An Improved Method for Raindrop Size Distribution Retrieval Using Combined Dual-frequency Radar DFR

Abstract. Accurate retrieval of raindrop size distributions (DSDs) is essential for understanding cloud and precipitation microphysics. The dual-frequency ratio (DFR) measured by dual-frequency radars is independent of the normalized intercept parameter (Nw) and depends solely on the mass-weighted mean diameter (Dm). This characteristic makes DFR a powerful parameter for DSD retrieval. However, the DFR-Dm relationship is subject to a dual-solution ambiguity, particularly for smaller particles. In this study, W-band reflectivity is synthetically incorporated through scattering simulations based on measured DSDs, and retrieval relationships are established among X/Ka-band DFR, Ka/W-band DFR, and Dm. The results show that the ambiguity in the DFR-Dm relationship is substantially reduced, and the proposed method demonstrates clear advantages over conventional approaches, especially when retrieving DSDs of weak echoes. This advancement effectively addresses a key gap in the measurement and analysis of light precipitation processes.