, ARL endorses strongly the need for long-term observations at the surface where 

people and other living organisms are actually affected by the environmental characteristics of 

climate and are impacted by its change. Attributing changes in any property to greenhouse effects 

or to other climate change forcing factors requires candid examination of the roles of other 

influences. This necessarily mandates concurrent measurement of other variables, as is inherent 

in the overall philosophy of coordinated observations and research to which the ARL mission 

ascribes.

3. Integrated Surface Irradiance Study Network (Level 1)

The ISIS measures the incoming radiation from the sun, with emphasis on the direct beam, the 

radiation scattered and absorbed by the atmosphere and its constituents, and the components of 

radiation especially harmful to living organisms. ISIS therefore measures direct and global 

shortwave surface radiation, plus surface UV radiation in the biologically important broad 
U.S. National Report on Systematic Observations, August 2001

17

wavelength band. The issues being addressed by ISIS relate to the solar radiation incident at the 

surface, for purposes such as the detection of changes in cloud cover, trends in atmospheric 

turbidity, and assessment of the change in UV radiation (which affects all exposed living 

organisms).

There are currently nine stations throughout the continental U.S. providing 15-minute data on 

one-second scans. The ISIS sites were established from March 1994 to August 1996 and are all 

expected to operate through 2005. A detailed description of ISIS and access to processed data 

from the ISIS Level 1 network can be found at http://www.atdd.noaa.gov/isis/isis_frame.htp. 

Hourly average data from all Level 1 sites are transmitted routinely to NCDC for archival, from 

where they are further submitted to the World Radiation Data Center in St. Petersburg, Russia. 

Quality assurance procedures are fully adequate with calibrations traceable to World Radiation 

Standards. Metadata are currently not available digitally; however, paper record conversion is 

currently underway. The UV components of this data set are routinely employed by NWS to 

benchmark the forecasts of UV Index, now operational.

The UV component of ISIS deserves special mention. Surface UV radiation remains difficult to 

measure. As a contribution to the national multi-agency UV monitoring program, ARL operates, 

as a collaborative venture with the National Institute of Standards and Technology (NIST), the 

national Central UV Calibration Facility. ARL also co-chairs (with NASA) the task team 

organized by the U.S. Global Change Research Program to coordinate the national UV 

measurement program.

ISIS is a limited refurbishment of nine SOLRAD Network stations with emphasis on data 

retrieval (data loggers) and timely QA/QC processing to provide high quality data. Some of the 

ISIS sites were relocated to coincide with the NWS modernization (moved from airport sites). 

Only the UVB sensors were added to the SOLRAD components. Sites with significant moves 

when relocated were in TN (~128 mi.), CA (~35 mi.), WA (~18 mi.), and WI (~7 mi.) with all 

other moves < 1 mi.

4. Surface Radiation Network (Level 2)

The motions of the lower atmosphere are largely governed by the rate of heat input at the surface. 

To obtain the necessary information and to help generate the understanding to interpret the 

relevant data, ARL operates a smaller subnetwork of ISIS where measurements are made of 

upwelling longwave and shortwave components of surface radiation as well as downwelling. 

From this perspective, the emission of thermal radiation (infrared) from the surface must be 

accounted for to obtain a complete measure of the radiant energy heating and cooling process. 

Therefore, this SURFRAD network; (see http://www.srrb.noaa.gov/surfrad/surfpage.htm) 

includes measurements of infrared radiation to the surface radiative flux suite. Since cloud cover 

is a crucial consideration, steps are currently being taken to augment SURFRAD stations with 

automated all-sky cloud cover sensors.

SURFRAD was established in 1993. Its primary objective is to support global change and related 

research with continuous measurements of the surface radiation budget, which includes upwardand downward-directed longwave and shortwave radiation. Measurements from SURFRAD are 

used for evaluating satellite-based estimates of surface radiation, and hydrologic, climate, and 

weather forecast models, as data for specialized research projects, and to monitor trends in 
U.S. National Report on Systematic Observations, August 2001

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parameters affecting Earth’s climate. Specific variables collected by the network include 

downwelling global, direct, diffuse, and upwelling shortwave irradiance, downwelling and 

upwelling longwave irradiance, broadband UVB and photosynthetically active irradiance, air 

temperature, relative humidity, and wind speed and direction. Total sky images and cloud cover 

fraction are also measured. All radiation and meteorological instruments operate continuously 

and record three-minute averages. The total sky imagers sample the hemispheric sky once each 

minute during the daylight hours.

Six stations make up the SURFRAD network. All six stations measure the variables listed in the 

previous paragraph. The SURFRAD stations are at located near Bondville, IL (40.06°N, 

88.37°W), at the Goodwin Creek Experimental Watershed near Batesville, MS (34.25°N, 

89.87°W), on the Fort Peck Tribes Reservation near Poplar, Montana (48.31°N, 105.10°W), at 

Table Mountain near Boulder, Colorado (40.125°N, 105.237°W), at the Penn State Experimental 

Research Farm near State College, Pennsylvania (40.72°N, 77.93°W), and at Desert Rock, 

Nevada (36.626°N, 116.018°W). The first four stations were installed in 1995 at Bondville, IL, 

Fort Peck, Montana; Goodwin Creek, Mississippi; and Boulder, Colorado. Originally, these first 

four stations did not have the diffuse shortwave measurement, but by the end of 1996, a shaded 

pyranometer was added to the instrument suites. The stations at State College and Desert Rock 

were added in 1998. The total sky imagers were installed at all stations in 1999 and 2000. In 

2000, the downwelling pyrgeometer at each station was moved from the main platform to the 

solar tracker, where its dome could be shaded according to Baseline Surface Radiation Network 

(BSRN) standards. This had a negligible effect on the downwelling infrared measurement record 

because the pyrgeometer has a built-in correction for errors caused by solar heating of the dome.

A seventh station may be added in West Virginia in 2001. From the beginning of the network to 

the present, ordinary thermopile pyranometers (Eppley model PSP) were used for the global, 

diffuse, and upwelling solar measurements. During the annual instrument exchanges in 2001, an 

Eppley model 8-48 pyranometer will replace the PSP for the diffuse solar measurement. This 

change will remove an erroneous negative offset (owing to the measurement surface artificially 

cooling to space) inherent to the Eppley PSP-type pyranometers. This offset may be as high as 10 

Wm-2 at night. Its effect during the day is unknown but is probably smaller in magnitude than the 

nighttime error. This may affect the climate record by showing a slight artificial increase in 

downwelling solar irradiance when the component sum (direct + diffuse) is used for the global 

measurement.

5. Surface Energy Balance Network (Level 3)

ARL is actively establishing a network subset of full energy balance monitoring stations to 

complete the overall scheme of relevant observations. Stations currently operational are at Oak 

Ridge, Tennessee; Bondville, Illinois; and Fort Peck, Montana. Installations at Goodwin Creek, 

Mississippi; and Davis, West Virginia, are being planned.

The data from these stations are being used to test and develop improved mesoscale models, for 

weather forecasting purposes. The next generation of numerical forecast models will necessarily 

involve improved depictions of air-surface exchange, for which this array of surface stations will 

provide the requisite “ground truth.”
U.S. National Report on Systematic Observations, August 2001

19

6. The CO2 Sequestration Network and AmeriFLUX (Level 4)

In addition to the eddy flux components of the surface heat balance, the augmented SURFRAD 

stations also measure fluxes of carbon dioxide. These measurements provide a direct 

quantification of the sequestering of atmospheric CO2 in the terrestrial biosystem, and the water 

exchange data serve similarly in hydrological studies of the water balance of the atmospherebiosphere system. These stations will contribute to the national (“AMERIFLUX”) and 

international (“FLUXNET”) networks now being set up to address the CO2 air-surface exchange 

question on a wide-spread, internationally cooperative basis. FLUXNET and AMERIFLUX 

details are to be found at http://www.atdd.noaa.gov/climate.

7. AIRMoN-dry Network (Level 5)

The ability to measure some of the suite of air-surface exchange variables (radioactive and eddy 

fluxes) leads into one of the more extensive parts of the ARL coordinated observation program, 

the Atmospheric Integrated Research Monitoring Network (see http://www.arl.noaa.gov/ 

research/programs/airmon.html). AIRMoN has been established to develop methodologies for 

monitoring the rates of deposition of air pollutants to natural landscapes. This deposition occurs 

in two forms–dry and wet. Dry deposition is the gravitational settling of particles and the 

turbulent exchange of trace gases (and particles too small to sediment in a turbulent atmosphere). 

Wet deposition is occasioned by precipitation. It entails the scavenging of pollutants by clouds 

and the washout of pollutants by raindrops falling from clouds. AIRMoN-dry is the dry 

deposition part of the overall AIRMoN program, described in detail at 

http://www.atdd.noaa.gov/airmon/airmon_frame.htm.

In AIRMoN-dry, measurements are made of the concentrations of selected pollutants in air, and 

of the atmospheric and surface variables that together control the efficiency associated with the 

turbulent exchange of these pollutants and their capture by the surface. The focus is on sulfur and 

nitrogen species, these being the key chemicals targeted by current U.S. federal regulations.

Methods for measuring dry deposition of airborne pollutants are not yet well developed. 

AIRMoN serves as the network in which new approaches are tested and site-specific 

requirements are addressed. For example, it is currently apparent that deposition in coastal and 

urban areas is an important issue; hence, it is expected that AIRMoN will move in related 

directions with a change in its site distribution. In accord with the driving principles of integrated 

monitoring, sites are selected where the data are most needed.

8. AIRMoN-wet Network (Level 6)

The wet deposition part of the overall AIRMoN program operates as a sub-network of the 

National Atmospheric Deposition Program (NADP; http://nadp.sws.uiuc.edu), the largest 

atmospheric deposition network in North America. In accord with the overall ARL monitoring 

philosophy, AIRMoN-wet is designed as a research sub-network of NADP, using more refined 

sampling protocols and exploring methodologies for accurately monitoring the deposition of 

quantities that NADP’s existing protocols do not address well. A key chemical in this category is 

ammonium. For this reason, AIRMoN-wet stations are predominantly in coastal regions, since 

near the coasts nitrogen deposition is seen as a major issue and AIRMoN-wet best addresses this 
U.S. National Report on Systematic Observations, August 2001

20

issue. A description can be found at http://www.arl.noaa.gov/research/programs/airmonwet.html. Data access is through NADP, via http://nadp.sws.uiuc.edu/airmon/GetAMdata.asp.

Variables collected in the network include precipitation amount, sample volume, calcium 

concentration, magnesium concentration, potassium concentration, sodium concentration, 

ammonium concentration, nitrate concentration, chloride concentration, sulfate concentration, 

pH, and conductivity. Each station in the network collects all of the variables named above. The 

network consists of nine stations, most of which started after 1992, and six of which have at least 

20 years of data. All stations are in the eastern U.S. Observation time is nominally 9 a.m. daily. 

Samples remain on the collector for no more than 24 hours. Current instrumentation at each 

station consists of an Aerochem Metrics 301 collector, Belfort 5-780 weighing rain gauge, NWS 

stick gauge, pH and conductivity meters, ion chromatographs, atomic absorption 

spectrophotometers, and automated colorimetric spectrophotometers. The data are quality 

assured via the Illinois State Water Survey. Digital metadata are available online at 

http://nadp.sws.uiuc.edu.

Some of the stations in the network were originally part of DOE’s Multistate Atmospheric Power 

Production Pollution Study (MAP3S) program, which began in the mid-1970s. NOAA/ARL 

picked up funding for six of the original nine MAP3S stations in 1991 following a two-year 

period of extreme turmoil, and worked with the NADP to provide a research arm to the national 

precipitation chemistry monitoring program. As a result of NOAA’s involvement, sampling 

protocols were changed from event (as defined by the field operator) to 24 hour. In addition, field 

and laboratory quality assurance was improved to mirror the program in place with the weekly 

NADP program. Major changes in communication and instrumentation are pending, to be made 

in accordance with budgets and decisions that will affect the entire NADP program. These 

changes should improve data quality, particularly for labile ions that are subject to degradation 

via biological activity. As with the metadata, all data are online at: http://nadp.sws.uiuc.edu. Data 

posting tends to run about six months behind the current date.

9. National Atmospheric Deposition Program National Trends Network

The NADP/ National Trends Network (NTN) is a nationwide network of precipitation 

monitoring sites. Managed by NOAA’s ARL, the network is a cooperative effort between many 

different groups, including the State Agricultural Experiment Stations, U.S. Geological Survey, 

U.S. Department of Agriculture, and numerous other governmental and private entities. For a full 

list of contributors, see the collaborating agencies page on the NADP web site: 

http://nadp.sws.uiuc.edu.

The purpose of the network is to collect data on the chemistry of precipitation for monitoring of 

geographical and temporal long-term trends. At present, there are approximately 230 stations in 

the NADP/NTN program spanning the continental U.S., Alaska, Puerto Rico, and the Virgin 

Islands. Approximately 178 stations have 10 years of data, and 69 stations have 20 years or more. 

Digital metadata and a sampling history for each station can be found at http://nadp.sws.uiuc.edu.

Variables collected by all stations in the network include precipitation amount, sample volume, 

pH, conductivity, and concentrations of calcium, magnesium, potassium, sodium, ammonium, 

nitrate, chloride, and sulfate. Data are collected weekly according to strict clean-handling 

procedures. Observation time is nominally 9 a.m. each Tuesday morning. Samples remain on the 
U.S. National Report on Systematic Observations, August 2001

21

collector for no more than seven days. Current instrumentation at each station includes an 

Aerochem Metrics model 301 collector, Belfort 5-780 weighing rain gauge, pH and conductivity 

meters, ion chromatographs, atomic absorption spectrophotometers, and automated colorimetric 

spectrophotometers. Collection methods have remained relatively constant over the years, though 

the shipping containers changed in 1992 following a lengthy process to address potential o-ring 

contamination from sample buckets (these problems posed no serious threat to data quality, 

except for samples collected in remote regions). Once collected, all data are quality assured by 

the Illinois State Water Survey on behalf of NOAA.

10. National Atmospheric Deposition Program/Mercury Deposition Network

The objective of the Mercury Deposition Network is to develop a national database of weekly 

concentrations of total mercury in precipitation and the seasonal and annual flux of total mercury 

in wet deposition. The data are used to develop information on spatial and seasonal trends in 

mercury deposited to surface waters, forested watersheds, and other sensitive receptors. The 

network is managed collectively by several state, federal, and private institutions. Additional 

information is available at http://nadp.sws.uiuc.edu.

The network consists of approximately 50 stations in the U.S. and Canada, 13 of which opened 

as early as 1995. Variables collected by all stations in the network include precipitation amount, 

sample volume, and total mercury (methyl mercury is also measured in some samples). The 

network uses standardized methods for collection and analyses. Weekly precipitation samples are 

collected in a modified Aerochem Metrics model 301. The “wet-side” sampling glassware is 

removed from the collector every Tuesday at about 9 a.m. and mailed to the Hg Analytical 

Laboratory at Frontier Geosciences in Seattle, Washington for analysis by cold vapor atomic 

fluorescence. Precipitation amount is measured using a Belfort 5-780 weighing gauge. Once 

collected, all data are quality assured by the Illinois State Water Survey on behalf of the various 

agencies involved in the network.

11. Interagency Monitoring of Protected Visual Environments Network (IMPROVE)

IMPROVE is a nationwide network of visibility monitoring sites managed by NOAA’s NWS. 

The network is a cooperative effort between many different groups and the state of Arizona. Its 

steering committee consists of the Environmental Protection Agency (EPA), National Park 

Service, USFS, Fish and Wildlife Service (FWS), and the Bureau of Land Management (BLM). 

The purpose of the network is to collect data required by law for federal visibility protection of 

specific National Parks and wilderness areas. At present there are approximately 107 stations in 

the IMPROVE program across the U.S. All stations in the network are expected to be in 

operation at least through the next decade, and because the network is intended to monitor trends 

through time, no changes are planned in the near future.

A number of visibility-related variables are collected in the network. Aerosol sampling and 

chemical speciation data (specifically, 24-hour duration samples and mass concentrations for PM 

2.5 and PM 10 collected every Wednesday and Saturday) are available for all stations in the 

network, 20 as far back as 1987. Light extinction coefficients (1-hour average values 

continuously using long-path transmission measurements from Optec LPV-2 Transmissometers) 

are available for 15 locations, all since 1987. Light scattering coefficients (1-hour averages using 

ambient temperature Optic NGN-2 Nephelometers) are available for 8 sites, all since 1992. 
U.S. National Report on Systematic Observations, August 2001

22

Temperature and RH are collected using Rotronics instruments at 20 sites (15 since 1987 and 5 

since 1992). Once collected, all data are quality assured by the NCDC and EPA’s Office of Air 

Quality Planning and Standards. Quality control procedures are considered fully documented and 

adequate.

12. Atmospheric Radiation Measurement (ARM) Program

The ARM program (http://www.arm.gov) is a multi-laboratory, interagency program created in 

1989 with funding from the U.S. DOE. The ARM program focuses on resolving the scientific 

uncertainties of the role of clouds on the Earth’s radiation budget. ARM’s goal is to improve the 

performance of general circulation models (GCM) used for climate research and prediction. 

These improved models will help scientists understand better the influences of human activities 

on the Earth’s climate.

In pursuit of its goal, the ARM Program establishes and operates field research sites, called 

Cloud and Radiation Testbeds (CART – see Table 4), in several climatically significant locations, 

all of which are included in the international BSRN. Scientists collect and analyze data obtained 

over extended periods from large arrays of instruments to study the effects and interactions of 

sunlight, radiant energy, and clouds on temperature, weather, and climate.

12a. ARM Sites

Southern Great Plains (SGP)

The U.S. SGP CART site was the first field measurement site established by DOE’s ARM 

program. The site consists of in-situ and remote-sensing instrument clusters arrayed across 

approximately 55,000 square miles in north-central Oklahoma and south-central Kansas. The 

34-instrumented clusters are categorized as central, extended, intermediate, and boundary 

facilities. These facilities are designed to measure aerosols, upper air profiling, clouds, short and 

longwave radiation, surface meteorology, and surface eddy fluxes.

The central facility is located between Lamont and Billings, Oklahoma. The 160-acre complex, 

the most heavily instrumented facility, houses the site data system, and provides on-site 

investigator support. The site data system is linked to hundreds of individual instruments 

clustered across the 55,000 square mile CART site.

Deployment of the first instrumentation to the SGP site occurred in the spring of 1992, just 24 

months after the program was approved. The site was dedicated in November 1992. Additional 

instrumentation and data processing capabilities have been incrementally added in the succeeding 

years.

Tropical Western Pacific (TWP)

The TWP locale is the second CART to be implemented by DOE’s ARM Program. TWP began 

phased operations in 1996 at its first site on Manus Island. The second site on Nauru Island was 

established in 1998.

The TWP locale is the area roughly between 10o N to 10o S of the equator, from Indonesia to near 

Christmas Island. This region of the world plays a large role in the interannual variability 

observed in the global climate system. For instance, the El Nino/Southern Oscillation 

phenomenon has far reaching implications for weather patterns over much of the Northern 
U.S. National Report on Systematic Observations, August 2001

23

Hemisphere, and perhaps the entire planet. The TWP consistently has the warmest sea surface 

temperatures on the planet, referred to as the Pacific “warm pool.” The warm pool supplies heat 

and moisture to the atmosphere above it, resulting in the formation of deep convective cloud 

systems that, in turn, produce high altitude cirrus clouds spreading out over much of the region. 

These cloud systems regulate the amount of solar energy reaching the surface of the earth and the 

amount of the earth’s heat energy that can escape to space. Improved understanding of the 

interaction between clouds and incoming and outgoing energy will improve the general 

circulation models used for climate research.

North Slope of Alaska (NSA)

The NSA/Adjacent Arctic Ocean (AAO) CART site is providing data about cloud and radiative 

processes at high latitudes. These data are being used to refine models and parameterizations as 

they relate to the Arctic. The NSA/AAO site consists of two facilities, one at Barrow and the 

second in the vicinity of Atqasuk. The AAO site was probed by the Surface Heat Budget of the 

Arctic (SHEBA) experiment, a multi-agency program led by the NSF and the Office of Naval 

Research. SHEBA involved the deployment of an instrumented ice camp within the perennial 

Arctic Ocean ice pack that began in October 1997 and lasted for 12 months.

Data Availability

All data are available from ARM archive: http://www.archive.arm.gov/.

12b. ARM Instrumentation

A complete list of ARM instruments is available on http://www.arm.gov/docs/instruments.html. 

The ARM program focuses on data collection and research activities in six areas: 1) aerosols, 

2) clouds, 3) longwave radiation, 4) shortwave radiation, 5) surface energy exchange (or flux), 

and 6) atmospheric state.

ARM data collection is continuous, and data are provided in near real-time. ARM also provides 

derived products through its value-added procedure (VAP). Many of the scientific needs of the 

ARM project are met through VAPs. Physical models using ARM instrument data as inputs are 

implemented as VAPs and help fill some of the unmet measurement needs of the program. A 

special class of VAPs, called quality measurement experiments, compares different data streams 

for consistency and allows for continuous assessment of the quality of the ARM data streams. 

These data streams may come from direct measurements, measurements derived from instrument 

observations via other VAPs, or model output also created by other VAPs.
U.S. National Report on Systematic Observations, August 2001

24

The following table provides the climate measurement areas being conducted at the 3 sites:

Table 5. ARM Climate Measurement Categories

Radiometers Clouds Atmospheric 

Profiling

Surface Eddy 

Flux Surface Meteorology

Atmospheric Emitted 

Radiance Interferometer

Belford Laser 

Ceilometer

Balloon-borne 

Sounding 

System

Eddy Correlation 

Systems

60-meter Meteorological 

Tower

Microwave Radiometer Micropulse 

Lidar

Microwave 

Radiometer

Energy Balance 

Bowen Ratio 

(EBBR) Stations

ARCS* Meteorological 

Instruments (TWP & NSA 

only)

Sunphotometer Millimeter -

Wavelength 

Cloud Radar

Raman Lidar 

System

Infrared 

Thermometer 

(IRT)

Chilled Mirror (SGP only)

Multifilter Rotating 

Shadowband 

Radiometer 

Microwave 

Radiometer

Wind Profilers 

(50 and 915 

MHz)

Soil Water and 

Temperature 

Systems

60-meter tower: Temperature 

and Humidity Sensors (SGP 

only)

Pyrheliometers

Pyrgeometers 40-meter tower and Nearby 

Sensors at Barrows, Alaska 

(NSA only)

Up- and Downwelling 

Radiometric Systems

Temperature, Humidity, 

Wind, and Pressure Sensors

Rotating Shadowband 

Spectrometer

Atmospheric radiation and cloud stations (ARCS) were designed to provide long-term, basic 

climatological observations. An ARCS consists of an integrated instrument set that measures the 

surface radiation balance, surface meteorology, cloud properties, and some limited atmospheric 

quantities. In addition to the suite of scientific instruments, an ARCS contains data acquisition 

systems, monitoring and control systems, satellite communications, a backup electrical generator, 

and other support equipment. The ARCS is housed in five specially modified 20-foot sea 

containers. The ARCS system is self-contained and designed to operate semi-autonomously with 

a minimum of onsite support.

The ARCS data management system (DMS) controls the flow of data through the ARCS. Its 

primary functions are data collection, storage, and processing. A major requirement for the DMS 

is to minimize the loss of data. Consequently, redundancy is found throughout the system. The 

heart of the DMS is a pair of Sun workstations that back up each other. Each instrument also has 

a data storage buffer to further insure the preservation of data should the DMS be inoperative for 

a period of time. All of the ARCS data are written to magnetic tapes and periodically shipped 

back to the U.S. where they are processed further, quality assured, archived, and distributed to 

investigators. In addition, hourly statistics of the data are calculated, encoded in a compact form, 

and transmitted hourly to the U.S.. The hourly data are used by scientists and engineers 

responsible for operating the site in assessing the health and status of the instruments. These data 

are also useful in examining the general nature of the meteorological measurements being made. 

The hourly health and status information is transmitted via the Geostationary Operational 

Environmental Satellite (GOES) system.
U.S. National Report on Systematic Observations, August 2001

25

The initial ARCS design uses a monitoring and control system (MACS) to monitor the 

environment inside the ARCS enclosures. Some of the parameters monitored are temperature and 

RH, whether the doors are open or closed, and power consumption. MACS also provides the 

capability to remotely turn the power on or off to individual systems and reboot computers. 

These capabilities are essential to the remote operations of an ARCS. A communication system 

provides the ability to issues commands to MACS to perform any of its functions. The system is 

also used to transmit unscheduled messages from on-site operators through a site data log or 

alarms triggered when environmental parameters fall outside an acceptable range. It utilizes the 

INMARSAT-C satellite system and can also serve as a backup for transmitting the hourly 

scientific data. Subsequent ARCS will use the INMARSAT-B satellite system.

Each ARCS enclosure has dual air conditioners with humidity control to maintain the required 

operating environment for the instruments, computers, and other equipment. Electrical power for 

the ARCS is normally supplied by local commercial power. A 50-kilowatt diesel generator serves 

as a backup. The generator system automatically starts when commercial power to the ARCS is 

interrupted and shuts down when the grid power resumes. It is capable of operating continuously 

should commercial power not be available. The generator's 700-gallon fuel capacity provides for 

about one month's run time before refueling.
U.S. National Report on Systematic Observations, August 2001

26
U.S. National Report on Systematic Observations, August 2001

27

Table S1. National Climate Monitoring Systems for Land Surface (Meteorological) Observations

Systems

Climate 

Parameters

(e.g. Temp, 

Precip, other)

Total #

Stns

Appropriate for

Characterizing

National Climate?

Fully Partly No

Time Series

# stations/platforms

(# Data Digitized)

>30y >50y >100y

Are QC Procedures 

Adequate?

Fully Partly No

Metadata 

available?

Total # Stations

(% Digitized)

Continuity

# expected 

operational in 

2005

Temperature 10,556 X 5,406 3,222 118 X

Yes

TBD ~10,000

Precipitation 17,700 X 7,995 4,915 144 X

Yes

TBD ~17,000

Stations Useful 

for National 

Climate 

Monitoring 

Purposes 

(Specify 

parameters 

observed) Snowfall 17,262 X 7,848 4,712 128 X

Yes

TBD ~17,000

Stations 

Reporting 

Internationally

Temperature 

and 

Precipitation

510 X 230 204 128 X Yes ~500

CLIMAT 

Reporting 

Stations

Temperature 

and 

Precipitation

188 X 160 150 85 X

Yes

188 ~200

Reference 

Climate 

Stations

Temperature, 

Rel Humidity, 

Precipitation, 

Solar 

Radiation, 

and Wind 

Speed

250 * X ~100-150

* U.S. Climate Reference Network Still Under Development; Plans are to Deploy the System at 250 Unique Geographic Sites
U.S. National Report on Systematic Observations, August 2001

28

Table S2. Available Homogeneous Data Sets for Land Surface (Meteorological) Observations.

Data Set 

Name Variable # Stations or 

Grid Resolution

Describe 

Period References

USHCN Temp 

Precip

1221 1900-2000 http://www.ncdc.noaa.gov/ol/climate/research/ushcn/ushcn.html

Easterling, D.R., and T.C. Peterson, 1995: A new method of detecting 

undocumented discontinuities in climatological time series, Int. J. of Climatol., 15, 

369-377. 

Karl, T.R., C.N. Williams, Jr., P.J. Young, and W.M. Wendland, 1986: A model to 

estimate the time of observation bias associated with monthly mean maximum, 

minimum, and mean temperature for the U.S., J. Climate Appl. Meteor., 25, 145-

160. 

Karl, T.R., and C.W. Williams, Jr., 1987: An approach to adjusting climatological 

time series for discontinuous inhomogeneities, J. Climate Appl. Meteor., 26, 1744-

1763. 

Karl, T.R., H.F. Diaz, and G. Kukla, 1988: Urbanization: its detection and effect in 

the U.S. climate record, J. Climate, 1, 1099-1123. 

Karl, T.R., C.N. Williams, Jr., F.T. Quinlan, and T.A. Boden, 1990: U.S. Historical 

Climatology Network (HCN) Serial Temperature and Precipitation Data, 

Environmental Science Division, Publication No. 3404, Carbon Dioxide Information 

and Analysis Center, Oak Ridge National Laboratory, Oak Ridge, TN, 389 pp. 

Peterson, T.C., and D.R. Easterling, 1994: Creation of homogeneous composite 

climatological reference series, Int. J. Climatol., 14, 671-680. 

Quayle, R.G., D.R. Easterling, T.R. Karl, and P.Y. Hughes, 1991: Effects of recent 

thermometer changes in the cooperative station network, Bull. Am. Meteorol. Soc., 

72, 1718-1724.
U.S. National Report on Systematic Observations, August 2001

29

Data Set 

Name Variable # Stations or Grid Resolution

Describe 

Period References

GHCN, 

Version 2

Precip

Mean 

Monthly 

Maximum 

and 

Minimum 

temp 

data and 

mean 

temp

20,000

~7,000

1697-Present

1697-Present

http://www.ncdc.noaa.gov/ol/climate/research/ghcn/ghcnoverview.html

Peterson, Thomas C. and Russell S. Vose, 1997: An overview of the Global 

Historical Climatology Network temperature data base, Bulletin of the American 

Meteorological Society, 78, 2837-2849.

Peterson, Thomas C., Russell S. Vose, Richard Schmoyer, and Vyachevslav 

Razuvaev, 1997: Quality control of monthly temperature data: The GHCN 

experience. International Journal of Climatology, submitted.

Easterling, David R., Thomas C. Peterson, and Thomas R. Karl, 1996: On the 

development and use of homogenized climate data sets. Journal of Climate, 9, 

1429-1434.

Easterling, D.R. and T.C. Peterson, 1995: The effect of artificial discontinuities on 

recent trends in minimum and maximum temperatures. Atmospheric Research, 37, 

19-26.

Easterling, David R. and Thomas C. Peterson, 1995: A new method for detecting 

and adjusting for undocumented discontinuities in climatological time series. 

International Journal of Climatology, 15, 369-377.

Peterson, Thomas C. and David R. Easterling, 1994: Creation of homogeneous 

composite climatological reference series. International Journal of Climatology, 14, 

671-679.

The Global Historical Climatology Network (GHCN) is jointly produced by the NCDC, the Carbon Dioxide Information Analysis Center/Oak Ridge National 

Laboratory/DOE, and Arizona State University. 
U.S. National Report on Systematic Observations, August 2001

30

Table S3. National Climate Monitoring Systems for Upper Air Observations (Meteorological)

Only active stations are included in the totals.

Systems Useful 

for National 

Climate 

Monitoring 

Purposes

Total #

Stns or 

platforms

Appropriate for

Characterizing

National Climate?

Fully Partly No

Time Series

#stations/platforms (#Data Digitized)

>5y >10y >30y >50y

Are QC Procedures 

Adequate?

Fully Partly No

Metadata 

available?

Total # 

Stations

(% Digitized)

Continuity?

# expected 

operational in 

2005

Radiosonde 

stations 299 Yes 86 69 66 55 X

Yes

102 ~300

Wind-only 

stations

Stations 

reporting 

Internationally

129 Yes 86 69 66 45 X

Yes

129 129

CLIMAT TEMP 

reporting 

stations

63 Yes 56 X

Yes

63 63

ASAP stations See 

Section II

Profilers 33 Yes 30 X 33

Aircraft (land 

locations)

GPS *

Others (e.g., 

satellite-based)

See 

Section IV Yes

Total Upper Air 

Network

* Under Development
U.S. National Report on Systematic Observations, August 2001

31

Table S4. Available Homogeneous Data Sets For Upper Air Observations (Meteorological)

Data Set Name Variable # Stations

or Grid Resolution

Describe

Period

References

None available

Table S5. National Climate Monitoring Systems for Atmospheric Constituents

(Source: Climate Monitoring and Diagnostics Laboratory)

Components

Total # 

Stations

or 

platforms

Appropriate for

 Characterizing

National Climate?

Fully Partly No

Time Series

#stations/platforms (#Data Digitized)

 >10y >20y >30y >50y

Are QC Procedures 

Adequate? 

 Fully Partly No 

Metadata 

available?

Total # 

Stations

(% Digitized)

Continuity?

# expected 

operational in 

2005

CO2 Stations 491

X

25

25

22

22

2

1

2

X

No

100% >49

Ozone (surface) 5 X 1 4 X

No

100% 6

Ozone (column) 162

X 2 5 9 X

No

100% 16

Ozone (profile) 8

3

X 6 2 X

No

100% 10

Atmospheric Water 

Vapor 1

4

X 1 X

No

100% 1

Other Greenhouse 

Gases (e.g. CH4 )

49 X 49 X

No

100% ~50

Aerosol 

Measurements 6 X 2 2 2 X

No

100% 7

Halocarbons 13 X 9 4 X

No

100% >13

Solar Radiation 7 X 3 3 1 X No

1005

7
U.S. National Report on Systematic Observations, August 2001

32

Table S6. Available Homogeneous Data Sets For Atmospheric Constituents

Data Set Name Variable # Stations or grid 

resolution DescribePeriod References

Carbon Cycle 

Gases; Carbon 

Dioxide Data

CO2 49 stations. Data files begin in 1971 with the bulk 

beginning in the early 1980s.

CMDL: www.cmdl.noaa.gov and go to CO2 data sets.

CDIAC: http://cdiac.esd.ornl.gov and go to CO2 data sets.

WMO: http://gaw.kishou.go.jpand go to CMDL CO2 data.

Ozone Data Ozone Up to 16 depending 

upon column or 

profile etc.

Some data files begin in 1962 with 

others in the 1980s.

CMDL: www.cmdl.noaa.gov and go to ozone data.

WMO: http://exp-studies.tor.ec.gc.ca/e/WOUDC.htm and 

go to ozone data.

Water Vapor Water Vapor Two long-term sites 

and 18 sites of 

varying length.

Two long records, one beginning in 

1964 and ending in 1980 and 

another beginning at a different 

location in 1980.

CMDL: www.cmdl.noaa.gov and go to water vapor data. 

Halocarbons,

CFCs

Other 

Greenhouse

Up to 13 global 

locations with the 

maximum number in 

later years.

Halocarbon Data begin in 1977 with 

CFC-11 and 12 and other 

halocarbon species beginning in the 

1980s and 1990s.

CMDL: www.cmdl.noaa.gov and go to halocarbon data.

