On the Role of Drop Size Distribution in Trmm Rain Profiling Algorithm

The selection of the drop size distribution (DSD) model is one of the critical steps in rain profiling algorithm (RPA) of the NASA Tropical Rainfall Measuring Mission (TRMM) (Iguchi et al. 2000). RPA requires R-Ze and K-Ze relations for convective and stratiform precipitation, where K and Ze represent the attenuation and equivalent reflectivity at 13.8 GHz, respectively, and R is the rain rate. These relations are derived from several samples of DSD measurements. An averaging is performed among the K-Ze and R-Z e relations to determine the initial coefficients and exponents for the profiling algorithm. The final coefficients and exponents are determined through surface reference technique (Meneghini et al. 2000). The convective stratiform partitioning is determined based on the DSD characteristics (Kozu et al. 2001). RPA, however, determines the precipitation type from three-dimensional characteristics of reflectivity following Awaka et al. (1985) and Steiner et al. (1995, SHY95 hereafter). The goal of this study is to investigate the variations in the DSD and its impact on K-Ze and R-Ze relations due to differences in climatic regimes and due to the differences in precipitation type algorithms.