In-Cloud Scavenging by Thermophoresis, Diffusiophoresis, and Brownian Diffusion

Abstract

The role of phoretic forces in providing an in-cloud scavenging mechanism is examined for the case of an evaporating cloud drop. A formula is presented which describes the coupled effects of diffusion and thermo- and diffusiophoresis around a stationary drop. Under those circumstances where the phoretically-induced collection dominates diffusion, the formula suggests that, regardless of the undersaturation experienced by the drop, causing it to evaporate, phoretic effects tend to be independent of their driving force. Such circumstances are also identified for the case of a failing cloud drop.