TRMM precipitation bias in extreme storms in South America

Abstract

Deep convective storms in subtropical South America are some of the most intense in the world, and the hydrological cycle plays an important role in both tropical and subtropical South America. Recent studies have suggested that the Tropical Rainfall Measuring Mission (TRMM) precipitation radar algorithm significantly underestimates surface rainfall in deep convection over land. This study investigates the range of the rain bias in storms containing four different types of extreme radar echoes: deep convective cores, deep and wide convective cores, wide convective cores, and broad stratiform regions over South America. Storms with deep convective cores show the greatest underestimation, and the bias is unrelated to their echo top height. The bias in wide convective cores relates to the echo top, indicating that storms with significant mixed phase and ice hydrometeors are similarly affected by assumptions in the TRMM algorithm. The relationship between storm type and rain bias remains similar in both subtropical and tropical regions. Key Points TRMM rain algorithm biases various types of extreme storms, not just deep ones Rain biases from deep convection are greater than wide convection or stratiform Convection containing significant precipitation ice is the most underestimated ©2013. American Geophysical Union. All Rights Reserved.