Notes. 1. The earliest continuous CO2 data come from Mauna Loa and South Pole dating from 1957 in a program started by Scripps Institution 

Oceanography and later taken up by NOAA. Other continuous stations were added in 1974 (Barrow and Samoa) and flask sites (which 

comprise the majority of the sampling locations) at various times from 1957 to date. The flask samples also are used measure some 

other greenhouse gases and isotopes for a total of 6 gases in 2001.

2. NOAA/CMDL maintains 10 Dobson stations and is assisted in the operation of 6 others through cooperative agencies. 

3. NOAA/CMDL maintains 4 long-term ozonesonde sites and has 4 sites set up for special projects with less than 4 years of data.

4. NOAA/CMDL maintains one permanent water vapour sonde site and has undertaken a number of measurements campaigns from a few 

months to a few years at 20 other sites. All data are available in the CMDL archives
U.S. National Report on Systematic Observations, August 2001

33

II. Oceanographic Observations

The GCOS requirements for ocean observations are the same as the climate requirements for the 

Global Ocean Observing System (GOOS). Both are based on the Ocean Observing System 

Development Panel (OOSDP) Report, (OOSDP, 1995), which can be found at 

http://www-ocean.tamu.edu/OOSDP/FinalRept/t_of_c.html. The GOOS, like GCOS, is based on 

a number of in-situ and space-based observing components. The U.S. contributes to all of these 

components. Long-term, sustained, systematic observations are critical not only to developing an 

understanding of oceanic processes as they relate to climate and to predicting climate variability 

but there are many other applications of these data with significant societal benefit. In coastal 

waters, these observations meet the needs of managing living resources, preserving healthy 

ecosystems, and aiding marine operations, as well as putting climate changes in perspective for 

the coastal regions. They also provide a baseline to enable local observation systems of higher 

resolution to meet national objectives. Surface ocean data from the ocean observing system for 

climate will be assimilated into weather prediction models and improve weather forecasts. Thus, 

the cost, complexity, and scale of observations for climate need not be justified only by their 

benefits to climate monitoring, detection, and prediction; the same observations and many 

resulting products will produce other benefits in the short term.

A. Recent Developments

The U.S. government, both the Executive Branch (Administration) and the Legislative Branch 

(Congress), are increasingly cognizant of the need for sustained ocean observations and are 

supportive of strong U.S. involvement in its implementation. In 1997, the U.S. established the 

National Oceanographic Partnership Program (NOPP) (http://core.cast.msstate.edu/ 

NOPPpg1.html) to coordinate and strengthen oceanographic efforts by identifying and carrying 

out partnerships among Federal agencies, academia, industry, and other members of the 

oceanographic scientific community in the areas of data, resources, education, and 

communication. The National Ocean Research Leadership Council (NORLC), comprised of the 

heads of 12 agencies with oceanographic programs and interests, oversees the activities of the 

NOPP.

In August 1998, Congress requested the NORLC of NOPP to "propose a plan to achieve a truly 

integrated ocean observing system." In response to that request, the report "Toward a U.S. Plan 

for an Integrated, Sustained Ocean Observing System” (http://core.cast.msstate.edu/ 

NOPPobsplan.html), was prepared by a joint federal/non-federal task team. This document 

represented the first significant step by the U.S. oceanographic community toward the 

development of a comprehensive plan. This initial plan engaged the broader community 

consisting of NORLC member agencies, other government entities, academia, the private sector, 

non-governmental organizations, and the Congress in a community-wide discussion, concerning 

implementation. In so doing, the NORLC recognized that a number of issues would be topics for 

debate including: (1) how to manage the overall effort; how to achieve the integration of present 

and future systems, integrating both within and between the coastal and open ocean elements; 

and (2) how to develop an ocean-wide program with the international community; and how to 

identify objectives, requirements, and priorities.
U.S. National Report on Systematic Observations, August 2001

34

The NORLC requested its advisory panel to accept responsibility for development of the next 

step toward a comprehensive plan, building on the initial report and the results of the 

community-wide debate. This resulted in the development of, "An Integrated Ocean Observing 

System: A Strategy for Implementing the First Steps of a U.S. Plan" (http://core.cast.msstate.edu/ 

oceanobs.html), developed by a working group of experts. In October 2000, the NOPP 

established an interagency office for integrated, sustained ocean observations (Ocean U.S.) to 

implement this plan.

B. Fixed Mooring Observational Programs

1. TAO/TRITON

Begun in 1980, the Tropical Atmosphere-Ocean Triangle Trans Ocean Buoy Network

(TAO/TRITON) array (http://www.pmel.noaa.gov/tao) (http://www.pmel of approximately 68 

Autonomous Temperature Line Acquisition System (ATLAS)-type and current meter moorings 

in the Tropical Pacific Ocean, began telemetering oceanographic and meteorological data in realtime via the Argos satellite system. Development of the array was spurred by the 1982-1983 El 

Niño event, which was neither predicted nor detected until nearly its peak. That event highlighted 

the need for real-time data from the tropical Pacific for monitoring, prediction, and improved 

understanding of El Niño. The development of the ATLAS mooring permitted the 

implementation of the large-scale array present today. This low-cost deep ocean mooring was 

designed to measure surface meteorological and subsurface oceanic parameters, and to transmit 

all data to shore in real-time via satellite relay. The mooring was also designed to last one year in 

the water before needing to be recovered for maintenance. The full array was completed in 

December of 1994. During the years in which the array was under development, over 400 buoys 

were deployed on 83 cruises, using 17 different ships from 5 different countries (U.S.A, Japan, 

France, Taiwan, and Korea). Presently, the U.S. maintains the array from the west coast of the 

Americas to 165EE. Beginning in 1999, the moorings along 156EE, 147EE, and 137EE became 

part of the TRITON array maintained by the Japan Marine Science and Technology Center. Each 

mooring is visited twice a year requiring approximately 300 days of ship time to maintain the 
U.S. National Report on Systematic Observations, August 2001

35

Servicing an ATLAS Mooring

array along and east of 165EE, and approximately 90 additional days to maintain the western 

portion of the array.

The operationally supported measurements of the TAO/TRITON array consist of winds, sea 

surface temperature, RH, air temperature, and subsurface temperature at 10 depths in the upper 

500 m. Five moorings along the equator also measure ocean velocity. Additional moorings 

and/or enhancements to the basic measurement suite are often incorporated to the operational 

array in support of research studies to understand specific physical processes not well measured 

by the existing network. Other measurements may be made for satellite or numerical model 

validation purposes. These research efforts are usually of limited duration and/or geographical 

scope, and done in collaboration with other institutions in the U.S. and abroad.

To meet the demands of both operational and research 

measurements in the TAO array, an engineering redesign of 

the ATLAS was initiated in 1994 to update it with greater 

measurement capabilities, improved ocean temperature 

sensor accuracies, and more modular construction. This 

Next Generation ATLAS has the capability to measure and 

transmit in real-time salinity, rain rate, long and shortwave 

radiation, barometric pressure, and ocean velocity. These 

measurements are made at selected sites to meet the needs of 

specialized research experiments.

The tropical mooring arrays in both the Pacific and Atlantic 

(following section) continue to be impacted by vandalism at 

an increasing rate. In the Pacific this is particularly prevalent in the western and eastern portions 

of the array. While funding is anticipated to be stable for the foreseeable future for the Pacific 

array, dramatic reductions in data return rates from some sites may result in those sites becoming 
U.S. National Report on Systematic Observations, August 2001

36

too costly to maintain. Costs for supporting the vessels necessary to maintain the Pacific array 

have been accelerating dramatically without commensurate budget increases. The combination of 

increasing costs and vandalism may result in some minor changes in the Pacific array.

2. Pilot Research Moored Array in the Tropical Atlantic

The Pilot Research Moored Array in the Tropical 

Atlantic (PIRATA) is a collaborative effort by 

scientists from Brazil, France, and the U.S. to 

install and maintain an array of moored ATLAS 

buoys for monitoring the surface variables and 

upper ocean thermal structure at key locations in 

the tropical Atlantic (http://www.ifremer.fr/ird/ 

pirata/pirataus.html). The measurements are 

transmitted via satellite (e.g. CLS-Argos) in realtime and are available to all interested users in the 

research or operational communities, and are 

implemented as a collaborative multinational 

effort. The data management protocols for 

PIRATA are similar to those for TAO.

It is anticipated that these tropical Atlantic observations (http://www.ifremer.fr/ird/pirata/ 

pirataus.html) will be maintained near their present levels for five years. As with the Pacific 

array, increasing vandalism is a serious problem for the tropical Atlantic array. This problem 

tends to be focused in the eastern portion of the array. The cost effectiveness of maintaining 

certain sites with low data return rates may result in configuration changes for the tropical 

Atlantic array.

3. Eastern Pacific Investigation of Climate Processes in the Coupled Ocean-Atmosphere System

Two observational programs being put in place for the Eastern Pacific Investigation of Climate 

(EPIC) in the Coupled Ocean-Atmosphere System program are intended to be sustained for 

approximately 4 years: 1) enhancements of the TAO Array along 95EW with ATLAS-type 

moorings at 3.5EN, 10EN, and 12EN; and 2) 

implementation of an IMET-type mooring in the 

stratus region off of South America at 85EW and 

18ES or 20ES (http://www.atmos. 

washington.ede/gcg/EPIC).

Improved Meteorological Instruments (IMET) 

was developed to meet the data quality 

requirements of the World Ocean Circulation 

Experiment (WOCE) (http://uop.whoi.edu/ 

uophome/technotes.html). This system is now in 

use on several research ships and is available 

commercially. The modules are self-powered, 

self-recording, and communicate on a data bus. 

Tropical Atlantic Mooring Array

Enhanced Mooring Array in the 

Eastern Tropical Pacific
U.S. National Report on Systematic Observations, August 2001

37

The following modules are currently in routine use:

1. Barometric Pressure

2. Sea Surface Temperature

3. Relative Humidity/Air Temperature

4. Air Temperature (Static or Aspirated)

5. Wind Speed and Direction

6. Precipitation

7. Longwave Radiation (incoming

8. Shortwave Radiation (incoming)

Custom modules have been designed for special 

applications such as:

1. Precipitation Temperature

2. Global Positioning System

3. ADCP Interface

4. ARGOS Satellite Telemetry

The IMET architecture is built around an addressable digital data bus. Each sensor is housed in a 

separate intelligent module that includes all of the sensor-specific functions and communicates 

with a central controller (PC, laptop, or any computer that has a serial port) via RS-485 in an 

ASCII protocol. The units are calibrated prior to an experiment and the calibration constants are 

stored in the module (EEPROM) so that all data is in calibrated engineering units. A postexperiment calibration is carried out to determine any drift (very small on most units). Should a 

module have to be changed during an experiment, the new module is plugged in and generates 

calibrated data. The concept permits adding multiple sensors of any type since each module is 

addressable. While averaging takes place within each module, the interrogation and storage of 

data are typically at a one-minute rate.

Ship and buoy IMET systems are integrated systems that have one central data logger and power 

supply as well as an interface to a satellite transmitter for real-time data recovery. VOS modules 

are designed for ease of carry-on installation on ships that cannot have permanently installed 

cables and central computers. The VOS units are self-powered (six months on eight D-cell 

batteries) and self-recording (on a four megabyte flash card, at the one-minute rate). The size of a 

VOS unit is about the same as an IMET unit.

4. Arctic

Moorings have been deployed in the Bering Strait since 1990 at two or more locations to monitor 

flow through the western (A1) and eastern (A2) channels of Bering Strait 

(http://psc.apl.washington.edu/HDL/Bstrait/bstrait.html). The moorings make long-term 

measurements of the variable inflow of Pacific waters to the Arctic Ocean through Bering Strait, 

together with the varying properties of those waters. The mooring A1 is in the Russian EEZ. In 

other years, a proxy site at A3 has monitored the western channel. This influx provides a key 

forcing for the Western Arctic shelf-slope-basin system, and the Pacific influence can be traced 

across the Arctic Ocean into the northern North Atlantic. A particularly important dynamical 

Bering Strait Moorings
U.S. National Report on Systematic Observations, August 2001

38

aspect of the Pacific presence in the Arctic Ocean is its contribution to stabilizing the upper 

ocean, thereby influencing ice thickness and Upper Ocean mixing.

Beginning in April 2001, bottom-moored instruments that sample from the surface to great 

depths over the 4000 m deep abyssal plain at the North Pole began to be maintained. 

Measurements include ice thickness and drift, water 

temperature and salinity, and current speed and 

direction. We anticipate other automated 

measurements being added in subsequent years, 

including concentrations of nutrients and a variety 

of other tracers. This moored time series station at 

the Pole has the following major objectives:

• Provide a platform for community-wide 

Eulerian measurements in the interior Arctic 

Ocean.

• Determine the statistics of both the ice drift 

and the planetary boundary layer in the upper ocean.

• Measure the low-frequency variability of the velocity field of the mixed layer and 

halocline, including the annual cycle and its inter-annual variability.

• Quantify the vertical and temporal scales of variability in the temperature and salinity 

fields, especially in the halocline and the Atlantic layer where many of the dramatic 

changes of the past decade have occurred.

• Assess the impact of large-scale changes in the circulation and properties of the Arctic 

Ocean in this region.

• Use the new measurements to increase the dynamical understanding of the interior Arctic 

Ocean and encourage improved modeling of this regime.

• Provide a long-term comparison base for earlier measurements in the region, including 

those incorporated into atlases.

• Measure Eulerian time series of sea ice drift and provide the quality-controlled, 

documented data sets to the arctic research community.

• Estimate the temporal variations of the sea ice thickness distribution, including its mean, 

modes, and open water fraction.

• In collaboration with other LTO participants, compare the observed variations in ice 

thickness with concurrent variations in the local ocean/atmosphere environment and with 

variations in the AO, NAO, and other indices of arctic change.

• Explore relationships between the observed variations in ice thickness in the central 

Arctic Ocean with ice and freshwater export through the Fram Strait.
U.S. National Report on Systematic Observations, August 2001

39

C. Marine Observational Network of the National Weather Service

Globally, weather and marine forecasters in coastal nations require frequent, high-quality marine 

observations for assimilation into models and for diagnosing conditions before forecasts are 

prepared. During the 1960's, about 50 individual buoy programs were conducted by a variety of 

ocean-oriented agencies in the U.S. In 1967, a consolidated national data buoy system was 

created and placed under the U.S. Coast Guard. NOAA was formed in 1970 and the NOAA Data 

Buoy Office (NDBO) at Stennis Space Center, Mississippi, was created under its National Ocean 

Service (NOS). In 1982, the NDBO was renamed the National Data Buoy Center (NDBC) and 

was placed under NOAA's NWS.

The NDBC (http://www.ndbc.noaa.gov/) operates the Marine Observational Network (MON) for 

the NWS. The components of the MON are also programs within the WMO’s Joint Commission 

for Oceanography and Marine Meteorology. Most of the assets that make up the network are 

defined as coastal, that is, they are within 50 miles of the coast. However, a few deep-water 

buoys lie beyond this distance. The oceanic components of the MON consist of:

• 69 moored buoys in the waters of the east, west, Alaskan and Gulf coasts, around Hawaii 

and in the Great Lakes.

• 55 stations of the Coastal-Marine Automated Network (C-MAN) along the east, west, 

Alaskan and Gulf coasts, the Great Lakes, and St. Lawrence Seaway.

• The VOS Program (discussed in the section on Voluntary and Ships of Opportunity).

Buoys are 3-, 10-, or 12-meter discus buoys or 6-meter Naval Oceanographic and Meteorological 

Automated Device (NOMAD) buoys. The majority falls in the 3-meter discus category. The CMAN stations are on towers, piers, lighthouses, etc. Measured parameters include air 

temperature, sea level pressure, wind speed and direction, sea temperature at one meter, and 

certain wave characteristics (depending on particular location).

At a minimum, the moored buoy and C-MAN stations provide 

hourly observations of wind speed, direction, and gust; barometric 

pressure; and air temperature. In addition, all buoys, and some CMAN stations, measure sea surface temperature and wave heights 

and periods. In general (exceptions will be presented) these data 

are transmitted hourly, via GOES to the NWS where gross quality 

control is preformed before being distributed on the GTS. Delayed 

mode quality control is performed by NDBC. Delayed mode data 

undergo more extensive quality control procedures and are 

available at higher resolution than the real-time data. Delayed 

mode data are available from the NDBC.

1. Moored Buoys

These buoys are deployed in the coastal and offshore waters from the western Atlantic to the 

Pacific Ocean around Hawaii, and from the Bering Sea to the South Pacific. NDBC's moored 

buoys measure and transmit barometric pressure; wind direction, speed, and gust; air and sea 

temperature; and wave energy spectra from which significant wave height, dominant wave 

3 Meter Discus Buoy
U.S. National Report on Systematic Observations, August 2001

40

period, and average wave period are derived. The direction of wave 

propagation is measured on many moored buoys 

(http://www.ndbc.noaa.gov/mooredbuoy.shtml).

The fleet of moored buoys includes six types: 3-m, 10-m, and 12-m 

discus hulls; 6-m boat-shaped (NOMAD) hulls; and the newest two, 

the coastal buoy and the coastal oceanographic line-of-sight 

(COLOS) buoy. The choice of hull type used usually depends on its 

intended deployment location and measurement requirements.

The steel-hulled, 12-meter discus buoys are sturdier in rough 

weather than the smaller, steel-hulled 10-meter discus buoy, but are 

more costly to maintain. The 10-meter buoy has been known to 

capsize in certain environmental conditions and the overall motion 

of the buoy is more lively than that of the 12- meter buoy. Due to 

their size, the 10- and 12-meter 

buoys generally have to be 

towed to their appropriate 

locations. The aluminumhulled, 3-meter discus is very 

cost-effective but does not offer 

long-term survivability that the 

larger discus hulls provide. The 

transportability of the 3-meter 

buoy is much improved over 

that of the larger discus buoys. 

Constructed of aluminum, it is 

less likely to corrode, and 

compass measurements are not 

affected.

The 6-meter NOMAD buoy is 

an aluminum-hulled, boatshaped buoy that provides 

relatively high cost 

effectiveness and excellent 

long-term survivability in severe seas. These buoys are highly 

directional and have a quick rotational response. There has been 

no known capsizing of 6-meter NOMAD hulls. The relatively 

small size of the NOMAD hulls allows for superb transportability. 

Like the 3-meter discus buoy, they are less likely to corrode and 

the magnetic effects on the compass are slight.

10-Meter Discus Buoy

National Weather Service Moored Buoy Locations

6-Meter NOMAD Buoy
U.S. National Report on Systematic Observations, August 2001

41

2. Coastal-Marine Automated Network

The (C-MAN) was established in the early 1980's in response to a need to maintain 

meteorological observations in U.S. coastal areas (http://www.ndbc.noaa.gov/ cman.phtml). 

Approximately 60 stations have been installed on lighthouses, at capes and beaches, on near 

shore islands, and on offshore platforms.

Besides the baseline measurements 

of wind speed and direction, air 

temperature, and barometric 

pressure, measurements of RH, 

precipitation, visibility, solar 

radiation, sea water temperature 

and salinity, sea level, ocean 

currents at depth, underwater light 

intensity, and others can be made. 

To meet the need for more frequent 

real-time observations, data from 

several select C-MAN locations 

can be accessed by telephone with 

data being updated at 15-minute 

intervals. Three stations have data 

updated for telephone access every 

5 minutes.

A few C-MAN stations located in Micronesia are at the fringe of, or lie outside, the GOES 

footprint. Data from these stations may be transmitted via either GOES or NOAA polar orbiting 

environmental satellites (POES), depending upon which provides better data relay capability. 

Arrangements have been made with the Japanese Meteorological Agency to transmit data from 

one western Pacific station through the Japanese geo-stationary 

meteorological satellite, referred to as GMS, via Tokyo to the 

NWS for processing and dissemination. Pictured is the C-MAN 

station located in Dry Tortugas, Florida, at 24.64E N, 82.86E W. 

The site elevation is 0.0 m above mean sea level; with the air 

temperature measured at 5.2 m above site elevation, the 

anemometer is at 5.7 m, and barometric pressure is measured at 

4.5 m.

Dry Tortugas, Florida C-MAN Station

National Weather Service Coastal Marine Automated Network 

Station Locations
U.S. National Report on Systematic Observations, August 2001

42

D. Drifting Buoy Program

1. Global Lagrangian Drifters

The objectives of this program are to assemble and provide 

uniform quality control of sea surface temperature (SST) and 

surface velocity measurements by maintaining an accurate and 

globally dense set of Argos-tracked Lagrangian drifters 

providing in-situ observations of sea-surface temperature 

(SST) and surface circulation. These measurements are 

obtained as part of an international program designed to make 

the data available in an effort to improve climate prediction. Climate prediction models require

accurate estimates of SST to initialize their ocean component. Drifting buoys provide essential 

ground truth SST data for this purpose. These models also require validation by comparison with 

independent data sets. Surface velocity measurements are used for this validation.

The U.S. presently 

deploys over 500 

drifters annually in 

all three basins 

using the VOS 

Program, research 

vessels and U.S. 

Navy aircraft. These 

drifters are tracked 

daily via the 

ARGOS satellite 

system where their 

positions and sea 

surface temperatures 

(and sometimes 

other parameters) 

are processed and 

inserted onto the 

GTS for global distribution. Approximately 630,000 SSTs are collected annually via this 

program. Additionally, the U.S. performs the added function of a Data Acquisition Center (DAC) 

for the Global Drifter Program (GDP) (http://www.aoml.noaa. gov/phod/dac). The global drifter 

program is a participating member of the Intergovernmental Oceanographic Commission 

(IOC)/World Meteorological Organization (WMO), Data Buoy Cooperation Panel (DBCP).

Recently deployments of barometer drifters have taken place in the Southern Ocean, South 

Atlantic Ocean, and northwest Pacific Ocean. These instruments require careful monitoring to 

ensure that they are operating in good condition and that the data used in numerical weather 

prediction in near real-time by meteorological centers throughout the world, are being put to best 

advantage. The U.S. will continue to support the deployment of drifters equipped with 

barometers in key regions for numerical weather prediction as well as for sea surface temperature 

and velocity observations. Deployment of a significant number of drifters equipped with wind 
U.S. National Report on Systematic Observations, August 2001

43

monitoring capability is occurring, primarily in the tropical North 

Atlantic for hurricane prediction and monitoring purposes.

2. Arctic

The International Arctic Buoy 

Programme (IABP) is funded and 

managed by its participants, 

representing eight nations 

(Canada, France, Germany, 

Japan, Norway, Russia, United 

Kingdom, and the U.S.). 

Participants include operational 

and research agencies, 

meteorological and 

oceanographic institutes, and 

nongovernmental organizations. 

The IABP maintains a network of automatic data buoys 

(http://iabp.apl.washington.edu/buoys.html) in the Arctic Basin which 

monitors synoptic-scale fields of pressure, temperature, and ice motion 

to support real-time operations and meteorological and oceanographic 

research. Each nation collaborates in the centralized deployment of 

buoys. Funding, equipment, and services are provided by a number of 

U.S. agencies and organizations through the Polar Science Center at the 

University of Washington/Applied Physics Laboratory 

(http://iabp.apl.washington.edu/).

Lagrangian Drifter Being

Deployed
U.S. National Report on Systematic Observations, August 2001

44

E. Voluntary and Ships of Opportunity

The WMO VOS is the international scheme by which ships plying the oceans and seas of the 

world are recruited by National Meteorological Services (NMS) for taking and transmitting 

meteorological observations. The contribution that VOS meteorological reports make to 

operational meteorology, marine meteorological services, and global climate studies is unique 

and irreplaceable. During the past few decades, the increasing recognition of the role of the 

oceans in the global climate system has placed even greater emphasis on marine meteorological 

and oceanographical observing systems.

One of the major continuing problems facing meteorology is the scarcity of data from vast areas 

of the world's oceans (the so-called 'data-sparse areas') in support of basic weather forecasting, 

provision of marine meteorological and oceanographic services, and climate analysis and 

research. While meteorological satellites help substantially to overcome these problems, data 

from more conventional platforms, in particular the voluntary observing ships, remain essential 

to provide ground truth for the satellite observations, and to provide important information which 

the satellites cannot observe. Tested instruments are supplied free of charge to the ship, and 

professionally installed, usually by a trained Port Meteorological Officer. The Officer provides 

advice on the technique of observing at sea, explains the use of the WMO SHIP code, and offers 

guidance on the transmission of the observations from the ship to shore. There are no charges to 

the ship for the transmission of these data. The instruments are professionally serviced, without 

charge to the ship or ship owner. The U.S. program operates over 1,500 vessels. As many 

observations as possible are transmitted in real-time and distributed on national and international 

circuits for operational uses such as weather prediction and ocean state estimation. All 

observations, those transmitted for operational uses and those whose transmission is delayed, are 

forwarded for use by the NCDC.

F. U.S. GOOS VOS Program

The U.S. GOOS VOS program presently operates a fleet of about 400 domestic and foreign 

commercial vessels, a subset of the global fleet. It also includes some research vessels. In 

Meteorological and XBT Observations Received from Voluntary Observing Ships
U.S. National Report on Systematic Observations, August 2001

45

addition to conducting sea surface meteorological observational programs, these ships are used to 

deploy sub surface eXpendable BathyThermographs (XBT), conduct underway shipboard 

ThermoSalinoGraph (TSG) and carbon dioxide (CO2) measurement programs, and atmospheric 

observations. These vessels also deploy drifting buoys and highly instrumented profiling floats, 

and sometimes tow other instruments. In any given year this network provides the following 

approximate number of observations:

ü 630,000 sea surface temperature observations from drifting buoys

ü 110,000 meteorological observations

ü 30,000 thermosalinograph observations

ü 15,000 expendable bathythermograph observations

1. Shipboard Environmental (Data) Acquisition System (SEAS)

The SEAS program provides accurate meteorological and oceanographic data in real-time from 

ships at sea through the use of satellite data transmission techniques (http://www.dbcp.nos. 

noaa.gov/seas/met.html). This is a specific hardware/software package to ensure that 

meteorological and XBT 

observations are transmitted in realtime through either the GOES or 

INMARSAT C satellites for use in 

weather and climate forecasting and 

ocean state estimation and analyses. 

SEAS- equipped voluntary observing 

ships are responsible for more than 

15,000 XBT (TZ) observations and 

as many as 80,000 meteorological 

observations per year. 

Meteorological observations consist 

of wind speed, air temperature, sealevel pressure (SLP), and SST.

2. Expendable Bathythermograph Program

The XBT program (http://www.aoml.noaa.gov/phod/uot/) 

utilizes approximately 70 VOSs to monitor, on a monthly basis, 

26 transects in all three ocean basins. It utilizes SEAS 

hardware/software to collect, quality control, and transmit in 

real-time subsurface oceanographic observations obtained using 

about 15,000 XBTs per year. The XBT is an expendable 

temperature probe that is manually launched from the bridge 

wings of commercial vessels approximately four times per day, 

along certain scientifically selected shipping lanes. The data 

transmitted via the wire link from the XBT probe is stored on the SEAS 

computer, where it is processed and formatted for satellite message 

transmission. The transmitted data is routed to a Center where it is further quality controlled, 

XBT
U.S. National Report on Systematic Observations, August 2001

46

then placed onto the GTS for global distribution. 

NCEP uses the data for weather and climate 

forecasting as well as for seasonal, inter-annual, and 

decadal climate research. The XBT program is a 

participating member of the IOC/WMO Ship of 

Opportunity Program Implementation Panel 

(SOOPIP).

3. Thermosalinograph (TSG)

A project has been developed to evaluate and 

implement TSG technology on VOS (http://www. 

aoml.noaa.gov/goos/goos-developing.html and 

http://www.aoml.noaa.gov/ goos/techtsg.html). The TSG determines 

sea surface temperature and conductivity from underway vessels 

through a stainless steel assembly mounted near the ship's seawater intake. The system also 

employs other devices such as sensors for dissolved oxygen and fluorescence. High-resolution 

data, along with the vessel's location from a GPS receiver, are recorded and archived for research 

purposes. A subset of these data is transmitted every 3 hours via the GOES. Water samples used 

to verify the TSG data are taken by the vessel's crew twice daily. TSGs have been operational on 

research vessels for a number of years; however, it has only been over the past two years that a 

Sea-Bird TSG has been operating on the VOS OLEANDER (Newark, N.J. to Bermuda) and 

more recently on the VOS SKAGAFOSS (Newfoundland to Iceland).

Shipboard Thermosalinograph 

and Observations

Automated XBT Launcher

XBT Probe
U.S. National Report on Systematic Observations, August 2001

47

4. Carbon Dioxide

The air-sea Flux (F) of CO2 is commonly determined from the gas transfer velocity (k) multiplied 

by the partial pressure difference (pCO2) across the air-water interface: F= kpCO2 . By 

measuring pCO2 with automated systems on ships of opportunity, a global flux map can be 

produced. Beginning in 1991, a semi-automated system was deployed on research vessels (three 

vessels today) measuring the pCO2 in air and water on all cruises in order to fill critical voids in 

the global data set of pCO2 measurements. The area of concentrated deployment has been the 

equatorial Pacific, where seasonal snapshots of surface water CO2 levels have been obtained in 

concert with the TAO array (http://www.aoml.noaa.gov/ocd/oaces/co2/).

5. Automated Shipboard Aerological Program (ASAP)

The ASAP in its present form began in the mid-1980s. It involves the generation of upper air 

profile data from data-sparse ocean areas using automated sounding systems carried on board 

merchant ships plying regular ocean routes. The profile data are all made available in real-time 

Underway pCO2 Monitoring
U.S. National Report on Systematic Observations, August 2001

48

on the GTS, for use by operational centers. The original 

ASAP system was developed as a modular 

"containerized" unit, which could be quickly installed or 

removed from a ship. The system is completely housed 

within a specially modified, standard 20-foot shipping 

container. This includes all of the necessary electronics 

and antennas, a balloon launching system, stowage for 

consumable supplies such as helium balloons and 

sondes, and adequate operator workspace. It requires 

only to be connected to the ship's power and secured to 

a suitable deck space. Several NMSs operate ASAP 

units. The program is coordinated through the ASAP panel, a component of the JCOMM Ship 

Observations Team. Most of the soundings are presently from the North Atlantic and North West 

Pacific Oceans, but the program is also expanding into other ocean basins. The U.S. presently 

collaborates in the maintenance of one around-the-world ASAP vessel.

The containerized ASAP has definite advantages in today's flexible shipping environment 

because it can easily accommodate abrupt changes in shipping routes by simply moving to 

another ship more suitable for ASAP operations. It becomes apparent, however, that the number 

of potential ships of opportunity, able to carry such a system, is limited. Substantial nonobstructed and easily accessible deck space is required. In addition, costs over and above the 

required maintenance of the electronic equipment are incurred by maintenance of the container 

and its peripheral equipment such as air conditioners and mechanical 

launching systems. As a result, an alternative “distributed” system 

configuration, was developed to expand the versatility of the ASAP 

concept. The distributed system is essentially limited to the required 

electronics installed in existing ship's spaces accessible to an operator, 

usually on the bridge or close by. Consumable supplies are stored in 

appropriate on-board space, and manual or remote launching 

techniques may be employed. Two U.S. research vessels (NOAA ships 

Ronald H. Brown and Ka’imimoana) have distributed systems 

installed on board. These vessels conduct routine upper air 

observations that contribute to the overall ASAP observational 

program as much as possible. The tropical Pacific is an area of vital 

importance for these observations. The Ka’imimoana supports the 

TAO array and, thus, can routinely provide upper air profiles from this 

region.

6. Improved Meteorology

In planning for WOCE, it was recognized that moored buoys and ships would provide especially 

attractive platforms from which to make accurate in-situ measurements of the basic surface 

meteorological observable parameters required to investigate the air-sea fluxes of momentum, 

heat, and mass. The Woods Hole Oceanographic Institution was funded to evaluate and choose 

sensors capable of meeting the WOCE goals and to develop the IMET system as a flexible data 

collection system. The IMET technology has evolved into new modules designed for use on VOS 

ships. These new VOS-IMET modules are self-powered, self-recording, stand-alone units. 

Radiosonde Launch from a 

Distributed ASAP System

Radiosonde Launch from an ASAP Container
U.S. National Report on Systematic Observations, August 2001

49

Currently installed sensor modules include the full 

flux suite consisting of wind speed and direction, 

RH and air temperature, barometric pressure, 

precipitation, shortwave radiation, longwave 

radiation, and SST (http://uop.whoi.edu/

uophome/asimet/asimet.html#instrumentation).

The U.S. VOSs are sold and change routes on a 

very regular basis. This has severe implications in 

that it is not 

feasible to run 

cables for 

system 

installations and it is normally not possible to obtain useable 

electrical power close to sensor mounting locations. One 

special problem is getting SST data from inside the hull of the 

ship at the waterline up to the rest of the modules. An acoustic 

modem that uses the ship’s steel hull at the acoustic path for 

20-baud data has recently been developed. The measurement 

system for a VOS therefore must be self-powered, selfrecording, and able to communicate data to the bridge area for 

both ship use and satellite transmission. This means that the 

VOS climate observing system uses nearly the same 

components as a buoy climate observing system. It is expected 

that the prototype climate observing system currently being 

tested on VOS will be available from commercial sources as an 

operational system. This commercial system will provide the 

same data quality and data time resolution as modules used 

previously to establish a better understanding of climate processes. This system or its 

components can provide the same performance from buoys and smaller ships.

G. Floats

Deployment of the broad-scale global array of free-drifting, profiling floats, known as Argo, 

began in 2000. The planned array of 3,000 floats distributed over the 

oceans at 3-degree spacing will measure the temperature and salinity of 

the upper 2,000 m of the ocean, providing continuous monitoring of the 

state of the ocean. It is expected that global coverage will be initially 

achieved in 2004 and fully completed in 2005. The U.S. plans call for 

supporting one-third of the global array.

Floats are capable of cycling from the surface to 2,000 m and have an 

expected lifetime of 4 to 5 years. Present plans are for a 10-day duty 

cycle, providing some 100,000 profiles annually when the array is 

complete. Argo data will be publicly available in near real-time via the 

GTS, and in scientifically quality-controlled form with a few months 

IMET on a Commercial Vessel

A Profiling Float

IMET System on the Bow of a Research Vessel
U.S. National Report on Systematic Observations, August 2001

50

delay. Conceptually, Argo builds on the existing upper-ocean 

temperature observing networks, extending their spatial and 

temporal coverage, depth range and accuracy, and enhancing 

them through addition of salinity and velocity measurements. 

