Polarimetric Observations and MRMS Algorithms with the All-Digital Horus Radar on Hail Producing Storms

Rapid-scan, polarimetric radar observations of hail have shown operational utility through a better understanding the microphysical evolution of hail and processes that drive hail evolution. In addition, radar-derived algorithms can provide hail size estimates, which aid in warning operations and may improve with faster temporal sampling. Recent emphasis has been on phased array radars (PARs), as these can provide update times on the order of seconds and dense vertical sampling, which may allow for a better understanding of how hail forms and descends. Improvements to the data quality in PARs can also improve our hail algorithms and hail tracking compared to the current operational radar network. However, there are very few datasets from phased array radars of hail-producing storms.

This study utilizes observations from the fully digital, polarimetric, S-band Horus phased array radar that has been recently developed at the Advanced Radar Research Center at the University of Oklahoma, with support from NOAA’s National Severe Storms Laboratory (NSSL). Horus provides volumetric update times on the order of a minute or less and offers much greater flexibility in scanning strategies compared to the existing WSR-88D radars. Horus data have been collected on hail-producing storms through the spring 2023 convective season, and data collection will continue into the fall. Horus data collected so far has been ingested into the WDSS-II software to explore the utility of the initial observations collected, with particular emphasis on the detection of hail as well as polarimetric signatures and observations associated with deep convection and hail. Horus data have also been used as an input to the Multi-Radar, Multi-Sensor (MRMS) algorithms, such as the hydrometeor classification algorithm and the maximum estimated size of hail (MESH), to compare the Horus-derived HCA, for example, to the operational MRMS output. The observations will be quantitatively compared to the nearby operational WSR-88D’s as well as co-located radars, such as RaXPol, to evaluate the performance of the polarimetric Horus observations relative to operational radars. These observations will serve as initial motivation for examining the operational utility of fully-digital PARs for observing severe convection and, in particular, hailstorms.