SO 2, sulfate and HNO 3 deposition velocities computed using regional landuse and meteorological data

Abstract

Deposition velocity fields were generated for SO 2, sulfate and HNO 3 over eastern United States and southeastern Canada by combining detailed landuse data with meteorological information predicted using a mesoscale meteorology model. When there is significant variation in land type within an averaging area, it was found that subgrid scale meteorological variations can significantly influence area-averaged deposition velocities. The assumption that uu is constant over the averaging area can realistically address the subgrid variations in wind speed and friction velocity. For a 3-day springtime simulation, domain-averaged mid-day SO 2, sulfate and HNO 3 deposition velocities at a height of approximately 40 m were found to be 0.8 cm s −1, 0.2 cm s −1, and 2.5 cm s −1, respectively. At night, the deposition velocities were approximately 50%, 45% and 70% of the corresponding daytime values for SO 2, sulfate and HNO 3. Using a simple parameterization to account for rainfall-wetted surfaces increased domain-averaged SO 2 deposition velocities by up to a factor of two, indicating that precipitation can significantly enhance dry deposition of SO 2.