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標題: | 遠距颱風伴隨臺灣降雨事件之分析 A Study of the Typhoon Remote Rainfall in Taiwan |
作者: | Ching-Wei Wang 王鏡惟 |
指導教授: | 李清勝(Cheng-Shang Lee) 李清勝(Cheng-Shang Lee | cslee@ntu.edu.tw | ), |
關鍵字: | 颱風,遠距颱風降雨,沿海降雨,臺灣地形, typhoon,typhoon remote rainfall,coastal rainfall,Taiwan topography, |
出版年 : | 2022 |
學位: | 碩士 |
摘要: | 部分颱風在距離一地數百至上千公里遠時,雖未直接侵襲該地,該地卻伴隨有強降雨事件發生,稱之「遠距颱風降雨」。過去針對臺灣地區未與季風共伴的遠距颱風降雨個案進行的分析與模擬,結果顯示,臺灣皆位於顯著低壓帶中,低層暖濕空氣伴隨盛行風移入臺灣地區,使迎風面地區易產生強對流系統。亦即,臺灣地形與綜觀環境流場為造成顯著降雨的主要因素;而遠距颱風的存在,僅造成降雨區域的改變,與中緯度預前降雨(Predecessor Rain Events, PREs)的機制明顯不同。西行通過東海並造成臺灣西南部沿海降雨的遠距颱風個案屬於過去研究並未討論的類型,本研究之目的在針對該類個案進行資料診斷分析與數值模擬,討論其中之重要機制與遠距颱風在臺灣降雨事件中所扮演的角色。 針對典型個案(2012年海葵颱風)的分析結果顯示,強降雨期間,綜觀環境一般為對流不穩定,盛行之西南風受地形影響於西南部沿海產生減速輻合,有利對流的發生;水氣通量輻合亦集中於西南沿海,與強降雨區域一致。調整臺灣地形之敏感度實驗結果顯示,若移除臺灣地形,降雨大幅減少且其分佈出現顯著差異。本研究亦分析相似路徑的其他颱風個案,結果顯示當臺灣西南沿海有降雨時,颱風的位置均十分相近;但由於個案的綜觀流場有些許不同,因此降雨區域也不盡相同。比較未與季風共伴的各類遠距颱風降雨個案,結果顯示各類個案的降雨均由綜觀環境及臺灣地形主導。綜合以上分析、模擬及比較結果顯示,臺灣地區之遠距颱風降雨的發生機制,應與環境流場分佈及臺灣地形密切相關,而颱風似扮演較次要的角色。 Severe rainfall may occur in Taiwan when typhoons are located around Taiwan but within a certain distance, which is called “Typhoon Remote Rainfall.” Some studies analyzed and simulated a few typhoon remote rainfall cases in Taiwan which were not accompanied by monsoon. Results show that there was a large-scale cyclonic circulation surrounding Taiwan in these cases. Low level warm, humid air flowed into Taiwan-nearby area, making it a favorable environment on the windward side for convection to develop. The synoptic pattern and Taiwan topography are the key factors to typhoon remote rainfall in Taiwan. The existence of remote typhoons, however, seems to lead to the adjustment of rainfall area only. The mechanism of typhoon remote rainfall in Taiwan is apparently different from Predecessor Rain Events (PREs) which occurred in midlatitudes. Some typhoon remote rainfall cases occurred when remote typhoons went westward and passed through the East China Sea. These cases are not discussed before. The purpose of this study is to understand the important process leading to such type of typhoon remote rainfall in Taiwan through synoptic diagnosis and model simulations. Results of a typical case study (typhoon HAIKUI, 2012) show that the synoptic environment was convective unstable during the heavy rainfall hour on the southwestern coast of Taiwan. Speed convergence occurred when southwesterlies encountered Taiwan topography. There was also horizontal moisture flux convergence over the southwest coast of Taiwan, which was consistent with the area of the heavy rainfall. Sensitivity experiments were conducted to understand the effects of Taiwan topography. Results show that the amount and pattern of rainfall changed dramatically when Taiwan topography was removed in the simulation. There are several typhoons with tracks similar to that of typhoon HAIKUI. Results of the comparison between these cases show that the locations of typhoons were similar when rainfall occurred over southwestern Taiwan, but there are still some differences in rainfall area due to the different patterns of synoptic flow. The comparison between different types of typhoon remote rainfall cases which were not accompanied by monsoon was also conducted. Results show that the heavy rainfall in these cases is associated with the synoptic flow and the topography. To sum up, the synoptic-scale pattern and the Taiwan topography play key roles in such typhoon remote rainfall events, which are not accompanied by monsoon. The remote typhoon only plays a secondary role in changing the location of heavy rainfall. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/85931 |
DOI: | 10.6342/NTU202204183 |
全文授權: | 同意授權(全球公開) |
電子全文公開日期: | 2022-10-20 |
顯示於系所單位: | 大氣科學系 |
文件中的檔案:
檔案 | 大小 | 格式 | |
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U0001-2809202200550500.pdf | 20.6 MB | Adobe PDF | 檢視/開啟 |
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