For the first time, the physical state of the upper ocean will be 

systematically measured and assimilated in near real-time.

Argo objectives fall into several categories. Argo will provide a 

quantitative description of the evolving state of the upper ocean 

and patterns of ocean climate variability. The data will enhance 

the value of the Jason altimeter through measurement of 

subsurface vertical structure (temperature and salinity) of the 

oceans. It will also measure velocity at the parking depth of 

the instruments, and provide sufficient coverage and resolution 

for interpretation of altimetric sea 

surface height variability. Argo data 

will be used to initialize ocean and 

coupled forecast models, data 

assimilation, and dynamical model 

testing. A primary focus of Argo is 

seasonal-to-decadal climate 

variability and predictability, but a 

wide range of applications for highquality global ocean analyses is 

anticipated.

The initial design of the Argo 

network is based on experience 

from the present upper ocean thermal observing system, on knowledge of variability gained from 

the TOPEX/Poseidon altimeter, and on estimated requirements for climate and high-resolution 

ocean models. The design emphasizes the need to integrate Argo 

within the overall framework of the global ocean observing system. 

The U.S. has funded the acquisition, deployment, and data 

management of 187 floats to be deployed in the 2001/2002 period as 

part of the sustained global array. All floats will have the same 

parking depth of 1000 meters. This is the deepest common level to 

date, and has the greatest likelihood for obtaining a common velocity 

field and accurate velocity information. The floats will have varying 

profiling depths between 1,000 and 2,000 meters depending on the 

location and float type. The present U.S. program will support the 

acquisition and deployment of approximately 150 to 160 floats 

annually and the operations of a global array of 600 floats. Plans call 

for increasing this deployment to around 270 floats annually and 

maintaining an array of 1,000 floats.

Planned U.S. Profiling Float Deployments in 2001 and Early 2002

A Typical Operating Cycle for a 

Profiling Float

Tide Gauge Station
U.S. National Report on Systematic Observations, August 2001

51

H. In-Situ Sea Level

Observations of in-situ sea level in the U.S. are centered at the University of Hawaii Sea Level 

Center (UHSLC), a research facility within the School of Ocean and Earth Science and 

Technology (SOEST), University of Hawaii. The UHSLC began in the 1970's as the Pacific Sea 

Level Network. In the mid-1980's the Tropical Ocean Global Atmosphere (TOGA) Sea Level 

Center (TSLC) and the IGOSS Sea Level Project in the 

Pacific were added and the network was expanded to the 

Indian Ocean. In the early 1990's the WOCE center was 

established. The program has three distinct activities: 

the Indo-Pacific Sea Level Network (IPSLN), the 

IGOSS (Integrated Global Ocean Services System) Sea 

Level Project in the Pacific (ISLP-Pac), and the UHSLC 

research databases. The principle mission of the 

UHSLC is to support climate research by collecting, 

processing, distributing, and analyzing in-situ tide gauge 

data from around the world. The program supports the 

JASON program in the development of in-situ tide 

gauge/GPS stations for monitoring the temporal drift of satellite altimeters. The UHSLC also 

hosts the Joint Archive for Sea Level (JASL), a collaborative effort with the National 

Oceanographic Data Center (NODC). The USHLC provides three on-line databases: the research 

quality data, the WOCE "fast delivery" data, and the ISLP-Pac map data.

The IPSLN is an observational network of sea level gauges, most with satellite data telemetry, 

located throughout the tropical portions of the Indian and Pacific Oceans. It is presently the 

largest open ocean sea level network in the world that is operated by a single group. Its purpose is 

to create and maintain an effective sea level observing system in the tropical portions of the 

Indian and Pacific Oceans. Station selection has been guided by the needs of ephemeral 

programs, such as TOGA or WOCE, as well 

as the needs of the Global Sea-Level 

Observing System (GLOSS). Presently just 

over 300 sites have been designated as 

GLOSS sites; nearly all of the IPSLN stations 

fall into this category. The ISLP-Pac produces 

and distributes, within five weeks of the end 

of each month, maps of Pacific Ocean sea 

surface topography variations. This activity 

was an early, and very successful, example of 

operational oceanography. Products include

monthly maps of Pacific sea level deviations 

from the long-term mean and maps of sea 

level anomalies from the long-term seasonal cycle corrected for atmospheric pressure anomalies. 

The ISLP-Pac also produces quarterly updates of an index of the tropical Pacific upper layer 

volume and annual updates of indices of the ridge-trough system and equatorial currents for the 

Pacific Ocean. As part of the ISLP-Pac, the UHSLC operates a Specialized Oceanographic 

Centre (SOC) that produces monthly sea surface topography maps and quarterly diagnostic time 

Indo-Pacific Sea Level Network
U.S. National Report on Systematic Observations, August 2001

52

series for the Pacific Ocean. The UHSLC presently distributes these products through the Internet 

and by mail to users, including several national agencies that reproduce them and further 

distribute them. These products are also submitted, along with a text description, to the IGOSS 

Products Bulletin. Approximately five weeks after the end of a month, hundreds of users 

throughout the world receive an analysis of the state of the Pacific Ocean sea surface topography 

for that month. All of the UHSLC data and products are available on the Internet 

(http://uhslc.soest.hawaii.edu/), and on CD-ROM.

The UHSLC databases are the result of work started by 

the TSLC and WOCE centers. The research quality 

database currently includes 330 sites with 3923 stationyears of quality assured data. The "fast delivery" 

database currently includes 125 stations, 105 of which 

are located at GLOSS sites. Sea level data from a 

globally distributed set of stations is processed and 

made available to users within three months of data 

collection. All of these data are available on the 

Internet. For 82 “fast delivery” stations, the existing time series has been extended back to 1985 

in order to link Geosat altimetric data with the present TOPEX/Poseidon data. The UHSLC and 

NODC collaborate to maintain the Joint Archive for Sea Level (JASL), which is a quality assured 

database of hourly sea level data from selected stations around the world. In the past year, the 

UHSLC increased its JASL holdings to 7477 station-years of hourly quality assured data. The 

JASL set now includes 4326 station years of data at 180 GLOSS sites. Of the 101 GLOSS 

stations presently operating on islands, data for 93 of them have been obtained by the UHSLC. 

Though the lag from collection to public dissemination is typically a few years, the August 1999 

submission of the JASL data to the world Data Center-A for Oceanography included 146 series 

that contained data through the year 1998.

Recent work emphasizes the 

importance of the tide gauge 

network for satellite altimeter 

calibration. In support of 

satellite altimeter calibration 

and validation, the UHSLC is 

installing co-located GPS 

(CGPS) systems at various tide 

gauge stations. The co-location 

of GPS and tide gauge stations 

at select sites is progressing, 

with the sixth and seventh 

installed this year.

The National Water Level 

Observation Program is 

managed by NOAA’s Center for Oceanographic Products and Services Division (CO-OPS) 

(http://www.co-ops.nos.noaa.gov/). Its primary mission is to provide basic tidal datums to 

determine U.S. coastal marine boundaries and to support nautical chart work. It also provides 
U.S. National Report on Systematic Observations, August 2001

53

support for NOAA's tsunami and storm surge warning 

programs, climate monitoring, coastal processes, and 

tectonic research. The program's operational component 

is the National Water Level Observation Network 

(NWLON). The NWLON consists of approximately 190 

water level measurement stations distributed along U.S. 

coasts, in the Great Lakes and connecting channels, and 

in the U.S. territories and possessions. One hundred 

forty stations are considered "long-term control" and 

"primary" stations. These have been in operation at least 

19 years, are still in continuous operation, and transmit 

data in near real-time, i.e., every three hours. In addition 

to these near real-time records, the program's online 

archives include historical data from secondary and 

tertiary stations, i.e., those with record lengths from 18 

years to a few weeks.

Using the NWLON, CO-OPS collects, processes, and 

analyzes the water level and ancillary data and produces standard time series and water level 

datum products. The benchmark information that controls the horizontal and vertical position of

each tide station is also part of the program's on-line archives (http://www.coops.nos.noaa.gov/data_res.html). The program is currently upgrading its water level 

measurement equipment from mechanical and electromechanical to a fully integrated, state-ofthe-art electronic data collection, processing, and dissemination system called the Next 

Generation Water Level Measurement System (NGWLMS). Most stations will consist of a 

primary data collection platform with a self- calibrating acoustic ranging sensor. Ancillary data, 

such as wind velocity, barometric pressure, air and water temperature, conductivity, and RH, can 

also be accommodated. Data are transmitted every three hours via GOES to CO-OPS computers 

for quality control, analysis, and dissemination. More that seventy five percent of the NWLON 

stations have been equipped with NGWLMS (http://www.co-ops.nos.noaa.gov/data_res.html).

I. Time Series

In 1988, JGOFS (Joint Global Ocean Flux Study) (http://www1.whoi.edu/jgofs.html) initiated 

two time-series measurement programs at Bermuda and Hawaii. The objectives of the time-series 

program are to provide well-sampled seasonal resolution of biogeochemical variability at a 

limited number of ocean observatories, provide support and background measurements for 

process-oriented research, as well as test and validate observations for biogeochemical models. 

The records now span a period greater than 10 years, with well over 100 successful cruises at 

each site and permanent moorings in place to assess ocean variability in the oligotrophic ocean.

National Water Level Observation Network Station 

Key West, Florida
U.S. National Report on Systematic Observations, August 2001

54

1. Bermuda Atlantic Time Series

The Bermuda Atlantic Time Series (BATS) 

builds on a program begun in 1954 with the 

establishment of “Hydrostation S" by Henry 

Stommel. Hydrostation S is located 12 nautical 

miles southeast of Bermuda at 32o 10' N, 64o 30' 

W and has been occupied biweekly nearly 

continuously since 1954 (http://www.bbsr.edu/ 

cintoo/hydrostation_s/hydrostation_s.html). The 

data from Hydrostation "S" are primarily 

physical consisting of temperature, salinity, and 

dissolved oxygen measurements.

BATS (http://www.bbsr.edu/ cintoo/bats/bats.html) 

encompasses three major in-situ programs: Hydrostation S, 

the ocean flux project, and the Bermuda testbed mooring 

(BTM). The BATS station is located approximately 80 km SE 

of Bermuda (31E 50' N, 64E 10' W). In addition to major 

monthly cruises, cruises of shorter duration are conducted to 

document the yearly overturn and bloom period. Standard 

JGOFS core measurements (with the exception of 

zooplankton) are made by researchers at the Bermuda 

Biological Station. Cruise results are initially sent to the U.S. 

JGOFS office at Woods Hole; they are then forwarded to the 

U.S. NODC where they are available to the community as a 

whole. BATS was originally planned to last 10 years (until 

1997) but now funds have been assigned to carry out activities 

indefinitely.

The BTM (http://www.opl.ucsb.edu/btm.html) has been 

deployed since June 1994 and provides the oceanographic 

community with a deep-water 

platform for developing, testing, 

calibration, and intercomparison of 

instruments that can obtain long-term 

data sets. Instruments are being used 

to collect meteorological and spectral 

radiometric measurements from a 

buoy tower. Subsurface 

measurements include: currents, 

temperature, conductivity, several 

inherent and apparent optical 

properties, pCO2, 

14C primary 

productivity, nitrate, and trace 

element concentrations. Data have 

been sent to shore and to a nearby 

Bermuda Testbed Mooring
U.S. National Report on Systematic Observations, August 2001

55

ship using a new inductive-link telemetry system. The high temporal resolution, long-term data 

collected from the mooring provide important information concerning episodic and periodic 

processes ranging in scale from minutes to years. For example, short nitrate pulses or injections 

and associated biological events have been observed in the mooring data sets but cannot be 

resolved in the shipboard data set. Evaluation of undersampling and aliasing effects characteristic 

of infrequent sampling (i.e., monthly or often less frequently) are also enabled with these data 

sets. Ground truthing of satellite data is another important component of the program.

International efforts to develop global scale ocean and climate observation systems will be aided 

by coordination of and access to existing observational and modeling efforts. With this in mind, 

the Sargasso Sea Ocean Observatory (S2O2) is being formed to 

coordinate and enhance the contributions of the many marine 

biological, biogeochemical, hydrographic, and atmospheric 

studies conducted in time series mode in and above the western 

North Atlantic. The S2O2 comprises several ongoing ocean and 

atmospheric observation and modeling programs, which are in 

turn managed by several institutions. Primary objectives of S2O2

will be to maintain the vigor of the local time series programs 

and to provide a fluid and timely data stream to the international 

community of ocean and climate scientists (http://www.bbsr. 

edu/Labs/hanselllab/s2o2/s2o2mainpage.html).

2. HOT Series

The benchmark study site for the Hawaii Ocean Time (HOT) -

series is station ALOHA (at 22E 45' N, 158E W) in the 

subtropical North Pacific gyre (http://hahana. soest.hawaii.edu/hot/hotjgofs.html). Core physical, 

chemical, and biological measurements are obtained on monthly intervals during research cruises 

of approximately four days’ duration. Higher frequency measurements of dynamic height, 

particle flux, and a comprehensive suite of physical and chemical and bio-optical parameters are 

obtained from three separate moorings deployed near this site. Data collected as part of the HOT 

program are publicly available via the World 

Wide Web (WWW). The basic HOT 

measurement program will continue until at 

least mid-2001. In addition to the JGOFS 

observational program, the physical 

oceanographic measurements contribute to the 

objectives of the World Climate Research 

Programme (WCRP) Climate Variability and 

Predictability (CLIVAR) Programme by 

providing information on interannual to decadal 

variability of the North Pacific Ocean 

(http://www.soest.hawaii.edu/HOT_WOCE/).

TOPEX/Poseidon Satellite 

Over the Earth
U.S. National Report on Systematic Observations, August 2001

56

J. Remote Sensing Systems

Note: This is also covered in Section IV on Remote Sensing; it is included here given the unique 

nature of oceanographic remote sensing systems and their close relationship to oceanographic insitu systems.

1. Altimetry

Launched into Earth orbit in August 1992, TOPEX/Poseidon is a partnership between the U.S 

and France to monitor global ocean circulation, discover the ties between the oceans and 

atmosphere, and improve global climate predictions. The TOPEX/Poseidon (http://topexwww.jpl.nasa.gov/discover/ discover.html) satellite measures global sea level with unparalleled 

accuracy. NASA provided the satellite bus and five instruments with their associated ground 

elements. NASA's Jet Propulsion Laboratory is responsible for project management and operates 

the satellite through NASA's Tracking and Data Relay Satellite System. The French Space 

Agency, Centre National d'Etudes Spatiales (CNES), furnished two instruments with their 

associated ground elements and a dedicated launch on a Ariane 42P rocket. Both CNES and 

NASA provide precision orbit determination and process 

and distribute data to 38 science investigators from nine

nations, as well as other interested scientists.

From its orbit 1,336 kilometers above the Earth's surface, 

TOPEX/Poseidon measures sea level along the same path 

every 10 days using the dual frequency altimeter developed 

by NASA and the CNES single frequency solid-state 

altimeter. This information is used to relate changes in 

ocean currents with atmospheric and climate patterns. 

Measurements from NASA's microwave radiometer 

provide estimates of the total water-vapor content in the 

atmosphere, which is used to correct errors in the altimeter measurements. These combined 

measurements allow scientists to chart the height of the seas across ocean basins to an accuracy 

of less than 10 centimeters.

Three independent techniques determine the satellite 

altitude within 10 centimeters of accuracy. NASA's laser 

retro-reflector array is used with a network of 10 to 15-

satellite laser ranging stations to provide the baseline 

tracking data for precision orbit determination and 

calibration of the radar altimeter bias. The DORIS system 

provides an alternate set of tracking data using microwave 

Doppler techniques. The system is composed of an on-board 

receiver and a network of 40 to 50 ground transmitting 

stations, providing all-weather, global tracking of the 

satellite. A GPS demonstration receiver provides precise, 

continuous tracking of the spacecraft. TOPEX/Poseidon's 

three-year prime mission ended in Fall, 1995 and is now in 

its extended observational phase. Its first follow-on mission, 

Jason-1, will continue this program of long-term SeaWinds QuikSCAT Spacecraft

TOPEX RMS Sea Level (cm) 1993-1996
U.S. National Report on Systematic Observations, August 2001

57

observations of ocean circulation from space into the next 

century.

2. Sea Surface Winds

The sea winds instrument on QuikSCAT mission is a 

"quick recovery" mission to fill the gap created by the loss 

of data from the NASA scatterometer (NSCAT), when the 

satellite it was flying on lost power in June 1997. 

QuikSCAT was launched on June 19, 1999, in a southsouthwesterly direction to achieve a sun-synchronous 

orbit, 803 kilometers, 98.6E inclination (http://winds.jpl. 

nasa.gov/missions/quikscat/quikindex.html). The designed 

mission life is 2 years (3 years for consumables).

The sea winds instrument is 

a specialized microwave radar that measures near-surface wind 

speed and direction under all weather and cloud conditions over 

Earth's oceans. It uses a rotating dish antenna with two spot beams 

that sweep in a circular pattern. The antenna radiates microwave 

pulses at a frequency of 13.4 GHz across broad regions on Earth's 

surface. The instrument collects data over ocean, land, and ice in a 

continuous, 1,800-kilometer-wide band, making approximately 

400,000 measurements and covering 90% of Earth's surface every 

day. The instrument provides wind speed measurements between 3 

to 20 meters/second, with an accuracy of 2 meters/second; and 

direction, with an accuracy of 20 degrees. Wind vector resolution 

is 25 kilometers. In addition to its mission to acquire all-weather, 

high-resolution measurements of near-surface winds over the 

global oceans, sea winds also provides information on 

daily/seasonal sea ice edge movement and Arctic/Antarctic ice 

pack changes.

Highquality 

research data products produced at 

NASA’s Jet Propulsion Laboratory are 

distributed to the science community 

within two weeks of receipt 

(http://podaac.jpl.nasa.gov).

Operational data products produced by 

NOAA for the international 

meteorological community are 

distributed within three hours of data 

collection.

The NPOESS (see SST - NPOESS)

will carry ocean wind instruments 

Ocean Surface Winds by QuikSCAT, 

August 1, 1999

Readying a TIROS-N for Launch

Polar Orbiting Satellite Over the Earth
U.S. National Report on Systematic Observations, August 2001

58

beginning in 2010. Studies are presently underway to determine the configuration of the 

NPOESS wind sensing system (http://www.ipo.noaa.gov/ windsat.html). It is probable that other 

ocean wind instruments will be available between QuikSCAT and NPOESS.

3. Sea Surface Temperature

Initial efforts at mapping SST were conducted using data from NASA's Nimbus series of 

satellites. The world's first meteorological satellite, a polar-orbiting satellite named TIROS 

(Television Infrared Observations Satellite), was launched in 1960. Between 1960 and 1978, 

twenty-four polar orbiting meteorological satellites in the TIROS series were launched. The fourchannel Advanced Very High Resolution Radiometer (AVHRR), flown on NOAA's TIROS-N (N

representing the next generation of operational satellites) weather satellites beginning in1978 

(NOAA-6) greatly increased the accuracy of SST measurements. The radiometer provides views 

in four different parts of the electromagnetic visible and infrared spectrum. Still greater increases 

in accuracy were achieved when a fifth channel was added to the AVHRR instrument flown on 

NOAA-7 in 1981 and on subsequent NOAA satellites. The fifth channel improved the 

measurement of SST by providing corrections for atmospheric water vapor that otherwise would 

have interfered with the temperature measurements.

In March 1983, the first of the Advanced TIROS-N (or 

ATN) satellites, designated as NOAA-8 was launched. 

These satellites are physically larger and have more 

power than their predecessors, and can accommodate 

more equipment. NOAA continues to operate the ATN 

series of satellites today with improved instruments 

(http://www.oso.noaa.gov/poes/index.htm). The current 

configuration includes NOAA-14, launched in 

December 1994; NOAA-15, launched in May 1998; and NOAA-16 launched in September 2000. 

NOAA-15 is the first in a series of five satellites with improved imaging and sounding 

capabilities that will operate over the next decade. This series is NOAA-K (15), NOAA-L (16), 

NOAA-M, NOAA-N, and NOAA-N'. The latest AVHRR (AVHRR/3) instrument, a six-channel 

instrument, is carried on NOAA-16.

4. National Polar orbiting Operational Environmental Satellite System (NPOESS)

In May 1994, the U.S. decided to merge the nation's military and civil operational meteorological 

satellite systems into a single, national system capable of satisfying both civil and national 

security requirements for space-based remotely sensed environmental data. The joint program 

formed is the NPOESS (http://www. ipo.noaa.gov/). NPOESS is a convergence of the nation’s 

two operational weather satellite systems - NOAA's Polar-orbiting Operational Environmental 

Satellite (POES) (http://poes2.gsfc.nasa.gov/), and the DoD’s Defense Meteorological Satellite 

Program (DMSP). In October 1994, NOAA, DoD, and NASA created an Integrated Program 

Office (IPO) that will develop, manage, acquire, and operate the NPOESS system. The IPO 

concept provides each of the participating agencies with lead responsibility for one of three 

primary functional areas. NOAA has overall responsibility for the converged system and is 

responsible for satellite operations. NOAA is also the primary interface with the international and 

civil user communities. The DoD is responsible to support the IPO for major systems 

Satellite Derived Sea Surface 

Temperature Distribution
U.S. National Report on Systematic Observations, August 2001

59

acquisitions, including launch support, while NASA has the primary responsibility for facilitating 

the development and incorporation of new cost-effective technologies into the converged system. 

The first converged NPOESS satellite is expected to be available for launch in the latter half of 

the decade, approximately 2008, depending on when the remaining POES and DMSP program 

satellite assets are exhausted. Present plans call for the program to run until 2018.

The Visible/Infrared Imager Radiometer Suite (VIIRS) on NPOESS (http://npoesslib.ipo.noaa. 

gov/S_viirs.htm) will collect visible/infrared imagery and radiometric data, including sea surface 

temperature and ocean color. The VIIRS combines the radiometric accuracy of the AVHRR 

currently flown on the NOAA polar orbiters with the high spatial resolution (0.65 kilometer) of 

the operational line-scan system (OLS) flown on DMSP. The VIIRS thus provides the 

capabilities to produce higher resolution and more accurate measurements of sea surface 

temperature than currently available from the AVHRR instrument on POES, as well as an 

operational capability for ocean color observations and a variety of derived ocean color products.

5. Ocean Color

For most regions of the world, the color of the ocean is determined primarily by the abundance of 

phytoplankton and their associated photosynthetic pigments. As the concentration of 

phytoplankton pigments increases, ocean color shifts from blue to green. Taking advantage of 

this change, NASA developed the Coastal Zone Color Scanner (CZCS) that was launched on the 

Nimbus-7 satellite in October 1978. During its 7 1/2 year lifetime (October 1978 - June 1986), 

CZCS acquired nearly 68,000 images, each covering up to 2 million square kilometers of ocean 

surface (http://daac.gsfc.nasa.gov/DATASETDOCS/czcsdataset.html).

The CZCS was a multi-spectral line scanner devoted principally to measurements of ocean color. 

It had six spectral bands (channels). Four channels were devoted to ocean color, each having a 20 

nanometer band width centered at 443, 520, 550, and 670 nanometers. These are referred to as 

channels 1 through 4, respectively. Channel 5 sensed reflected solar radiance and had a 100-

nanometer bandwidth centered at 750 nanometers and a dynamic range more suited to land. 

Channel 6 operated in the 10.5 to 12.5 micrometer region and sensed emitted thermal radiance 

for derivation of equivalent black body temperature. The CZCS level 1, 2, and 3 data products 

are available from the Goddard Space Flight Center Distributed Active Archive Center (DAAC).

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (http://seawifs.gsfc.nasa.gov/ 

SEAWIFS.html) is a follow-on sensor to the CZCS to study ocean productivity and interactions 

between the ocean ecosystems and the atmosphere. 

The SeaStar satellite carrying the SeaWiFS was placed 

in an initial parking orbit of 278 kilometers using an 

aircraft/rocket launch procedure. Once the systems 

were tested, the satellite's orbit was slowly raised 

through a series of very short rocket firings over a 30-

day period until it reached its operational altitude of 

705 kilometers. On September 4, 1997, the SeaWiFS 

instrument was turned on.

SeaStar Satellite Carrying SeaWiFS
U.S. National Report on Systematic Observations, August 2001

60

The purposes of SeaWiFS data are to examine oceanic 

factors that affect global change and to assess the oceans' 

role in the global carbon cycle, as well as other 

biogeochemical cycles, through a comprehensive 

research program. Coupled ocean-atmosphere models 

indicate that changes in phytoplankton community 

structure and the resulting elemental interactions can 

drastically affect the rate of CO2 increase in the 

atmosphere. Moreover, ocean biogeochemistry and 

circulation interact over a large range of temporal and 

spatial scales. This coupling between large and small 

scales leads to the fundamental sampling requirement of 

global scale, long time series (decades) at moderate 

temporal and spatial scales (days and kilometers). The 

NPOESS will continue to monitor ocean color globally.

K. Miscellaneous

1. Current Transport from Voltage Measurements

The motion of an ocean current through the earth's 

magnetic field creates a cross-stream voltage 

proportional to the transport of a mass of water. The 

data are used in models of the ocean circulation to 

evaluate numerical models being developed for 

climate studies. Such voltage measurements are 

being made in several other locations by a number of 

different researchers in the Pacific and Atlantic 

Oceans, and are in the planning stages for other 

cables. Motion-induced voltages were used to 

monitor the flow of the Florida current from 1982 to 

1991 by the use of an out-of-service 

cable spanning the Florida Current at 

27E N between Jupiter Inlet, Florida, 

and Settlement Point, Grand Bahama 

Island. Voltage measurements between 

West Palm Beach, Florida, and Eight 

Mile Rock, Grand Bahama Island, 

observed since 1985 (except for a brief 

period in 1999-2000) using an in-service 

cable, are now being used to continue 

Undersea Cables Used to Monitor the 

Flow of the Florida Current

Image of the Global Biosphere (September 97 -

August 98) Atlantic Projection

Daily (Green) and Mean (Blue) Transport of the Florida Current
U.S. National Report on Systematic Observations, August 2001

61

these measurements of the Florida current transport. The voltage-derived transports are compared 

with transport derived from profiling at 27E N that provides the calibration factor to convert 

voltage to transport (http://www.pmel.noaa.gov/wbcurrents/cabletransport.html).

2. Coral Reef Observations

Coral reefs are in serious decline globally, especially those near 

shallow shelves and dense populations. It has been estimated that 

10 percent of the earth's coral reefs have already been seriously 

degraded and a much greater percentage is threatened. If allowed 

to continue, this decline is likely to lead to the loss of most of the 

world's reef resources during the next century. NOAA's Coral 

Health and Monitoring Program (CHAMP) provides facilities for 

researchers and laypersons to witness, act upon and learn about 

threats to the health of all coral reefs. The Global Coral Reef 

Monitoring Network (GCRMN) has been established to address 

these problems. Its major product will be the facilitation of 

networks of people trained to look closely at coral reefs and to 

monitor their progress over time.

The U.S. is developing a Coral Reef Early Warning System 

(CREWS) as part of the GCRMN. CREW is a combination of 

observing systems for near real-time monitoring of oceanographic 

and atmospheric conditions and software/ communications to 

acquire and transmit the data in near real-time for processing and dissemination. CREWS 

interfaces with existing systems such as NWS’ C-MAN stations and augments those systems 

when necessary. The CREWS atmospheric observations are barometric pressure, wind speed and 

direction, wind gust, and air temperature. Oceanographic observations are photosynthetically 

active radiation, temperature, salinity, fluorometry, transmissometry, and tides. New 

instrumentation under development includes UV-B radiation, pCO2, and nutrients. In addition to 

six sites in the Florida Keys, a new site is being implemented at Lee Stocking Island in the 

Bahama Islands. Sites are proposed for 

St. John’s in the U.S. Virgin Islands, 

Puerto Rico, and American Samoa.

3. Trans-Pacific Profiler Network

The development of a set of baseline 

climate observations, calibrations, and 

model initialization and validation has 

been severely hampered by the lack of 

baseline atmospheric observations over 

the oceans. There is a serious lack of 

information on the distribution of key 

surface parameters, such as rainfall, as 

well as upper air parameters. The 

Trans-Pacific Profiler Network 

A CREWS Platform

Lee Stocking Island, Bahamas
U.S. National Report on Systematic Observations, August 2001

62

(http://www.al.noaa.gov/WWWHD/pubdocs/ElNino.html) comprises vertically directed Doppler 

radars, called wind profilers, located on six remote island sites spanning the tropical Pacific 

Ocean. The instruments use "clear air" atmospheric echoes to measure a "profile" of both 

horizontal winds and vertical motions, at heights from the surface to 5-15 kilometers (depending 

on the frequency of the instrument). In addition to the wind profile, information about 

precipitation and atmospheric turbulence is obtained.
U.S. National Report on Systematic Observations, August 2001

63

Table S7. National Climate Monitoring Systems for Oceanographic Observations.

Network Component

Total # 

Stations

Appropriate for

Characterizing

National/Regional 

Climate?

Time Series

#stations/platforms (#Data 

Digitized)

Are QC Procedures Adequate?

Fully Partly No 30y 50y 100y Fully Partly No

Metadata 

available?

Total # 

Stations

(%Digitized)

Continuity

# expected 

operational 

in 2005

Sea Level e.g., Tide 

gauges

244 X X 244

SST (e.g., Moored 

Buoys, Drifting 

Buoys)

~642 X X ~640

Meteorological Obs 

(e.g., Temp, Precip, 

Pressure)

1,478 X X ~1,478

Sub-Surface Profiles 

(e.g., moorings, 

floats, stations, as of 

2001)

260 X X ~1,000

Ocean Circulation

Carbon Fluxes (e.g., 

ships and moorings)

Continuous 

Shipboard 

Observations (# of 

legs of cruises)

114 X X

Not 

Applicable

Energy Fluxes 1 X X 0
U.S. National Report on Systematic Observations, August 2001

64

Table S8. Available Homogeneous Data Sets for Oceanographic Observations.

Integrated Data Sets

Name and Brief Description Variable Platforms and/or grid resolution DescribePeriod References

WORLD OCEAN ATLAS 1998 

FIGURES

Temperature, salinity, 

oxygen, nutrients, and 

chlorophyll.

http://www.nodc.noaa.gov/OC5/WOA98F/open_1st.html

WOCE Global Data Version 2.0 

2000

Summaries 

 Acoustic Doppler Current Profilers 

 Bathymetry

 Current Meters

 Drifting Buoys

 Floats

 Hydrography

 Satellite Observations

 Sea Level

 Surface Meteorology

 Upper Ocean Thermal Data

1990-

1998

http://www.cms.udel.edu/woce/

World Ocean Database 1998 Expands on World 

Ocean Atlas 1994 

(WOA94) by including 

the additional variables 

nitrite, pH, alkalinity, 

chlorophyll, and 

plankton, as well as all 

available metadata and

meteorology.

http://www.nodc.noaa.gov/OC5/pr_wodv2.html

World Ocean Atlas 1994 In-situ temperature, 

salinity, oxygen, 

phosphate, nitrate, and 

silicate.

The series contains the objectively 

analyzed one-degree latitudelongitude mean fields for each of the 

measured parameters, and two 

derived parameters (Apparent Oxygen 

Utilization and Oxygen Saturation), 

and five-degree square statistics of 

standard level values.

http://www.nodc.noaa.gov/OC5/woadet.html

Oceanographic Station Profile Time 

Series

Temperature, salinity, 

density, and nutrients.

27 North Pacific sections; 56 North 

Atlantic sections; sections along 

coastal California from the California 

Cooperative Fisheries Investigations 

(CALCOFI); 19 sections from other 

ocean regions; and data from the 10 

Ocean Weather Stations.

http://www.nodc.noaa.gov/General/CDR-detdesc/timeseries.html
U.S. National Report on Systematic Observations, August 2001

65

Integrated Data Sets

Name and Brief Description Variable Platforms and/or grid resolution DescribePeriod References

Global Ocean Temperature and 

Salinity Profiles

Temperature, salinity. Two CD-ROMs contains global ocean 

temperature and salinity profiles 

derived from six major NODC archive 

files:

(1) Oceanographic Station Data,

(2) CTD/STD Data,

(3) Expendable Bathythermograph 

Data,

(4) Mechanical Bathythermograph 

Data,

(5) Radio Message Bathythermograph 

Data, and

(6) Selected Level Bathythermograph 

Data.

1.62 million profiles from the Atlantic 

and Indian Oceans; 1.57 million 

profiles from the Pacific Ocean

1900-

1990

http://www.nodc.noaa.gov/General/CDRdetdesc/gots_cds.html

Atlas of Surface Marine Data 1994 Wind, air and sea 

surface temperature, 

sea level pressure, 

humidity, and present 

weather.

Voluntary Observing Fleet. 

Observations included in this historical 

collection have also been taken by 

various military ships, ocean weather 

ships, light ships, research vessels, 

buoys, and bathythermographs.

1945-

1989

http://www.nodc.noaa.gov/OC5/asmdesm.html

Geosat Global Wind/Wave Data Global wind/wave data derived from 

altimeter data

March 31, 

1985 

through 

Septembe

r 30, 1986

http://www.nodc.noaa.gov/General/CDRdetdesc/geosatww.html

Ocean Current Drifter Data Ship and Subsurface Float 1972-

1992

http://www.nodc.noaa.gov/General/CDRdetdesc/ocurdesc.html

Sea Level Data http://www.nodc.noaa.gov/General/CDRdetdesc/sealevel_cd.html

Comprehensive Ocean-Atmosphere 

Data Set (COADS)

Sea surface 

temperature, wind, 

cloudiness, air 

temperature, sea level 

pressure, relative 

humidity

Individual observations (surface 

marine reports from ships, buoys, etc.) 

monthly summary statistics for 2° 

latitude x 2° longitude boxes (and for 

1°x1° boxes since 1960)

1784-

1997

http://www.cdc.noaa.gov/coads/products.html
U.S. National Report on Systematic Observations, August 2001

66

Integrated Data Sets

Name and Brief Description Variable Platforms and/or grid resolution DescribePeriod References

Carbon Dioxide Information 

Analysis Center (CDIAC)

CO2-related parameters 

(TCO2, pCO2, alkalinity, 

and pH), salinity, and 

the concentrations of 

dissolved oxygen and 

macro-nutrients along 

constant seawater 

density surfaces.

