The effect of drop-size distribution variability on radiometric estimates of rainfall rates for frequencies from 3 to 10 GHz

Abstract

From 3 to 10 GHz emissions from raindrops and from clouds dominate the radiative transfer equation. Because emission and absorption are reciprocal, the combined absorption coefficient of the cloud and the rain can be estimated from the upwelling radiation at these frequencies. After extracting the component due to rain (ka), it may be used to estimate the rainfall rate ξ(R). The physical link between R and ka varies depending upon the microwave frequency. The weaker the relation the more sensitive ka and ξ(R) are to variations in the drop-size distribution. In this study it is shown that the scatter in ka and ξ(R), in response to variations in the drop-size distribution, is greatest at 8 and smallest at 3 GHz. -from Author