Some Factors Governing Ice Particle Multiplication in Cumulus Clouds

Abstract

Field evidence of high ice crystal concentrations in cumulus clouds at temperatures warmer than ?10°C is consistent with the operation of a Hallett-Mossop ?multiplication? process. This mechanism requires the generation of large drops in the cloud below the ?8°C level, which is governed in turn by the cloud base temperature and cloud drop concentration. These two parameters are shown to he useful in delineating a ?multiplication boundary,? separating cloud conditions in which multiplication takes place from those in which it does not.