An effort to measure the global spatial 

and temporal distributions of T(CO2) 

and other related parameters. Goals of 

the survey are to estimate the 

meridional transport of inorganic 

carbon in a manner analogous to the 

oceanic heat transport, and to build a 

data base suitable for carbon cycle 

modeling and the estimation of 

anthropogenic CO2 increase in the 

oceans. The CO2 survey is taking

advantage of the sampling 

opportunities provided by the WOCE 

Hydrographic Program and JGOFS 

cruises.

1990-

1998

http://cdiac.esd.ornl.gov/oceans/home.html

Ocean Atmosphere Carbon 

Exchange Study

Partial pressure of CO2

in the surface ocean 

and overlying 

atmosphere, and total 

dissolved inorganic CO2

(DIC) in the surface and 

deep ocean water 

masses.

Investigations of processes controlling 

air-sea exchange of carbon dioxide, as 

well as the rate and direction of that 

exchange throughout the major basins

of the world oceans. Core components 

of this effort are (1) process studies 

conducted cooperatively with JGOFS 

pilot studies, (2) "long lines" occupied 

on approximately five year intervals 

along WOCE lines, and (3) continuous 

underway sampling from research 

vessels.

1986-

Present

http://ingrid.ldgo.columbia.edu/SOURCES/.LDEO/. 

Takahashi

http://www.aoml.noaa.gov/ocd/oaces/co2/

http://www.pmel.noaa.gov/co2/co2-home.html

Joint Archive for Sea Level Hourly sea level heights JASL prepares scientifically valid data 

sets of hourly, daily, and monthly 

values which are submitted annually to 

international data banks and are made 

readily available in a more timely 

fashion through the Internet.. As of 

November 2000, 474 series with 8216 

series-years of quality-assured data. 

The objective is to assemble a 

scientifically valid, well-documented 

archive of hourly, daily, and monthly 

sea level values in standardized 

formats.

Generally 

1970-

Present 

with a few 

sites 

going 

back to 

1930.

http://ilikai.soest.hawaii.edu/UHSLC/jasldr00/manual.html
U.S. National Report on Systematic Observations, August 2001

67

III. Terrestrial Observations

A. Status of the National Terrestrial Portion of the GCOS Program

The requirements for terrestrial climate observations were developed jointly between GCOS and 

the Global Terrestrial Observing System (GTOS) through the Terrestrial Observations Panel for 

Climate (TOPC); reference GCOS publication 32. As with atmospheric and oceanographic 

observations, terrestrial observing is also highly dependent on the importance of satellite 

observations, and again, while this section focuses on in-situ observing systems, a full picture of 

satellite observing can be found in section IV of this report.

1. U.S. Component of the Global Terrestrial Network for Permafrost

The GCOS and the GTOS have identified the permafrost thermal state and the permafrost active 

layer as key variables for monitoring the state of the cyrosphere. Changes in permafrost 

temperature and active layer thickness frequently reflect changes in surface climate over time, 

and therefore serve as useful indicators of climate change. The GCOS steering committee 

recently (February 1999) approved the development of a globally comprehensive permafrost 

monitoring network to detect temporal changes in the solid earth component of the cryosphere. 

As such, the Global Terrestrial Network for Permafrost (GTN-P) is quite new and still very much 

in the developmental stage. The International Permafrost Association (IPA) has taken the 

responsibility for managing and implementing the GTN-P (see http://www.geodata.soton. 

ac.uk/ipa).

The GTN-P network has two primary observational components: the active layer (i.e. the surface 

layer that freezes and thaws annually) and the thermal state of the underlying permafrost. Despite 

its youth, parts of the GTN-P are already in place through nationally and regionally funded 

programs. The active layer is monitored by a network of stations (Circumpolar Active Layer 

Monitoring network, CALM) involving 12 countries. These stations provide an important 

component of the GTN-P. In addition, borehole temperature measurements used to characterize 

the thermal state of permafrost, have been made for years under various national and regional 

programs. The GTN-P serves to organize this work into an international monitoring effort.

In the U.S., the GTN-P network is funded primarily by the NSF and the Department of the 

Interior (DOI). This is accomplished through grants to various universities. The DOI contribution 

results from a collaboration between the USGS, the BLM, and the FWS (the USGS is the lead 

agency). The U.S. Forest Service also has two sites. All of the U.S. GTN-P stations are located in 

Alaska.

Active layer thickness is currently being monitored at 27 sites in Alaska. Many of these 

instrumented sites also monitor soil temperature (at several depths), soil moisture, snow depth, 

and air temperature. Sixteen of the active layer sites are co-located with boreholes where the 

permafrost thermal state can be monitored. All sites are appropriate for characterizing national 

climate. The first of the GTN-P active layer monitoring stations were installed in 1991. Station 

data are provided annually to the University of Cincinnati, where active layer data management 

for the Northern Hemisphere occurs. Summary data are then made available via the Internet 

(http://www.geography.uc.edu/CALM).
U.S. National Report on Systematic Observations, August 2001

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Forty-eight boreholes exist in Alaska where permafrost thermal state can be determined. Of 

these, 4 are classified as Surface (0-10 m) sites, 1 is Shallow (10-25 m), 22 are Intermediate 

Depth (25-125 m), and 21 are Deep Boreholes (>125 m). The frequency of measurement varies 

greatly according to the total depth of the boreholes. The Geological Survey of Canada is 

providing the international data management for the GTN-P borehole temperature monitoring 

(permafrost thermal state) program and maintains the GTN-P web site (http://sts.gsc.nrcan.gc.ca/ 

gtnp/index.html). GTN-P data, both active layer and permafrost thermal state, will subsequently 

be archived at the National Snow and Ice Data Center (Boulder, CO) as part of IPA's Global 

Geocryological Database.

One issue concerning the U.S. contribution to the GTN-P network is that all funding currently 

comes from short-term (3-5 yr) research projects. All sites require logistical support and funding 

for equipment maintenance and upgrades if they are to continue to operate. More substantial, 

long-term commitments are needed if the GTN-P is to be a viable long-term monitoring network. 

While the current network should be expanded to include the sub-arctic and high elevation sites 

in the contiguous U.S. (where changes are expected to happen more quickly), and to identifying 

sites in the Antarctic, the current federal budget plan for fiscal year 2002 does not accommodate 

that expansion.

2. U.S. Component of the Global Terrestrial Network for Glaciers (GTN-G)

The USGS operates a long-term "benchmark" glacier program to intensively monitor climate, 

glacier motion, glacier mass balance, glacier geometry, and stream runoff at a few select sites. 

The data collected are used to understand glacier-related hydrologic processes and improve the 

quantitative prediction of water resources, glacier-related hazards, and the consequences of 

climate change.

The approach has been to establish long-term mass balance monitoring programs at three widely 

spaced glacier basins in the U.S. that clearly sample different climate-glacier-runoff regimes. The

three glacier basins are South Cascade Glacier in Washington State, and Gulkana and Wolverine 

Glaciers in Alaska. Mass balance data are available beginning in 1959 for the South Cascade 

Glacier, and beginning in 1966 for the Gulkana and Wolverine Glaciers. Additional information 

and data for the benchmark glaciers is available at http://ak.water.usgs.gov/glaciology/.

3. U.S. Component of the Global Terrestrial Network for Carbon (FLUXNET - AmeriFlux)

The U.S. DOE’s Global Terrestrial Network for Carbon (FLUXNET - AmeriFlux) network 

(http://cdiac.esd.ornl.gov/programs/ameriflux/) generally endeavors to establish an infrastructure 

for guiding, collecting, synthesizing, and disseminating long-term measurements of CO2, water, 

and energy exchange from a variety of ecosystems. Its objectives are to collect critical new 

information to help define the current global CO2 budget, enable improved predictions of future 

concentrations of atmospheric CO2, and enhance the understanding of carbon fluxes, Net 

Ecosystem Production (NEP), and carbon sequestration in the terrestrial biosphere. Other major 

sponsors of the Ameriflux network include NOAA, USFS, NASA, NSF, DOD, and USGS.

The AmeriFlux data archive at the Carbon Dioxide Information Analysis Center (CDIAC) offers 

two types of AmeriFlux data. Preliminary data are contributed by AmeriFlux principal 

investigators (PI). The file formats and contents are unchanged from their original submission 
U.S. National Report on Systematic Observations, August 2001

69

state. Any descriptive files provided are those furnished by the site PIs. The values provided in 

these preliminary files have been scrutinized by the PIs but are subject to change. Users are 

required to communicate with the contributing PIs before performing data analyses and are 

reminded that data used for publication are subject to AmeriFlux FAIR USE rules.

Preliminary AmeriFlux data sent to CDIAC are checked, processed into a consistent data format, 

and documented by CDIAC before release as a final data set. Again, users are required to interact 

with the contributing PIs before publishing any results based on final AmeriFlux data and 

reminded that data used for publication are subject to AmeriFlux Fair Use rules. This includes 

informing the appropriate Principal Investigator of how site data is being used and of any 

associated publication plans.

The AmeriFlux network is included in and coordinated with the worldwide FLUXNET CO2 flux 

measurements.

4. Streamflow and Surface Water Gaging

The USGS operates a network of about 6,760 streamgaging stations at which continuous records 

of water level (stage) and streamflow (discharge) are obtained. The USGS compiles, analyzes, 

and publishes data for these stations annually. In addition, the USGS publishes furnished data for 

about 630 streamgaging stations operated by other Federal, state, and local agencies. These 7,400 
U.S. National Report on Systematic Observations, August 2001

70

stations have a mean record length of 39 years, with a maximum record length of 126 years. 

Historical streamflow data for all of the streamgaging stations and real-time data for about 5,350 

stations that are equipped with telemetry can be retrieved from the Internet at 

http://water.usgs.gov/nwis.

Most of the streamgaging stations in the USGS network are not useful for analyzing changes in 

climate because the stations are affected by human influences, such as diversions, dam 

regulations, and urban land uses. A group of 1,659 stations, named the Hydro-Climatic Data 

Network (HCDN), was identified and data was compiled for the stations for use in studies of 

climate change. The HCDN stations are described and data for them can be obtained from the 

WWW at http://wwwrvares.er.usgs.gov/hcdn_cdrom/1st_page.html. Periods of data collection 

spanned 44 years on average for the HCDN stations in 1988, when the data were compiled. Data 

began as early as 1874. Since 1988, however, 444 of the original 1,659 HCDN stations have 

ceased operating, primarily because of lack of funding.

Concern about losses to its streamgaging network has prompted the USGS and its partners to 

develop the National Streamflow Information Program (NSIP). Information on NSIP can be 

obtained at http://water.usgs.gov/nsip/. The NSIP plan would increase the level of streamflow 

information available for National needs, improve the way streamgaging stations are funded and 

located, and develop new ways to collect, store, and distribute streamflow information. Those 

streamgaging stations providing data that meet Federal needs, such as analyses of climate change, 

would be funded entirely through Federal appropriations under the NSIP plan rather than funded 

in cooperation with other agencies, as is the current practice. During the previous two fiscal 

years, the USGS has received increased appropriations that were used to begin implementing the 

NSIP.

The USCOE uses data from 8,810 gaging stations that produce about 150,000 pieces of data 

daily. This represents the bulk of surface water data collected and/or used by DOD within the 

USA. About 85 percent of the data are recorded hourly and telemetered in real-time. Each station 

measures from one to twelve parameters. A site commonly measures precipitation, temperature, 

and stream water levels, but may include evaporation, wind speed, barometric pressure and water 

quality parameters.

Unlike most agencies, the primary purpose of USCOE gages is tied to its civil works mission of 

planning, constructing, and operating water projects. In addition to projects owned by the 

USCOE, during floods the USCOE takes control all federal flood control storage regardless of 

project ownership. Also, it performs emergency activities wherever needed. USCOE 

responsibilities include about 600 USCOE dams, reservoirs, pump stations and local protection 

projects, 108 non-USCOE flood control reservoirs, and 8,500 miles of federal levees and channel 

diversions or modifications. Emergency activities include flood fighting and technical assistance, 

providing materials, and temporary construction. Because the gaging stations are related to 

projects, their locations are not evenly distributed, but grouped by river basins to meet project 

data needs.

Significant flood damage reduction benefits are derived from the project regulation via 

data from the gauging system. Over the past ten years (1991-2000) the USCOE prevented an 

average of $20.8 billion in damages annually. In addition, with flood reduction projects in 

operation the number of flood-related lives lost has dramatically fallen. The year 1980 marked 
U.S. National Report on Systematic Observations, August 2001

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the completion of most large flood reduction projects. Despite major flooding in 1983, 1986, 

1993 and 1997, the ten-year average of flood-related fatalities has dropped from 176 deaths in 

1981 to 89 in 2000. Although flood reduction projects are not the only factor impacting this 

statistic, they significantly contribute to the reduction. The benefits of flood control projects 

regulated by the gaging system are available at http://www.usace.army.mil/inet/functions/.

All USCOE data is available for climate change analysis. Even though streamgaging data are 

affected by river regulation, coefficient data from historic records and the USCOE river model 

can reconstruct natural river flows. USCOE computer models also use the data to forecast future 

river and streamflow levels. Regulators use forecasts to fine-tune discharge amounts from dams 

to optimize flood reduction and to improve environmental conditions. Data and forecasts are 

archived and shared with multiple agencies. NOAA/NWS uses 100 percent of SCOE data in its 

models. The USGS archives much of the streamflow data. Other federal, state and local agencies 

mutually share their data with the USCOE.

5. Hydromet System

The Bureau of Reclamation’s (BR) Hydromet system 

is a data collection and distribution system that 

supports the BR's mission of water resource 

management. Hydromet data collection supports 

reservoir and water project operations, water 

management, and water supply forecasting for BR's 

multipurpose reservoir systems in a number of basins 

including the Columbia and Snake River basins. Water uses supported by the Hydromet system 

include flood control, irrigation, power generation, water quality, water conservation, fish and 

wildlife management, research, and recreation. The Hydromet database provides an excellent 

source of information for water management planning activities. 

Hydromet consists of approximately 400 unstaffed data collection platforms located at dams, 

streams and mountain areas in the Pacific Northwest and Great Plains. The system also collects 

data from approximately 1100 similar stations maintained by other organizations. These stations 

typically collect data in 15- or 60-minute increments, and then transmit collected data every 4 

hours via the GOES satellite network. Data indicating abnormal conditions can be transmitted 

more frequently on special satellite channels. Data are received at a central downlink site in 

Boise, Idaho, as well as at NASA’s facility in Wallops Island, Virginia.

Other sources of Hydromet data include radio-controlled stations that can be interrogated at any 

time and instrument readings manually entered into the computer system. The relatively shortrange radio-controlled sites are commonly found near large water projects where bi-directional 

control systems or time-critical data are important. Data from the radio sites are transmitted to 

the central Boise site via the Internet.

Data collection platforms carry a variety of environmental sensors that monitor conditions such 

as water level, gate position, temperature, precipitation, water and barometric pressure, dissolved 

gas content, solar radiation, evaporation, wind speed and direction. Many data collection 

platforms are a result of cooperative agreements between the Bureau of Reclamation and other 
U.S. National Report on Systematic Observations, August 2001

72

organizations. Hydromet station information and data are available at: http://www.gp.usbr.gov/ 

www/hydromet.htm and http://mac1.pn.usbr.gov/hydromet/mcf_list.html.

6. Ground Water Monitoring Wells

The USGS operates a national network of 150 ground-water monitoring wells for use in climate 

change studies. Explanation of the network and a list of stations are provided on the WWW at 

http://water.usgs.gov/ogw/CBR.html. The wells have a mean record length of 32 years, with a 

maximum record length of 83 years. Historical water levels for all of the wells and real-time data 

for 27 wells that are equipped with telemetry can be retrieved at http://water.usgs.gov/nwis.

7. Manual Snow Courses

The USDA's Natural Resources Conservation Service (NRCS) operates a manual network of 

1205 snow courses located in the western U.S., including Alaska. Some snow courses have more 

than 90 years of record, and many have at least 30 years. The manual snow course network is a 

transect made up of 5 to 50 measurement points measured using a federal snow sampler. The 

distance between each sample point is consistent, with most being 5 to 50 feet apart. Most 

manual snow courses have 5 to 10 sample points. Manual snow courses are typically measured 

on a monthly basis from January through May. Snow depth, water content, and snow density are 

averaged for each snow course. Nearly 900 additional snow courses have from 1 to 60 years of 

historical record but have now been discontinued. Of the 1205 operational courses, 

approximately 50% of the available metadata have been digitized and are available upon request.

8. SNOwpack TELemetry (SNOTEL)

The SNOTEL system began operation by NRCS in 

the late 1970’s. It is designed to provide near realtime snowpack information. The SNOTEL system 

operates in the western U.S. and Alaska. It uses 

meteor burst communication technology to obtain 

remote site information and deliver it to the 

National Water and Climate Center (NWCC) 

central computer system. Once the data are ingested 

into the NWCC computer system, they are made 

available to users in a variety of ways. SNOTEL 

collects, at a minimum, daily Snow Water 

Equivalent (SWE), accumulated water year precipitation, current, maximum, minimum, and 

average daily air temperature at all sites. About 15% of the SNOTEL system has additional 

sensors, measuring wind speed and direction, soil moisture and temperature, and other elements. 

At present, 200 of the 665 operational SNOTEL stations have nearly 25 years of record. Daily 

time increment SNOTEL data are thoroughly quality controlled, while hourly data receive a 

much lower level of quality control. Approximately 50% of the total potential metadata for all 

SNOTEL stations has been digitized and can be made available upon request. Details of station 

moves, instrumentation changes, location information, and other metadata are less likely to be 

available, at least not in a readily accessible format. Information about the SNOTEL network, 
U.S. National Report on Systematic Observations, August 2001

73

and access to the data, is available by clicking on "snow" at the NWCC homepage: 

http://www.wcc.nrcs.usda.gov/.

9. Airborne, Satellite, and Modeled Snow Cover Data

NOAA’s National Operational Hydrologic Remote Sensing Center (NOHRSC) provides 

remotely sensed and modeled products and data sets to support the NWS Hydrologic Services 

Program for the U.S. The NOHRSC generates satellite-derived a real extent of snow cover 

observations, and makes airborne snow water equivalent measurements over large regions of the 

country.

The NOHRSC satellite remote sensing program 

uses NOAA GOES and AVHRR data. Data ingest 

and pre-processing steps are performed 

automatically, including data calibration and 

orbital navigation, image alignment with surface 

features, solar normalization of visible data, and 

cloud detection (Carroll, et al., 2000). Manual 

image analysis is used to classify snow cover from 

image data. The image-processing environment 

incorporates a variety of geospatial data sets to 

facilitate the image classification process. The principal product is a daily map of areal extent of 

snow and cloud cover for the continental U.S. Additionally, the NOHRSC maintains an Airborne 

Gamma Radiation Snow Survey Program to make near real-time snow water equivalent 

measurements over a network of 1,900 flight lines covering portions of 29 states and 7 Canadian 

provinces (Carroll, 1985). The ability to make reliable airborne gamma radiation snow water 

equivalent measurements is based on the fact that natural terrestrial gamma radiation is emitted 

from the potassium, uranium, and thorium radioisotopes in the upper 20 cm of soil. The radiation 

is sensed from a low-flying aircraft flying 150 m above the ground. Water mass in the snow 

cover attenuates, or blocks, the terrestrial radiation signal. Consequently, the difference between 

terrestrial radiation measurements made over bare ground and over snow-covered ground can be 

used to estimate the mean areal snow water equivalent over the approximately 2-3 km2flight line 

with a root mean square error of less than one cm.

Satellite-derived snow- and cloud-cover products are used in conjunction with airborne and 

ground-based observations of snow water equivalence to perform analyses of the spatial 

distribution of snow water equivalent. Daily maps of snow water equivalence are generated using 

available ground-based and airborne snow water equivalent data sets. Additionally, regional 

snow water equivalent maps for the central and eastern U.S. are produced following each 

NOHRSC airborne snow survey mission. Alphanumeric summaries of these maps are provided, 

in near real-time, to operational hydrologic forecasters in NWS field offices to support river, 

flood, and water supply forecasting. Lastly, the NOHRSC routinely generates daily surface 

temperature, cumulative freezing and thawing degree-day, and snow depth (from cooperative 

observer data) products for the coterminous U.S. Temporal composites of satellite-derived areal 

extent of snow cover and cooperative observer snow depth products are generated each week. 

Information about NOHRSC and its data products is available at http://www.nohrsc.nws.gov/.
U.S. National Report on Systematic Observations, August 2001

74

Additionally, the office ingests a wide variety of near real-time, ground-based 

hydrometeorological data sets along with real-time, numerical weather prediction (NWP) model 

data sets for the country. NWP model output data sets are used to force a physically-based, snowmodeling, and snow-data-assimilation system. The ground-based, airborne, and satellite snow 

cover observations will soon be assimilated, in near real-time, into the gridded fields generated 

by the snow accumulation and ablation model. Snow model products include a variety of 

alphanumeric and gridded representations of the snow pack state variables. A distributed, energyand-mass-balance snow model and data assimilation system has been developed and 

implemented at the NOHRSC to augment basic hydrologic analysis. The purpose of the Snow 

Data Assimilation System (SNODAS) is to provide a physically consistent framework for 

integrating the wide variety of snow data that is available at various times. SNODAS includes: 

(1) data ingest and downscaling procedures; (2) a spatially distributed energy-and-mass-balance 

snow model that is run once each day, for the previous 24-hour period and for a 12-hour forecast 

period, at high spatial (1 km) and temporal (1 hr) resolutions; and (3) data assimilation and 

updating procedures. The snow model is driven by downscaled analysis and forecast fields from 

a mesoscale, NWP model, surface weather observations, satellite-derived solar radiation data, 

and radar-derived precipitation data. The snow model states can be updated using satellite, 

airborne, and ground-based snow observations. The model is cast in an assimilation framework 

and serves to organize various snow observations and to track the evolution of the snow pack 

between observations. SNODAS permits more frequent and timely product generation–near realtime model analyses and forecasts–and provides several new products, including maps of 

modeled snow characteristics such as snow ripeness, melt rates, and sublimation losses.

10. Soil Climate Analysis Network (SCAN)

Currently, NRCS operates the Soil Climate Analysis 

Network (SCAN), which has data sites across the 

U.S., including Puerto Rico. Most of the SCAN 

sites have been funded by sources outside NRCS. 

SCAN will focus on agricultural areas of the U.S. If 

SCAN were fully funded, it would allow for 1,000 

new sites and integrate an additional 1,000 existing 

cooperator sites to form the basis for the network. 

The typical SCAN station reports precipitation, air 

temperature, and maximum, minimum, average 

hourly and average twenty-four hour temperature information. They also measure solar radiation, 

relative humidity, wind speed and direction, soil moisture and temperature down to 40 inches 

deep. All basic SCAN data are available via the NRCS web page http://www.nrcs.usda.gov/.

Approximately 10 of the 44 operational SCAN stations have nearly 20 years of record. Daily 

time increment SCAN data are thoroughly quality controlled, while hourly data receive a much 

lower level of quality control. Approximately 50% of the total potential metadata for all SCAN 

stations has been digitized and can be made available upon request. Details of station moves, 

instrumentation changes, detailed location information, and other metadata are less likely to be 

available–at least not in a readily available format.
U.S. National Report on Systematic Observations, August 2001

75

11. Paleoclimatology

Unlike instrumental data, the paleoclimate data in Table S10 come from 

a variety of sources. Each source represents a "proxy" for climatic 

conditions that are derived from these biological or environmental data. 

Temperature measurements in deep boreholes provide a direct signal of 

past temperatures at the surface. Using mathematical inversion 

techniques, temperature records at decadal to millennial scales can be 

computed. Geochemical analyses of coral skeletons provide seasonal to 

annual scale records of past temperature, rainfall, cloudiness, and 

environmental factors. Growth rings and inclusions in the skeleton can 

yield additional annual records of climate. Flora and fauna change in 

their distributions as they experience changes in climate. These lower 

time-resolution data can be dated radiometrically with high precision, 

but response times of the organisms must be factored in as well. This applies to faunal records, 

plant macrofossils, and pollen. Records from paleolimnological and paleoceanographic sources 

provide annually dated records in some locales and decadal scale records in others. However, the 

abundance of biota in lakes and oceans can change rapidly (within a season) in response to 

climate signals, thus avoiding problems of response time. These can provide records as to 

temperature, rainfall, wind, upwelling, and other environmental changes. Trees respond to 

climate and change their ring growth patterns at sub-seasonal time scales. These annually 

resolved records provide air temperature, precipitation and other environmental data that have 

been critical in regional to global reconstructions of temperature and drought and can provide 

information as detailed as mean annual streamflow.

Table S11 provides data on reconstructions of either large-scale climate indices or gridded 

climatic data. Each source of proxy data has its own advantages and disadvantages. Most 

reconstructions use a multi-proxy approach, mathematically building climate fields from spatially 

distributed networks of data from multiple data types. This effort is not without its difficulties, 

and the reconstructions are becoming better each year. The data sources in Table S11 include the 

best reconstructions and data sets of pre-instrumental climate available today. These 

reconstructions and the proxy data in Table S10 can be found at the NOAA Paleoclimatology 

Program website at http://www.ngdc.noaa.gov/paleo.

The following figures depict various 

paleoclimatology programs documented in 

Table S10.

Coral Data at 1 U.S. Site and 61 Global Sites

Extracting Coral Core with 

a Hydraulic Drill
U.S. National Report on Systematic Observations, August 2001

76

12. Ecological Observation Networks

a. Fire Inventory and Analysis Program

The Fire Inventory and Analysis (FIA) Program of the USFS has been monitoring and reporting 

on status, condition, and trends in the nation's forests for over 70 years (http://fia.fs.fed.us). FIA 

inventories provide a basic suite of vegetative data across all forested landscapes measured in a 

consistent and compatible manner on a systematic national grid. FIA collects, analyzes, and 

reports information on the status and trends of America’s forests. These include how much forest 

exists, where it exists, who owns it, and how it is changing, as well as how the trees and other 

forest vegetation are growing and how much has died or has been removed in recent years. This 

information is combined with related data on insects, diseases, and other types of forest damages 

and stressors to assess the health condition and potential future risks to forests.

Data collection is based upon double sampling for stratification. FIA has 3 phases: (1) remotely 

sensed data interpretation, known as Phase 1; (2) general field data collection through plot visits, 

known as Phase 2; and (3) detailed health and vitality measures on a subset of the phase 2 plots, 

known as Phase 3. Phase 1 provides primary information on the extent and distribution of forest 

cover. Phase 1 uses remote sensing in a combination of aerial photography, 30-meter TM 

imagery, and AVHRR imagery to determine forest areas to be selected for Phase 2 field data 

collection. Field visits confirm data and interpretations made from the remotely sensed data and 

provide additional data not observable from Phase 1, some 300 different variables. There are 

approximately 125,000 forested, Phase 2, sample plots across the U.S., roughly one for every 

6,000 acres of forest. Tree measurements on Phase 2 plots include species, diameter breast height 

Tree Ring Data at 1029 U.S. Sites and 1854 Global Sites

Pollen Data at 474 U.S. Sites and 1424 Global Sites

Plant Microfossil Data at 42 U.S. Sites
U.S. National Report on Systematic Observations, August 2001

77

(dbh), and total height, as well as more detailed 

measurements of status and vigor. On a subset of the 

Phase 2 plots, measures related to forest ecosystem 

function, condition, and health are collected. The current 

measurements include crown condition, soil erosion 

potential, soil chemical analyses, lichen communities, 

ozone bioindicator plants, vegetation structure, and down 

woody debris. Forest inventory data is the basis for 

monitoring changes in carbon stocks over intervals of 5-10 

years. The high sampling intensity allows detailed 

description of some of the causes of observed carbon stock changes, such as the effects of 

vegetation growth, mortality, and harvesting. Field information from phase 3 may be used to 

confirm indicator findings of Long-term Ecological Research LTER research (see section 11b 

below) on a broader scale.

Consistency is maintained through a nationwide forest survey field manual that specifies a core 

set of definitions, accuracy requirements, measurement standards, and reporting requirements. 

The current national standards provide an accuracy of ±3-5 percent per million acres 

(approximately ±1-2% per million hectares) of forested land and ±5-7 percent per billion cubic 

feet (approximately ± 3-4% per 100 million cubic meters) of volume or biomass. FIA fact sheets, 

statistics, online databases, and a map of U.S. forest distributions are available at 

http://fia.fs.fed.us.

b. LTER Network

Twenty-four research sites and a Network Office make up the U.S. Long-term Ecological 

Research (LTER) network (http://lternet.edu/data). Focusing on fundamental ecological research, 

each LTER site is supported by an individual grant from the NSF, with significant support from 

USGS, USFWS, NOAA, EPA, USDA, and numerous universities and other partners. The LTER 

sites are found in forest, desert, prairie, alpine, coastal and marine environments. The research 

topics addressed at sites are similarly varied, with research on ecological succession, disturbance, 

landscape ecology, elemental cycling, trophic structure, biodiversity, organic matter and primary 

productivity ongoing at each site. The sites also differ in their degree of centralization, with 

researchers from up to 15 universities at a single site.

The types of data collected and used at LTER sites are highly variable. Satellite images, scanned 

aerial photos, and output from spatially explicit models fall at the high-end of size, with an 

individual image requiring over 300 MB of disk space. At the other end of the spectrum are types 

of data, such as deep soil cores where a small number of samples are subjected to a large number 

of different tests. NSF’s proposed National Ecological Observatory Network (NEON) will 

establish 10 observatories located around the country that will serve as national research 

platforms for integrated studies in field biology. Each observatory will provide state-of-the-art 

infrastructure to support interdisciplinary, integrated research. Collectively, the network of 10 

observatories will allow scientists to conduct comprehensive, continental-scale experiments on 

ecological systems. Each NEON observatory will include site-based experimental infrastructure; 

natural history archive facilities; and facilities for biological, physical and data analyses; see 

http://www.mpcer.nau.edu/neon/ for more details.
U.S. National Report on Systematic Observations, August 2001

78

13. Fire Weather Observations Remote Automated Weather Stations

Remote Automated Weather Stations (RAWS) are weather stations set up on tripods, and are an 

important input to the USFS’ Weather Information Management System (WIMS). 

Approximately 1150 RAWS sites (depicted in red below) are strategically positioned throughout 

the U.S. Sensors on every RAWS unit are calibrated annually. RAWS sensors monitor: (1) wind 

speed and direction; (2) wind gusts; (3) precipitation; (4) air temperature; (5) relative humidity; 

and (6) fuel moisture. RAWS units collect, store, and forward data hourly, via the GOES satellite 

to a computer system located at the National Interagency Fire Center in Boise, Idaho. RAWS are 

often located in isolated areas accessible only by all-terrain vehicles, helicopters, snowmobiles, 

or backpacking trails. Fire managers use RAWS weather data to predict fire behavior and 

monitor fuels. Resource managers also use RAWS to monitor environmental conditions and air 

quality. Some RAWS units are used as early-alert warning systems for floods, mudslides, or 

hazardous material levels. RAWS station information and data are available at: 

http://raws.boi.noaa.gov/rawsidx.html and http://raws.boi.noaa.gov/rawsobs.html.

14. Global, National, and Regional Land Cover Characterization

The USGS began the Land Cover Characterization Program (LCCP) in 1995 to develop land 

cover and other land characterization databases to address national and international 

requirements that were becoming increasingly sophisticated and diverse. To meet these 

requirements, USGS develops multiscale land cover characteristics databases used by scientists,

resource managers, planners, and educators (Global and National Land Cover Characterization), 

and contributes to the understanding of the patterns, characteristics, and dynamics of land cover 

across the Nation and the Earth (Urban Dynamics and Land Cover Trends). The program also 

conducts research to improve the utility and efficiency of large-area land cover characterization 

and land cover characteristics databases.
U.S. National Report on Systematic Observations, August 2001

79

a) Global Land Cover Characterization: The initial goal to develop a global 1-km land cover 

characteristics database was achieved in 1997. Current efforts focus on revising the database 

utilizing input from users around the world.

The USGS, the University of Nebraska-Lincoln, 

and the European Commission's Joint Research 

Centre generated the initial 1-km resolution 

Global Land Cover Characteristics database using 

1-km NOAA AVHRR data from April 1992 

through March 1993. This was done on a 

continent-by-continent basis using standard map 

projections and 1-km nominal spatial resolution; 

each continental database contains unique 

elements based on the geographic aspects of the 

specific continent. The continental databases are combined to make seven global data sets, each 

representing a different landscape based on a particular classification legend.

Two versions of the Global Land Cover Characteristics database are now available 

(http://edcdaac.usgs.gov/glcc/glcc.html). The first version (Version 1.2) was released to the 

public in November 1997. It was produced as an International Geosphere-Biosphere Program 

Data and Information System (IGBP-DIS) initiative lead by the Land Cover Working Group and 

has been subjected to a formal accuracy assessment (the IGBP DISCover classification). Many 

users of the land cover data set provided suggestions for additions and improvements that have 

been incorporated into Version 2.0. A formal accuracy assessment has not yet been conducted for 

this version.

This effort is part of the NASA Earth Observing System Pathfinder Program; funding was 

provided by the USGS, NASA, EPA, NOAA, USFS, and the United Nations Environment 

Program. IGBP-DIS has adopted the database to satisfy its requirement for a global 1-km land 

cover data set. Unless protected by copyrights or trade secret agreements, all data used or 

generated during the course of the project (source, interpretations, attributes, and derived data) 

are distributed through the USGS EROS Data Center Distributed Active Archive Center (DAAC) 

for land processes data.

b) National Land Cover Characterization: The USGS has also led an effort to produce a U.S. 

National Land Cover Data set (NLCD) based on 30-meter Landsat Thematic Mapper data 

(http://landcover.usgs.gov/nationallandcover.html). The National Land Cover Characterization 

project began in 1995 using Landsat-5 data from the interagency Multi-Resolution Land 

Characterization (MRLC) Consortium Image Database assembled by the partners (USGS, EPA, 

NOAA, and USFS). The National Land Cover Dataset 1992 (NLCD 92) contains 21 USGS 

Anderson land cover classes in a nationally consistent 30-meter spatial resolution raster format. 

Land cover mapping for the conterminous U.S. was completed in September 2000. In addition to 

Landsat data, developers of NLCD 92 used a variety of supporting information, including 

topography, census, agricultural statistics, soil characteristics, other land cover maps, and 

wetlands data to determine and label each land cover type. An accuracy assessment was 

performed and the results are posted on the web site. The NLCD is being used for a wide variety 

of national and regional applications, including watershed management, environmental 

inventories, transportation modeling, fire risk assessment, and land management.

