MEASUREMENTS OF PRECIPITATION COMPOSITION AT UK EMEP SITES 1987-1992 AND COMPARISON WITH THE HARM MODEL

Precipitation composition has been measured daily at five UK EMEP site s since 1987. Sulphur dioxide and sulphate aerosol concentrations are also measured daily at the sites. Back trajectories and wind sectors c alculated by the Norwegian Meteorological Institute have been used to characterise the variation in wet deposition in terms of air mass sour ce. Contributions to wet deposition from various source regions have b een estimated for Eskdalemuir. Observations from the EMEP sites have b een compared with output from the Hull Acid Rain Model (HARM). HARM is a Lagrangian model using simplified meteorology but straight-line tra jectories. Results are compared on a site-by-site and sector-by-sector basis and the model reproduces the general features of pollutant conc entration and wet deposition indicated by the measurements. The possib le effects of future reductions in emissions of SO2 and NOx on precipi tation concentrations by wind sector are described.