| Summary: | 碩士 === 國立中央大學 === 大氣物理研究所 === 100 === This study used the Weather Research and Forecasting (WRF) Model to simulate Typhoon Fanapi (2010), and investigated the mechanisms of the torrential rainfall in south Taiwan and near the coastal Kaohsiung. In this study, FORMOSAT-3/COSMIC GPS RO、GTS and DOTSTAR dropsonde data were assimilated to improve the model initial conditions. An ocean mixed layer was also employed during the model integration to allow the ocean mixed-layer feedback to modulate sea surface temperature.
By using a tropical-cyclone bogus method, the model results show that the simulated typhoon’s intensity is closer to the observations. However, the track becomes deflected somewhat northward after landfall in Taiwan causing degraded rainfall prediction as compared to the control experiment which matches the observed quite well. Assimilation with the above observational data appears to have no major impact on track prediction. When the typhoon is approaching and passing over Taiwan, its intense circulation interacts with the Central Mountain Range (CMR), leading to the major rainfall production right over the steep slopes. As the typhoon is moving away from south Taiwan, the vigorous rainband is produced near the coastal plains of Kaohsiung, thus appearing as a separation of intense rainfall. It was found that reducing the environmental moisture southwest of Taiwan doesn’t contribute to a noticeable impact on the above rainfall rate, while the rainfall intensity becomes significantly weakened as the environmental moisture southeast of Taiwan has been cut down by half. Finally, the terrain sensitivity experiments indicate that Taiwan terrain height plays an important role in intensity as well as distribution of the rainfall in Taiwan. The double rain bands are no longer existent and become united as the CMR height is reduced by 75%.
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