Global Land Cover Characterization Database
U.S. National Report on Systematic Observations, August 2001

80

Based on the growing need for landcover and other geospatial data 

within the Federal Government and 

the success of the MRLC 

Consortium, the Partners agreed to 

fund a Landsat-7 Image Database. 

These data are being used to develop 

a second-generation national landcover product, the National Land 

Cover Database 2000 (NLCD 2000). 

This land cover mapping effort will 

be developed using a database 

approach, which provides flexibility 

in developing a suite of independent 

data layers that provide more 

flexibility in applying the database to 

relevant applications.

c) Urban Dynamics and Land Cover Trends: USGS is mapping and documenting landscape 

transformations that result from the growth of metropolitan regions. Using historical maps and 

Landsat satellite data, urban land use databases are being assembled and used to analyze the 

effects of urbanization and to model growth and land use change under various growth scenarios 

(http://edcdgs9.cr.usgs.gov/urban/).

Projects are underway in several U.S. metropolitan regions: Washington, D.C.-Baltimore, 

Philadelphia, New York, Chicago, Milwaukee, Portland, Vancouver, San Francisco, and Las 

Vegas. Additional work is being done in the Detroit River corridor, California's Central Valley, 

the Front Range corridor of Colorado, South Florida, and in the Middle Rio Grande Basin in 

New Mexico. The Urban Dynamics Program is a joint activity between the USGS and the 

University of California, Santa Barbara. Other partners have been included in specific areas. For 

example, the Washington-Baltimore study was supported by the University of MarylandBaltimore County, NASA, the Census Bureau, Library of Congress, Smithsonian Institution, and 

the Maryland Historic Trust.

The Urban Dynamics program 

provides temporal land use 

databases, analyses of land use 

change, and landscape change 

predictions. Databases for study 

sites contain digital maps of 

urban extent, transportation 

routes, water features, and other 

significant land uses compatible 

for use in geographic 

information systems. Digital 

animations are available to help 

visualize the temporal patterns 

Urban Area Growth (in red) for the Washington DC-Baltimore MD Area 

Between 1792 and 1992 (background is a shaded relief image)

National Land Cover Dataset 1992
U.S. National Report on Systematic Observations, August 2001

81

inherent in the data. A land use change model and documentation are also available. Interpretive 

papers and maps based on the data and models are published in a variety of formats.

USGS and EPA are collaborating through the Land Cover Trends Project (LCTP) to document 

the rates, causes, and consequences of land use and land cover change for the conterminous U.S. 

for the 1972-2000 period. A scientific understanding of the rates of change, the driving forces of 

change, and the associated impacts of change is needed to resolve national policy questions 

associated with issues such as carbon budgets and carbon credits. Fundamental questions that 

must be addressed include: (1) what are the overall rates of land cover change, and what are the 

rates of change by sector (i.e., what are the rates of conversion from agricultural to urban land 

cover); and (2) how do the rates of change vary locally, regionally, and temporally?

The LCTP has developed a comprehensive methodology for using sampling and change analysis 

techniques and Landsat MSS and TM data for measuring land cover change in 85 U.S. landscape 

ecoregions. The goals are to: (1) estimate the types, rates, and temporal variability of change for 

each ecoregion; (2) document regional driving forces and consequences of change; and (3) 

prepare a national synthesis of land cover change. Datasets representing these activities are being 

developed.

B. International Data Exchange

The National Snow and Ice Data Center (NSIDC) at the University of Colorado had published a 

number of data sets made available through the U.S.-Russia Bilateral Data Exchange Working 

Group VIII. These historical baseline data sets include fresh water ice data (river freeze-up events 

at 50 stations in northern Russia dating back to 1917 from the State Hydrological Institute, St. 

Petersburg, Russia), soil temperature data (about 140 station records digitized at the Soil 

Institute, RAS, Pushchino), and snow cover (snow depth and snow water equivalent data from 

1345 stations from the Institute of Geography, Moscow). In 1998, NSIDC also published a CDROM providing a global synthesis of permafrost distribution in space and time (Circumpolar 

Active-Layer Permafrost System Version 1.0). The 1998 CD-ROM contains 40 data sets of 

active layer, borehole temperature profiles, and rock glaciers from representative sites throughout 

the world.

The Arctic Climatology Project Arctic Meteorology and Climate Atlas on CD-ROM was 

published in 2000 by the NSIDC with Russian partners at the Arctic and Antarctic Research 

Institute, St. Petersburg, and with partners at the University of Washington. The atlas contains 

previously unavailable Russian synoptic meteorology data material as well as a glossary of 

meteorological terms in English and Russian. Development of the atlas was funded by NOAA 

and the Environmental Working Group (EWG). EWG was established in 1995 under the 

framework of the U.S.-Russian Joint Commission on Economic and Technological Cooperation.

The Lake Ice Analysis Group (LIAG), an international ad hoc group of scientists, contributed to 

the Global Lake and River Ice Phenology Database published in 2001 by NSIDC. The data set

contains freeze and breakup dates for 747 lakes and rivers. Four hundred twenty-eight water 

bodies have records longer than 19 years (287 in North America and 141 in Eurasia); 170 

exceeded 50 years; and 28 exceeded 100 years.
U.S. National Report on Systematic Observations, August 2001

82

Table S9. National Climate Monitoring Systems for Terrestrial Observations

Systems useful for national 

climate monitoring

Total # stations Appropriate for

 Characterizing

National Climate?

 Fully Partly No

Time Series

#Stations/platforms (#Data Digitized)

 >30y >50y >100y

Are QC procedures adequate? 

 Fully Partly No

Metadata available?

Total # Stations

(%Digitized)

Continuity? 

# Expected 

operational in 

2005

River Discharge (Streamflow 

Gages)

USGS: 7,388

USCOE: 3,491

1,166

1,074

~ 1,500

~1,500

3,822

1,842

2,398

784

32

17

6,760

2,976

630

300

7,038

2,500

7,500 

3,500 

Ground Water Storage (e.g., 

Boreholes)

150 150 60 25 150 150 150

Snow 

 Manual Snow Courses

 SNOTEL

1205

665

1205

665

600

0

50

0

0

0

1205

665

1205 (50%)

665 (50%)

1205

670

Glaciers 3 3 3 3

Permafrost , Active Layer 

Thickness

 DOI

 NSF

 USFS

 Total

8

19

2

29

Yes

Yes

Yes

0

0

2

2

0

0

0

0

0

0

0

0

Yes

Yes

Yes

8

19

2

29

~10

~20

~2

~30

Permafrost, Thermal State+

 DOI

 NSF

 Total

SU SH IB DB+ Total

0 0 0 21 21

4 1 22 0 27

4 1 22 21 48

Yes

Yes

0

0

0

0

0

0

0

0

0

Yes

Yes

21

27

48

21

27

48

Ice 

FluxNet-AmeriFlux 47 Yes <10 yrs Yes Yes , 24 stations

100% digitized

50 stations

Radiation 

Soil 

 SCAN 44 44 0 0 0 44 44(50%) 50

Water Level – Tidal 84 - USCOE 84 42 32 10 76 8 36 80

+Permafrost thermal state is determined by periodically measuring temperatures in geophysical boreholes. Boreholes are classified according to their depth:

SU (Surface 0-10m), SH (Shallow 10-125 m), DB (Deep>125m)
U.S. National Report on Systematic Observations, August 2001

83

Table S10. National Climate Monitoring Systems for Ecological Observations

Systems useful for 

national climate 

monitoring

Total # 

stations

Appropriate for

 Characterizing

National Climate?

 Fully Partly No

Time Series

#stations/platforms (#Data Digitized)

 >30y >50y >100 y >300y

Are QC Procedures 

Adequate? 

 Fully Partly No

Metadata 

available?

Total # 

Stations

(%Digitized)

Continuity?

# Expected 

operational in 

2005

Phenological No Data

Biomass Change 11 11 11 Yes 11 11

Vegetation Type 24 24 24 Yes 24 24

Land Cover 24 24 24 Yes 24 24

Fire Weather (RAWS) 1150 1150 Yes 1150 >1150

Land Use Change No Data

Paleoclimatic Data, US

 Borehole Data 133 133 133 133

 Corals 1 1

 Fauna 219 219 219 219

 Paleolimnology 9 9 9 9

 Paleoceanography 19 19

 Plant Macrofossils 37 37 37 37

 Pollen 474 474 474 474

 Tree Ring 1029 1010 19 329 700 1029

 Other Paleo Data 0

Total U.S. Paleo 1921 1682 239 329 1572 Yes 1901 NA

Paleoclimatic Data, 

non-US

 Borehole Data 483 483 483 483

 Corals 61 56 5 9 38 9 61 61

 Fauna 1 1 1 1

 Ice Cores 23 23 23 23

 Insecta 7 7 7

 Paleolimnology 6 6 6 6

 Paleoceanography 1100 1100 1100 1100

 Plant Macrofossils 42 42 42 42

 Pollen 950 950 950 950

 Tree Ring 825 800 25 450 375 825

 Other Paleo Data 5 5 5 5

Total non-US Paleo 3465 3435 30 460 2995 Yes 3458 NA

Table S11. Available Homogeneous Data Sets for Sustained Terrestrial and Ecological Observations.
U.S. National Report on Systematic Observations, August 2001

84

Data Set Name Variable # Stations

or Grid Resolution

Describe

Period References

Paleoclimatic Data Sets, US

Tree-ring Reconstructed Palmer 

Drought Severity Index

PDSI 388 chronologies, 155 grid 

points, 2x3° grid

1700-1978 http://www.ngdc.noaa.gov/paleo/usclient2.html Cook et al. 1999. 

Journal of Climate, 12:1145-1162.

Paleoclimatic Data Sets, Global

Mann et al. 1998 Temperatures Reconstructed 

Annual 

Average 

Temperature

5x5° grid 1730-1980 http://www.ngdc.noaa.gov/paleo/pubs/mann1998/frames.htm

Mann et al. 1998, Nature 392:779-787.

Reconstructed 

Annual 

Average 

Temperature

N. Hemisphere Avg. 1400-1980

Reconstructed 

Mean 

Temperature 

within NINO3

8 gridpoints within NINO3 

box 1650-1980

Jones et al. 1998 Temperatures Reconstructed 

Annual 

Average 

Temperature

2 (N. And S. Hemisphere 

averages) 1000-1991 ftp://ftp.ngdc.noaa.gov/paleo/contributions_by_author/jones1998/ Jones et al. 1998, The Holocene 8:455-471.

Overpeck et al. 1997 Arctic 

Temperatures

Reconstructed 

Air 

Temperature

29 sites 1600-1990 http://www.ngdc.noaa.gov/paleo/sciencepub/front.htm Overpeck 

et al. 1997 Science 278:1251-1256.

Mann et al. 2000 Temperatures Reconstructed 

Annual 

Average, 

Boreal 

Summer, 

Boreal Winter 

Temperature

5x5° grid 1730-1980 http://www.ngdc.noaa.gov/paleo/ei/ei_cover.html Mann et al. 

2000 Earth Interactions, 4-4, 1-29, 2000.

Net Primary Productivity 

Database

Biomass 

production 11 sites 1975-1998 http://intranet.lternet.edu/cgi-bin/anpp.pl Alan K. Knapp and Melinda D. Smith
U.S. National Report on Systematic Observations, August 2001

85

IV.Satellite and Remote Sensing Observations

A. Objectives

Space-based remote sensing observations of the 

atmosphere-ocean-land system have evolved 

substantially since the early 1970’s when the first 

operational weather satellite systems were launched. 

Over the last decade satellites have proven their 

observational capabilities to accurately monitor nearly 

all aspects of the total Earth system on a global basis. 

This is a capability unmatched by surface based 

systems which are limited to land areas covering only 

about 30% of the planetary surface. Currently, satellite 

systems monitor the evolution and impacts of the El 

Nino, weather phenomena, natural hazards, and 

extreme events such as floods and droughts, vegetation 

cycles, the ozone hole, solar fluctuations, changes in 

snow cover, sea ice and ice sheets, ocean surface 

temperatures and biological activity, coastal zones and algae blooms, deforestation, forest fires, 

urban development, volcanic activity, tectonic plate motions, and others. These various 

observations are used extensively in real-time decision-making and the strategic planning and 

management of industrial, economic, and natural resources. Examples include weather and 

climate forecasting, agriculture, transportation, energy and water resource management, urban 

planning, forestry, fisheries, and early warning systems for natural disasters and human health 

impacts.

The current generation of satellite instruments exceeds the GCOS requirements for the absolute 

calibration of sensors, something that was lacking in the early satellite platforms used for realtime operational purposes. However, several of the data series from these operational satellites 

have been re-processed using substantially improved retrieval algorithms and, therefore, provide 

high quality global data products for the purposes of GCOS, climate system variability, and 

climate change research and applications. It is underscored, however, that satellite observations 

cannot measure all parameters of the Earth system. Also needed are surface-based, and in-situ 

observing systems for the calibration and validation of satellite-derived geophysical, chemical, 

and biospheric parameters. Thus, the future evolution of global climate observing is seen as one 

that calls for an integrated approach or strategy involving both space-based systems and surfacebased in-situ observing networks.

All satellite systems carry instruments that sense electromagnetic radiation in spectral bands that 

are related, via retrieval algorithms, to some property of the Earth’s atmosphere, ocean, or land 

surface. The precise technology used, spectral discrimination, number of channels, and view 

angles differ, but they possess common objectives in terms to what they are designed to “see” 

from the standpoint of applications and research. Most satellites carry passive sensors, which 

detect the natural radiation reflected or emitted by an object. Increasingly, however, new 

True Color Image of North and South America 

Combining NASA MODIS Data (land surface) and 

NOAA GOES Data (clouds)
U.S. National Report on Systematic Observations, August 2001

86

generation satellites carry active sensors such as synthetic aperture radar, microwave radar, and 

laser scatterometers.

In recent years, there have been well-articulated moves towards the establishment of an IGOS. 

IGOS2 is a strategic planning process, uniting the major satellite and surface-based systems for 

global environmental observations of the atmosphere, oceans, and land, in a framework for 

decisions and resource allocations by individual funding agencies. Its purview includes not only 

observations for climate, but also the needs of multiple domains, the entirety of which no single 

Partner is able to address alone. It takes a strategic view across all Earth observing requirements, 

evaluates capabilities of current and planned observing systems, and has begun (at least among 

the space agencies) to obtain commitments for addressing the gaps. GCOS is in fact a major 

contributor to the IGOS-Partnership.

Operational weather satellites are internationally coordinated through the Coordination Group for 

Meteorological Satellites (CGMS) of which the WMO is a member and a major beneficiary. 

CGMS has six satellite agency members. The primary body for policy and technical issues of 

common interest related to the whole spectrum of Earth observation satellite missions is the 

Committee on Earth Observation Satellites (CEOS). CEOS has 22 space agency members, 

including both research and operational satellite agencies, with funding and program 

responsibilities for a satellite Earth observation program currently operating or in the later stages 

of system development. U.S. members of CEOS are NASA, NOAA, and USGS. CEOS 

encourages complementarity and compatibility among space-borne Earth observing systems 

through coordination in mission planning, promotion of full and non-discriminatory data access, 

setting of data product standards, and development of compatible data products, services, 

applications, and policies. Multidisciplinary programs such as the IGBP and the WCRP, among 

others, rely on data from both operational and research satellite systems. Several international 

observing system programs have also been established in recent years that endeavor to coordinate 

both satellite and in-situ measurements to meet the requirements of operational and research 

applications objectives. These include the GCOS; the GOOS; and the GTOS. The lead agencies 

for their coordination are, respectively, the WMO in Geneva, Switzerland, the IOC in Paris, 

France, and the Food and Agricultural Organization (FAO) in Rome, Italy.

In the context of the evolution of GCOS and the IGOS, there is a convergence between research 

and operational requirements, despite an apparent divergence in the past. As the "prediction" 

time-window is broadened beyond weather time scales (days to a week) to include (quasioperationally) seasonal-to-interannual (e.g., El-Nino), and decadal (e.g., climate change and 

impacts) time scales, a substantially larger number of components and processes of the Earth 

system need to be observed and modeled. And, they need to be observed on a global basis. Such 

a need may be construed as a driving requirement for the improvement of operational observing 

systems, and also for the transition of research to operational platforms. Global-scale 

observations would, by definition of the land/ocean distribution, be heavily dependent on spacebased systems. Of course, space-based systems would benefit from improved in-situ 

observational coverage. Furthermore, better observations of sub-surface parameters such as soil 

moisture, ocean sub-surface T/S profiles, and continental/ocean snow/ice depth/thickness are 

 

2

The IGOS Partners include the GCOS, GOOS, and GTOS Secretariats; the FAO, ICSU, IOC-UNESCO, UNEP, and WMO; 

Committee on Earth Observation Satellites (which includes national and regional government agencies with an Earth observing 

satellite system); research programs (IGBP and the WCRP); and IGFA for Global Change Research.)
U.S. National Report on Systematic Observations, August 2001

87

required. Accurate, high-resolution tropospheric (and ocean surface) winds on a global basis 

would be important to improve weather forecasts (especially hurricanes/typhoons). Atmospheric 

T/H and surface hydrological parameters, atmospheric chemistry/constituents, ocean circulation, 

and others would be essential to address climate variability/change questions and environmental 

resource management issues. The monitoring of water resources (water cycle), ecosystems (and 

carbon cycle/budgets), snow/ice, and others are important categories in which observations are 

needed to improve prediction models and address impacts and resilience/vulnerability 

assessments. These questions and issues have gone well beyond the strictly research domain. 

They are now coming from policy-makers and the general public. Consequently, they are 

becoming, de-facto, operational needs (though currently, quasi-operational) even if some of them 

may happen to reside within the research framework at this time.

In accord with the evolutionary Earth-system observational concepts mentioned above, it is 

considered important to adopt planning strategies that orient global observational programs 

toward answering key scientific and management questions. It becomes equally important for 

such objectives to be integrated with parallel efforts to deliver the requisite data, analysis, and 

information products needed by the scientific community as well as operational managers and 

policy makers.

B. Implementation Status of Satellite Series and Platforms

Several U.S. agencies have been and are involved in the development, management, and 

operation of satellite observing systems. In general, satellite observing systems may be 

categorized as “operational” systems or “research” and “experimental” systems. Measurements 

taken by operational systems are likely to be continuous and maintained for an indefinite period 

of time. Typically, they also refer to observations required for a variety of real-time or near-realtime operational applications. Due to their long-term continuity, they contribute substantially to 

climate research, even if their data quality requirements have historically been less stringent than 

those required by research. Research or experimental satellite systems are likely to be new 

technological developments that measure a host of new parameters needed for research studies 

on the complex processes of the Earth-climate system Due to the nature of the time scales 

involved in climate system processes, some research satellite systems are designed to provide 

“systematic” measurements of select key parameters for a substantial period of time. Generally, 

systematic observing systems also aim for measurement continuity, but their implementation 

plans may not provide for instantaneous in-orbit replacements in case of premature sensor or 

spacecraft failure. Another sub-category of research or experimental satellites is exploratory, i.e. 

missions that can yield new scientific breakthroughs. Such exploratory satellite observing 

systems are often one-time missions that have the potential to deliver conclusive scientific results 

addressing a very tightly focused set of scientific objectives. These missions are also important to 

climate research and GCOS. A particular challenge arises when the systematic observations 

obtained in a research-oriented program have proven to be useful or essential to operational 

applications. That is, there is a need for mechanisms to facilitate the transition of the specialized 

or enhanced technologies used in research platforms to operational observing systems. In the 

U.S. for example, there is a coordinated effort to ensure the continuity of the measurements made 

by the research-based Earth Observing System (EOS) satellite series, and future operational 

environmental satellites.
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This section provides summaries, in tabular form, of U.S. satellite observing series contributing 

to GCOS. Tables 6-8, found at the end of this section, are briefly described below.

Table 6 summarizes the U.S. satellite series and/or platforms that contribute to GCOS. The table 

responds to the UNFCCC guidelines for data exchange, barriers to data exchange, international 

participation, and applications to capacity building. Information is also summarized on the 

availability of data and data sets. In general, all U.S. satellite data relevant to GCOS are 

extensively documented in the Global Change Master Directory (GCMD) coordinated by the 

interagency USGCRP. Table 6 identifies the major agencies responsible for the satellite series 

and the primary centers that distribute data. Comprehensive details on these and other data 

centers, and data set descriptions, are available from the GCMD, which can be accessed on the 

Internet. The search engine for obtaining details on each satellite platform or instrument is built 

into the GCMD. Likewise, information may be retrieved by parameter, application, or scientific 

theme through a plain-language query. For satellites that are not yet launched, information on 

instruments, launch schedules, data processing, and mission objectives is provided on the web 

site.

Table 7 provides information on the types of observations obtainable from the U.S. satellite 

systems contributing to GCOS, typical space/time resolutions, the continuity of the satellite series 

(and data), and the degree to which processed/derived data sets comply with GCOS climate 

monitoring principles, as identified by the COP-UNFCCC. Only those satellites (and satellite 

series) that either have historical data continuity or are currently operational, are included in this 

table. Satellites that have not yet been launched, but have been approved (i.e., future approved 

missions), are described in Table 6.

Table 8 summarizes the status of the potential for the transition of research satellite remote 

sensing instruments to operational systems. The five sub-tables are cross-mapped against the five 

major scientific themes identified earlier as scientific questions that need to be addressed, 

namely: Variability (“V”), Forcing (“F”), Response (R”), Consequences (“C”), and Prediction 

(“P). In Table 8, the number following a letter such as “V2” refers to the bullet number 

corresponding to a particular scientific question. While substantial international cooperative 

efforts are necessary for the development and implementation of next-generation operational 

observing systems, such an activity is seen as a key element for the further advancement of an 

optimum, operational, global observing system for GCOS that would also support the objectives 

of the Integrated Global Observing Strategy promulgated by the CEOS and the WMO-GOS.
U.S. National Report on Systematic Observations, August 2001

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C. Operational U.S. Satellite Observing Systems

1. Polar Operational Environmental Satellites (POES)

The first meteorological satellite observations of the 

Earth began with the launch, by NASA, of the first 

Television and Infrared (IR) Observation Satellite 

(TIROS-I) on April 1, 1960 to demonstrate the 

feasibility of observing the Earth’s cloud cover and 

weather by means of slow-scan television cameras in 

an Earth-orbiting, spin stabilized satellite. TIROS-II 

was launched on November 23, 1960, to demonstrate, 

in addition to the wide- and narrow- angle television 

cameras, an experimental 5-channel scanning IR 

radiometer and a 2-channel non-scanning IR device. 

They measured the thermal energy of the Earth’s 

surface and atmosphere to provide data on the planet’s 

heat balance and add a new dimension to the 

understanding of weather. A series of these TIROS 

satellites, developed by NASA and operated by NOAA, were launched throughout the 1960s. A 

2-channel Scanning Radiometer (SR) was launched on a NOAA satellite in June 1974 and lasted 

until February 1978. One channel was in the visible part of the spectrum, while the other channel 

was in the thermal infrared window. The first operational Earth Radiation Budget measurements 

were made by the SR. Beginning with TIROS-N, in 1978, an AVHRR sensor was carried on 

board NOAA’s POES. The NOAA/TIROS POES continuously orbits the Earth from North to 

South Pole (hence the name polar orbiting) at an altitude of approximately 830 to 870 km.

POES data has been crucial in depicting global distributions of a number of important climate 

parameters such as ozone, aerosols, outgoing long-wave radiation, Microwave Sounding Unit 

(MSU) temperature times series, snow cover, and water vapor. The NOAA/POES series 

currently carry scanning radiometers as imaging and radiometric devices and sounders to obtain 

information on the vertical profiles of selected parameters. Key instrument packages include:

• The AVHRR, currently, a 5-channel, cross-track scanning instrument, providing image 

and radiometric data in the visible, near-infrared, and far infrared portions of the 

spectrum, is used to observe clouds, land-water boundaries, snow and ice, water vapor, 

temperature of clouds, land and sea surface temperature, aerosols, and the Normalized 

Difference Vegetation Index (NDVI) as an indicator of green biomass.

• The TIROS Operational Vertical Sounder (TOVS), a three-part TIROS system is used to 

measure temperature profiles of the Earth’s atmosphere from the surface to about 10 

millibars, water content of the Earth’s atmosphere, and total column ozone content of the 

atmosphere. The TOVS system comprises three separate sensors: (1) the High Resolution 

Infrared Sounder (HIRS), a 20 channel, step-scanned visible and infrared spectrometer 

used to produce tropospheric temperature profiles; (2) the Stratospheric Sounding Unit 

(SSU), a 3-channel, pulse modulated, step-scanned, far-infrared spectrometer used to 

produce temperature profiles of the stratosphere; and (3) the Advanced MSU (AMSU-A 

NOAA AVHRR False Scale Image of SST and 

Vegetation Anomaly
U.S. National Report on Systematic Observations, August 2001

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and AMSU-B), a 4-channel, step-scanned spectrometer with a response in the 60-GHz 

oxygen band, used to produce temperature profiles in the atmosphere in the presence of 

clouds.

• A Solar Backscatter Ultraviolet (SBUV) system for ozone measurements (added to TOVS 

starting with the NOAA-9 spacecraft). It also carries a space environment monitor to 

measure energetic particles emitted by the Sun. 

A few prime examples of climate related data sets produced as a result of POES data include the 

following that deal with temperature anomalies, snow cover, and precipitation.

Northern Hemisphere Snow Cover Anomaly (Robinson, 2000)

Global Tropospheric Temperature Anomalies, January 1979 - February 2000 (Christy et al., 2000)
U.S. National Report on Systematic Observations, August 2001

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2. Defense Meteorological Satellite Program

The Defense Meteorological Satellite Program (DMSP) is a DOD program run by the Air Force 

Space and Missile Systems Center (SMC). The DMSP program designs, builds, launches, and 

maintains several near-polar orbiting, sun synchronous satellites monitoring the meteorological, 

oceanographic, and solar-terrestrial physics environments. DMSP satellites are in a near-polar, 

sun synchronous orbit at an altitude of approximately 830 km above the earth. Each satellite 

crosses any point on the earth up to two times a day and has an orbital period of about 101 

minutes thus providing nearly complete global coverage of clouds every six hours. 

Each DMSP satellite monitors the atmospheric, oceanographic and solar-geophysical 

environment of the Earth. The visible and infrared sensors collect images of global cloud 

distribution across a 3,000 km swath during both daytime and nighttime conditions. The 

coverage of the microwave imager and sounders are one-half the visible and infrared sensors 

coverage, thus they cover the polar regions above 60 degrees on a twice daily basis but the 

equatorial region on a daily basis. The space environmental sensors record along track plasma 

densities, velocities, composition and drifts. DMSP satellites have been operational since 1976. 

The Operational Linescan System (OLS) on-board the DMPS Block 5D-1 and 5D-2 series, 

includes two telescopes and a photo-multiplier tube. Visible and infrared imagery from the OLS 

instruments is used to monitor the global distribution of clouds and cloud-top temperatures twice 

daily, during day and night. The archive data sets contain imagery from low-resolution (2.7 km) 

global coverage and high resolution (0.55 km) regional coverage. Nighttime visible data are 

obtained from the photo-multiplier tube designed to produce cloud imagery by moonlight. In 

Precipitation (5N-5S, 170W-120W), 1979-1998 (Gruber, 2000)
U.S. National Report on Systematic Observations, August 2001

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addition to cloud information, OLS data are being used for a variety of studies and applications 

such as land surface fires, natural gas flaring, urban lights leading to information on natural fires, 

biomass burning, power failures and population density.

The Special Sensor Microwave/Imager (SSM/I) instrument has been flown on the DMSP weather 

satellites since June 1987. It is a well calibrated passive microwave radiometer particularly well 

suited for measuring hydrological cycle parameters under all-weather conditions. These include 

measurements of snow cover, frozen ground, land classification, sea ice, wind speed over the 

oceans, cloud liquid water and water vapor, and rainfall. The SSM/I instrument series (six 

instruments have been flown, with a seventh scheduled for a future flight) will continue before 

being replaced by its successor SSM/IS which is a combined passive microwave imager and 

sounder. The SSM/I itself is a successor to the earlier Nimbus-7 Scanning Multichannel 

Microwave Radiometer (SMMR) developed and launched by NASA in 1978 and providing data 

through 1987. The combined SSM/I-SMMR data time series exceeds 20 years and provides an 

invaluable, albeit unanticipated, all-weather data set for GCOS and global change studies.

3. NPOESS

The NPOESS program, scheduled to begin around 2008, provides continuity to the 

NOAA-POES series and the DoD series of polar-orbiting, operational, environmental satellite 

systems. Building on new technologies the program is designed to create a new system 

supporting long-term data for environmental monitoring and global change assessments. 

NPOESS merges DoD and NOAA meteorological satellite systems into a single national asset. 

Currently, the first phase of NPOESS is planned to extend through 2018. The satellite series will 

carry an enhanced suite of instruments incorporating new technologies from NOAA, DoD, and 

NASA. A tri-agency effort established an NPOESS Integrated Program Office (IPO) to develop, 

acquire, manage, and operate the next generation of polar-orbiting, operational, environmental 

satellites.

The NPOESS mission is to provide an Operational remote sensing capability to acquire and 

receive in real-time at field terminals, and to acquire, store and disseminate to processing centers, 

global and regional environmental imagery and specialized Meteorological, Climatic, Terrestrial, 

Oceanographic and Solar-Geophysical and other data in support of Civilian and National 

Security missions.

To achieve this mission, NPOESS has undertaken a far-reaching program of sensor development 

and satellite transition to provide complete coverage of meteorological conditions for civil, 

military, and scientific purposes while cutting operational costs dramatically. The program will 

adapt existing technology and develop new sensors. To accomplish this, NPOESS satellites in 

two orbital planes will replace the two-satellite constellations, DMSP and POES, respectively. A 

satellite of the European Meteorological Satellite Organization (EUMETSAT), METOP will 

provide data in the mid-morning third orbital plane, jointly establishing a coordinated, three-orbit 

constellation. NPOESS and EUMETSAT will share data from their polar-orbiting satellites. The 

sensors onboard NPOESS will collect and disseminate data about Earth's oceans, atmosphere, 

land, climate, and space environment. NPOESS will include the following new sensors under 

development:
U.S. National Report on Systematic Observations, August 2001

93

• VIIRS—Visible/Infrared Imager/Radiometer Suite. Collects visible and infrared 

radiometric data of the Earth's atmosphere, ocean, and land surfaces. Data types include 

atmospheric, clouds, Earth radiation budget, land/water surfaces, sea surface temperature, 

ocean color, and low light imagery.

• CMIS—Conical scanning Microwave Imager and Sounder for clouds, sea surface winds, 

atmospheric temperature and moisture profiles, all-weather land/water surfaces, 

hurricanes, and rainfall. Collects global microwave radiometry and sounding data to 

produce microwave imagery and other meteorological and oceanographic data.

• CrIS—Cross-track Infrared Sounder for atmospheric profiles. Measures the Earth's 

atmospheric radiation to determine the vertical distribution of temperature, moisture, and 

pressure in the atmosphere.

• ATMS—Advanced Technology Microwave Sounder. In conjunction with CrIS, ATMS 

will take global observations of temperature, moisture and pressure profiles at high 

temporal resolution on a daily basis.

• GPSOS—Global Positioning System Occultation Sensor. Measures the refraction of 

microwave signals from the GPS and Russia's Global Navigation Satellite System 

(GLONASS) to characterize the ionosphere. Primary instrument for electron density 

profiles. Secondary measurements for Tropospheric temperature and humidity profiles.

• OMPS—Ozone Mapping and Profiler Suite. Collects data to permit the calculation of the 

vertical and horizontal distribution of ozone in the Earth's atmosphere.

• SESS—Space Environment Sensor Suite for magnetic fields, electron, and aurora. 

Measures neutral and charged particles, electron and magnetic fields, and optical 

signatures of aurora sensors being developed by other agencies.

• ALT—Radar ALTIMETER. ALT maps the topography (heights) of the ocean surface 

with respect to the geoid and determines ocean wave characteristics.

• ERB—Earth Radiation Budget Sensor. ERB measures major components of the Earth’s 

radiation budget and atmospheric radiation from the top of the stratosphere to the surface.

• TSIS—Total Solar Irradiance Sensor. TSIS is a broad-banded Total Solar Irradiance 

monitor plus two narrow bands to monitor the highly variable, active regions of the sun in 

the ultraviolet and near-infrared spectral regions.

• CAPS—Cloud and Aerosol Polarimeter Sensor. CAPS will measure cloud and aerosol 

properties such as aerosol and cloud particle size distributions, aerosol indices of 

refraction and scattering albedos.

• DCS—Data Collection System. DCS will continue the heritage to collect environmental 

data from autonomous platforms and will deliver these data to users worldwide.

• SARSAT—Search and Rescue System. SARSAT will continue the heritage to provide 

free-of-charge distress alert and location for maritime, aviation and land users in distress.
U.S. National Report on systematic Observations, August 2001

94

4. NPOESS Preparatory Project (NPP)

Prior to the launch of NPOESS in 2008, an NPP satellite will be launched in the 2005 timeframe 

as a bridge mission to provide continuity for selected key observations between the EOS series of 

satellites (Terra and Aqua) and NPOESS. The VIIRS, CrlS, and ATMS sensors are currently 

under development for the NPP mission to demonstrate advanced technology for atmospheric 

temperature and humidity soundings, sea surface temperatures, land and ocean biological 

productivity, and cloud and aerosol properties, among others. They will provide continuing 

observations for global change after Terra and Aqua.

