COMPLETE MICROWAVE SCATTERING AND EXTINCTION PROPERTIES OF POLYDISPERSED CLOUD AND RAIN ELEMENTS

Abstract : This report determines the extinction, the albedo of single scattering, the differential scattering cross section, and the complete polarization properties, per unit volume of cloud and rain elements, when these elements are irradiated by microwave radiation at various frequencies. Continuous drop-size distribution functions are introduced to represent real clouds and precipitation, and the absorption and scattering parameters are integrated with high accuracy. A Rayleigh approximation is found adequate for the cloud model but the complete Mie expressions had to be used for precipitation-sized particles. Older estimates have been corroborated but some new features have been brought out for the first time, such as the scattered intensity and polarization (including its ellipticity) as a function of scattering angle. The quantitative results, presented graphically and in extensive tables, will be useful in advancing cloud physics research by means of active and passive microwave techniques. The same results can be used in the theoretical interpretation of the observed continuous and discrete microwave emissions from certain planets. (Author)