Analysis of microphysical data in an orographic environment to evaluate a polarization radar-based hydrometeor classification scheme

The orographic environment provides an ideal location to observe changes in frozen particle types, because the forcing for updrafts and the production of supercooled water is a function of the wind speed and local terrain slope. In this paper we use microphysical data collected with the NCAR Electra aircraft on the Mediterranean side of the Alps during the Mesoscale Alpine Program (MAP) to evaluate the NCAR/NSSL polarization radar-based hydrometeor typing algorithm developed by Vivekanandan et al. (1999). To accomplish this, we are comparing aircraft and radar data collected in an orographic environment by the Electra and the NCAR S-Pol radar. To account for the differences in sampling methods between aircraft sensors and radar, we have developed an algorithm that matches the radar pulse volume corresponding most closely in space and time to the volume of cloud measured by the aircraft. We looked at all skinpaints, instances in which the location of the Electra shows up in the radar data as a localized reflectivity maximum greater than 40 dBZ, to test the accuracy of the matched locations between aircraft and radar data. Co-located radar and aircraft data from seven research flights are then used to evaluate if the polarization radar-based hydrometeor typing algorithm captures changes apparent in the aircraft microphysical data and if the aircraft measurements support the decisions of the radar-based typing scheme. The evaluation procedure and the updated algorithm will be presented at the conference.

J. Vivekanandan, D. S. Zrnic , S. M. Ellis, R. Oye, A. V. Ryzhkov, and J. Straka, 1999: Cloud Microphysics Retrieval Using S-band Dual-Polarization Radar Measurements. Bull. Amer. Meteor. Soc., 80, 381-388.