The primary mission of NPP is to demonstrate advanced technology for atmospheric sounding 

and imaging, giving continuing observations about global change after EOS-Terra and EOS 

Aqua. It is an instrument risk reduction project for the following NPOESS sensors under 

development: VIIRS, CrIS, and ATMS. It will supply data on atmospheric and sea surface 

temperatures, humidity soundings, land and ocean biological productivity, and cloud and aerosol 

properties. NPP will contribute to instrument risk reduction by offering early instrument and 

system level testing, lessons learned for design modifications in time to ensure NPOESS launch 

readiness, ground system risk reduction, early user evaluation of NPOESS data products, such as 

algorithms, and instrument verification, and opportunities for instrument calibration. Additional 

information on NPOESS is available at http://www.ipo.noaa.gov/. The NPP and NPOESS 

programs will lead to the evolution of the U.S. polar satellite observation program as follows:

Future (2013)

3-Orbit System

- 2 U.S. Converged

- 1 U.S. “Lite”

- 1 EUMETSAT/METOP

- Specialized Satellites

Tomorrow (2005)

4-Orbit System

- 2 U.S. Military

- 1 U.S. Civilian

- 1 EUMETSAT/METOP

Today (2001)

4-Orbit System

- 2 U.S. Military

- 2 U.S. Civilian

Evolution

U.S. civil and defense programs, working in partnership with EUMETSAT, will ensure improved 

global coverage and long-term continuity of observations at a loweer cost!
U.S. National Report on Systematic Observations, August 2001

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5. Geostationary Operational Environmental Satellites (GOES)

Geostationary satellites observe the Earth from above the equator and maintain 

their position relative to the Earth at an altitude of 35,790 km or 22,240 miles. 

The satellite travels around the Earth in the same direction as the rotation of the 

Earth with an orbital period equal to that of the rotation of the Earth (23 hours, 

56 minutes, 04.09 seconds). The U.S. GOES satellites, developed by NASA and 

operated by NOAA, are positioned around 75 degrees west and 135 degrees 

west. A worldwide network of operational geostationary meteorological satellites provides 

visible and infrared images of the Earth’s surface and atmosphere on a global basis. The satellite 

systems include the GOES (USA), METEOSAT (launched by the European Space Agency, and 

operated by the European Meteorological Satellite Organization-EUMETSAT), the Japanese 

Geostationary Meteorological Satellite (GMS), and the geostationary satellites operated by India 

and China.

Operational geostationary satellites have made a considerable contribution to data products for 

climate. Among them are snow cover, surface insolation, clouds and precipitation and of course 

vertical moisture and temperature profiles. Clouds and precipitation make extensive use of the 

worldwide operational geostationary satellites. The former is through the International Satellite 

Cloud Climatology Project (ISCCP), and the latter through the Global Precipitation Climatology 

Project (GPCP). The GPCP data is composed of merged POES, geostationary, and gauge data to 

provide a global map of monthly mean precipitation. The satellite data portion of the GPCP data 

set specifically consists of geostationary IR from GOES, GMS, Meteosat, NOAA polar orbiting 

IR data, and DMSP microwave data. The following figure shows the annual mean precipitation 

for the period 1979 through 1998 and demonstrates the usefulness of GOES data to producing 

climate data sets.
U.S. National Report on Systematic Observations, August 2001

96

The NOAA-GOES carries three major sensor systems:

• A multi-spectral, five-channel, imaging instrument capable of simultaneously sweeping 

one visible and four infrared channels in a North-to-South swath across an east-to-west 

path, providing full disk imagery once every 30 minutes.

• A sounder with more spectral bands than the imager, to produce high quality profiles of 

temperature and moisture, surface and cloud temperatures, and ozone distribution, 

capable of stepping one visible and eight infrared channels in a north-to-south swath 

across an east-to-west path. The most recent GOES-11 satellite has a sounder with a 19-

channel discrete filter radiometer.

• The Space Environment Monitor (SEM) to measure the condition of the Earth’s magnetic 

field, solar activity and radiation around the spacecraft.

GOES-M, an advanced environmental satellite equipped with instruments to monitor Earth’s 

weather and a telescope for detecting solar storms, was launched on July 23, 2001, by NASA for 

NOAA. Following scheduled apogee motor firings and adjustment maneuvers, the spacecraft was 

placed in a geosynchronous orbit, 35,790 km above the Earth’s equator, at 90 degrees West 

longitude. As with other GOES satellites, GOES-M will be renamed and will be commissioned 

by NOAA as GOES-12. Currently, GOES-M provides a fully capable spacecraft in on-orbit 

storage that can be activated on short notice to assure continuity of service from the current twospacecraft operational constellation. GOES-M is also the first GOES satellite equipped with a 

Solar X-ray Imager (SXI) instrument that will be used to aid in forecasting Earth’s space weather 

due to solar activity. The SXI will gather full and detailed data of the sun's atmosphere each 

minute. The data will be used to forecast the intensity and speed of solar disturbances that could 

destroy satellite electronics, disrupt long-distance radio communications, or surge power grids.

6. Landsat

Landsat is a series of satellites designed to gather 

data on the Earth’s resources for application to 

global change research, land cover classification, 

geological and mineralogical exploration, crop 

and forest assessment, and cartography. Landsat1 was developed and launched by NASA in 1972 

following the early success of NASA’s TIROS 

and Nimbus series, to expand the possibilities for 

Earth remote sensing from space. This was in 

response not only to geologists and biologists, 

but also a broad community of scientists, natural 

resource managers, and engineers. The MultiSpectral Scanner (MSS) proved to be so valuable 

that a version of it has been flown on each of the 

first five Landsat missions. With the 1982 launch 

of Landsat-4, the Thematic Mapper (TM) was 

introduced. The TM was a significant improvement over the MSS, providing greater spatial 

resolution in the visible and near-infrared regions (30 m vs. 80 m), and three additional spectral 

Landsat 7 Image of Severe Flooding of the 

Mozambique Coastline, March 2000
U.S. National Report on Systematic Observations, August 2001

97

bands. Landsat-5, launched in 1984, continues to provide coverage well beyond its design 

lifetime, and is operated by the USGS. Landsat-6 failed to reach orbit in 1993. Landsat-7, which 

is also operated by the USGS, was launched by NASA on April 15, 1999, in sun-synchronous 

orbit (705 km) to provide continuity and enhanced coverage to characterize, monitor, manage, 

explore, and observe the continental Earth’s surface. Landsat-7’s payload consists of the 

Enhanced Thematic Mapper Plus (ETM+). New features on Landsat-7 include a panchromatic 

band with 15-meter spatial resolution, a thermal infrared channel with 60-meter resolution, both 

high and low gain, on-board radiometric calibration, and a solid-state tape recorder to collect 

imagery outside the range of ground 

stations. The tape recorder has a capacity 

of 380 gigabytes (100 scenes). ETM+ 

provides continuity with the Thematic 

Mapper that flew on Landsat-4 and 

Landsat-5 and assures worldwide 

coverage as defined in a Long Term 

Acquisition Plan (LTAP). All Landsat 

data captured by the U.S. since 1972 are 

archived, managed, and distributed by 

the USGS Earth Resources Observation 

Systems (EROS) Data Center (EDC).

D. Research and Experimental Satellites

1. ACRIM-III

The Active Cavity Radiometer Irradiance Monitor (ACRIM-III), a small satellite-dedicated 

mission, called ACRIMSAT, launched in December 1999, continues the series of satellite data 

monitoring solar irradiance. ACRIM-III instrument is a miniaturized version of the technology 

flown successfully on SMM, Spacelab-1, and Atlas missions. Surveillance of radiation received 

from the sun began with instruments on board Nimbus-7 in 1978, which continued through early 

1993, providing the longest data set currently available for solar measurements. The 

unambiguous evidence of variability in total solar irradiance (TSI) was first obtained from the 

highly precise ACRIM instrument on the SMM in 1980. The satellite is spin stabilized with the 

instrument’s solar viewing axis aligned with the sun within 0.25o using magnetic torquers. The 

sun is a variable star, and luminosity has been found to vary by about 0.1% over a solar cycle in 

phase with the level of solar magnetic activity. Sustained change in total solar irradiance (TSI), as 

small as a few tenths of one percent per century, could be a primary cause for significant climate 

change. A precision TSI database, with resolution adequate to correlate centuries of systematic 

TSI variation to climate change, must be compiled from the results of many flight experiments. 

With a nominal lifetime of 5 years per experiment, their contiguous results must be related with 

the maximum precision accessible to current technology, on the order of 10 ppm. This far 

exceeds the capabilities of current “ambient temperature” flight instrumentation to define the 

“absolute uncertainty” of the TSI (>1000 ppm) and even that of cryogenic instrumentation 

currently under development (>100 ppm). Modeling TSI using ground-based observations of 

proxy solar emission features is orders of magnitude less precise. The single approach capable of 

Location and Area Coverage of U.S. and International 

Landsat 7 Ground Stations
U.S. National Report on Systematic Observations, August 2001

98

providing the required precision for the long-term TSI database using current measurement 

technology employs an “overlap strategy” in which successive ambient temperature TSI satellite 

experiments (each with a nominal lifetime of 5 years) are compared in flight, transferring their 

operational precision to the database. The current generation of ambient temperature ACRIM 

flight instrumentation has demonstrated a capability of providing annual precision of 

approximately 5 ppm of TSI. A second phase ACRIM instrument is planned for launch in late 

2001. It will combine the TSI database maintenance function with a new technology designed to 

develop a prototype instrument for both total and limited spectral solar monitoring on an 

operational basis in the NPOESS program. The Total Solar Irradiance Mission (TSIM), planned 

for launch in 2002, will carry a combination of solar radiometer and spectrophotometer 

instruments to measure: total (full spectrum) solar irradiance with absolute accuracy of 0.1% or 

better, and relative precision of 2 x 10-5 per year; and solar radiation spectrum in the range 200 

nm (ultraviolet) to 2500 nm (short-wave infrared) with absolute accuracy of 2% or better and 

relative precision of 2 x 10-4 per year.

2. TOMS

The Total Ozone Mapping Spectrometer (TOMS) 

instrument, which measures atmospheric total 

column ozone, has flown on various spacecraft 

since 1978. It has been the mainstay of 

international efforts by the WMO, the United 

Nations Environment Program (UNEP), and other 

agencies to monitor Antarctic, Arctic, and global 

ozone depletion in support of the Montreal 

Protocol on ozone depletion. NASA flew the first 

TOMS instrument on-board the Nimbus-7 

satellite in 1978. It operated for almost 15 years 

(until May 1993). A second TOMS was flown 

aboard the Meteor-3 (Russia) satellite, which 

operated from August 1991 to December 1994. A 

third TOMS was flown aboard the ADEOS-I 

(Japan) satellite operating from August 1996 to 

June 1997. A fourth TOMS was launched on 

board an Earth probe mission in July 1996 and 

remains operational. The gap in TOMS coverage (December 1994 – July 1996) has been filled by 

SBUV/2 (on NOAA-11) data and European Global Ozone Monitoring Experiment (GOME) 

data. QuikTOMS is scheduled for launch in June 2001 to bridge any possible gaps in data 

continuity before ADEOS-II (Japan) is launched with a TOMS instrument. Stratospheric ozone 

and aerosol profile data have mainly been obtained from the Stratospheric Aerosol and Gas 

Experiment (SAGE) program. SAGE-type instruments (SAM-II, SAGE-I, SAGE-II) have been 

flown since 1978. SAGE-III which takes advantage of both solar and lunar occultation is 

scheduled to be launched on board the Meteor 3M-1 (Russia).

TOMS Images Depicting the Progressive Depletion of 

Ozone Over Antarctica from 1981-1999
U.S. National Report on Systematic Observations, August 2001

99

3. UARS

Launched by NASA in September 1991, the Upper Atmospheric Research Satellite (UARS) was 

the first satellite dedicated to increasing our understanding of the chemistry and dynamics of the 

Earth’s stratosphere and mesosphere. UARS measures atmospheric ozone depletion chemistry, 

trace gases, water vapor, winds, and solar variations. It confirmed the role of CFCs in ozone 

depletion and clarified chemical processes that cause the Antarctic ozone hole. UARS made the 

first measurements of key stratospheric gases chlorine nitrate (CLONO2), chlorine monoxide 

(CLO), hydrogen fluoride (HF), hydrogen chloride (HCL), and dinitrogen pentoxide (N2O5). 

These measurements along with the measurements of nitric oxide (NO), nitrogen dioxide (NO2), 

and nitric acid (HNO3) provide a comprehensive picture of stratospheric photochemical 

processes involved in ozone depletion. UARS provided the first comprehensive mapping of 

volcanic aerosol layers and documented the slow increase in aerosol amounts following the 

eruption of Mt. Pinatubo in the Philippines. The satellite also gave us the first global picture of 

atmospheric tides, a clearer understanding of solar ultraviolet radiation (UV) variations, insight 

into the relationship between upper tropospheric water vapor and climate, and multiyear 

information on the transport of trace gases into the stratosphere. UARS was designed to make 

observations of the upper atmosphere for 18 months. More than 7 years after launch, UARS 

continued to make observations with 8 of 10 instruments and continues to collect data. The 

UARS measures the following parameters with associated instrumentation. These include: (1) 

Chemistry: Cryogenic Limb Array Etalon Spectrometer (CLAES), Halogen Occultation 

Experiment (HALOE), Improved Stratospheric and Mesospheric Sounder (ISAMS), Microwave 

Limb Sounder (MLS); (2) Wind Measurements: High Resolution Doppler Imager (HRDI), Wind 

Imaging Interferometer (WINDII); (3) Solar Measurements: Active Cavity Radiometer Irradiance 

Monitor (ACRIM II), Solar/Stellar Irradiance Comparison Experiment (SOLSTICE), Solar 

Ultraviolet Spectral Irradiance Monitor (SUSIM); and (4) Energetic Particle Measurements: 

Particle Environment Monitor (PEM).

The EOS-Aura satellite (previously CHEM–see full description in section H-7) is scheduled for 

the 2003-2008 timeframe, and builds on the heritage of measurements initiated by the still active 

UARS. Aura will also carry a totally new, high spectral resolution (~0.025 cm-1) Tropospheric 

Emission Spectrometer (TES), that will allow vertically resolved measurements of ozone and 

trace gas constituents.

4. TOPEX/Poseidon

Jointly developed by NASA and CNES (France), the TOPEX/Poseidon (Ocean Topography 

Experiment) carrying dual and single frequency altimeters was launched in August 1992 to 

accurately measure the altitude of the satellite above the sea surface, sea surface wind speed and 

wave energy. The dual-frequency altimeter corrects for ionospheric effects. A GPS receiver is 

one of the three systems used to precisely track the satellite orbit. A laser retroreflector, used with 

ground-based lasers, measures satellite position and verifies the satellite altimeter’s height 

measurements. A microwave radiometer measures atmospheric water vapor content and is used 

to correct altimeter measurements for pulse delay caused by water vapor. Sea surface height is 

measured to within 4.3 cms. The triple tracking system determines the satellite's location to 

within 2.8 cms. The distance between the ocean surface and the satellite is measured with an 
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100

accuracy of 3.2 cms. The follow-on to TOPEX/Poseidon is Jason-1, scheduled for launch in Fall 

2001.

5. SeaWiFS 

SeaWiFS was launched in August 1994, and resumed the measurement of ocean color 

(phytoplankton) made from 1978 to 1986 by the CZCS satellite. Aerosols directly affect the 

radiative transfer in the atmosphere, and therefore, the radiation received by a satellite from the 

surface of the Earth (land and ocean). When surface or near-surface signals are received from 

sensor-measured radiances at satellite altitude, the atmospheric effect must be removed. This 

atmospheric correction removes more than 90% of the observed radiance at visible wavelengths 

measured at the top of the atmosphere. The SeaWiFS satellite’s atmospheric correction algorithm 

uses radiances measured at two near-infrared wavelengths, 765 nm and 865 nm, at which the 

ocean appears black due to strong absorption by water to estimate the aerosol optical properties 

and extrapolate them into the visible spectrum. This enables SeaWiFS to measure global ocean 

color and ocean bio-optical properties. Aerosol optical properties, particularly optical depth or 

thickness, is an important byproduct of the SeaWiFS atmospheric correction.

E. Recently Launched “Next” Generation Research Satellites and Instruments

Substantially improved satellite instruments have been under development for the past five or 

ten years. They address several of the deficiencies found in the older technologies used even in 

the current generation of operational satellites. They typically have a broader spectral range, 

better spectral resolution, more flexibility in terms of view angles, and much better spatial 

resolutions. Importantly, they have the best possible on-board calibration systems. The sections 

that follow describe some next-generation satellite instruments, several of which have already 

been recently launched.

1. Tropical Rainfall Measuring Mission (TRMM)

In November 1997, the TRMM was 

launched as a collaborative venture 

between NASA and the National 

Space Development Agency 

(NASDA) of Japan. It measures 

rainfall, clouds, sea surface 

temperature, radiation, and lightening 

using five instruments: the first 

space-borne precipitation radar (PR), 

the TRMM Microwave Imager 

(TMI), a Visible and Infrared Scanner 

(VIRS), a Cloud and Earth Radiant 

Energy System (CERES), and a Lightning Imaging Sensor (LIS). The precipitation radar and 

microwave radiometer measure the vertical distribution of precipitation over the tropics between 

+/- 35o in latitude, from the surface to about 20 km: horizontal resolution: 4 km; swath width: 

220 km. Rain rates down to about 0.7 mm/hour can be detected. TRMM will reduce the 
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101

uncertainty in global tropical rainfall estimates to about 10%, an 80% improvement over the 

current uncertainty of about 50%. The TMI has a full suite of channels ranging from 10.7 GHz to 

85 GHz and is the first satellite sensor capable of accurately measuring SST through clouds. 

When rain is not present, attenuation at 10.7 GHz is small and 97% of the sea surface radiation 

reaches the top of the atmosphere. The high frequency channels (19 to 37 GHz) can precisely 

estimate the 3% attenuation due to oxygen, water vapor, and clouds. The 37-GHz channels are 

very sensitive to rain and are used to determine when rain is in the radiometer’s field of view. At 

frequencies below about 12 GHz, microwaves penetrate clouds with little attenuation providing a 

clear view of the sea surface under all weather conditions except rain. At these frequencies 

aerosols have no effect. The first satellite microwave radiometers operating at such low 

frequencies were successfully demonstrated on Nimbus-7 and Seasat in 1978, but they were 

limited by poor calibration systems. The VIRS senses radiation in five spectral regions ranging 

from the visible to infrared (0.63 to 12 μm). It serves as a rainfall indicator and a transfer 

standard between TRMM measurements and those made routinely on the operational POES and 

GOES satellites.

2. NASA-Shuttle Radar Topography Mission

NASA’s-Shuttle Radar Topography Mission (SRTM) radar system was flown on board Space 

Shuttle Endeavor on February 11, 2000. Its mission was to gather high resolution topographic 

data over approximately 80% of the land surfaces of the Earth, creating the first-ever, near global 

data set of land elevations. To acquire topographic (elevation) data the SRTM payload was 

outfitted with two radar antennas, one in the shuttle payload bay, and the other on the end of a 

60m mast extended from the payload once the shuttle was in orbit. While various preliminary 

images and maps have already been released, the full calibration of the SRTM was completed in 

early 2001, and production processing is scheduled to begin in late 2001.

3. NASA’s EOS Satellite Series

NASA’s EOS is a series of polar orbiting and mid-inclination satellites specifically developed to 

monitor nearly all aspects of the Earth system with unprecedented calibration, accuracy, spectral 

discrimination, and spatial resolution. The first major satellite of the EOS-series began in 1999 

with the launch of EOS-Terra. It had a sun-synchronous polar orbit, descending southward across 

the equator in the morning. The second, to be launched in 2001 will be EOS-Aqua in a sunsynchronous polar orbit ascending northward across the equator in the afternoon. This will be 

followed in later years by EOS-Aura. The key instrument developed to fly on Terra and Aqua is 

the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS will continue to take 

measurements in spectral regions that have been and are currently being measured by other 

satellites, or “heritage” instruments. Therefore, MODIS will extend the time series of data sets 

taken by such instruments as AVHRR, used for meteorology and monitoring sea surface 

temperature, sea ice, and vegetation; and the CZCS used to monitor ocean biomass and ocean 

circulation patterns.

The EOS satellite sensors have unprecedented on-board calibration systems, enabling a 

characterization of their performance throughout the lifetime of each satellite’s mission; and the 

correction of errors introduced into the data due to system degradation. Calibration is a set of 

operations or processes used to determine the relationship between satellite instrument output 
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(i.e., digital counts) and corresponding known values of a standard, expressed in Systeme 

Internationale (SI) units. Pre-flight calibration and characterization includes radiometric and 

geometric calibration. Radiometric calibration involves determining the relationship between 

instrument output and radiant input while the instrument views a calibrated radiant source. For 

the solar spectrum (400 to 2500 nm), the calibrated radiant source is an integrating sphere which 

has been calibrated using standards. For thermal infrared (above 2500 nm) the calibrated source 

is a variable temperature blackbody. Pre-flight geometric calibration involves the determination 

of the detailed spatial response of each instrument band with respect to the nominal instrument 

telescope pointing direction. Geometric calibration is necessary for converting the instrument 

radiometric data into images with known relationships to observed Earth targets. Instruments will 

also be radiometrically and geometrically calibrated on orbit using solar diffusers, blackbodies, 

space viewports, and, in the case of MODIS, a monochromatic source known as the 

spectroradiometric calibration assembly. The moon will also be used by EOS and other satellite 

instruments as a common, stable, on-orbit radiance reference target. The accuracy and precision 

of Earth remote sensing data sets produced by different instruments are achieved only by the 

consistent use of common on-orbit calibration sources and measurement methodologies. EOSTerra will perform an on-orbit, pitch-based, calibration attitude maneuver to enable the 

instruments to view deep space and the moon. The deep space view provides CERES and 

ASTER an accurate determination of the DC offsets in their thermal bands, and it provides 

MODIS the opportunity to characterize the dependence of the thermal infrared reflectance on the 

angle of incidence of the scan mirror. The same pitch-based maneuver also provides EOS 

instruments the opportunity to view the Moon at a lunar phase of 22o. The moon affords the 

ability to monitor radiometric responsivity and stability in the visible, near-infrared, and 

shortwave infrared wavelengths, among others. Validation of satellite measurements is carried 

out through various means such as cross-comparing the satellite measurements with aircraft 

observations.

F. Specific EOS-Terra Research Instruments

1. EOS-Terra

With an AM equatorial crossing, EOS-Terra was launched on December 18, 1999, by NASA. 

Terra houses five instruments for simultaneous, geolocated measurements and for the 

intercomparison of new measurement techniques. For example, the MODIS detailed internal 

calibrations will be used, through simultaneous geolocated measurements, to help in the 

calibration of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). 

The MODIS and ASTER high-resolution multi-channel observations of clouds will be used by 

the Clouds and the Earths Radiant Energy System’s (CERES) low resolution radiative flux 

measurements, and by the Measurement of Pollution in the Troposphere (MOPITT) instrument to 

determine the location, distribution and properties of clouds. The Multi-angle Imaging 

Spectrometer’s (MISR) multi-angle measurements will determine the angular reflectance 

properties of land surface features, aerosols, and clouds, all of which will be used in the data 

analysis of MODIS, ASTER and CERES. Vegetation properties will be derived from both 

MODIS and MISR data. Aerosol properties will be measured by MODIS using its wide spectral 

range and 1-2 day single view coverage, and also independently by MISR using its multi-angle 
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data, narrow spectral range, and 2-9 day coverage. Water vapor will be derived independently 

from MODIS measurements of reflected near-infrared sunlight and emitted terrestrial infrared 

radiation. Emitted smoke particles from biomass burnings and forest fires will be observed by 

MISR and MODIS, and emitted trace gases (carbon monoxide and methane) observed by 

MOPITT. Terra will provide, for the first time, simultaneous measurements of clouds, aerosols, 

atmospheric trace gases, land and ocean surface properties, and Earth radiation budget 

parameters. The first CERES instrument was flown on TRMM and will also provide continuity 

to Earth Radiation Budget Experiment (ERBE) and pre-ERBE Earth radiation budget 

measurements. ASTER, developed and built by the Ministry of International Trade and Industry 

(MITI) in Japan, has 14 spectral bands in the visible, near-infrared, shortwave infrared and 

thermal infrared wavelengths, and spatial resolutions ranging from about 15 to 90 meters. MISR, 

a new instrument, views the Earth in four color bands (blue: 446 nm; green: 558 nm; red: 672 

nm; and near-infrared: 866 nm) and from nine view angles with nine cameras pointed in different 

directions. MODIS views the Earth every 1-2 days making observations in 36 co-registered 

spectral bands at moderate resolution (250 m to 1 km). MOPITT, developed by the University of 

Toronto, Canada, employs gas correlation spectroscopy to measure upwelling and reflected 

radiation in three absorption bands of CO and CH4. EOS-Terra instruments are described in the 

following sections. With a development time of approximately 10 years, the EOS series of 

NASA’s flagship satellites represents an unprecedented effort in space-based remote sensing of 

the Earth system as a whole, and meets and exceeds the requirements of GCOS and the climate 

monitoring principles identified by UNFCCC/COP-5. These satellites are likely to be the main 

stay of Earth science research for the next decade. It is noteworthy that NASA’s EOS has 

involved a large number of partnerships between NASA and the space agencies of many different 

countries. The enterprise represents a significant achievement in international collaboration.

2. EOS-Terra/CERES

CERES is based on NASA’s Earth Radiation Budget Experiment 

(ERBE), which used three satellites to provide global energy budget 

measurements from 1984 to 1990. The first CERES instrument was 

flown on TRMM. CERES will provide continuity to ERBE and preERBE measurements. It is a broadband scanning thermistor 

bolometer package with extremely high radiometric measurement 

precision and accuracy. Terra/CERES will carry two identical 

instruments; one will operate in a cross-track mode and the other in 

a biaxial scan mode. The cross-track mode will essentially continue 

the measurements of the ERBE and TRMM missions, while the 

biaxial mode will provide new angular flux information that will 

improve the accuracy of angular models used to derive the Earth’s 

radiation balance. Each CERES instrument has three channels–a shortwave channel for 

measuring reflected sunlight, a longwave channel for measuring Earth emitted thermal radiation 

in the 8-12 μm “window” region, and a total channel for total radiation. On-board calibration 

hardware includes a solar diffuser, a tungsten lamp system with a stability monitor, and a pair of 

black-body sources. Cold space and internal calibration looks are performed during each normal 

Earth scan. Both CERES scanners operate continuously throughout the day and night portions of 

an orbit. In the cross-track scan mode, calibration occurs biweekly. In the biaxial mode, 

Terra-CERES Monthly Global 

Longwave and Shortwave Radiation
U.S. National Report on Systematic Observations, August 2001

104

calibrations also occur biweekly, and sun avoidance short scans occur twice per orbit. CERES 

will be used to study cloud radiative forcings and feedbacks, develop an observational baseline 

for clear-sky radiative fluxes, determine radiant input to atmospheric and oceanic energetics 

models, validate general circulation models, and enhance extended-range weather predictions.

3. EOS-Terra/MODIS 

MODIS views the entire Earth’s surface every 1-2 

days, making observations in 36 co-registered 

spectral bands at moderate resolution (0.25 – 1 

km). MODIS is a whiskbroom scanning imaging 

radiometer consisting of a cross-track scan mirror, 

collecting optics, and a set of linear arrays with 

spectral interference filters located in four focal 

planes. With a viewing swath width of 2330 km 

(the field of view sweeps +/- 55o cross-track), 

MODIS will provide high radiometric resolution 

images of daylight-reflected solar radiation and 

day/night thermal emissions over all regions of the 

globe. Spatial resolution varies from 250 m to 1 

km at nadir: 250 m (2 bands), 500 m (5 bands), 

1000 m (29 bands) at nadir. The broad spectral coverage of the instrument (0.4 – 14.4 μm) is 

divided into 36 bands of various bandwidths optimized for imaging specific surface and 

atmospheric features: 21 bands within 0.4 to 3.0 μm; 15 within 3 to 14.5 μm. Polarization 

sensitivity: 2% from 0.43 μm to 2.2 μm and +/- 45o scan. Absolute irradiance accuracy: 5% for 

<3 μm and 1% for >3μm. The observational requirements also lead to a need for very high 

radiometric sensitivity, precise spectral band and geometric registration, and high calibration 

accuracy and precision. The MODIS instrument has one of the most comprehensive onboard 

calibration subsystems ever flown on a remote sensing instrument. Calibration hardware includes 

a solar diffuser stability monitor, a spectroradiometric calibration assembly, a plate-type black 

body, and a space view port.

4. EOS-Terra/ASTER

Developed and built by MITI-Japan, ASTER has a broad 

spectral coverage and high spectral resolution with 14 

spectral bands covering visible and near-infrared 

(VNIR), shortwave-infrared (SWIR) and thermal 

infrared (TIR) wavelengths. Spatial resolution is high 

ranging from about 15 to 90 meters. Spectral separation 

is accomplished through discrete bandpass filters and 

dichroics. The VNIR subsystem operates in three VNIR 

bands, with 15 m resolution and 60 km swath width. It 

consists of two telescopes, one that looks backward 

(along track) and one that looks at nadir, which together 

produce same-orbit stereo images. The telescope pair is pointable cross-track over a +/- 24o angle 

to increase the revisit frequency of any given Earth location. Light from either of two on-board 

Terra/MODIS True Color Image of the Chesapeake Bay, 

March 2000

Terra/ASTER Image of Mount St. Helens Volcano, 

Washington State, August 2000
U.S. National Report on Systematic Observations, August 2001

105

halogen lamps will be used periodically for calibration. The SWIR subsystem operates in six 

SWIR channels, with a 30 m resolution and 60 km swath width. It contains a mirror that can 

point +/- 8.54o from nadir to allow coverage of any point over the spacecraft’s 16-day cycle. The 

mirror is used periodically to direct light from either of two on-board calibration lamps into the 

subsystem’s fixed aspheric refracting telescope. The TIR subsystem operates in five TIR 

channels with 90 m resolution and 60 km swath width. It contains a scan mirror used for both

scanning and pointing up to +/- 8.54 degrees from nadir. As with the SWIR, this mirror is also 

used periodically to view the on-board blackbody for calibration. Light from the TIR scan mirror 

is reflected into a Newtonian catadioptric telescope system with an aspheric primary mirror and 

lens for aberration correction. ASTER instruments operate for a limited time during the day and 

night portions of an orbit. The full configuration (all bands plus stereo) collects data for an 

average of 8 minutes per orbit. Reduced configurations (limited bands, different gains, etc.) can 

be implemented as requested by investigators. ASTER is the highest spatial resolution instrument 

on EOS-Terra and the only one that does not acquire data continuously. Monitoring application 

products include active volcanoes, crops and crop stress, cloud morphology and physical 

properties, wetlands evaluations, thermal pollution, coral reef degradation, and surface heat 

balance.

5. EOS-Terra/MISR

MISR is a new instrument on board 

EOS-Terra, which will view the Earth in 

four color bands (446 nm–blue, 558 

nm–green, 672 nm–red, and 866 nm–

near-infrared) and from nine view 

angles with nine cameras pointed in 

different directions. Spatial resolution is 

about 275 meters to 1.1 km, with swaths 

of 360 km. The nine angles are: 70.5, 

60.0, 45.6, and 26.1 degrees in the 

forward and aft directions, and 0.0 

degrees. MISR is the first instrument to 

carry sensors making simultaneous observations at different angles from the same platform. 

Different combinations of look angles and spectral band are optimized to meet different scientific 

objectives. Over a period of 7 minutes, a 360 km wide swath of the Earth comes into view at all 

nine angles. Highly accurate absolute and relative radiometric calibration is achieved on-board 

using deployable solar diffuser plates and several types of photodiodes. On-board calibration is 

complemented by in-situ field instruments (such as PARABOLA-III), which automatically scan 

the sky and ground at many different angles, and multi-angle aircraft cameras (AirMISR). Global 

coverage is acquired every nine days at the equator. MISR will monitor the monthly, seasonal, 

and long-term trends in the amount and type of atmospheric aerosol particles (natural and human 

produced); amount, type, and heights of clouds; and the distribution of land surface cover, 

including vegetation canopy structure.

MISR Image of James Bay Canada Showing Contrast Between Summer 

(left) and Winter (Right), August 2000 and January 2001
U.S. National Report on Systematic Observations, August 2001

106

6. EOS-Terra/MOPITT

MOPITT, developed by the University of 

Toronto, Canada, is a scanning radiometer 

employing gas correlation spectroscopy to 

measure upwelling and reflected infrared 

radiance in three absorption bands of carbon 

monoxide and methane. The instrument 

modulates sample gas density by changing the 

length or the pressure of the gas sample in the 

optical path of the instrument, with detectors at 

2.3, 2.4, and 4.7 μm. CO concentrations are 

obtained using pressure and length modulation 

with three independent pieces of information 

represented by values on seven pressure levels 

as well as CO and CH4 columns. Spatial 

resolution: 22 km at nadir. Swath width: 640 

km. MOPITT operates continuously, providing 

data on both day and night portions of an orbit. 

Calibration using on-board blackbodies and a 

space look occurs monthly and provides calibration at an elevated blackbody temperature. 

MOPITT data will be used to measure and model CO and CH4 in the troposphere; obtain CO 

profiles with a resolution of 22 km horizontally and 3 km vertically, with an accuracy of 10%; 

measure the CH4 column in the troposphere with a resolution of 22 km and a precision of better 

than 1%; and generate global maps of CO and CH4 distribution, providing increased knowledge 

of tropospheric chemistry. Heritage: AVHRR, HIRS, Landsat TM, Nimbus-7 Color Scanner.

G. Future (Approved) NASA Research Satellites

1. QuiKTOMS

QuiKTOMS, scheduled for launch in Summer 2001 will measure the atmospheric ozone column 

and provide continuity to TOMS measurements. (See TOMS for description.)

2. Jason-1

Scheduled for launch in Fall 2001, Jason-1 (France), with the Poseidon-2/JMR/DORIS 

instrument package, will provide sea surface height (sea level), sea surface wave height, sea 

surface winds, and ocean surface circulation parameters. Poseidon-2 is the key instrument 

measuring sea surface heights, with DORIS providing precise orbit determination, and JMR 

providing range correction. Jason-1 will provide continuity to TOPEX/Poseidon (Joint USFrance).

3. EOS-Aqua 

Scheduled for launch in Fall 2001, Aqua will monitor the Earth system at a PM equatorial 

crossing time, complementing EOS-Terra (AM crossing). The instrument suite on board Aqua 
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107

includes: MODIS (also on Terra), CERES (also on Terra), The Advanced Scanning Microwave 

Radiometer (ASMR-E, with Japan), Atmospheric Infrared Sounder (AIRS), AMSU-A, and HSB. 

