Theoretical Experiments on Cumulus Dynamics

Abstract

The sensitivity of a two-dimensional cloud model to changes in microphysical characteristics was examined using two soundings. The dynamical evolution of clouds having relatively warm bases was controlled more by rapidity of the production of liquid-phase precipitation than by the differences in the concentration of ice particles. There was little change in the dynamical properties of the relatively cold-base clouds with changes in either liquid or ice phases. A study of the components of the forces causing evolution of the clouds indicated that the net force acting at a given location was often quite small compared to several individual components of the force. Anything causing these individual forces to move relative to one another will make changes in the net force and alter the dynamical properties of the cloud. The earlier versus later formation of precipitation causes changes in location of the forces of condensate loading, and these changes apparently are the explanation of the differences in the behavior of the warm-base cloud.