Studies of raindrop size characteristics in different types of tropical rain using a simple raindrop recorder

Abstract

The paper describes an easily constructed raindrop recorder for obtaining a continuous record  of the time of occurrence, duration and range of raindrop sizes of all types of rain (thunderstorm, showers, and continuous type of rain). The important meteorological parameters such as liquid water content W, intensity of rainfall R’, size distribution of raindrops for all types of rain N_D, radar reflectivity Z can all be obtained from the recorder. Regression equations connecting the intensity of rainfall with the various rainfall parameter have been developed and compared with the findings of other investigators all over the world. A brief description of a suitable rain receiver, tilting bucket raingauge is also given for determining the intensity of rainfall at minute intervals for various types of rain from a continuous photographic record. It is shown, in agreement with results obtained by Blanchard (1953) and Atlas and Chmela (1957) that the rain intensity corresponding to most size spectra can be represented by a uniform collection of drops with size equal to the median volume diameter D_o.  The study clearly shows that any two of the four raindrop size parameters R', Z, W, D_o fix the other two. The physical basis for the Z-R' correlation for different types of rainfall are explained using Bartnoff and Atlas's equation (1951). The presence or absence or appreciable electric charge in rain helps to find out whether the rain is from freezing or non-freezing clouds.