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• Main Authors: Yi-Ting Yang, 楊宜庭
• Other Authors: Gin-Rong Liu
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/74963124918191378788

碩士 === 國立中央大學 === 大氣物理研究所 === 103 === Typhoons are one of the most disastrous weather systems and frequently bring strong winds and heavy rains to Taiwan in summers. And some typhoons, which tracks in Type-I and Type-II track categories, passed westward around northern Taiwan region often cause the southwesterly flow from South China Sea (SCS) into Taiwan. Then the water vapor through the terrain uplifting, causing heavy rains and severe disasters in central and southern Taiwan regions. In this study, the aim is to investigate the southwesterly flow effect on typhoon rainfall patterns. Mainly the NCEP FNL Analysis data and GSMAP data are used to analyze Type-I and Type-II typhoon cases during 2000-2014. The result shows that the SCS monsoons modulate the relationship with typhoons and southwesterly flow. For instance, the active monsoons provide evidently favorable conditions for prolonging heavy rainfall while the typhoons passed. There are compact isobaric lines extending from the east of typhoon centers toward the southwest when the typhoons to the northward, and enhance the southwesterly flow in SCS. Under such environmental conditions, rich moisture is thus transported northeastward by the strong southwesterly flow, resulting in heavy rainfall in southern and central Taiwan. The study also delineates the rainfall distributions with the Improved TRaP (I-TRaP) when Type-I and Type-II typhoons around Taiwan. By comparing with gauge rainfall, the patterns show that I-TRaP underestimates rainfall amounts in southern and central Taiwan. Therefore, the quantitative precipitation forecast (QPF) models must further consider that the westward extension of the Pacific high pressures, wind fields, and water vapors in South China Sea to obtain more accurate rainfall potential over Taiwan.