Study of interaction between cloud microphysics and chemistry using coupled bin microphysics and bin aqueous chemistry scheme

Abstract

A bin chemistry scheme was developed to study sulfate production and the effect of aqueous chemistry on cloud microphysics in precipitating stratocumulus cloud using a 2D kinematical model. The impact of air pollution on aerosol processing was investigated by a comprehensive sensitivity study. The numerical simulations were carried out at different concentrations of condensation nuclei and trace gases of SO2, H2O2, O3 and NH3. The results show: (i) Significant amount of sulfate formed due to cloud chemistry even in less polluted atmosphere. The amount of sulfate formed due to the oxidation of S(IV) was affected less by the initial condensation nuclei (hereinafter: CN) concentration and more by the initial mixing ratio of gases in the atmosphere. The amount of sulfate staying in the atmosphere was affected by the initial CN concentration, because it impacted the efficiency of washout. (ii) The aqueous sulfate production impacts the characteristics of aerosol size distribution by increasing mean size and by increasing the concentration of the micron size aerosol particles. The change of aerosol size distribution due to sulfate production has no effect on the amount of surface precipitation if the CN concentration is low (100 cm−3), and significantly reduces accumulated surface precipitation if CN concentration is large (540 cm−3). (iii) Compared to the bin chemistry scheme the bulk chemistry scheme underestimates the sulfate production and overestimates the role of O3 in the sulfate production.