Drop Size Distribution Retrieval from Polarimetric Radar Data to Enhance the Spectral Bin Classification in Detecting Icing Conditions

The emerging Appendix O restrictions on flight into and out of terminal airspaces (TASs) require discrimination between freezing rain, freezing drizzle, and other forms of winter precipitation. This, in turn, requires reliable estimates of the drop size distribution (DSD) over the entire volume of air within each TAS. In this research, different methods for extracting the DSD from polarimetric radar data were evaluated as well as their efficacy for refining hydrometeor phase delineation within a Spectral Bin Classification (SBC) algorithm that is currently being implemented within the Multi-Radar/Multi-Sensor (MRMS) system. Sensitivity tests of different DSD-extraction methods indicate that reliable results can be obtained with a simple reflectivity-only based Marshall-Palmer type distribution, which allows for a real time implementation of this technique in the near future. These modifications are currently being tested within the MRMS framework. In comparison to the original version of the code, more realistic fine-scale detail of the hydrometeor phase distribution is obtained, as is a more refined analysis of the liquid-water fraction. These changes along with novel ways of visualizing hydrometeor phase across the DSD for each TAS will be presented as well as a timeline for operational implementation within the National Weather Service.