Brown/Abstract The broad objective of the proposed research is to develop improved models of the rainfall process and to seek appropriate field data in order to reconcile theory and observation. The work will entail improved model formulation of raindrop coalescence and breakup for detailed study of the rain process and for application in models of cloud systems. The research will focus on prediction of the raindrop size distribution that describes the number and sizes of drops within a unit volume of air. The form of the drop size distribution is of both theoretical and practical importance, as it affects the dynamics and thermodynamics of the storm and determines the rate at which the rain removes pollutants from the atmosphere. Specific objectives of the research are: to determine the range of uncertainty in the current model formulation of drop breakup and to identify specific needs for data acquisition and qpecific problems in data representation; to improve an existing model of rainfall in a vertical shaft by incorporating a model of cloud-water to rain-water conversion at the upper boundary and to compare the model solutions with observed drop size distributions; to develop a parameterization of the raindrop size distribution within the shaft for use in models of cloud systems; to investigate the common but unexplained phenomenon of oscillation in rainfall intensity; and to develop an entirely new model that details the collision of two raindrops. The active prospect of obtaining new field measurements, using various radars, will be pursued.
