MATHEMATICAL-MODELING OF CLOUD CHEMISTRY IN THE LOS-ANGELES BASIN

A mathematical model of cloud chemistry was evaluated with the cloud chemistry data collected by Richards et al. (1983, Atmospheric Environment 17, 911-914) from 1981 to 1985 in stratus clouds in the Los Angeles Basin. The model simulates atmospheric chemistry including gas-phase chemistry, aqueous-phase chemistry and droplet mass transfer, vertical transport, rainfall and turbulent diffusion. Evaluation of the model entailed two major part. First, the equilibrium chemistry is evaluated with a total of 52 case studies. Then, the model with treatment of cloud chemistry, vertical transport and diffusion is evaluated with two case studies. The results of the model simulations show the importance of vertical transport in determining the chemical composition of stratiform clouds. The sensitivity of sulfate, nitrate, ammonium and hydrogen ion concentrations to precursor levels, various chemical kinetic and cloud microphysical parameters and various environmental conditions is discussed. © 1990.