Modeling SO2 oxidation in clouds and its effect on aerosol size distributions using a two-dimensional microphysical representation

Evolution of aerosol particles (APs) and cloud droplets is simulated using a joint two-dimensional size distribution, in which the wet particle size/volume and the dry particle size/volume are two independent variables. Unlike other bin models, this formulation preserves the dry distribution of APs exactly during the water condensation-evaporation cycle and provides a framework for predicting changes in the AP distribution due to drop coalescence and aqueous chemistry. These benefits come with a burden of carrying ~1100 bins of the two-dimensional particle distribution. The new microphysics module is introduced in both a parcel (box) model and a fully interactive multidimensional framework. The simulations are performed for the low-level stratiform clouds assuming a uniform chemical AP composition (i. e., every AP is ammonium bi-sulfate). Advantages and limitations of the approach are discussed as are various aspects of numerical implementation and accuracy of the algorithm.