Contributing Networks

Networks contributing to the GAW Programme

A contributing network is one that has signed a letter of agreement (LoA) with WMO. Any such agreement should contain a list and the characteristics of the stations that will be included in the GAW network as Contributing stations. List of stations that are contributing to the GAW Programme is given after the short network descriptions.

GAW Contributing networks:


The Total Carbon Column Observing Network (TCCON; and is a ground-based network of high resolution Fourier transform spectrometers (FTSs) that records the near infrared solar absorption spectrum and retrieves column-average mixing ratios of CO2, CH4, N2O and several other gases with high precision and accuracy.  TCCON data are a valuable complement to in-situ surface data and can be included in global inversions and other models of greenhouse gases, including studies of the carbon and nitrogen cycles.  Furthermore, the column measurements serve to validate satellite measurements from the current satellites GOSAT and SCIAMACHY and future satellite missions such as OCO-2. 

List of stations


The European Aerosol Research Lidar Network (EARLINET; is European coordinated lidar network, established in 2000, measuring aerosol backscatter coefficient and aerosol extinction profiles for climatological studies of the aerosol distribution over Europe.

List of stations


The Interagency Monitoring of Protected Visual Environments (IMPROVE) program is a cooperative measurement effort governed by a steering committee composed of representatives from Federal and regional-state organizations ( IMPROVE-Optical monitoring network uses open air nephelometers to measure hourly particulate scattering in primarily rural environments.  In addition, hourly temperature and relative humidity are measured at each site.  These data are used in conjunction with IMPROVE aerosol data to assess the status and trends in light scattering and better understand the optical properties of aerosols.

List of stations


The Asian Dust and Aerosol Lidar Observation Network (AD-Net: is an Asian coordinated lidar network, established in 2001, measuring aerosol backscattering and the depolarization for Asian dust and performing regional air pollution studies over East Asia.

List of stations


The Latin America Lidar Network (LALINET a.k.a ALINE, is a Latin American coordinated lidar network, established in 2001, measuring aerosol backscatter coefficient and aerosol extinction profiles for climatological studies of the aerosol distribution over Latin America, as well as other atmospheric species such as ozone and water vapor. This federative lidar network aims to establish a consistent and statistically sound database for enhancement of the understanding of the aerosol distribution over the continent and its direct and indirect influence on climate.

List of stations


The U.S.-based National Atmospheric Deposition Program (NADP) is a long-term, measurement cooperative composed of representatives from federal, state, tribal, and national agencies, universities, private companies, and non-governmental organizations. Most NADP stations are located in the United States but several are located in Canada and in other nations. NADP operates three precipitation chemistry networks: the National Trends Network (NTN), the Atmospheric Integrated Research Monitoring Network (AIRMoN); and the Mercury Deposition Network (MDN), and two gaseous atmospheric chemistry networks: the Atmospheric Mercury Network (AMNet) and the Ammonia Monitoring Network (AMoN). A central office coordinates Program activities and oversees field and lab operations, data management, and quality assurance for each network.  Each monitoring network follows well-defined protocols to measure acidic compounds, nutrients, base cations, and mercury in precipitation (NTN, AIRMoN, and MDN), and ambient concentrations of ammonia and mercury for estimates of dry deposition (AMoN and AMNet).  Program data are used to assess the geographic patterns and long-term temporal trends in the concentration and deposition of major ions and mercury in precipitation, and to better understand the cycling of these chemicals in a variety of physical environments for a multitude of applications.


The international program Deposition of Biogeochemically Important Trace Species (DEBITS) started in 1990 as part of the IGAC/IGBP (International Global Atmospheric Chemistry/ International Geosphere-Biosphere Programme) core project. The aim of the project is to assess the wet- and dry- atmospheric deposition in tropical regions.

