The potential for elucidating sulfate and acidity production in clouds using a mesoscale model with quasi-spectral micro physics

A three-dimensional mesoscale numerical model with detailed parameterized microphysics of clouds and precipitation has been applied to the study of gas and aerosol wet removal. Two-dimensional sensitivity tests combining meteorological predictions with pollutant scavenging and aqueous chemistry parameterizations have been carried out for continental and maritime clouds over an idealized topography. Model results indicate that nucleation scavenging is the most efficient in-cloud removal mechanism. Furthermore, differences in cloud droplet spectra in continental versus maritime cases, lead to different contributions of nucleation scavenging, in-solution oxidation of SO₂ by ozone and hydrogen peroxide, to wet sulfate deposition and acidity production. This results emphasizes the need for coupled treatment of dynamical, microphysical and chemical processes.