Polarimetric radar analysis of convection in northwestern Mexico

The overarching goal of the North American Monsoon Experiment (NAME) is to improve prediction of warm-season rainfall over North America, and especially over the southwestern portion of the U.S. where summer rains are forced by the North American Monsoon (NAM). For NAME, a comprehensive network of instrumentation was deployed during summer 2004 in order to document the variability of precipitation across the Sierra Madre Occidental (SMO) and adjacent coastal plain and Gulf of California (GoC), regions central to supplying moisture to the NAM and generating rain over the southwestern U.S. This report focuses on statistical analysis of the ground-based radar observations collected by the S-Pol radar, an S-band polarimetric Doppler radar operated by the National Center for Atmospheric Research (NCAR) during the NAME Enhanced Observing Period (EOP). The NAME EOP took place between July-August 2004. The main dataset for the presented analyses consists of 3-D Cartesian grids, which include all major polarimetric variables (co-polar reflectivity, differential reflectivity, specific differential phase, linear depolarization ratio, and correlation coefficient) as well as fuzzy-logic-based hydrometeor identification.

Statistical analyses of the S-Pol radar 3-D dataset are being done in order to extract the salient characteristics and microphysical processes of convection in the NAME region. The dataset is being analyzed to derive statistics for warm rain vs. ice-based precipitation, properties of the rain drop size distributions, and vertical reflectivity and microphysical profiles evaluated as functions of topography, diurnal cycle, and intraseasonal variability. The ultimate goal of this work is to provide a better understanding of the structure and variability of convection in the NAME region.