Application of raindrop size distribution of super typhoon "Yagi" to quantitative precipitation estimation

The characteristics of rain drop size distribution (DSD) in super typhoons are critical for the application of radar-retrieved precipitation to typhoon short-term forecasting. Based on disdrometer data collected at 12 national surface stations in Hainan, this study comprehensively analyzes the characteristics of DSD within the eyewall, inner rainbands, and outer rainbands of super typhoon "Yagi", and further investigates their application potential in quantitative precipitation estimation (QPE) using weather radar. The results indicate that the normalized Γ distribution can effectively characterize DSD features across distinct structural regions of the typhoon, while the mean precipitation spectrum in each region exhibits a distinct unimodal pattern. The precipitation formation mechanism of super typhoon "Yagi" is dominated by warm-cloud and ice-phase mixed microphysical processes, with medium-size raindrops making the dominant contribution to the rainfall intensity across all typhoon structural regions. Compared with typhoons of similar intensity, super typhoon "Yagi" exhibits smaller raindrop particles in its eyewall region. These raindrops make a greater contribution to the total rainfall intensity and lower the coefficient A in the corresponding Z-R relationship, which further promotes the formation of intense precipitation. Applying the fitted local parameters to QPE using the new-generation weather radar in Haikou yields better performance than the operational default scheme: The correlation coefficient reaches 0.9264, the normalized mean absolute error (NMAE) and root mean square error (RMSE) decrease by 0.1024 and 0.9 mm, respectively, and the retrieval results are more consistent with actual observations after incorporating surface rain gauge correction.