Vertical Structure of Raindrop Size Distribution at Kototabang as Retrieved by Micro Rain Radar

Abstract

Vertical structure of raindrops size distribution (RDSD) as retrieved by Micro Rain Radar (MRR) during January-December 2012 at Kototabang, west Sumatera had been investigated. The performance of MRR was examined by comparing the rainfall rate (R) and RDSD obtained by the MRR with that obtained by the Optical Rain Gauge (ORG) and Parsivel. Thus the MRR at Kototabang collected precipitation data in good accuracy. The RDSD was parameterized by modified gamma distribution and its parameter was calculated by the moment method. It was found that the growth of RDSD from the altitude of 4.65 km to 0.15 km was significant that may be due to the collision-induced coalesence process. This can be inferred from a significant increase of large-sized drops with decreasing height. The increase of such drops influenced the integral rainfall parameters such as radar reflectivity (Z) and R that leads to an increase of A coefficient of Z=ARbequation with decreasing height. Thus, the usage of constant Z-R equation in rain coulumn for radar meteorology in tropical regions particulary in West Sumatera, are not acceptable.Hlm.27-3