Shape of the rain drop size distributions and classification of rain type at Gadanki

Abstract

Three different rain drop size distribution (RDSD) models namely exponential, lognormal and gamma distribution are fitted to RDSD as spectra observed from Joss-Waldvodgel Disdrometer (JWD) at Gadanki (13.8ºN, 79.18ºE). Gamma distribution shows overall good agreement with observed RDSD for all ranges of rainfall rate. Rainfall rate calculated from gamma drop size distribution is found to have minimum root mean square error and biasing compared to exponential or lognormal distribution. The intrinsic shape of RDSD is found out from normalized RDSD which follows an “S” shape for both low rain £ 10 mm h^-1 and high rain > 10 mm h^-1. The convective and stratiform rains are separated for an event. The equations of separation for convective and stratiform rains have been derived assuming power law for log₁₀(<i style="">R</i>) - <i style="">D</i>_m, log₁₀(<i style="">N</i>₀^*) - log₁₀(<i style="">R</i>) and log₁₀ (<i style="">N</i>₀^*) -<i style=""> D</i>_m. The coefficients and exponent for these equations are ⍺_DR=0.145, ⍺_RN=10³, ⍺_DN= 0.85x10^3.15 and β_DR=4.70 , β_RN=-0.15 , β_DR=-0.94 respectively.