Precipitation Microphysics Characteristics of a Typhoon Matmo (2014) Rainband after Landfall over Eastern China based on Polarimetric Radar Observations

The evolution of microphysics characteristics of a rainband in the landfalling typhoon Matmo (201410) during its reorganization, including onset, developing, mature, and dissipating stages, is documented in this study using the observations from an S-band polarimetric radar, an S-band Doppler radar, and a 2-dimentional video disdrometer (2DVD). The drop size distributions (DSDs) observed by 2DVD and retrieved from polarimetric radar indicate that the DSDs generally have smaller size and higher number concentration than the maritime type precipitation. The average mass-weighted mean diameter Dm of convective precipitation is about 1.48 mm and the averaged logarithmic normalized intercept Nw is 4.55 log10 mm^-1 m^-3.

To further investigate the dominant microphysical process, the evolution of the vertical structure of polarimetric variables is fully illustrated. Corresponding microphysical processes is identified using the polarimetric radar fingerprint of the vertical profiles of horizontal polarization Z_H, differential reflectivity Z_DR, and the specific differential phase K_DP. Results show that complex cold processes are involved above the freezing level, while only the coalescence and/or accretion processes are active below freezing level during the evolution of the rainband. Further combining the polarimetric fingerprint and the vertical water vapor profile estimated from Z_H and Z_DR, results indicate that the conversion of cloud water into rainwater through cloud water accretion by raindrops dominates the heavy rainfall, while the ice particles generated by the cold processes play an important roll in accelerating the accretion process. The precipitation efficiency is, for the first time, estimated from the observations for the typhoon system. The precipitation efficiency over 60% suggests the accretion of cloud water is an important mechanism to produce heavy rainfall.