Modified gamma model for Singapore rain drop size distribution

A modified gamma model is used to describe the rain drop size distribution in Singapore (1/spl deg/21'N, 103/spl deg/41'). The general expression of the moment estimates for the model is derived first. Since Joss type Distrometer RD69 is used in the measurement, the special equations for such data are then derived. The parameters for the modified gamma model are calculated for ten rainfall rates ranging from 1 mm/hr to 140 mm/hr. Using the least square fitting method, the general model suitable for all rainfall rates is obtained. The theoretical model is compared with the measured data. It shows that the derived model can be used to represent the Singapore rain drop size distribution.