Radar, Rainfall, and Lightning Characteristics of Tropical Rainfall Systems according to the Tropical Rainfall Measuring Mission

Dr. Steve Nesbitt
Radar Meteorology Group
Department of Atmospheric Science
Colorado State University

The multi-year database of observations of radar, passive microwave, and lightning flash rates from the TRMM satellite has allowed examination of the properties of tropical rainfall systems. A general overview of results using the University of Utah multi-year TRMM database will be presented, including regional rainfall, convective intensities, and diurnal cycles as a function of storm morphology.  New results will be presented focusing on the properties of rainfall systems having horizontal dimensions of rainfall on the mesoscale. Quantification of these systems properties is important for many climate implications because of their significant contribution to rainfall, heating budgets, rainfall estimation and hydrology, and the global electric circuit.

The goals of this study are three-fold, including:

(1) examining the sensitivity in regional rainfall contribution as a function of the definition of a mesoscale convective system (MCS), whether it be defined by radar or passive microwave sensors, rainfall or convective intensity thresholds, and/or by length or areal scales,

(2) quantify the bulk regional and seasonal rainfall contribution, convective intensity, convective-stratiform partitioning, and lightning characteristics of MCSs based on radar or ice scattering definitions,

(3) examine the internal vertical and horizontal structures (including rainfall rates) of MCSs on a regional basis by examining their radar reflectivity profiles, ice scattering intensities, and lightning flash rates as a function of horizontal and vertical morphology in both convective and stratiform regions. This is performed by using the standard TRMM convective-stratiform separation as well as an automated pattern recognition algorithm to identify characteristic reflectivity structures (e.g. linear convective pattern vs. an embedded convection pattern).