An aqueous chemistry module was created and included into a complex 3D cloud-resolving mesoscale advanced regional prediction system (ARPS) model to examine the characteristics of in-cloud sulfate. The complex orography of Serbia was included in the model. The chemical species included in the module were sulfur dioxide, sulfate ion, ammonium ion, hydrogen peroxide and ozone. Six water categories are considered: water vapor, cloud water, rain, cloud ice, snow and hail. Each chemical species in

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... ch microphysical category was represented by a differential equation of mass continuity. This paper gives a detailed description of the chemistry module and demonstrates the utility of an atmospheric model coupled with the chemistry module in forecasting the redistribution of chemical species in all water categories. The main mean microphysical and chemical conversion rates of sulfate averaged over a 2 h simulation period for a base run were for the oxidation of S(IV) in rain water and cloud water, SO 4 2scavenging by Brownian diffusion in cloud droplets and cloud ice as well as the impact scavenging of SO 4 2by rain. The calculated values of sulfates in all water categories and the shape of the sulfate profiles depend on radar reflectivity.