Growth of cloud drops by condensation: effect of surface tension on the dispersion of drop sizes

Abstract

It will be shown that because of the surface tension effect, both the difference of the squared radii of any two cloud drops and the variance of the squared radius of the distribution do not remain constant but rather increase with the progress of condensation. The increase will be related to the vertical air velocity, the drop concentration, and the nucleus distribution. The approximate analytical result will be verified by numerical solution of the equations for the growth of cloud drops by condensation in which both surface tension and solute effects will be included. This means that numerical cloud models in which the microphysics of condensation are approximated by neglecting the surface tension and solute effects may be seriously in error. Based on the approximate solution for the width obtained here, an improved method for including the microphysics of condensation in numerical cloud models. -from Author