Entrainment rates in the cloud zones of continental shallow cumulus

Abstract

Entrainment rates from in situ measurements and Large Eddy simulations (LES) of shallow clouds over the Indian peninsula are presented in this study. It is noted that the coherent motions of counter-rotating vortices originate from the updraft zones within clouds, and they subside around shallow clouds. Clouds with stronger updrafts gain depth and have high liquid water content near the cloud top. A three-parameter clustering algorithm (K means) identifies the subregions of the cloud from its core to the surrounding subsiding region. The extreme core region has the highest liquid water content, droplet number concentration, updrafts, and minimum entrainment rates. The varying degree of dilution in the cloud zones is identified here, featuring the dynamics associated with the moist adiabat. Parametric relationships between the entrainment rate and buoyancy in the different cloud zones are illustrated, which could be useful in large-scale models.