Regional air pollution model for calculating short‐term (daily) patterns and transfrontier exchanges of airborne sulfur in Europe

An air pollution model, EURMAP‐2, has been developed to simulate and assess the effects of daily variation in sulfur emissions on short‐term (daily) air quality in central and western Europe. The model has been used to calculate daily concentrations, daily depositions, and daily transfrontier exchanges of SO2 and SO4= during the episodes of August 25–26 and September 14–16, 1974. A comparison between model‐calculated and measured concentrations of SO2 and SO4 shows a reasonably good agreement over large portions of the model grid, although calculated concentrations are lower than measured values in the eastern portion. Calculated patterns for dry SO2 deposition show strong correlation with emissions; patterns for wet deposition correspond closely to natural inhomogeneities in precipitation. Discrepancies between model results and measurements are attributed to nonrepresentativeness of emissions data in the eastern portion of the model domain and the inability of the model to realistically incorporate the effects of complex terrain, vertical diffusion, transformation, and deposition rates. A comparison between the results of EURMAP‐2 and the NILU (trajectory) model developed by the Norwegian Institute for Air Research shows some significant differences, perhaps a result of the different treatments of some physical elements in the two models.