A NEW ALGORITHM FOR CLASSIFICATION OF TROPICAL CONVECTIVE PRECIPITATING CLOUDS OVER NORTH-EASTERN REGION OF INDIA

The North East (NE) region of India is prone to severe thunderstorm during pre monsoon period. These pre-monsoon precipitations are measured at Guwahati (26o 17’ N, 91o 77’ E) using a laser based particle size and velocity (PARSIVEL) disdrometer from 15 April to 31 May 2010 under a national field campaign named Severe Thunderstorm Observational and Regional Modeling (STORM). For the improved understanding of these pre-monsoon thunderstorm a new cloud classification hybrid algorithm is developed based on thermodynamics and microphysical characterstics of precipitation. This algorithm can classify the premonsoon precipitaitng clouds into thuderstrom (TS), non- thuderstrom (NTS) and futher into convective & stratiform cloud fractions based on thermodynamic indices and rain integral parameters. The observation results showed that raindrops of Small and mid (large) size are having same concentration in convective (stratiform) regions of both TS and NTS precipitations. There is a large spread in the mean diameter (Dm) and total concentration (NT) at higher rainrate of TS than NTS. The coefficient (A) of the radar reflectivity and rainrate relation (Z-R) is found to be smaller for TS than NTS. There is a significant difference in Raindrop concentration in stratiform, convective regions of TS and NTS precipitation.