Microphysical Observation and Analysis in the Eyewall and Inner Rainbands of Typhoons

Based on the observations of disdrometers and dual-plorization radars in Eastern China, microphysical difference in precipitation was found between the eyewall and inner rainbands of typhoons. The surface disdrometer observations showed that the average raindrop diameter parameter D_m (concentration parameter log₁₀N_w) generally decreases (increases) radially from the TC center. Namely, the eyewall rain has a larger mean raindrop diameter and a smaller mean concentration than the inner-rainband rain on the ground. Also, the dual-polarization radar observation confirmed larger sizes of raindrops near the ground in the eyewall. However, the vertical profiles of polarimetric variables showed larger values almost throughout the atmosphere in the eyewall, suggesting that more efficient ice- and warm-cloud processes are evident for the production of ice and rain particles. This result looks contradictory to the lower concentration of the eyewall rain than the inner-rainband rain as measured by surface disdrometers. This is because stronger updrafts observed in the eyewall not only facilitate the production and growth of hydrometeors, but also prevent small raindrops from falling to the ground. Consequently, the surface rain in the eyewall has larger raindrop diameter and lower concentration than that in the inner rainbands, despite a larger number of ice and rain particles in the atmosphere.