Sponsor: National Science Foundation

Title: Polarimetric Radar Observations of Precipitation: Measurements, Analysis, Modeling and Retrievals

Investigator(s): V. Chandrasekar

Abstract
This research centers on using the CHILL research radar at Colorado State University to study the polarization properties of radar echoes from precipitation. One objective is to compare the polarimetric information available from two modes of operation: (1) rapidly switching the transmitted wave form between horizontal and vertical polarization; (2) transmitting circular polarization and simultaneously receiving the horizontal and vertical components - the so-called hybrid mode. Experiments will determine which of these modes is more suitable for applications such as estimating rainfall rate by combining measurements of the radar reflectivity with various parameters that describe the polarimetric properties of the radar signal. Another objective is to evaluate and refine a method based on fuzzy logic of classifying the type of precipitation (rain, hail, snow, melting snow, etc.) by a suitable combination of polarimetric parameters. The method will be evaluated by in-situ observations by a storm-penetrating research aircraft (the South Dakota School of Mines and Technology armored T-28). Also to be investigated are ways to estimate the raindrop size distribution from polarimetric observations, using both airborne and ground-based measurements for verification. These studies will provide important guidance for the planning, now under way, to introduce polarimetric measurements in the network of weather surveillance radars operated by the National Weather Service.