GAW Research Infrastructure
Surface-based observations (in situ and ground-based remote sensing) of atmospheric composition variables are a key component of the GAW strategy. The network comprises different levels of stations namely global, regional, local, and mobile operated by WMO Members, research institutions and/or agencies. Stations can be operated within other national or international networks which upon signing an agreement with the GAW Programme become contributing networks. Contributing networks augment the information obtained from the GAW network by covering additional regions, vertical regimes, or parameters, or through employing different measurement techniques. They thus provide added scientific expertise and support research and service activities of GAW and the broader scientific community. The GAW coordinated observational network contributes to the WMO Integrated Global Observing System (WIGOS).
To obtain a complete picture of the atmospheric chemical composition, it is necessary to complement fixed-placed surface-based observations by mobile (e.g. airborne and ship) observations. A number of national and international aircraft observation/research networks and initiatives (e.g. operated by the National Oceanic and Atmospheric Administration (NOAA) for the North America Carbon Programme, by the Japan Meteorological Agency (JMA) on Japan Airlines (JAL) which conducts routine monthly aircraft observations of tropospheric greenhouse gases in the western North Pacific, regular observations within the IAGOS Research Infrastructure and aircraft observations by Brazil) also contribute to the GAW observational network. These observations are augmented by observations from various short-term research campaigns. The observing system of ground-based observations would be incomplete without contribution of satellite observations that provide global coverage for many atmospheric composition parameters. So far the role of satellite observations in GAW has been quite limited. In view of many applications, the role of satellite observations will increase within the period of implementation of this plan. Satellite data on atmospheric composition are actively assimilated to improve weather forecasts, used in the air quality forecasting system as well as often used in inverse modelling to improve emission estimates.
The utility of atmospheric composition observations for use in specific analysis and applications depends on many factors. The GAW designation of a station as a global, regional, local or mobile station is an indication of the station location and also conveys information on the overall activities of the site (e.g. the number of parameters measured, history of data submission, and extent of analysis of the data). However, it is possible that a station can measure background conditions with respect to one variable while it encounters significant pollution with respect to other variables (e.g. strong influence from local ozone precursors but no CFCs or vice versa). Additional information regarding the station location with respect to local and regional pollution sources and the environment in which it is located is needed to improve the wider-spread use of GAW data. Increased efforts are needed to enhance the description of the used metadata. The standardization of such descriptions will be developed in collaboration with WIGOS.
The enhanced use of atmospheric composition information for research and applications also requires increased efforts to evolve the global atmospheric composition observing system in support of specific applications. This will be accomplished through the implementation of WIGOS and the Rolling Review of Requirements (RRR) process, where measurements should meet user requirements for quality, spatial and temporal resolution, which vary depending on the objective. The role of the RRR process is to guide Members to develop the observing system that will address their needs. The requirements formulated at the beginning of the process are technology free and help to design a system that meets requirement in a cost effective way.