MODIS and CERES on Aqua provide complementary and higher diurnal time resolution with the 

identical instruments on Terra (AM crossing). AIRS will fly on Aqua with two operational 

microwave sounders, the Advanced Microwave Sounding Unit (AMSU) and Humidity Sounder 

for Brazil (HSB). The AMSU and the HSB measurements will be analyzed jointly with AIRS to 

filter out the effects of clouds from the IR data in order to derive clear column air temperature 

profiles with very high vertical resolution and accuracy, plus high accuracy sea surface 

temperatures. The HSB microwave radiometer is being developed by Brazil.

4. SeaWinds

Scheduled for launch in November 2001, SeaWinds will measure surface winds and wind stress 

over the ocean surface. SeaWinds builds on the heritage of the NASA Scatterometer (NSCAT) 

instrument flown aboard the Japanese ADEOS-I in 1996-1997. For continuity, NASA flew 

QuickScat in June 1999 and will also fly the instrument on board ADEOS-II (Japan) to further 

improve and test the active scatterometer technique. Concurrently, the U.S. Navy is preparing an 

experimental satellite mission (CORIOLIS) to test the passive microwave polarimetry-radiometer 

technique for vector wind finding applications. NSCAT will be flown on ADEOS-II (Japan) 

when launched.

5. EOS-ICESat

Scheduled for launch in December 2001, the first precision altimetry mission of the Ice, Cloud 

and Land Elevation Satellite (EOS-ICESat) will carry the Geoscience Laser Altimetry System 

(GLAS) and a GPS orbit determination system, to measure along-track ice sheet and land 

topography to an absolute accuracy of 10 cm or better, and within a footprint of 70 m or less. The 

mission will also provide cloud profile information with reduced vertical information. A repeat 

mission, focused on the primary science goal of measuring changes in the topography and mass 

balance of polar ice sheets is under planning for the 2010 time frame.

6. Solar Radiation and Climate Experiment

Scheduled for launch in July 2002, the Solar Radiation and Climate Experiment (SORCE) will 

provide daily measurements of Total Solar Irradiance (TSI), and spectral solar irradiance between 

1 nm and 2000 nm, incorporating absolute sensors, in-flight calibration, and, in the case of the 

UV observations, comparisons to bright early-type stars. (Also see description under ACRIMIII).

7. EOS-Aura

Scheduled for launch in June 2003, EOS-Aura (previously EOS-CHEM) will comprehensively 

measure atmospheric chemical composition, building on the heritage of the still active UARS, 

and SAGE. Aura will make the first global measurements of tropospheric chemistry. Instruments 

include the microwave limb sounder (MLS), and the High Resolution Dynamic Limb Sounder 

(HIRDLS). MLS measures lower stratospheric temperature and concentrations of H2O, O3, ClO, 

BrO, HCl, OH, HNO3, HCN, and N2O for their effects on (and diagnosis of) ozone depletion, 

transformation of greenhouse gases, and radiative forcing of climate change. HRDLS is an 
U.S. National Report on Systematic Observations, August 2001

108

infrared limb sounder to sound the upper troposphere, stratosphere, and mesosphere to 

determine: temperature; concentrations of O3, H2O, CH4, N2O, NO2, HNO3, N2O5, CFC11, CFC12, 

CLONO2; aerosols; and polar stratospheric clouds and cloud tops. CHEM will also carry a totally 

new, high spectral resolution (~0.025 cm-1) Tropospheric Emission Spectrometer (TES), which 

will allow vertically resolved measurements of ozone and trace gas constituents. Data continuity 

for GCOS research purposes is provided by similar instruments which are also on-board by 

UARS.

H. Future (Approved) Experimental Satellites

1. Gravity Recovery and Climate Experiment (GRACE)

The observational goals of the GRACE are achieved by making accurate measurements of the 

inter-satellite range between two co-planar, low altitude polar orbiting satellites, using a 

microwave tracking system. In addition, each satellite will carry geodetic quality GPS receivers 

and high accuracy accelerometers to enable accurate orbit determination, spatial registration of 

gravity data, and the estimation of gravity field models. The differential influence of the gravity 

field is manifest as a difference in the orbit motion of the center of gravity of the GRACE 

satellite. The distance change, and hence the gravity field variations, must be inferred from the 

phase change measurements made between the spacecraft antenna phase centers on the two 

satellites using the K-band ranging instrument. In essence, the two satellites themselves become 

the instrument.

2. CloudSAT

CloudSAT will use advanced radar to “slice” through clouds to see their vertical structure, 

providing a completely new observational capability from space. Current satellites can only 

image the uppermost layers of clouds. CloudSAT will be one of the first satellites to study clouds 

on a global basis and look at their structure, composition and effects. Instruments include a 94-

GHz Cloud Profiling Radar (CPR), and a Profiling Oxygen A-Band Spectrometer/Visible Imager 

(PABSI). The satellite will be launched (scheduled: May 2003) into a 705 km sun-synchronous 

orbit, and fly in formation with EOS-Aqua and PICASSO-CENA.

3. Vegetation Canopy Lidar (VCL)

The VCL carries a Multi-Bream Laser Altimeter (MBLA) for the characterization of the 

three-dimensional structure of the Earth’s surface, including the vegetation canopy heights and 

the vertical distribution of intercepted surfaces such as leaves and branches. The VCL/MBLA is 

an active lidar remote sensing system consisting of a five-beam instrument with a 25 m 

contiguous along-track resolution. The five beams are in circular configuration 8 km across, and 

each beam traces a separate ground track spaced 2 km apart, eventually producing 2 km coverage 

between 67oN and 67oS.

4. PICASSO-CENA

PICASSO-CENA, with a scheduled launch date of August 2004, will fly a 3-channel lidar with a 

suite of passive instruments in formation with EOS-Terra to obtain coincident observations of 
U.S. National Report on Systematic Observations, August 2001

109

radiative fluxes and atmospheric state. This comprehensive set of measurements is essential for 

accurate quantification of global aerosol and cloud radiative effects. Instruments include: a 

2-wavelength (532 nm and 1064 nm) polarization-sensitive lidar, a high spectral resolution 

(0.5 cm – 1 cm) A-band spectrometer, an imaging infrared radiometer, and a high-resolution 

wide field camera.

5. Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)

The GPS/MET (Ware et al., 1996) project demonstrated atmospheric and ionospheric limb 

sounding from low-earth-orbit (LEO) with high vertical resolution, high accuracy, and global 

coverage. Based on the scientific results of GPS/MET, a follow-on project for weather, climate, 

and space weather observations and research is currently being implemented. COSMIC will 

launch six LEO satellites in FY 2004. Each of these spacecraft will carry three science payloads: 

(1) GPS receiver, (2) Tiny Ionospheric Photometer (TIP), and (3) Triband Beacon Transmitters 

(TBB). Each of the satellites will continuously track the signals transmitted by 12 or more of the 

24 GPS radio beacons. Each COSMIC satellite can retrieve about 500 daily profiles of key 

ionospheric and atmospheric properties from the tracked GPS radio-signals as they are occulted 

behind the Earth limb. The constellation will provide frequent global snapshots of the 

atmosphere and ionosphere with about 3,000 daily soundings down to about 1000 m from the 

surface. TIP will measure electron densities at the peak of the F2 layer along the satellite track. 

TBB transmissions will be received on the ground for high-resolution ionospheric tomography. 

COSMIC orbits and GPS tracking data also promise to benefit geodetic studies. COSMIC is a 

joint U.S.–Taiwan project, and is sponsored in the U.S. by the NSF, NASA, DOD, and NOAA.

Information on the above missions is summarized in Table 6, together with all other satellite 

missions supporting or contributing to GCOS.
U.S. National Report on Systematic Observations, August 2001

110

Table 6. Satellite Series/Systems, Responsible Agencies, Data Exchange/Availability, Applications

All U.S. Satellites contributing to GCOS

Satellite 

Platform/ 

Series

Implement. 

Time Frame

Responsible 

Agencies

Participation/Use 

in other 

Programs

Data 

Exchange

Barriers 

to Data 

Exch.

Applications Internat’nl.

Participat’n

Data Center(s)

(Observed data and 

derived data products)

NOAA/POES2 sat. system

Continuity: 

Indefinite: 

(NPP, 

NPOESS)

1978-present

Design life: 

5 years (per 

satellite) 

NPP: 2005 

NPOESS: 

Launch-2008

NOAA

(& NASA, 

DOD for NPP, 

NPOESS)

International 

Partners

All Open None Operational Weather Forecasting; 

El-Nino Prediction; Climate 

Monitoring/Prediction; Ozone 

monitoring; Resource management; 

Environmental monitoring; Solar 

flux; Volcanoes

Extensive 

Open to all 

countries

NOAA (NESDIS, NCDC); 

WMO/WMC’s

Data availability info:

http://www.saa.noaa.gov/

NOAA/GOES2 sat. system

Continuity: 

Indefinite

1979-present

Design life: 

5 years (per 

satellite)

NOAA

NASA for

R & D

All Open None Operational weather forecasting; 

Climate monitoring and prediction; 

Resource management 

applications; Space environment

Extensive 

Open to all 

countries

NOAA/NESDIS

WMO/WMC’s

Data availability info:

http://www.goes.noaa.gov/

DOD/DMSPmulti-satellites

Continuity: 

Indefinite 

1976-present

Design life: 

3 years (per 

satellite)

DOD

NOAA for 

operations

All Open None Operational weather forecasting; 

All weather Ocean/Land surface 

monitoring;

Open to 

participating 

countries

NOAA (NESDIS, NSIDC, 

NCDC)

Data availability info:

http://www.ngdc.noaa.gov/d

msp/dmsp.html

Landsat 5&7

Continuity: 

Landsat Data 

Continuity 

Mission 

(LDCM)

1972-present

Landsat-7: 

Launch: April 

1999. Design 

life: 5 years

NASA

USGS 

All Open None Resource management

Land surf. Characterization

Land use/cover mapping, 

monitoring; Mineral surveying; 

global change research

Network of 

International 

Ground 

Stations

USGS/EDC

Data availability info:

http://landsat7.usgs.gov

ACRIM (III) 

ACRIMSAT 

Continuity: 

NPP, 

NPOESS)

1978-present

ACRIMSAT: 

Launch: Dec 

1999. Design 

life: 5 years

NASA SolarTerrestrial;

Climate 

Change

Open None Solar-Terrestrial interactions; Solar 

monitoring; Climate variability and 

climate change monitoring and 

prediction

Open to all 

countries

NASA/LARC

Data availability info:

http://gcmd.gsfc.nasa.gov

UARS

Continuity: 

EOS-Aura

1991-present

Design life: 

3 years

NASA

International 

Partners

All Open None Ozone depletion, atmospheric 

chemistry, climate 

monitoring/prediction, solar 

radiation

Open to all 

countries

NASA/LARC

Data availability info:

http://gcmd.gsfc.nasa.gov
U.S. National Report on Systematic Observations, August 2001

111

Satellite 

Platform/ 

Series

Implement. 

Time Frame

Responsible 

Agencies

Participation/Use 

in other 

Programs

Data 

Exchange

Barriers 

to Data 

Exch.

Applications Internat’nl.

Participat’n

Data Center(s)

(Observed data and 

derived data products)

TOMS

Continuity:

 QuickTOMS, 

ADEOS-II

1978-present

QuickTOMS: 

Fall 2001. 

Design life: 

5 years; 

NASA

NASDA

Ozone;

Global 

change

Open None Ozone depletion; climate modeling 

and climate change prediction

Open to all 

countries

NASA/GSFC, NASDA

Data availability info:

http://gcmd.gsfc.nasa.gov

TOPEX/ 

Poseidon

Continuity: 

Jason-1

Aug 1992-

present

Design life: 

5 years 

Jason-1 

scheduled: 

Fall 2001

NASA/CNES Atmospher

e; Ocean

Open None Weather forecasting; Ocean surface 

winds, sea level and state 

monitoring; El-Nino prediction; 

Geodesy/gravity

Open to all 

countries

NASA (JPL, GSFC)

CNES

Data availability info:

http://gcmd.gsfc.nasa.gov

SeaWiFS

Continuity:

EOSTerra/Aqua

Aug 1994-

present

Design life: 

5 years

NASA 

(Through data 

buy)

All Open None Carbon cycle, vegetation, ocean 

biomass, atmospheric aerosols; 

fisheries, natural resources 

management

Open to 

participating 

countries

NASA/GSFC

Data availability info:

http://gcmd.gsfc.nasa.gov

TRMM

Continuity:

GPM (TBD)

Nov 1997-

present

Design Life: 

3 years

NASA

NASDA

All Open None Weather forecasting, Tropical 

Rainfall, El-Nino monitoring & 

prediction; climate monitoring & 

prediction; water cycle and water 

resources

Open to all 

countries

NASA/GSFC

NASDA

Data availability info:

http://gcmd.gsfc.nasa.gov

SRTM 

(Shuttle Radar 

Topo. Miss.)

Continuity/Re

peat: TBD

Mission: 

Feb 2000

(Calibrated 

data–early 

2001)

NASA

DoD

USGS

All Open None Near-Global high resolution data 

base of Earth’s topography

Open to all 

countries

NASA/JPL

DoD/NIMA

USGS/EDC

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

EOS-Terra

[MODIS, 

CERES, 

ASTER, 

MISR, 

MOPITT)

Continuity:

TBD

Dec 1999-

present

Design life: 

6 years

NASA with 

International 

partners

All Open None Weather and climate system 

monitoring and prediction; 

atmosphere/ocean/land/cryo; 

natural resources monitoring; ElNino monitoring/prediction; 

Carbon cycle & vegetation/ocean 

biomass; Water and Energy cycles; 

Aerosols and radiation budget

Open to all 

countries

NASA (GSFC, LARC)

USGS/EROS

International partners

Data availability info:

http://gcmd.gsfc.nasa.gov
U.S. National Report on Systematic Observations, August 2001

112

Satellite 

Platform/ 

Series

Implement. 

Time Frame

Responsible 

Agencies

Participation/Use 

in other 

Programs

Data 

Exchange

Barriers 

to Data 

Exch.

Applications Internat’nl.

Participat’n

Data Center(s)

(Observed data and 

derived data products)

EO-1 (First 

New 

Millennium 

mission)

Continuity 

TBD.

Dec 2000-

present

Design life: 

3 years

NASA All Open None Similar to Landsat-7

(See Landsat)

Open to all 

participating 

countries

NASA

USGS/EDC

Data availability info:

http://gcmd.gsfc.nasa.gov

EOS-Aqua 

(pm)

(MODIS, 

CERES, 

AMSR-E, 

AIRS, AMSUA, HSB)

Continuity: 

TBD

Scheduled: 

Fall 2001

Design Life: 

6 years

NASA with 

international 

partners

All Open None Weather and climate system 

monitoring and prediction; 

atmosphere-ocean-land-cryo 

interaction; natural resources 

management; carbon, water and 

energy cycles; aerosols and 

radiation budget

Open to all 

countries

NASA/GSFC

National & International 

partners

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

EOS-Aura 

(MLS, 

HIRDLS, 

TES)

Continuity:

TBD

Scheduled: 

July 2003

Design Life: 5 

yrs

NASA Ozone, 

Trace 

gases, 

Atmos. 

Chemistry

Open None Montreal Protocol; Framework 

Convention on Climate Change; 

Climate monitoring, modeling and 

prediction

Open to all 

countries

NASA (LARC, GSFC)

National & International 

partners

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

Jason-1 

(Poseidon2/JMR/DORIS 

instrument 

package)

Continuity for 

TOPEX/ 

Poseidon 

Scheduled: 

Fall 2001

Design life: 

3 years

NASA/CNES

(Contributing 

agencies: 

NOAA

EUMETSAT)

Atmos/

Ocean

Open None Sea surface winds, state, level; ElNino monitoring & prediction; 

fisheries; ocean circulation

Open to all 

countries

NASA/GSFC

CNES

NOAA, EUMETSAT

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

SeaWinds 

(NASCAT)

Continuity: 

ADEOS-II

Scheduled: 

Nov 2001; 

Quick-SCAT: 

6/1999 Design 

Life:

3 years

NASA

NASDA

Atmos/

Ocean

Open None Weather forecasting; 

Oceanography; El-Nino prediction; 

Climate modeling/prediction

Open to all 

countries

NASA/GSFC

NASDA

Data availability info:

http://www.earth.nasa.gov/

missions/index.html
U.S. National Report on Systematic Observations, August 2001

113

Satellite 

Platform/ 

Series

Implement. 

Time Frame

Responsible 

Agencies

Participation/Use 

in other 

Programs

Data 

Exchange

Barriers 

to Data 

Exch.

Applications Internat’nl.

Participat’n

Data Center(s)

(Observed data and 

derived data products)

EOS-IceSAT 

(GLAS)

Continuity: 

TBD (possible 

repeat mission 

in 2010)

Scheduled: 

Dec 2001

Design Life: 

3 years

NASA Ice, and 

Land 

elevation/

topograph

y

Open None Ice sheet mass balance; Climate 

system monitoring, modeling and 

prediction

Open to all 

countries

NASA (WFF, GSFC)

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

SORCE (TIM, 

SOLSTICE, 

SIM, XUV)

Continuity: 

See ACRIMIII, NPOESS

Scheduled: 

July 2002

Design Life: 

5 years

NASA Solar & 

solarterrestrial 

interaction

Open None Solar irradiance and variability Open to all 

countries

NASA/GSFC

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

Approved 

satellites: 

(ESSP-VCL; 

GRACE; 

PICASSOCENA; 

Cloudsat)

Scheduled: 

2001-2004

Design Life: 

Various (3-5 

years)

NASA with 

International 

partners

Various Open None Various Open to all 

countries

NASA

International partners

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

ESSPGRACE.

Continuity: 

TBD

Scheduled 

Nov. 2001

Design life: 

5 years

NASA

DLR 

(Germany)

Earth Syst. 

Gravity 

field

Open None Ocean surface currents, ocean heat 

transport, Mass balance of Ice 

sheets, Changes in Storage of 

water/snow on continents

Open to all 

countries

NASA/JPL

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

ESSPCloudSat.

Continuity: 

TBD

Scheduled

May 2003

Design life: 

3 years

NASA All Open None Vertical Profile of clouds, Cloud 

base/top, optical depth, 

atmospheric heating rate, cloud 

water, ice, particle size, 

precipitation, Vis/IR radiances, 

cloud-climate feedback, effect of 

aerosols on clouds

Open to all 

countries

NASA/GSFC

Data availability info:

http://www.earth.nasa.go

v/missions/index.html

ESSP-VCL.

Continuity: 

TBD

Scheduled: 

TBD 

(Aug 2003)

Design life: 

3 years)

NASA Atm/Land

Surf/Veg

Open None Land cover/vegetation structure, 

climate, topography,

Open to all 

countries

NASA/GSFC

USGS/EROS

Data availability info:

http://www.earth.nasa.gov/

missions/index.html
U.S. National Report on Systematic Observations, August 2001

114

Satellite 

Platform/ 

Series

Implement. 

Time Frame

Responsible 

Agencies

Participation/Use 

in other 

Programs

Data 

Exchange

Barriers 

to Data 

Exch.

Applications Internat’nl.

Participat’n

Data Center(s)

(Observed data and 

derived data products)

ESSPPICASSOCENA.

Continuity: 

TBD

Scheduled: 

Aug 2004

Design life: 

5 years

NASA

CNES

All Open None Clouds and aerosols vertical 

distributions, optical depth, albedo, 

emissivity, particle size; surface 

and atmospheric radiative fluxes

Open to all 

countries

NASA/LARC

CNES

Data availability info:

http://www.earth.nasa.gov/

missions/index.html

NPP 

(NPOESS 

Preparatory 

Project)

Scheduled: 

Dec 2005

NOAA, DoD, 

NASA;

EUMETSAT/

METOP

All Open None Demonstrate advanced technology. 

Bridge between EOS-Terra/Aqua 

and NPOESS

Extensive

Open to all 

countries

NOAA/NESDIS

Data availability info:

http://www.ipo.noaa.gov/sat

_evolu.html

NPOESS 

Continuity: 

indefinite

Scheduled: 

2008

Design life: 

5 years per 

satellite

NOAA, DoD, 

NASA;

EUMETSAT/

METOP

All Open None Operational Weather Forecasting; 

El-Nino/Climate Monitoring & 

Prediction; Ozone monitoring; 

Resource management; 

Environmental monitoring; Solar 

flux; Volcanoes; Aerosols; 

Extensive 

Open to all 

countries

NOAA/NESDIS

Data availability info:

http://www.ipo.noaa.gov/
U.S. National Report on Systematic Observations, August 2001

115

Table 7. Satellite Series, Observations, Series Duration/Continuity, Compliance with GCOS Principles

(Excluded: Satellites not yet launched. For these satellites, see Table 6)

Satellite

Series & Compliance With 

GCOS Principles

Coverage & 

Space

Resolution

Time 

Resol. Atmosph.

Atmos.

Comp/

Chem

Land Surface/

Terrestrial Ocean Cryos. Series Duration & Continuity

NOAA/POES (two)

(Vis, IR, Microwave)

Most recent: NOAA-16

Compliance: Good for 

reprocessed data

Global

1-4 km

Orbit: 870 km

2/day

am & pm

Temp, 

moisture, 

clouds, 

weather, 

radiation

Ozone Temp, vegetation 

(NDVI), snow, ice

Temp, land-water

boundaries, 

precipitation 

(index)

Snow, ice 1978-present, 2 

satellite system.

Continuity: NPP, 

NPOESS

NOAA/GOES (two)

(Vis & IR)

Most Recent: 

GOES-11

Compliance: Good for 

reprocessed data

Regional. 

Locations: 75W 

and 135W

Orbit: 35,790 

km

Full disc 

every 30 

min

Temp, 

moisture, 

Clouds, 

weather, cloud 

tracked winds

Ozone Temperature Temperature, 

precipitation 

(index)

Snow, ice 1979-present, 2 

Satellite system

Continuity: 

Indefinite

DOD/DMSP

(Vis, IR, Microwave)

Most recent: DMSP-14

Compliance: Good for 

reprocessed data

Global: 2.7 km

Regional: 0.55 

km

2/day Clouds, Cloud 

water, 

temperature, 

moisture

N/A Temperature, snow 

cover, frozen 

ground, rainfall, 

fires

Temperature, sea 

ice, wind speed, 

rainfall

Snow 

cover, sea 

ice

1976-present, 5 

satellite system

Continuity: NPP, 

NPOESS

NASA/USGS-Landsat

(Vis, Near-IR, IR). Most 

recent: Landsat-7

Compliance: Very good

Global

15 m – 80 m

Orbit: Sun 

Synchronous; 

Altitude: 705 

km; Inclination: 

98o; Period: 98.9 

min

16-day

each 

satellite

(8-day 

repeat 

with 

Landsat 

5&7)

Secondary N/A Land surface 

properties/characte

rization, land use, 

land cover, 

vegetation, soils, 

minerals, water 

bodies

Land-ocean 

boundaries, inland 

seas/water bodies

Snow 

cover, ice

1972-present

Continuity: 

Indefinite (TBD)

NASA/ACRIM –III 

(ACRIMSAT: Dec. 99). 

Heritage: ACRIM-I on SMM; 

ACRIM-II on UARS

Compliance: Very good

Global (Solar)

5 ppm of TSI.

Spin stabilized 

to within 0.25o

Orbit: 685 km

N/A N/A

(Solar)

N/A

(Solar)

N/A 

(Solar)

N/A

(Solar)

N/A

(Solar)

1978- present. 

Continuity: 

Indefinite (TBD)
U.S. National Report on Systematic Observations, August 2001

116

Satellite

Series & Compliance With 

GCOS Principles

Coverage & 

Space

Resolution

Time 

Resol. Atmosph.

Atmos.

Comp/

Chem

Land Surface/

Terrestrial Ocean Cryos. Series Duration 

& Continuity

NASA/UARS

UV, Vis, IR, Microwave

-

Compliance: Very good

Orbit altitude: 

600 km

Resolutions: 

various for 

different 

instruments

1 day Stratosphere/ 

mesosphere:

Temperature, 

moisture, 

winds, 

energetic 

particles

Also: solar 

observations

Aerosols, 

Ozone 

depletion 

chemist: 

CLONO2, 

CLO, HF, 

HCL, NO2, 

N2O5, NO 

HNO3, 

others

N/A N/A N/A 1991-present.

Continuity: EOSAura (Launch: 

June 2003)

NASA/TOMS

(Total Ozone Mapping 

Spectrometer)

Heritage: TOMS 

Compliance: Very good

Global

42 km at subsatellite point

Orbit: 800 km; 

Cross-track: 

2300 km

1 day N/A Ozone & 

SO2

Smoke

Smog

N/A N/A N/A 1978-present

Continuity: 

QuikTOMS 

(Launch: Fall 

2001), ADEOS-II 

NASA/CNESTOPEX/Poseidon

(Laser altimeter, Microwave 

radiometer)

Compliance: Very good

Global

Sea surface 

height to within 

4.3 cm. Satellite 

location to 

within 2.8 cm

1 day;

Repeat 

cycle: 10 

days for 

global sea 

level 

fields

Water vapor 

content

N/A N/A Sea surface height, 

sea surface wind 

speed and wave 

energy

N/A 1992-present

Continuity: 

Jason-1 (Launch: 

Fall 2001)

NASA-SeaWiFS 

(W/Commercial partners). 

Heritage: CZCS

(Vis. Near-IR, IR)

Compliance: Very good

Global 1 day Water vapor Aerosolsoptical 

properties 

& optical 

depth

Land vegetation 

cover

Ocean bio-optical 

properties, ocean 

biomass

Secondary 1994-present

Continuity: EOSTerra/Aqua.

Historical data: 

1978-1986 CZCS

NASA-TRMM (with 

NASDA/Japan)

(Active precipitation radar, 

Microwave, Vis, IR)

Compliance: Excellent

Global belt: +/-

35o N/S

Horiz. 

Resolution: 4 

km; swath 

width: 220 km

Rain rates down 

to 0.7 mm/hr

Instantane

ous for 

local; 

climatolog

y for 

global 

precip.

Temperature, 

water vapor, 

clouds, 

radiation, 

lightening

Aerosols Tropical 

precipitation 

(vertical 

distribution). 

Sea surface 

temperature (all 

weather and thru’ 

clouds)

1997-present.

Continuity: GPM 

(TBD)
U.S. National Report on Systematic Observations, August 2001

117

Satellite

Series & Compliance With 

GCOS Principles

Coverage & 

Space

Resolution

Time 

Resol. Atmosph.

Atmos.

Comp/

Chem

Land Surface/

Terrestrial Ocean Cryos. Series Duration 

& Continuity

NASA/EOS-Terra-CERES

(Also flown on TRMM)

(SW, LW, Total radiation, 

Vis, IR). On-board calibration.

Compliance: Excellent

Global

15m –

Orbit: Polar, 

705 km; 

Inclination: 

98.2o; 

Descending 

node: 10.30 am; 

Period: 98.88 

min

1 day Clouds, 

Earth’s 

radiation 

budget, cloud 

radiative 

forcing/ 

feedback

N/A Clear sky radiative 

fluxes

Clear sky radiative 

fluxes

Clear sky 

radiative 

fluxes

1999-present

Continuity: 6 yr 

Life duration of 

Satellite. Future: 

TBD.

Historical: 

NASA/ERBE 

(1984-1990); 

TRMM: since 

1997.

NASA/EOS-Terra-MODIS

(Vis & IR w/high spectral 

discrimination). On board 

calibration.

Compliance: Excellent

Global

Resolution: 250 

m to 1.0 km

Orbit: Polar, 

705 km; 

Inclination: 

98.2o; 

Descending 

node: 10.30 am; 

Period: 98.88 

min

1 day Clouds, water 

vapor, 

temperature

Aerosols Temperature, land 

surface cover, 

vegetation, fires

Surface 

temperature, ocean 

color (sediment, 

phytoplankton), 

primary 

productivity

Snow 

cover, Ice 

cover

1999-present

Continuity: 6 yr 

Life duration of 

instrument.

Future: TBD

NASA/EOS-Terra-ASTER 

(w/MITI-Japan)

(Vis., Near IR, SW-IR, 

Thermal-IR). On-board 

calibration.

Compliance: Excellent

Global

15m to 90 m

60 km swath

Orbit: Polar, 

705 km; 

Inclination: 

98.2o; 

Descending 

node: 10.30 am; 

Period: 98.88 

min

Noncontinuous

(Full 

configurati

on data for 

8 min per 

orbit. 

Reduced 

configurati

on data–on 

demand)

Cloud 

morphology, 

cloud 

properties

Aerosols/V

olcanic 

eruptions

Surface 

temperature and 

emissivity, Surface 

digital elevation, 

surface 

composition and 

vegetation, 

Sea ice and polar 

ice

Sea ice 

and polar 

ice

1999-present.

Continuity: 6 yr 

Life duration of 

instrument.

Future: TBD
U.S. National Report on Systematic Observations, August 2001

118

Satellite

Series & Compliance With 

GCOS Principles

Coverage & 

Space

Resolution

Time 

Resol. Atmosph.

Atmos.

Comp/

Chem

Land Surface/

Terrestrial Ocean Cryos. Series Duration 

& Continuity

NASA/EOS-Terra-MOPITT 

(w/ Canada)

(Scanning radiometer using 

gas correlation IR 

spectroscopy)

On-board calibration.

Compliance: Excellent

Global 

Resolution: 22 

km; Swath: 640 

km

Orbit: Polar, 

705 km; 

Inclination: 

98.2o; 

Descending 

node: 10.30 am; 

Period: 98.88 

min

Day and 

night

CO, 

Methane 

(CH4),

N/A N/A N/A 1999-present

Continuity: 6 yr 

Life duration of 

instrument.

Future: EOSAura or TBD
U.S. National Report on Systematic Observations, August 2001

119

Table 8. Status of the Potential for the Transition of Research Satellite Remote Sensing Instruments to Operational Systems

NOTE: Under “Parameter/Question”, the notation in parenthesis “( )” refers to the Science Questions in Section 1 of this Chapter on 

satellite systems. V = Variations; F = Forcings; R = Response; C = Consequences; P = Prediction. Example: V1 denotes bullet #1 

under Science Question referring to Variations and Trends.

NOTE: The parameters identified in the Tables are those for which systematic measurements are considered necessary. Not included

are several other satellite observations, needed for research, that may not be required on a continual, systematic basis, and/or those not 

yet being considered for near future operational systems.

Table 8a. Key Observations for Identifying Earth-Climate System Variations and Trends.

Parameter/ 

Question

Satellite Instrument 

Implementation Detail

Corresponding In-situ 

Measurement Systems

Technical Readiness of 

Satellite Instrument(s) Operational Potential Partnership Potential

Atmospheric 

Temperature (V1)

Passive Sounding Radiosondes

(NOAA, WWW, NASA, NDSC)

Excellent NPOESS requirement EUMETSAT 

Coordination

Active Sounding (GPS) Global GPS network Full demonstration needed NPOESS requirement EUMETSAT 

Coordination

Atmospheric 

Water Vapor (V1)

Passive Sounding Radiosondes, Ly-α, μwave 

(NASA, NOAA, WWW)

Satisfactory NPOESS requirement EUMETSAT

Coordination

Global 

Precipitation (V1)

Requires 6-8 satellite 

constellation for

time resolution

Rain gauges, weather radar

(NOAA, WWW)

Demonstrated by TRMM 

and passive μwave imagers

TBD; only passive μwave 

currently planned

Excellent – several 

needed

Soil Moisture 

(V1)

Requires relatively low 

(L-band) μwave frequency

Neutron probes, 

Lysimeters 

(USDA, USGS, FAO)

Very large real or synthetic 

antenna to be demonstrated

Highly desired; subject to 

operational viability

Likely with European 

Space Agency

Ocean Surface 

Topography (V2)

Prefer non-polar orbit to 

avoid tidal aliasing

Tide gauges

(Global Geodetic Network)

Demonstrated 

Development needed for 

denser coverage

Included on one NPOESS 

sat. but polar orbit is 

problematic

Continuation of current 

partnerships likely

Ocean Surface 

Winds (V2)

Active μwave technique 

preferred

Ships, buoys

(NOAA, WWW)

Demonstrated by NSCAT 

and Seawinds

NPOESS need nominally 

fulfilled by passive sensor

Seawinds and follow-on 

cooperation with Japan

Sea Surface 

Temperature (V2)

Both IR and microwave 

needed for all-weather 

observation

Ships, buoys

(NOAA, WWW)

Excellent NPOESS requirement EUMETSAT 

Coordination

Sea Ice Extent 

(V2)

Microwave radiometry 

needed for all-weather 

measurements 

Ships, airborne reconnaissance 

(Navy, USCG, NOAA)

Excellent NPOESS requirement NASDA cooperation

Terrestrial 

Primary

Productivity (V3)

1 km or better resolution 

needed

Crop, forest inventory. (USDA, 

FAO, LTER (NSF), GTOS

Excellent NPOESS requirement EUMETSAT 

Coordination
U.S. National Report on Systematic Observations, August 2001

120

Parameter/ 

Question

Satellite Instrument 

Implementation Detail

Corresponding In-situ 

Measurement Systems

Technical Readiness of 

Satellite Instrument(s) Operational Potential Partnership Potential

Marine Primary 

Productivity (V3)

Very precise inter-calibration 

is essential

NASA-SIMBIOS time series 

studies

Demonstrated Partially provided by 

NPOESS

Cooperation with Japan, 

Europe possible

Total Column 

Ozone (V4)

High long-term accuracy 

needed for trend studies

Dobson, Brewer, FTIR, UV/VIS 

(NASA, NOAA)

Excellent NPOESS requirement EUMETSAT 

Coordination

Ozone Vertical 

Profile (V4)

Good vertical resolution 

needed near tropopause

Ozonesondes, lidar, μwave , IR, 

(NASA, NOAA)

Excellent NPOESS requirement Coordination potential 

exists

Ice Surface 

Topography (V5)

Excellent vertical resolution 

and accuracy needed for mass 

balance studies

GPS (NASA, NSF) ICEsat lidar altimetry 

demonstration pending

Not currently an 

operational requirement

Coordination with 

European radar 

altimetry satellite
U.S. National Report on Systematic Observations, August 2001

121

Table 8b. Key Observational Requirements for Determining Primary Forcings on Earth-Climate System

Parameter/ 

Question

Satellite Instrument 

Implementation Detail

Corresponding In-Situ 

Measurement Systems

Technical Readiness of 

Satellite Instrument(s) Operational Potential Partnership Potential

Total Solar 

Irradiance (F1)

High absolute accuracy, 

overlap of successive records 

required 

global surface networks 

(BSRN, WRDC, SURFRAD)

Excellent NPOESS requirement Possible

Solar UV 

Irradiance (F1)

Need for spectral resolution 

and good radiometric 

accuracy

USGCRP UV network, NDSC 

(multi-agency)

Excellent NPOESS measurement 

planned

Strong history of 

cooperation

Stratospheric

Aerosol 

Distribution (F1)

Good vertical resolution and 

large dynamic range required

Lidar, backscatter-sondes (NASA, 

NOAA, NSF)

Excellent NPOESS meas. possible 

but resolution is 

problematic

Possible 

Total Aerosol 

Amount (F1)

Global coverage over ocean 

and land needed

AERONET, USDA network, 

NOAA/BSRN, DOE/ARM

Excellent NPOESS requirement Possible

Aerosol 

Properties (F1)

Need in-situ and groundbased measurements AERONET, NOAA/CMDL, 

airborne aerosol spectrometers

Further development needed 

for space measure.

