Microphysical processes of super typhoon Lekima (2019) and their impacts on polarimetric radar remote sensing of precipitation

The complex precipitation microphysics associated with super typhoon Lekima (2019) and its potential impacts on the consistency of multi-source datasets and radar quantitative precipitation estimation were disentangled using a suite of in situ and remote sensing observations around the waterlogged area in the groove windward slope (GWS) of Yandang Mountain (YDM) and Kuocang Mountain, China. The main findings include the following: (i) the quality control processing for radar and disdrometers, which collect raindrop size distribution (DSD) data, effectively enhances the self-consistency between radar measurements, such as radar reflectivity (Z(H)), differential reflectivity (Z(DR)), and the specific differential phase (K-DP), as well as the consistency between radar, disdrometers, and gauges. (ii) The microphysical processes, in which breakup overwhelms coalescence in the coalescence-breakup balance of precipitation particles, noticeably make radar measurements prone to be breakup-dominated in radar volume gates, which accounts for the phenomenon where the high number concentration rather than the large size of drops contributes more to a given attenuation-corrected Z(H) (Z(H)(c)) and the significant deviation of attenuation-corrected Z(DR) (Z(DR)(c)) from its expected values (Z(DR)) estimated by DSD-simulated Z(DR)-Z(H) relationships. (iii) The twin-parameter radar rainfall estimates based on measured Z(H) (Z(H)(M)) and Z(DR) (ZMDR), and their corrected counterparts Z(H)(c) and Z(DR)(c), i.e., R(Z(H)(M), Z(DR)(M)) and R(Z(H)(c), Z(DR)(c)), both tend to overestimate rainfall around the GWS of YDM, mainly ascribed to the unique microphysical process in which the breakup-dominated small-sized drops above transition to the coalescence-dominated large-sized drops falling near the surface. (iv) The improved performance of R(Z(H)(c), Z(DR)) is attributed to the utilization of Z(DR), which equals physically converting breakup-dominated measurements in radar volume gates to their coalescence-dominated counterparts, and this also benefits from the better self-consistency between Z(H)(c), Z(DR), and K-DP, as well as their consistency with the surface counterparts.