Precipitation is an important factor in the dynamics of clouds. For example, evaporation of raindrops below cloud base cools the surrounding air and influences cloud development. Since the rate of water evaporation depends on the surface area of the drops, the drop size distribution plays an important role in the cloud evolution. In order to model the dynamics of convective clouds, it thus is necessary to include a realistic formulation of the raindrop size distribution. Such models must take account of the interaction between the small-scale microphysical process (such as water drop evaporation) and the larger-scale microphysical processes (such as air motion). Since the two types of processes operate on significantly different time and space scales, it is not feasible from a computational standpoint to include in the models detailed solution of the microphysical equations. Instead, such models must rely on the use of simple formulas to approximate the evolution of the raindrop distribution. Professor Brown's object in this research is twofold: to obtain a better knowledge of the relevant microphysical processes through analysis of model equations and observational data; and from this knowledge to develop simple parameterization formulas describing the evolving raindrop size distribution for use in convective cloud models. The analysis and parameterization are to take account of the microphysical processes of drop coalescence, breakup and evaporation.//
