This chapter summarizes the surface-based WMO-GAW reactive gas measurement network; describes the currently adopted GAW techniques for nitrogen oxides (NOx), volatile organic compounds (VOCs), and surface ozone (O3); and presents brief summaries of recent GAW observations of these gases. Within GAW, there are currently nine sites performing continuous in situ measurements of nitrogen oxides using the recommended method of ozone chemiluminescence detection and NO2 photolytic conversion to NO. These sites, which are mostly in Europe except one station in Cape Verde, span a range of environmental conditions from the pristine marine background and free troposphere, to continental background, to continental air. Similarly, online continuous VOC measurements by gas chromatography (GC) are reported from 16 stations in 13 countries, mostly in Europe, with additional online PTR-MS measurements performed in Finland. Additional to these online measurements, flask measurements of VOCs are available within a globally distributed network of 29 stations in 22 countries for light alkanes (glass flasks) and for ~50 VOCs from 15 stations in 5 countries, mostly in Europe (steel flasks). The GAW ozone observation network is extensive and has continued to be an important resource for studies of tropospheric ozone’s global distribution, trends, and impact. An analysis within the framework of the Tropospheric Ozone Assessment Report (TOAR) of several mountaintop sites in remote areas of the Northern Hemisphere (most affiliated with GAW), updated for this chapter, shows that lower tropospheric ozone has generally increased since the 1970s and 1980s. The Global Burden of Disease (GBD) project, which provides regular estimates of global-scale premature death and disability including from poor air quality, fuses global ozone observations from the TOAR Database with output from several global models to calculate ozone exposure maps, an endeavor made possible by GAW observations.
|Title of host publication
|Handbook of Air Quality and Climate Change
|H Akimoto, H Tanimoto
|Place of Publication
|Published - 26 May 2022