Analysis of TRMM Precipitation Radar Algorithms and Rain over the Tropics and Southeast Texas

Abstract

The Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) 2A23 algorithm classifies rain echo as stratiform or convective while the 2A25 algorithm corrects vertical profiles of radar reflectivity for attenuation and calculates rain rates associated with the attenuation-corrected reflectivity. Updates to the 2A23 algorithm for Version 7 (V7) have resulted in an increase (decrease) in the fraction of rain echo classified as convective (stratiform) compared with previous versions of the algorithm. The tropics-wide (20°N-20°S) stratiform rain fraction has decreased correspondingly, which has implications for studying the impact of convection on the large-scale circulation because of the elevated heating associated with stratiform rain. Updates to the 2A25 algorithm have resulted in changes in the rain rates derived from radar reflectivity, with convective rain over land increasing between V6 and V7. Drop size distributions (DSD) from 2A25 are compared to rainfall data collected at two ground instrument sites in southeast Texas and show that the TRMM PR is still likely underestimating heavy rain rates over land, with implications for quantifying flash flood events and model evaluations of rain rate distributions.