Minimum Collection Efficiency Diameter during Snow Scavenging Process

Abstract

The scavenging of atmospheric aerosols by below-cloud scavenging processes during rain or snow precipitation plays an important role in the removal of aerosols in the atmosphere. Because of a variety of frozen precipitation types and their physical properties, the snow scavenging is a more complicated process compared with the rain scavenging. This study determined the minimum collection efficiency and minimum collection efficiency diameter for polydispersed hydrometeor size distributions during the snow precipitation. Three types of collectors (graupel, dendrite, and column) were considered and the obtained minimum collection efficiency and the corresponding minimum collection efficiency diameter were intercompared. Results showed that the minimum collection efficiency diameters for snow were smaller than those for rain. The minimum collection efficiency diameters of graupel decreased as the collector diameter increased, whereas other collectors (i.e., dendrite and column) did not show this decreasing tendency. The minimum collection efficiencies of graupels were larger than those of dendrite and column collectors. It was also shown that column collectors had the largest scavenging coefficients.