An Improved Scheme for Convective/Stratiform Echo Classification Using Radar Reflectivity

Abstract

An improved algorithm for the partitioning of radar reflectivity into convective and stratiform rain classifications has been developed and tested using data from the Houston, Texas, Weather Surveillance Radar-1988 Doppler. The algorithm starts with output from the current operational version of the Tropical Rainfall Measuring Mission (TRMM) convective/stratiform classification scheme for the ground-based validation sites and corrects the output based on physical characteristics of convective and stratiform rain diagnosed from the three-dimensional structure of the radar reflectivity field. The modified algorithm improved the performance of echo classification by correcting two main sources of error. Heavy stratiform rain, originally classified as convective, and the periphery of convective cores, originally classified as stratiform, were both reclassified by the modified algorithm. When applied to a large dataset of convective storms comprising squall lines, unorganized convection, and embedded convection, it was found that roughly 25% of the total echo area and 14% of the total rain volume were reclassified. The magnitudes of the differences between the original and modified algorithms varied with the morphology of the storm system, suggesting that the quality of current echo classification information supplied by the TRMM program could vary by location depending on the structure of the dominant precipitation systems within a given region. The analysis presented here helps to establish the level of uncertainty in the existing echo classification products available from TRMM.