For tropical Africa, the IDAF (IGAC/DEBITS AFRICA) project started in 1994 and implemented in partnership with INSU (Institut National des Sciences de l’Univers, France) and the CNRS (Centre National de la Recherche Scientifique, France) as a part of the Observatory Service (SO, France) networks. The SO/IDAF has the mission of establishing long-term measuring network to study the atmospheric composition and wet- and dry- atmospheric processes. As such, IDAF activity is based on high quality measurements of atmospheric chemical data (gaseous concentrations and precipitation chemical composition) on the basis of a multi-year monitoring. This project implemented ten monitoring sites distributed in the major African ecosystems over West and Central Africa and South Africa: dry savanna (Niger, Mali, South Africa), wet savanna (Côte d’Ivoire and Benin) and equatorial forest (Cameroon, Congo).  Sites in West and Central Africa are coordinated by the laboratoire d’Aérologie in Toulouse (France) and sustained by a French national proposal funded by the INSU/CNRS. South African sites are coordinated by the North West University in Potchefstroom (South Africa) sustained by national and/or private south African projects.

List of the IDAF stations contributing to GAW.


The NASA Micro-Pulse Lidar Network (MPLNET)

The NASA Micro-Pulse Lidar Network (MPLNET) is a federated network of Micro-Pulse Lidar (MPL) systems designed to measure aerosol and cloud vertical structure continuously, day and night, over long time periods required to contribute to climate change studies, related aerosol and cloud research, and to provide ground validation for satellite sensors in the Earth Observing System (EOS).  Most MPLNET sites are co-located with sites in the NASA Aerosol Robotic Network (AERONET).  These joint super sites provide both column and vertically resolved aerosol and cloud data, such as: optical depth, single scatter albedo, size distribution, aerosol and cloud heights, planetary boundary layer (PBL) structure and evolution, and profiles of extinction and backscatter.  MPLNET is a federated network, and is composed of NASA sites, and others run by, or with help from, partner research groups from around the world.  Principal investigators for individual sites may be from NASA, other US government agencies, universities, or foreign research groups.

List of the MPLNET stations contributing to GAW


The Clean Air Status and Trends Network (CASTNET)

The Clean Air Status and Trends Network (CASTNET) is a well-established national air quality monitoring network in the United States of America designed to provide data to assess trends in air quality, atmospheric deposition, and ecological effects due to changes in air pollutant emissions. CASTNET began collecting measurements in 1991 with the incorporation of 50 sites from the National Dry Deposition Network, which had been in operation since 1987. The National Park Service (NPS) operates more than 20 CASTNET sites within national parks and Class 1 areas. The Bureau of Land Management, Wyoming State Office joined CASTNET in 2012 when they converted five Wyoming Air Resource Monitoring System (WARMS) sites to CASTNET protocol sites. CASTNET provides long-term monitoring of air quality in rural areas to determine trends in regional atmospheric nitrogen, sulfur, and ozone concentrations and deposition fluxes of sulfur and nitrogen pollutants in order to evaluate the effectiveness of national and regional air pollution control programs. CASTNET operates more than 85 regional sites throughout the contiguous United States, Alaska, and Canada. Sites are located in areas where urban influences are minimal. These stations therefore ideally complement the measurements of Regional and Global GAW stations in North America.

List of the CASTNET stations contributing to GAW.

In-service Aircraft for Global Observing System (IAGOS)

The European Research Infrastructure IAGOS (In-service Aircraft for a Global Observing System, operates a global-scale monitoring system for atmospheric trace gases, aerosols and clouds utilising the existing global civil aircraft. This new monitoring infrastructure builds on the heritage of the former research projects MOZAIC (Measurement of Ozone and Water Vapour on Airbus In-service Aircraft) and CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container). CARIBIC continues within IAGOS and acts as an important airborne measurement reference standard within the wider IAGOS fleet. IAGOS is a major contributor to the in-situ component of the Copernicus Atmosphere Monitoring Service (CAMS), and is providing data for users in science, weather services and international policy making related to atmospheric composition. IAGOS is unique in collecting regular in-situ observations of reactive gases and greenhouse gases concentrations and aerosol properties in the upper troposphere and lowermost stratosphere (UTLS) at high spatial resolution. It also provides routine vertical profiles of these species in the troposphere over continental sites or regions, many of which are under sampled by other networks, particularly in Africa, Southeast Asia and South America. These “stations” therefore ideally complement the measurements of Regional and Global GAW stations. Besides, in combination with MOZAIC and CARIBIC, IAGOS has provided long-term observations of atmospheric chemical composition in the UTLS since 1994.

