Polarimetric Radar Signatures and Performance of Various Radar Rainfall Estimators during an Extreme Precipitation Event over the Thousand-Island Lake Area in Eastern China

Polarimetric radar provides more choices and advantages for quantitative precipitation estimation (QPE). Utilizing the C-band polarimetric (CPOL) radar in Hangzhou, China, six radar QPE estimators based on the horizontal reflectivity (Z_H), the specific attenuation (A_H), the specific differential phase (K_DP), and their corresponding double-parameters that further integrate the differential reflectivity (Z_DR), namely R(Z_H, Z_DR), R(K_DP, Z_DR) and R(A_H, Z_DR), are investigated for an extreme precipitation event occurred in Eastern China on 1 June 2016. These radar QPE estimators are respectively evaluated and compared with a local rain gauge network and drop size distribution (DSD) data observed by two disdrometers. The results show that (i) Each radar QPE estimator has its own advantages and disadvantages depending on the specific rainfall patterns, and it can outperform other estimators at a certain period of time; (ii) although R(A_H, Z_DR) underestimates in the light rain pattern, it performs best of all radar QPE estimators according to statistical scores; (iii) Both the optimal radar rainfall relationship and the consistency between radar measurements aloft and surface observations are required to obtain accurate rainfall estimates close to the ground. The contamination of melting solid hydrometeors on A_H and/or K_DP may make them less effective than Z_H. In addition, appropriate α coefficient can eliminate the melting impact on the A_H-based rainfall estimator.