A Calculation of Percentage Area Covered by Convective Clouds from Moisture Convergence

Abstract

In large-scale tropical flows an estimate of the percentage area covered by active convective cloud elements may be made according to certain theoretical formulations involving parameterization of convective-scale motions. Such an example is Kuo's model cloud which is based on replacing the ambient tropical atmosphere with a moist adiabatic cloud element over a portion of a synoptic-scale grid network. Quantities such as friction layer mass convergence, moisture convergence, and other relevant parameters like net moisture convergence over vertical columns extending over the depth of the troposphere are determined to evaluate the percentage area occupied by convective clouds. An application to a case study of an easterly wave below a cold low is made. Some radar pictures are presented for comparison purposes.