List of the IAGOS airport

Integrated Carbon Observation System Research Infrastructure (ICOS RI)

Integrated Carbon Observation System Research Infrastructure (ICOS RI) integrates atmosphere, ecosystem and ocean greenhouse gas observations to provide timely and reliable data for research, policy making, and the general public. ICOS RI brings together high quality European national research communities and measurement stations and, through coordination and support, constitutes a European-wide research infrastructure that serves both scientists and society. ICOS RI consists of a number of researchers and measurement stations, governance bodies and a carbon data portal, collaborating across Europe.

Since mid-2018, the European atmosphere station network of the ICOS RI is a GAW-contributing network. Many ICOS atmosphere stations have already been in operation a long time, but ICOS has now also been extended into new regions and with new sites. ICOS has developed community-defined standardized measurement designs and protocols that for atmospheric GHG observations build and extend upon the WMO recommendations with regards to compatibility, calibration to WMO mole fraction scales and transparency of the data lifecycle. All ICOS stations have to meet the agreed standards. All data are processed by the ICOS Atmosphere Thematic Centre and checked and annotated on a daily basis by the responsible station managers. The Central Analytical Laboratories perform analyses of flask samples, e.g. for 14CO2 radiocarbon detection of fossil fuel emissions, and provide all stations with WMO scale calibrated working standards. All fully quality-controlled ICOS atmosphere data are published as open data through the ICOS Carbon Portal and are updated currently about twice per year. Near-real-time data, utilizing automatic quality control, are published with a maximum delay of one day from the time of the last final full quality-controlled release onwards. The atmospheric data will also be accessible through WDCGG, are part of the regular updates of the NOAA Obspack data products, and are delivered on a daily basis to the COPERNICUS services.

List of ICOS stations

Acid Deposition Monitoring Network in East Asia (EANET)

The Acid Deposition Monitoring Network in East Asia (EANET) started in 1998 as an intergovernmental initiative to create a common understanding of the state of acid deposition problem in East Asia, to provide useful inputs for decision making at various levels with the aim of preventing or reducing the adverse impacts on the environment, and to promote cooperation among countries. Thirteen countries in East Asia are participating in EANET at present. Information from the participating countries is provided in factsheets which can be downloaded here. United Nations Environment Programme (UNEP) for Asia and the Pacific located in Thailand is the Secretariat and the Asia Center for Air Pollution Research (ACAP) located in Japan is the Network Center for the EANET. 

Acid deposition monitoring covers four environmental media - wet deposition, dry deposition, soil and vegetation, and inland aquatic environment. Monitoring for wet and dry deposition are implemented in order to measure concentrations and fluxes of acidic substances deposited to the ground, while monitoring for soil and vegetation, and inland aquatic environment are being implemented to assess adverse impacts on terrestrial and aquatic ecosystems.

EANET runs the network according to the principles shown in the Guidelines for Acid Deposition Monitoring in East Asia, Technical Manual for Air Concentration Monitoring in East Asia, Technical Manual for Wet Deposition Monitoring in East Asia -2010, Technical Manual on Dry Deposition Flux Estimation in East Asia, Quality assurance/Quality control (QA/QC) Guidebook for Acid Deposition Monitoring Network in East Asia- 2016  and related EANET policies and publications.

List of EANET stations