Automatic Detection of the Melting Layer with a Polarimetric Prototype of the WSR-88D Radar

Melting layer detection is necessary to delineate liquid from frozen hydrometeors and to identify regions in which radar rainfall estimates are potentially biased due to contamination from frozen particles. A method for automatic melting layer detection was developed and tested using a polarimetric prototype of the WSR-88D radar. The approach capitalizes on radial dependencies of radar reflectivity factor Z, differential reflectivity ZDR, and cross-correlation coefficient ρHV to estimate the height of the top and bottom of the melting layer. Melting layer designation is made using polarimetric data collected at antenna elevation angles between 4 and 10 degrees. Special consideration is given to the impact of melting layer contamination on the quality of polarimetric rainfall estimation and hydrometeor classification at the lowest radar scan and at large distances from the radar. Inroads are made into the impact of beam broadening on melting layer height interpretation.

The automatic detection procedure was tested on several events collected during Oklahoma field campaigns of 2003 and 2004. The performance of the procedure has been validated using available soundings and RUC model analysis output.