Kinetic Threshold Conditions for Fog Formation in Cloud Chambers and Marine Environment

Abstract

A kinetic analysis of the fog formation process due to the contact of warm, moist air with a cold wall is presented. The analysis reveals that a wave in the nominal saturation ratio forms at and spreads away from the wall. The threshold conditions under which the maximum saturation ratio at the wave head becomes unity are derived. Comparison is made between the thermodynamic treatment of air mass mixing and the kinetic treatment. It is shown that the difference in diffusivities of vapor and temperature is responsible for the discrepancy of the two treatments. Results are applied to the problems of air sample processing, to avoid transient supersaturations, in cold chambers. The necessity of considering the kinetic effects of molecular diffusion in advection fog formation over the ocean is demonstrated.