The World Meteorological Organization Global Assessment of Precipitation Chemistry and Deposition

Robert Vet*, R. Artz, S. Carou, V. Bowersox, C.-U. Ro, M. Shaw, W. Aas, A. Baker, F. Dentener, C. Galy-Lacaux, R. Gillett, S. Gromov, H. Hara, T. Khodzhur, K. Pienaar, Nickovic, K. Pienaar and P.S.P. Rao

A Global Assessment of Precipitation Chemistry and Deposition is being written for the World Meteorological Organization by scientists from South Africa, Norway, Russia, Australia, Japan, India, Italy, Switzerland, France, England, the USA and Canada. The Assessment covers the period 2000 to 2007 and describes the global composition of precipitation and patterns of wet deposition of SO42-, NO3-, Cl-, H+, pH, NH4+, Ca2+, Mg2+, Na+, K+, P and organic acids. The global discussion is supplemented by detailed regional discussions of Africa, South America, North America, Europe, Asia and Australia, focusing on the characterization of acid-base chemistry, temporal trends and, in some regions, dry deposition fluxes.

Given the paucity of measurements in many areas of the world, the global and regional wet deposition patterns were developed from measurement data combined with model predictions. The data were collected from the major deposition monitoring networks of the world (including NADP) and the model predictions were obtained from the Coordinated Model Studies Activity of the Task Force on Hemispheric Transport of Air Pollution (TF HTAP) under the framework of the United Nations Economic Commission for Europe (UN ECE) Convention on Long-Range Transboundary Air Pollution (CLRTAP). The measurement-model results were combined into maps of sulfur and nitrogen wet deposition and, where possible, dry deposition.

The production of the global and regional deposition maps and the assessment of precipitation deposition science required considerable effort to gather, quality control and interpret the measurement data. In this context, the NTN and AIRMON networks of the National Atmospheric Deposition Program and the Clean Air Status and Trends Network in the United States and the Canadian Air and Precipitation Monitoring Network were vital. Their roles and contributions are discussed in this global context.

*Head, Quality Assurance and Data Management Unit, Air Quality Research Division,Environment Canada, 4905 Dufferin Street, Toronto, Ontario, Canada M3H 5T4,e-mail: Telephone: 416-739-4853