Effect of raindrop size distribution on scavenging of aerosol particles from Gaussian air pollution plumes and puffs in turbulent atmosphere

We obtained exact analytical solution of advection–diffusion equation assuming turbulence parameterization for Gaussian pollution dispersion and taking into account scavenging of aerosol particles by rain. The effect of raindrops size distribution was taken into account by using Monte Carlo simulations whereby we assumed the log-normal size distribution of raindrops with Feingold and Levin parameterization. The developed approach allows analyzing spatial and temporal evolution of aerosol concentration in the gaseous phase as well as in the raindrops. We derived explicit analytical expression which allows analyzing the dependence of the rate of the below-cloud aerosols scavenging from Gaussian air pollution plumes on different parameters, e.g. rain intensity, pollutant emission rate, droplet size distribution. It is found that maximum ground level concentration of aerosols depends on rainfall intensity, and the location of the maximum approaches the emission source when rainfall intensity increases. Comparison of predictions of theoretical model with experimental data available in the literature showed fairly good agreement between theoretical results and experiments. The obtained results can be useful in the analysis of different meteorology–chemistry models including scavenging of aerosols in air pollution plumes by rain and for the assessment of human exposure to various chemical, biological and radiological contaminants.