An Observational and Theoretical Study of Atmospheric Flow Over a Heated Island: Part II

Abstract

A two-dimensional theoretical model is developed to analyze the properties of perturbations induced when air flows over an isolated warm portion of the earth's surface. The model equations include continuity equations that predict water vapor, cloud water, and liquid water. The nonadiabatic effects of condensational heating and evaporational cooling are also incorporated. The theoretical model is developed in conjunction with a specially designed observational field program for testing the model predictions. The field program and its results are described in Part I. The model has been able to reproduce the observed conditions quite realistically; in particular, the observed and predicted patterns of cloud distributions and rainfall compare very well. The study has demonstrated the important influence of evaporational cooling of the environment on the behavior of perturbations induced by the heat source. Numerical integrations of the model have also been performed to examine the dependence of the induced perturbations on the following factors: (1) temperature excess of the heat source, (2) speed of the normal component of the prevailing flow, (3) speed of the parallel component of the prevailing flow, and (4) width of the heat source. The results show that the larger the temperature excess of the heat source, the greater the intensity of the induced disturbance. The strength of the normal and the parallel components of the prevailing flow have opposite influences on the perturbations?a stronger normal component tends to weaken the disturbance whereas a stronger parallel component tends to intensify it.