Analysis of Z-R relations based on LDR signatures within the melting layer

The inclusion of polarimetric measurements for the quantitative precipitation estimation (QPE) by weather radars as well as space- and airborne radars is considered most promising now-a-days. Because the melting layer region is usually marked by a distinct peak of the linear depolarization ratio (LDR), a possible correlation between LDR peak values and underlying drop sizes in terms of the Z-R relation is investigated, that is, the empirical relation between radar reflectivity factor Z and rain rate R. For this purpose, data taken during the Convective and Orographically Induced Precipitation Study (COPS) campaign in 2007 from two vertically pointing radars-a 24.15-GHz Micro Rain Radar (MRR) and a 35.5-GHz polarimetric cloud radar-were analyzed. In this analysis a correlation between parameters of the Z-R relation and LDR peak values are revealed, implying that the LDR magnitude within the melting layer must be influenced by the size of melting particles. Furthermore, an LDR classification scheme shows an improvement of R retrieval with respect to the global Z-R relation optimized for the dataset herein. However, to asses the impact for improved QPE in the abovementioned applications, future research is necessary. © 2010 American Meteorological Society