Gamma distribution of raindrop sizes and its application to Singapore's tropical environment

Abstract

The use of a gamma distribution of raindrop sizes in the calculation of microwave rain attenuation is gaining acceptance. A method of calculating the general gamma distribution of raindrop sizes based on the rain attenuation relation aRb has been developed in this article using the measured microwave attenuation data with respect to the rain rates. The method, which has been tested using the CCIR model, overcomes the common problems of instability and does not suffer from the possibility of multiple solutions. The parameters of the gamma distribution suitable for the moderate climatic region are computed from the calculated attenuation data provided by CCIR model. Comparison of the calculated results with the data from the CCIR model shows that the method provides the ideal modeling of raindrop size distribution (DSD). As an application, the two-year experimental data recorded in Singapore have been used to obtain another set of parameters of the gamma DSD function for the tropical region.