Cloud droplets may collide and capture aerosol particles because of their different responses to gravitational, inertial, phoretic, or electrical forces. Dr. Tinsley has shown theoretically that electroscavenging, which refers to the electrostatically-induced capture of charged aerosol particles by charged cloud droplets, can be important even in weakly electrified clouds. On this grant he will extend his calculations of collection efficiency to aerosol particles with radii ranging from 0.001 to 10 micrometers over a wide range of combinations of temperature, pressure, humidity, particle charge, particle density, and drop size. Electrical, inertial, and phoretic effects will be treated separately and in combination. An exact formulation of the electrical forces between conducting charged spheres will be compared with the image charge theory used earlier. The results will be used for estimating the rate of scavenging of aerosol particles by clouds, an important consideration for atmospheric chemistry and possibly for the formation of precipitation through the collision of droplets with ice-forming nuclei. An effort will be made to parameterize the results for use in numerical cloud models.
