On the mechanisms of downdraft maintenance in cumulonimbus clouds

Abstract

The mechanisms of maintenance of cold steady downdraft in convective clouds have been investigated in numerical experiments using a one-dimensional steady-state model of the updraft-downdraft interaction. It was found that evaporation of cloud water entrained from the updraft in the presence of dry air entrained from the environment may in certain circumstances provide cooling sufficient for development and persistence of a quasisteady downdraft in the middle part of a cumulonimbus cloud. This effect may be essentially enhanced if the equivalent-potential temperature, θ_e, has a distinct minimum in the middle troposphere.