Collaborative Research: Comparison between In-situ and Polarimetric Radar Hail Observations in Convective Storms

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The system of operational weather radars in the United States makes use of polarimetric observations, where radar beams are sent out in vertical and horizontal configurations to retrieve an estimate of the shapes of precipitation particles. This award will make use of existing polarimetric radar data and observations from a Storm Penetrating Aircraft (SPA) to improve estimates of the properties of hail from radar data. Hail is a public safety and economic hazard, and improved radar information about hail could provide operational forecasters with an additional tool to provide early warnings. Multiple students will be trained under this project and software used by the scientific community will be enhanced.The research team plans to revisit existing observations of hail that were made concurrently with a research aircraft and polarimetric radars to provide insight into how hail shapes, orientation, sizes, and concentrations influence radar signatures. The South Dakota School of Mines and Technology operated a T-28 storm penetrating aircraft under NSF support from 1987-2003. During that time, the aircraft was involved in 18 projects, many of which included measurements of hail using a hail spectrometer and cloud probes. These campaigns were often conducted within a close distance of a dual-polarimetric radar, including the CSU-CHILL and NCAR SPOL radars. In this project, existing analyses of these data will be augmented by the addition of new flights and flight periods, the inclusion of data from cloud and precipitation probes (2D-C, HVPS), and a unique source of data from a microphone that recorded the sound of hail hitting the aircraft windshield. The main tasks include: 1) Processing hydrometeor images from spectrometer probes, including the calculation of polarimetric radar signatures using discrete dipole and T-matrix software, 2) Analyzing radar data to identify the time the radar swept through the storm volume with the hail encounter and extraction of polarimetric parameters, and 3) Synthesis of the data, with objectives of comparing characteristics of conditions leading to better or worse agreement of computed and observed radar signatures, and evaluation of hail physical characteristics to which each computed polarimetric parameter is most sensitive.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.