1 A dual-polarization radar hydrometeor classification algorithm for ...

443444445446447448449450451452453454455456457458459460461462463464465band signature is often not very consistent or well-defined in wintertime K dp is not trustworthy inand around the ML so it was excluded from the ML detection algorithm.K dp and Z dr are the most important and heavily weighted variables for distinguishingdendrites, plates, and aggregates since ! hv and Z h are usually innocuous (Trapp et al. 2001). Thealgorithm worked best when K dp was weighted slightly more than Z dr for classifying dendritesand plates, but with equal weights between K dp and Z dr for aggregates. This is presumablybecause K dp is less affected by aggregation and radar calibration than Z dr (Vivekanandan et al.2004), so it is perhaps a better indicator of pristine crystals.Temperature dominates the classification between freezing/frozen and liquid rain, butcontrary to most previous HCAs, temperature is not included in any other decision process. Weabandoned this methodology early on because it tended to produce horizontally stratified, nonmeteorologicalcrystal classifications above the melting layer. Dendritic and plate growth zoneclassification examples using polarimetric radar confirmed by surface observations and soundinginformation aloft within this study and others suggest that plates occur in a “cocoon” (Williamset al. 2011) near the top of the radar echo and dendrites tend to be found in “pockets” containedwithin the echo surrounded by decreasing values of K dp and Z dr (KR11, Andric et al. 2012).Aircraft observations of environmental conditions and precipitation type would provide furtheralgorithm validation of these phenomena.5. Hydrometeor classification algorithm case studiesThe winter HCA was tested on four different polarimetric radars spanning three differentfrequencies: C-band OU-PRIME and X-band CASA radars in central OK (McLaughlin et al.2005, Junyent et al. 2010, Palmer et al. 2011), an S-band WSR-88DP in Wichita, KS, and thedual-wavelength X- and S-band CSU-CHILL radar in northern CO (Brunkow et al. 2000). Please21