NPOESS requirement Possible, important 

for ground-based 

measurements 

Sfc. Trace Gas 

Concentration 

(F1)

Ground-based measurements 

fulfill requirements

NASA AGAGE, NOAA flask 

network and CO2 meas. 

Need simpler instruments 

with better time resolution 

NOAA flask sampling 

network, NASA

AGAGE

Helps support 

ground network

Volcanic Gas & 

Ash Emissions 

(F1)

Global observation of ash and 

gas plumes

In-situ optical calibration Further progress needed to 

characterize tropospheric 

constituents

Significant on account of 

impact on aviation

Possible

Fire Occurrences 

(F2)

Global observation of infrared 

and vis/near-ir; hyperspectral 

for fuel load

Aeronet (NASA), burn scar inven. 

(USFS, int’l.), In-situ optical 

calibration

Excellent NPOESS EDR application NPOESS EDR 

application

Trace Gas 

Sources (F2) 

CO2 column mapping is 

greatest priority

Flask network (NOAA), Ameriflux 

(DOE, USDA, NASA), FluxNet

Technical developments 

needed for exploratory 

mission 

Unlikely TBD

Land Cover/ 

Land Use 

Inventories (F2)

High spatial resolution 

required (few tens of meters) 

Land Cover Maps (USGS), Veg. 

Inventories (DOI, USDA)

Excellent, need to reduce cost Government/commercial 

partnership possible

Possible with U.S. 

industry 

Surface Stress 

and Deformation 

(F2)

Special focus on active 

earthquake and volcanic 

regions 

Regional GPS networks, geological 

observations

Excellent Joint support of ground 

arrays by local agencies

Multi-national 

support for ground 

arrays
U.S. National Report on Systematic Observations, August 2001

122

Table 8c. Special Observational Requirements for Response and Feedback Process Studies

Parameter/ 

Question

Satellite Instrument 

Implementation Detail

Corresponding In-situ 

Measurement Systems

Technical Readiness of 

Satellite Instrument(s) Operational Potential Partnership Potential

Cloud System 

Structure (R1)

Multispectral visible and IR 

radiometry 

Radiosondes, lidar (NASA, NOAA, 

FAA)

Excellent NOAA & NPOESS 

requirement

EUMETSAT and Japan's 

ADEOS/GLI

Cloud Particle 

Properties and 

Distribution (R1)

Active sensor to resolve threedimensional structure None Demonstration of cloud radar 

and lidar pending

Desirable; subject to 

operational viability 

DOD is contributing to 

Cloudsat project

Earth radiation 

Budget (R1)

Broadband radiometry None Excellent Planned on NPOESS Possible

Soil Moisture (R1) Spatial resolution and ability to 

penetrate vegetation are the 

issues

Neutron probes, 

lysimeters

(USDA, USGS, FAO)

Approaching readiness (done 

from aircraft)

Highly desired; subject to 

operational viability

Likely with European 

Space Agency

Snow Cover & 

Accumulation 

(R1)

Need to assess snow depth or 

water equivalent quantitatively

Snow transects

(NOAA/NWS)

Awaiting demonstration NPOESS requirement for 

snow cover

Possible

Freeze-Thaw 

Transition (R1)

Need to assess in all cloud and 

vegetation conditions

Not a routine measurement Awaiting demonstration Desired; subject to 

operational viability

Possible

Biomass (R2) Based on resolving canopy 

vertical structure; requires 

active lidar sensor

Crop/Timber yield (USDA, DOI), 

carbon database (DOE)

Demonstration pending (VCL) TBD Possible

Marine 

Productivity in 

Coastal regions 

(R2)

High spatial and temporal 

resolutions needed to resolve 

specific events

NASA-SIMBIOS; Coastal biooptics (NOAA, EPA)Excellent Possible NPOESS derived 

product

International product 

inter-comparison 

Carbon Sources 

and Sinks (R2)

CO2, CH4 column mapping is 

most promising approach;

Flask network (NOAA), 

Ameriflux/Flux

Net (DOE, USDA, NASA)

Experimental technique needs 

further development

Unlikely Possible

Sea Surface 

Salinity (R3)

Very high radiometric 

precision needed for passive 

μwave observation

Ships and moored/drifting buoys 

(NOAA/NSF)

Approaching readiness (done 

from aircraft)

Unfulfilled NPOESS 

requirement 

Likely with European 

Space Agency

Sea Ice Thickness 

(R3)

Significance of ice freeboard 

observations remains to be 

established 

Moored buoys (ONR) High spatial resolution radar; 

development needed

Desirable, subject to 

operational viability

Possible with 

international/ 

commercial partners

Atmospheric 

Properties in 

Tropopause 

Region (R4)

Need ozone, water vapor, 

temperature at high vertical 

resolution

Sondes (WWW, NOAA) Limb viewing sensors not yet 

demonstrated

TBD Interest exists

Polar ice sheet 

velocity (R5)

Synthetic aperture radar 

interferometry; high latitude 

coverage (polar orbit) needed

GPS (NASA, NSF) Demonstrated Government/commercial 

partnership possible

Possible
U.S. National Report on Systematic Observations, August 2001

123

Parameter/ 

Question

Satellite Instrument 

Implementation Detail

Corresponding In-situ 

Measurement Systems

Technical Readiness of 

Satellite Instrument(s) Operational Potential Partnership Potential

Tropospheric 

Ozone and 

Precursors (R6)

Need excellent vertical 

resolution through entire 

troposphere, implies active 

lidar sensor

Airborne in-situ for DC-8, R-2, 

WB-57

Experimental technique, needs 

further develop. 

TBD Interest exists

Global 

Precipitation (C1)

Requires Constellation for 

Good Time Resolution

Rain gauges, weather radar

(NOAA, WWW)

Demonstrated via TRMM TBD; only passive μwave 

currently planned

Excellent – several 

needed

Ocean Surface 

Winds (C1)

Active μwave technique Ships, buoys

(NOAA, WWW)

Demonstrated by NSCAT and 

SeaWinds 

NPOESS need nominally 

fulfilled by passive sensor

Seawinds cooperation 

with Japan; EUMETSAT

Passive μwave 

radiometry/polarimetry 

probably sufficient for 

meteorological applications

Windsat/Coriolis demonstration 

funded by DOD, USN, 

NPOESS

NPOESS requirement Possible

Meteorological 

Properties Around 

Storms (C1) 

Requires vertical profiling 

from a geostationary platform

Radiosondes

(NOAA, WWW)

Demonstration planned with 

GIFTS

May become operational 

GOES sensor if 

successfully demonstrated

Possible 

Lightning Rate 

(C1)

Requires geostationary 

implementation for temporal 

resolution

Sferics Demonstrated by OTD and LIS Could be implemented on 

future GOES 

Possible

River Stage 

Height/

Discharge Rate 

(C1)

Requires high precision, 

vertical resolution, and 

frequent sampling 

River gauges

(USGS)

Capability demonstrated by 

TOPEX/Poseidon

TBD TBD

Primary 

Productivity (C2)

1 km or better resolution 

needed

NASA-SIMBIOS, GOOS, GTOS, 

crop, forest inventories (USDA, 

FAO), LTER (NSF)

Excellent NPOESS requirement EUMETSAT 

coordination

Land Cover / Land 

Use Change (C2)

High spatial resolution (few 

meters) crucial

Land cover maps (USGS), veg. 

Inventories (DOI, USDA)

Excellent, need to reduce cost Government/commercial 

partnership possible

Possible with U.S. 

industry 

Coastal Region 

Properties and 

Productivity (C3)

Multispectral radiometry at 

high spatial and temporal 

resolution from GEO 

Coastal observations (NOAA, EPA) Excellent Could be implemented on 

future GOES 

Possible
U.S. National Report on Systematic Observations, August 2001

124

Table 8d. Special Observational Requirements for Prediction and Assessments

Parameter/ 

Question

Satellite Instrument 

Implementation Detail

Corresponding In-situ 

Measurement Systems

Technical Readiness of 

Satellite Instrument(s) Operational Potential Partnership Potential

Tropospheric 

Winds (P1)

Active Doppler lidar remote 

sensing 

Rawinsondes

(NOAA, WWW)

Technical developments, 

demonstration needed

Very high, when 

demonstrated

Commercial data purchase 

possible

Ocean Surface 

Winds (P1)

Active μwave technique Ships, buoys

(NOAA. WWW)

Demonstrated by NSCAT & 

SeaWinds

NPOESS requirement 

nominally fulfilled by 

passive sensor

Seawinds cooperation with 

Japan; EUMETSAT data 

acquisition

Passive μwave 

radiometry/polarimetry

Windsat/Coriolis demonstration 

funded by DOD, USN, NPOESS

NPOESS requirement Possible

Global 

Precipitation (P1)

Requires Constellation for

Good Time Resolution

Rain gauges, weather radar

(NOAA, WWW)

Demonstrated via TRMM TBD; only passive μwave 

currently planned

Excellent – several needed

Freeze-Thaw 

Transition (P1)

Need to assess in all cloud and 

vegetation conditions

Not a routine measurement Awaiting demonstration Desired; subject to 

operational viability

Possible

Lightning Rate 

(P1)

Requires geostationary 

implementation for temporal 

resolution

Sferics Demonstrated by OTD and LIS Could be implemented on 

future GOES 

Possible

Soil Moisture (P1, 

P2)

Spatial resolution and ability to 

penetrate vegetation are crucial

Neutron probes, 

lysimeters

(USDA, USGS, FAO)

Approaching readiness (done 

from aircraft)

Highly desired, subject to 

operational. viability

Possible

Sea Surface 

Temperature (P2)

Both IR and μwave observations 

needed for all-weather 

measurement

Ships, buoys

(NOAA, WWW)

Excellent NPOESS requirement EUMETSAT coordination

Sea Level Height 

(P2)

Prefer non-polar orbit to avoid 

tidal aliasing

Tide gauges; 

Global Geodetic Network for 

reference frame

Demonstrated Included on one NPOESS 

satellite, polar orbit is 

problematic

Continuation of past 

partnership likely

Deep Ocean 

Circulation (P3)

Requires in-situ oceanographic 

observations

Ships and ARGO floats (NOAA, 

NSF)

WOCE, GODAE research 

projects provide initial data base

Operational Global Ocean 

Observing System is 

being envisaged 

Multi-agency, international 

cooperation is anticipated

Total Column 

Ozone (P4)

High long-term accuracy needed 

for trend studies

Dobson, Brewer, FTIR, UV/VIS 

(NASA, NOAA)

Excellent NPOESS requirement EUMETSAT coordination

Trends in Carbon 

sources and sinks 

(P5)

CO2 and CH4 column mapping is 

most promising approach

Flask network (NOAA), 

Ameriflux/FluxNet (DOE, 

USDA, NASA)

Experimental technique; needs 

further development

Unlikely Possible

Land Cover/Land 

use Change (P5)

High spatial resolution (few 

meters) crucial

Land cover maps (USGS), Veg. 

Inventories (DOI, USDA)

Excellent, need to reduce cost Commercial data purchase 

likely

Possible with U.S. industry
U.S. National Report on Systematic Observations, August 2001

125

V. Data and Information Management Related to GCOS

Achieving the goals of the U.S. climate-observing program will require multidisciplinary analysis 

of data and information to an extent never before attempted. This includes the analysis of 

interlinked environmental changes that occur on multiple temporal and spatial scales, which is 

very challenging both technically and intellectually. For example, many types of satellite and insitu observations at multiple scales need to be integrated with models and the results presented in 

understandable ways to all levels of the research community, decision makers, and the public. 

Additionally, very large volumes of data from a wide variety of sources and results from many 

different investigations need to be readily accessible to scientists and other stakeholders in usable 

forms.

Various U.S. agencies have engaged in extensive development of interagency data and 

information processes to address these needs, primarily through fostering better integration 

among U.S. Government data and information centers that have traditionally developed along 

disciplinary lines to serve specific scientific and operational communities. Included has been the 

development of the Global Change Data and Information System (GCDIS) in response to the 

need to coordinate among the disparate data centers and systems in the participating agencies and 

to facilitate making data readily available to users. GCDIS currently provides a gateway for 

discovery and information access among more than 70 federally funded sources of data, both 

governmental and academic. During the last decade, significant strides have been made in 

GCDIS’s seamless connections between diverse data sets and sources as well its ability to search 

across the full complement of sources. The Internet has facilitated immeasurably this coordinated 

effort. However, important challenges remain. A number of U.S. Government agencies are 

involved in climatological data management activities, and links to these can be found at 

http://www.ofcm.gov/Climate/climate.htm, a site maintained by the U.S. Office of the Federal 

Coordinator for Meteorology.

The provision of data and information in forms needed for cross-disciplinary analysis and 

projection remain a challenge even as the increasing focus of U.S. agencies on investigating the 

impacts and consequences of change heightens the need for multidisciplinary research. Physical 

and biological data will need to be related to data on environmental conditions and 

socioeconomic trends originally compiled by agencies and groups primarily for purposes other 

than global change research. This is a particularly important challenge in addressing potential 

regional consequences of multiple stresses and determining the vulnerability of different 

resources and communities.

Similarly, the need to effectively link global observation data activities supported by the U.S. and 

its international partners is increasing. Further, observational data on individual variables must be 

combined into long-term, integrated measures of environmental changes. Both need to be 

coupled with modeling efforts at multiple scales to provide the synergy necessary to understand 

the relationships between complex variables, such as the relationships between air and water 

quality and human health.

The data centers in Federal agencies, which are the repositories of both USGCRP and external 

data and information, are experiencing either flat or declining budgets while their workload from 

data and user volume is increasing. During the past five years, the volume of data at Federal 
U.S. National Report on Systematic Observations, August 2001

126

centers has increased by two- to six-fold, and this growth rate is expected to increase at even 

higher rates in the next decade. As examples, NASA's Earth Science data holdings increased by a 

factor of six from 1994 to 1999, and the total amount of data then doubled between 1999 and 

2000. NOAA’s data center holdings are expected to increase by ten-fold in the next decade.

Over the past decade the meteorological community has witnessed an ever-increasing demand for 

current and historical data related to extreme weather and climate events. Such data are necessary 

for seasonal and interannual climate prediction as well as for climate research, monitoring of 

climate variability, and detection of climate change. The importance of these activities has been 

recognized on numerous occasions by governments at various meetings, in particular by the 

Intergovernmental Panel on Climate Change (IPCC) and by the Conference of the Parties to the 

UNFCCC. In response to these requirements from the climatological community, the GCOS 

program, established in 1992, developed the GSN, which consists of 989 meteorological surface 

reporting stations from 50 member states of the WMO (http://www.wmo.ch).

NCDC is responsible for building a permanent data base of GSN daily and monthly data 

submissions, along with the appropriate station metadata history, and for providing free and open 

user access to this information via the Internet. This site contains all of the historical daily and 

monthly CLIMAT-formatted GSN data received at NCDC from 250 of these surface stations in 

28 nations. As more data are received they will be integrated into the system and made available 

for use. The visitor may view data in both textual and graphical form and, through the use of 

copy and paste, can download subsets of the database to their own system for later use and 

analysis. As new station information is made available to NCDC, the GSN database will be 

updated and information will be posted on their web site at http://lwf.ncdc.noaa.gov/servlets/gsn.

The Global Observing System Information Center (GOSIC) web site located at 

http://oceanic.cms.udel.edu/gos/ is a data and information management facility established by the 

Joint Data and Information Management Panel (JDIMP) of the GCOS program. The JDIMP no 

longer exists, but a GOSIC advisory group has taken its place to guide the requirements for the 

GOSIC. This site provides additional information on the observing requirements, operational 

data systems, and the access procedures for finding and obtaining data and products of the G3OS. 

The G3OS consists of GCOS, GOOS, and the GTOS. The University of Delaware, with funding 

and support from NOAA, currently operates GOSIC. The GOSIC is going through a new 3-year 

developmental effort that will be followed by a 2-year transition period to an operational agency.

Through the EOS Data and Information Systems (EOSDIS), Earth science data products are 

provided routinely to end-users within five days of receipt or production of the requested data 

product. These products comprise data from currently operating space assets, including: 

precipitation measurements and observations of tropical storms from TRMM, ocean productivity 

measurements from the SeaWiFS, detection of ocean surface height changes used to predict El 

Niño occurrence and strength from TOPEX/Poseidon, and sea-ice motion and Antarctic mapping 

from Canada’s RADARSAT. The data also include measurements of stratospheric trace 

chemicals from the UARS, Antarctic ozone hole measurements from the TOMS, land use and 

land cover data from heritage Landsat missions, and measurements of incoming solar radiation 

and outgoing radiation from the Earth by the ERBE. Similar arrangements are in place to meet 

the anticipated demand for data products from EOS-Terra, EOS-Aqua, and other satellite 

missions.
U.S. National Report on Systematic Observations, August 2001

127

A wide net has been cast to include information on observations falling into each of the 

observing categories of this report. The U.S. Government and the U.S. climate research 

community support the 10 Climate Monitoring Principles of observations. High standards must 

be met if a particular set of observations is to truly serve the purpose of monitoring the climate 

system to detect long-term change. In general, the observing programs and resulting datasets 

described herein do not meet the ten “Climate Monitoring Principles” endorsed by the U.S. and, 

indeed, by the UNFCCC. This shortfall stems from two main factors: 1) the principles were 

articulated only within the past decade (Karl et al. 1995), long after the initiation of most of our 

long-term observing systems; and 2) more recent observing programs, in general, do not have 

climate monitoring as their prime function.

The U.S. is beginning to develop climate-monitoring systems that more fully incorporate the 

climate monitoring principles. For example, a climate reference network for surface 

meteorological data is currently being implemented. Beyond these incipient observations, only 

our trace gas monitoring efforts have yielded long-term homogeneous observations of the climate 

system. Here we use the term homogeneous to refer to a data set with sufficient continuity and 

quality that it can be used, without adjustments, for detection of long-term change.

This does not mean that other climate observations are not potentially useful for such detection 

studies. Several examples exist of data products based on originally inhomogeneous records that, 

by careful scrutiny, winnowing of bad data, and, in some cases, adjustment of parts of the record 

to remove artificial signals, have been made into more useful climate records. The global surface 

temperature datasets are a prime example. Thus, we can draw a distinction between originally 

homogeneous observations, which can be used without adjustment, and ‘homogenized’ data 

products, which are the result of research activities to improve otherwise inhomogeneous data. In 

both cases, however, it cannot be assumed that a set of observations is sufficiently homogeneous 

for analysis of long-term change without actually attempting such analysis. The scientific 

publication and peer review process provides a means for identifying homogeneous or 

homogenized datasets. Therefore, the supplementary tables in the report list homogenous and 

homogenized datasets, with relevant references to the scientific literature in which their 

homogeneity has been documented.

The U.S. hopes that the documentation of our current climate-related observations in this report 

will provide a basis for improved global climate observing systems that directly address the 

climate monitoring principles, which are key to detection of long-term climate change.

The 10 Climate Monitoring Principles are as follows:

• The impact of new systems or changes to existing systems should be assessed prior to 

implementation.

• A suitable period of overlap of new and old observing systems should be required.

• The results of calibration, validation and data homogeneity assessments and assessments 

of algorithm changes should be treated with the same care as data.

• A capability to routinely assess the quality and homogeneity of data on extreme events, 

including high-resolution data and related descriptive information should be ensured.
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128

• Consideration of environmental climate-monitoring products and assessments, such as 

Intergovernmental Panel on Climate Change (IPCC) assessments, should be integrated 

into national, regional and global observing priorities.

• Uninterrupted station operations and observing systems should be maintained.

• A high priority should be given to additional observations in data-poor regions and 

regions sensitive to change.

• Long-term requirements should be specified to network designers, operators and 

instrument engineers at the outset of new system design and implementation.

• The carefully planned conversion of research observing systems to long-term operations 

should be promoted.

• Data management systems that facilitate access, use and interpretation should be included 

as essential elements of climate monitoring systems.
U.S. National Report on Systematic Observations, August 2001

129

REFERENCES

Carroll, T.R. (1985). Snow Surveying. McGraw-Hill 1985 Yearbook of Science and Technology.

Carroll, T.R., Cline, D.W., & Li, L. (2000). Applications of Remotely Sensed Data at the 

National Operational Hydrologic Remote Sensing Center. Presented at the International 

Association of Hydrological Sciences, Remote Sensing and Hydrology 2000. Santa Fe, 

New Mexico. April 2-7, 2000.

Christy, J.R., Spencer, R.W., & Braswell, W.D. (2000). MSU Tropospheric Temperatures: 

Dataset Construction and Radiosonde Comparison, Submitted to the Journal of 

Atmospheric and Oceanographic Technology.

Gruber, A., Personal Communication, 2000.

Karl, T.R., Derr, V.E., Easterling, D.R., Folland, C.K., Hofmann, D.J., Levitus, S., Nicholls, N., 

Parker, D.E., & Withee, G.W. (1995). Critical Issues for Long-Term Climate Monitoring. 

Climatic Change 31.

Ohring, G., & Gruber, A. Climate Monitoring from Operational Satellites: Accomplishments, 

Problems, and Prospects. Advances in Space Research. In Press, 2001.

National Research Council. (1999). Adequacy of Climate Observing Systems, Washington, D.C., 

National Academy Press.

Robinson, D.A., (2000). Weekly Northern Hemisphere Snow Maps: 1966-1999, Proceedings of 

the 12th Conference on Applied Climatology, Asheville, NC, American Meteorological 

Society.

Ware et al., (1996) Bulletin of the American Meteorological Society 77.
U.S. National Report on Systematic Observations, August 2001

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ACRONYMS

AAO Adjacent Arctic Ocean

ACARS Aircraft Communications, Addressing, and Reporting System

ACORN Atmospheric Coordinated Observations and Research Network

ACRIM Active Cavity Radiometer Irradiance Monitor

AIRMoN Atmospheric Integrated Research Monitoring Network

AIRS Atmospheric Infrared Sounder

AMSU Advanced Microwave Sounding Unit

AO Arctic Oscillation

ARCS Atmospheric Radiation and Cloud Stations

ARL Air Resources Laboratory

ARM Atmospheric Radiation Measurement

ART Automated Radiotheodolite

ASAP Automated Shipboard Aerological Program

ASDAR Aircraft-to-Satellite Data Relay

ASMR Advanced Scanning Microwave Radiometer

ASOS Automated Surface Observing System

ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer

ATLAS Autonomous Temperature Line Acquisition System

ATMS Advanced Technology Microwave Sounder

ATN Advanced TIROS-N 

AWOS Automated Weather Observing System

AVHRR Advanced Very High Resolution Radiometer

BATS Bermuda Atlantic Time Series

BLM Bureau of Land Management

BR Bureau of Reclamation

BSRN Baseline Surface Radiation Network

BTM Bermuda Testbed Mooring

C-MAN Coastal-Marine Automated Network

CALM Circumpolar Active Layer Monitoring

CART Cloud and Radiation Testbed

CDC Climate Diagnostics Center
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CDIAC Carbon Dioxide Information Analysis Center 

CDR Climate Data Record

CERES Clouds and the Earth’s Radiant Energy System

CEOS Committee on Earth Observation Satellites

CES Committee on Earth Studies

CFC Chlorofluorocarbon

CGMS Coordination Group for Meteorological Satellites

CHAMP Coral Health and Monitoring Program

CLAES Cryogenic Limb Array Etalon Spectrometer

CLIVAR Climate Variability and Predictability Proramme

CMDL Climate Monitoring and Diagnostic Laboratory

CMIS Conical Microwave Imager/Sounder

CNES Centre National de’Etudes Spatiales

CO2 Carbon Dioxide

CO-OPS Center for Oceanographic Products and Services Division

COOP Cooperative Observing Network

COP Conference of the Parties

COSMIC Constellation Observing System for Meteorology, Ionosphere and Climate

CREWS Coral Reef Early Warning System

CrIS Cross-track Infrared Sounder

CRN Climate Reference Network

CZCS Coastal Zone Color Scanner

DAC Data Acquisition Center

DAAC Distributed Active Archive Center

DMS Data Management System

DMSP Defense Meteorological Satellite Program

DOC Department of Commerce

DOD Department of Defense

DODS Distributed Oceanographic Data System

DOE Department of Energy

DOI Department of the Interior

EDC EROS Data Center
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EDR Environmental Data Record

EEZ Exclusive Economic Zone

EOS Earth Observing Satellite

EOSDIS Earth Observing Satellite Data and Information Systems

EPA Environmental Protection Agency

EPIC Eastern Pacific Investigation of Climate Processes

ERBE Earth Radiation Budget Experiment

EROS Earth Resources Observations Systems

ETM Enhanced Thematic Mapper

EUMETSAT European Meteorological Satellite Organization

EWG Environmental Working Group 

FAA Federal Aviation Administration

FAO Food and Agriculture Organization

FIA Fire Inventory and Analysis

FWS Fish and Wildlife Service

G3

OS Three Global Observing Systems (GCOS, GOOS, and GTOS) 

GAW Global Atmosphere Watch

GCM General (or Global) Circulation Model

GCMD Global Change Master Directory

GCDIS Global Change Data and Information System

GCOS Global Climate Observing System

GCRMN Global Coral Reef Monitoring Network

GDP Global Drifter Program

GHCN Global Historical Climatological Network

GLOSS Global Sea Level Observing System

GMS Geostationary Meteorological Satellite (Japanese) 

GOES Geostationary Operational Environmental Satellite

GOME Global Ozone Monitoring Experiment

GOOS Global Ocean Observing System

GOSIC Global Observing System Information Center

GPCP Global Precipitation Climatology Project

GPS Global Positioning Satellite
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GPSOS GPS Occultation 

GRACE Gravity Recovery and Climate Experiment

GSN GCOS Surface Network

GTN-G Global Terrestrial Network for Glaciers

GTN-P Global Terrestrial Network for Permafrost

GTOS Global Terrestrial Observing System

GTS Global Telecommunications System

GUAN GCOS Upper Air Network

HALOE Halogen Occultation Experiment

HCDN Hydro-Climatic Data Network

HIRDLS High Resolution Dynamic Limb Sounder

HIRS High Resolution Infrared Sensor

HRDI High Resolution Doppler Imager

HOTS Hawaii Ocean Time Series

HSB Humidity Sounder for Brazil

IABP International Arctic Buoy Program

ICES Ice Cloud and Land Elevation Satellite

IGBP International Geosphere-Biosphere Program

IGBP-DIS International Geosphere-Biosphere Program Data and Information System

IGFA International Group of Funding Agencies for Global Change Research 

IGOS International Global Observing Strategy

IGOSS Integrated Global Ocean Services System 

IMET Improved Meteorological instruments

IMPROVE Interagency Monitoring of Protected Visual Environments Network

IOC International Oceanographic Commission

IORD Integrated Operational Requirements Document

IPA International Permafrost Association

IPCC Intergovernmental Panel on Climate Change

IPO Integrated Program Office

IPSLN Indo-Pacific Sea Level Network

IPW Integrated Precipitable Water

ISAMS Improved Stratospheric and Mesopheric Sounder
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ISCCP International Satellite Cloud Climatology Project 

ISIS Integrated Surface Irradiance Study

ISLP-Pac IGOSS Sea Level Project in the Pacific

JASL Joint Archive for Sea Level

JDIMP Joint Data and Information Management Panel

JGOFS Joint Global Ocean Flux Study

LCCP Land Cover Characterization Program

LCTP Land Cover Trends Project

LDCM Landsat Data Continuity Mission

LEO Low Earth Orbit

LIAG Lake Ice Analysis Group

LTAP Long Term Acquisition Plan

LTER Long Term Ecological Research

MACS Monitoring and Control System

MAP3S Multistate Atmospheric Power Production Pollution Study

MBLA Multi-Beam Laser Altimeter

METOP Mid-morning Orbital Plane Satellite

MISR Multi-angle Imaging Spectrometer

MLS Microwave Limb Sounder

MISR Multi-angle Imaging SpectroRadiometer

MITI Japan's Ministry of International Trade and Industry

MMTS Maximum-Minimum Temperature Systems

MODIS Moderate Resolution Imaging Spectroradiometer

MON Marine Observational Network

MOPITT Measurement of Pollution in the Troposphere

MRLC Multi-Resolution Land Characterization 

MSS Multi-Spectral Scanner

MSU Microwave Sounding Unit

NADP National Atmospheric Deposition Program

NAO North Atlantic Oscillation

NASA National Aeronautics and Space Administration

NAVAID Navigational Aid
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NCAR National Center for Atmospheric Research

NCDC National Climatic Data Center

NCEP National Centers for Environmental Prediction

NDBC National Data Buoy Center

NDBO NOAA Data Buoy Office

NDSC Network for the Detection of Stratospheric Change

NDVI Normalized Difference Vegetation Index

NEON National Ecological Observation Network

NEP Net Ecosystem Production

NESDIS National Environmental Satellite, Data, and Information Service

NEXRAD Next Generation Weather Radar

NGWLMS Next Generation Water Level Measurement System

NIST National Institute of Standards and Technology

NLCD National Land Cover Dataset

NMS National Meteorological Services

NOAA National Oceanic and Atmospheric Administration

NODC National Oceanographic Data Center

NOHRSC National Operational Hydrologic Remote Sensing Center 

NOMAD Naval Oceanographic and Meteorological Automated Device

NOPP National Oceanographic Partnership Program

NORLC National Ocean Research Leadership Council

NOS National Ocean Service

NPOESS National Polar-orbiting Operational Environmental Satellite System

NPP NPOESS Preparatory Project

NRC National Research Council

NRCS Natural Resources Conservation Service

NSA North Slope of Alaska

NSCAT NASA Scatterometer

NSF National Science Foundation 

NSIDC National Snow and Ice Data Center

NSIP National Streamflow Information Program

NTN National Trends Network
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NWCC National Water and Climate Center

NWLON National Water Level Observation Network

NWP Numerical Weather Processing

NWS National Weather Service

OAR Oceanic and Atmospheric Research

OFCM Office of the Federal Coordinator for Meteorology

OGP Office of Global Programs

OLS Operational Linescan System

OMPS Ozone Mapping and Profiler Suite

OOSDP Ocean Observing System Development Panel 

QME Quality Measurement Experiment

PEM Particle Environment Monitor

PI Principal Investigator

PIRATA Pilot Research Moored Array in the Tropical Atlantic

POES Polar Orbiting Environmental Satellite

RASS Radio-Acoustic Sounding System

RAWS Remote Automated Weather Stations

RCC Regional Climate Centers

RH Relative Humidity

S2O2 Sargasso Sea Ocean Observatory 

SAB Science Advisory Board

SAGE Stratospheric Aerosol and Gas Experiment

SBUV Solar Backscatter Ultraviolet

SC State Climatologist

SCAN Soil Climate Analysis Network

SDD Space Data Division

SEAS Shipboard Environmental (data) Acquisition System

SeaWiFS Sea-viewing Wide-Field-of-view Sensor

SEM Space Environment Monitor

SESS Space Environment Sensor Suite

SGP Southern Great Plains

SHEBA Surface Heat Budget of the Arctic
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SLP Sea-Level Pressure

SMM Solar Maximum Mission

SMMR Scanning Multichannel Microwave Radiometer

SNODAS Snow Data Assimilation System

SNOTEL Snowpack Telemetry System

SOC Specialized Oceanographic Centre

SOEST School of Ocean and Earth Science and Technology

SOLSTICE Solar/Stellar Irradiance Comparison Experiment

SOOP Ships of Opportunity

SORCE Solar Radiation and Climate Experiment 

SR Scanning Radiometer

SRTM Shuttle Radar Topography Mission

SSM/I Special Sensor Microwave/Imager

SST Sea Surface Temperature

SSU Stratospheric Sounding Unit

SURFRAD Surface Radiation Network

SUSIM Solar Ultraviolet Spectral Irradiance Monitor

SWIR Shortwave-Infrared

SXI Solar X-Ray Imager

TAO Tropical Atmosphere Ocean

TBB Triband Beacon Transmitters 

TES Tropospheric Emission Spectrometer

TIP Tiny Ionospheric Photometer

TIR Thermal-Infrared

TIROS Television Infrared Observations Satellite

TIROS-N Next Generation TIROS

TM Thematic Mapper

TOGA Tropical Ocean Global Atmosphere

TOMS Total Ozone Mapping Spectrometer

TOVS Tiros Operational Vehicle Sounder

TRITON Triangle Trans Ocean Buoy Network

TRMM Tropical Rainfall Measuring Mission
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TSI Total Solar Irradiance

TSLC TOGA Sea Level Center

TSG ThermoSalinoGraph

TSIS Total Solar Irradiance Sensor 

TWP Tropical Western Pacific

UARS Upper Atmosphere Research Satellite

UHSLC University of Hawaii Sea Level Center

UNEP United Nations Environment Program

UNFCCC United Nations Framework Convention on Climate Change

USCOE United States Army Corps of Engineers

USDA United States Department of Agriculture

USFS United States Forest Service

USGCRP United States Global Change Research Program

USGS United States Geological Survey

USHCN United States Historical Climatology Network 

UTC Universal Coordinated Time 

VCL Vegetation Canopy Lidar

UV Ultraviolet

VAP Value Added Procedure

VIIRS Visible Infrared Imager Radiometer Suite

VNIR Visible and Near-Infrared

VOS Voluntary Observing Ship

WCRP World Climate Research Program

WFO Weather Forecast Office

WIMS Weather Information Management System

WMO World Meteorological Organization

WOA World Ocean Atlas

WOCE World Ocean Circulation Experiment

WSR-88D Weather Surveillance Radar - Doppler

WWW World Wide Web

XBT eXpendable Bathy Thermograph