Regional modeling of atmospheric mercury: impact of meteorological variables

The atmospheric mercury concentration in Europe was simulated with the regional atmospheric chemistry transport model CMAQ-Hg. Two sets of meteorological fields, one from MM5 and one from COSMO-CLM (CCLM) were used to drive the model. The results differ significantly, in particular gaseous elemental mercury (Hg0) concentrations are much lower in the run with meteorological fields from MM5 compared to the run with CCLM meteorology. Looking at the mercury sinks within the model domain, it was found that dry deposition of Hg0 is the main sink in both model runs. Remarkably, dry deposition velocities are much higher when calculated with MM5 meteorological fields. Wet deposition of oxidized mercury is a factor of 5-6 lower than dry deposition of Hg0. In CMAQ with MM5 meteorology wet deposition is about afactor of two higher compared to the run with CCLM.