Dry deposition flux calculations for the national dry deposition network. Report for January 1991-September 1992

The National Dry Deposition Network (NDDN) was established in 1987 to document the magnitude, spatial variability, and trends in dry deposition of ozone and acidic particles and gases across the United States. Currently, the network consists of 50 stations: 41 in the eastern United States and 9 in the western United States. The NDDN will be assimilated into the Clean Air Status and Trends Network (CASTNet). Dry deposition is not measured directly in the NDDN, but is determined by an inferential approach, i.e., dry deposition fluxes are calculated as the product of measured ambient concentration and modeled deposition velocity. Chemical species include O3, sulfate, nitrate, sulfur dioxide, and nitric acid. The temporal resolution for the dry deposition calculations is hourly for O3 and weekly for the acidic particles and gases. The report describes the dry deposition calculation method used in the NDDN/CASTNet program and presents dry deposition data for the network for 1990 and 1991. Sources of uncertainty in the calculations are discussed.