HUMIDITY AUGMENTATION AS THE INITIAL IMPULSE IN A NUMERICAL CLOUD MODEL

Abstract

A perturbation of relative humidity is used as a trigger to start the convection in a two-dimensional numerical model of a cumulus cloud. The effects of varying the width and depth of the perturbation are studied. The rate of growth, eventual cloud height, liquid water content, and updraft strength are strongly dependent on depth of the impulse; but for realistically shallow depths, these values are in reasonable agreement with observations of real clouds. As in the case of one-dimensional models, the ultimate cloud height is dependent on the width of the impulse, but perhaps to a lesser extent.