Some dynamical aspects of precipitating convection.

Abstract

A simple linear model is developed to distinguish the dynamics of precipitating convection from those of the nonprecipitating variety. In particular, it is shown that the slope and propagation of squall lines in a fully nonlinear numerical model operates also within a linear model. It is demonstrated that 1) precipitating convection in a basic state consisting of a resting, uniform, unstable cloud can propagate and exhibit sloping up- and down-drafts; 2) subcloud evaporation of falling precipitation leads to modifications of the instabilities and the formation of a new mode has peak amplitude in the subcloud layer; and 3) the introduction of a shear layer at the cloud base serves to couple the subcloud layer mode mentioned here with the cloud layer and yields a deep, rapidly growing, down- shear propagating mode.-from Author