Entrainment and Mixing as Related to the Microphysical Properties of Shallow Warm Cumulus Clouds

Abstract

A method is presented to investigate the relation between entrainment and the microphysical characteristics of warm cumuli, under the assumption that the Paluch analysis leads to the conclusion that there are two and only two sources of the cloudy air. The analysis is based on the dependence of these characteristics upon the fraction of cloud base air in a sample of cloudy air. Mixing between two different cloudy air regions is also investigated in a similar way. A case study concerning a nonprecipitating cumulus observed on 9 September 1983 (VOVES experiment, France) is presented. The analysis supports the idea of coexistence of inhomogeneous and homogeneous mixing. Further, entrainment in this case appears to occur at cloud top and initiates downdrafts by evaporative cooling. Mixing at lower levels takes place between adiabatic ascending parcels and diluted parcels in downdrafts, supporting the ETEM process postulated by Telford.