Some Factors Governing Ice Particle Multiplication in Cumulus Clouds

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  • 1 Division of Cloud Physics, CSIRO, Sydney, Australia
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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.

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.

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