ESTIMATION OF RAINDROP SIZE DISTRIBUTION AND PRECIPITATION USING X-BAND MULTI-PARAMETER RADAR INFORMATION

Abstract

 To accurately estimate raindrop size distribution (DSD) and rain rate from multi-parameter radar, in this study, an advanced estimation algorithm was proposed basing on a conventional method proposed by Yamaguchi (2012) (Yamaguchi method). Yamaguchi method retrieves DSD parameters from radar reflectivity (Z_h) and specific differential phase shift (K_DP). However, Z_h is often underestimated due to rain attenuation, in the case that rain attenuation is strongly occurring. In this study, a new advanced method to retrieve accurate DSD information has been developed to solve the rain attenuation problem. DSD retrieved from K_DP and difference reflectivity (Z_DP) theoretically showed higher accuracy than that from K_DP and Z_h in large attenuation cases under pseudo observation experiments. This fact was also evaluated by observation data using an operational X-band multi-parameter radar and a raindrop disdrometer. These results are induced by the fact that Z_h is largely affected by intense rainfall attenuation compared with Z_DP. Therefore, it is concluded that the proposed new method is possible to retrieve DSD with higher accuracy than Yamaguchi method because rain attenuation is greatly affect retrieval accuracy of DSD.