Study of scavenging of submicron-sized aerosol particles by thunderstorm rain events

Observed scavenging coefficients for 0.013-0.75 mu m particles are between 1.08 x 10(-5) and 7.58 x 10(-4) s(-1). Based on observed results a correlation between scavenging coefficient and rain intensity is obtained to study below thundercloud scavenging of atmospheric aerosols during thunderstorm rain events. When the rain intensity increases from 5.24 to 45.54 min h(-1), the corresponding scavenging coefficient increases from 0.5 x 10-5 to 4 x 10(-5) s(-1) for thunderstorm rain episodes. The overall scavenging coefficients for 0.02 - 10 mu m particles at different rainfall rates are estimated from contributions of Brownian diffusion, directional interception, inertial impaction, thermophoresis, diffusiophoresis and electrical forces during thunderstorms. The evolutions of PSD are predicted at different time intervals with theoretical scavenging rates. Comparison of observed evolutions of PSD during thunderstorm rain events with predicted evolutions of PSD shows an order of discrepancy between the observed and model results. Possible causes for discrepancy are discussed in terms of uncertainties in observed data and shortcomings in theoretical approach. The present results are useful for recommendations for the type of experimental setup essential for the field study of precipitation scavenging and improvements in theoretical approach close to atmospheric conditions during thunderstorm rain events. (c) 2005 Elsevier Ltd. All rights reserved.