| Summary: | 碩士 === 國立中央大學 === 大氣物理研究所 === 95 === Precipitation characteristics of the torrential rainfall event on 10th Sep. 2006 in northern Taiwan will be discussed in this thesis. The maximum daily accumulated rainfall was 556 mm at Zhuzihu. The heavist rainfall took place during 06-12UTC. The data collected by NCU dual-polarimetric radar and RCWF radar are mainly used to analyze mesoscale features, such as space-time distribution of precipitation, possible mechanisms, as well as microphysics characteristics.
In synoptic scale, a continental high in China and a low locating on Bashi Channel influenced Taiwan. They caused a low level convergent zone in the north-eastern area of Taiwan. Because the continental high moved out of China and it turned to westerly on high level, the climate character was categorized to early autumn.
The horizontal reflectivity patterns were diverse. Convections moved from east to west. Statistic result shows that the strong reflectivity dispersed to three areas, northeastern sea of Taiwan, Mt. Datun and Tamsui River estuary. The environment provided favorable conditions for these precipitation systems, such as convergence and terrain upslope enhancement.
From dual-polarization data, shallow convections were embedded in large and long-lasting stratiform system. ZDR was increasing as height decreasing. Within near saturated environment, the bigger drops in lower level indicated that precipitation may be enhanced by collision and coalescence. Using dual-polarization radar data to retrieve raindrop size distribution, and combing kinematics analysis, we could prescribe a simple microphysics conceptual model. The long-lasting stratiform system continuously provided droplets to low level convections in a wide spread region. Wherever there is more upward motion, more vapor would condense. A wider spread of DSD set up the stage of seeder-feeder mechanism.
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