Precipitation Characteristics of an Autumn Torrential Rainfall Event in Northern Taiwan as Determined from Dual-Polarization Radar Data

Abstract

In Taiwan, comparing with the major hazardous Mei-Yu fronts and typhoons in summer, a synoptic condition with the relatively weak high and low pressure systems at certain locations in the autumn season may bring torrential rainfall to northern Taiwan. A detailed dual-polarimetric/Doppler radar analysis was carried out for one case under this condition to reveal the mesoscale precipitation mechanisms and microphysical characteristics over terrain.The high pressure system moving eastward off China and the low pressure system over the ocean in the southeast of of south-eastern Taiwan formed a convergent zone at the low levels, resulting in a sequence of convective activities. These convective cells moved westward, and became more organized and intense in the Mt. Datun area and the estuary of Tamsui River near the lee side of Mt. Datun.Moderate intensity convective cells were embedded in the wide, long-lasting stratiform regions. In the mountain area with intense precipitation, terrain-induced upward motion of the cells enhanced condensation, significantly increased drop counts, and acted as a feeder. The older cells in this convective system continued to provide lighter hydrometeors in the upper layer and formed a widespread stratiform region as a seeder. The wider spectrum of drop size distribution set the stage for collision and coalescence process, resulted in the larger drops formed at the low level of the mountain area. Along with the increasing concentration of raindrops, the total effect finally caused heavy rainfall over the mountain area.

Mesoscale convective systems in the third pole region: Characteristics, mechanisms and impact on precipitation

“…A case of heavy precipitation originating from the TP was found to be enhanced with dominant rimming and aggregation processes due to the "seeder-feeder" mechanism, where the seeder was the original cloud system and the feeder was from low-level water vapor transportation (Chen Y. et al, 2020). The mechanism in this case though is not a typical "seeder-feeder" mechanism where the seeder clouds are widespread clouds and the lowlevel feeder clouds are forced by hills (Feng and Wang, 2011;Kim et al, 2022). Nevertheless, the microphysics processes are indeed essential to the MCSs development in this area.…”

Regional Variability of Raindrop Size Distribution from a Network of Disdrometers over Complex Terrain in Southern China

“…This variation of N w may be explained by distance from the ocean. The supply of water vapor near the coastal areas is much more than in the inland areas which develop condensation into droplets and small raindrops increasing the raindrop number concentration [45]. In addition, Meixian, Luoding and Xuwen, with lower annual rainfall, have a smaller D m than Haifeng, Enping and Qingyuan which are the heavy rainfall areas of Guangdong.…”