Observed structure of convective echoes over southern Indian peninsula during pre-monsoon using TRMM Precipitation Radar

Abstract

Height of convective echoes over southern Indian peninsula (SIP) is studied using Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) measured attenuation corrected radar reflectivity (2A25) data (Z_e). 25 cases of severe thunderstorm events are selected from Disaster Weather Events, an annual publication of India Meteorological Department (IMD). An intense convective echo is defined as a set of 4 or more contiguous convective pixels (area ≥ 100 km²) with Z_e exceeding 40 dBz or more at any level. A total of 492 intense convective echoes are observed by TRMM PR during 25 passes. It is found that 18.1% of convective echoes have height ≤ 8 km, 29.3% have height between 8-10 km, 43.3% between 10-15 km and 9.1% of them have height exceeding 15 km in the pre-monsoon season over SIP. Height of 30 and 40 dBz is considered as a proxy for convective intensity. The frequency of 30 dBz height shows peaks at 6 and 7 km while 40 dBz heights show a single maxima at 6 km. The cumulative frequency distribution of 30 and 40 dBz heights show that nearly 23% and 7% of the convective echoes cross 10 km height during pre-monsoon season. The median heights of 30 and 40 dBz echoes were found to be 7.5 and 5.5 km respectively