臺灣博碩士論文加值系統

桔梗颱風（2013）為少數於臺灣鄰近地區形成的颱風，其形成過程與康芮颱風（2013）殘餘之中層氣旋式環流有關。康芮颱風於2013年8月28日向北移動至臺灣東部近海時，受強烈垂直風切影響，其低層與中層環流出現分離現象；低層環流持續往北移動，而中層環流則向西北移動通過中央山脈。此中層環流移至臺灣海峽北部後，於該處滯留了一至二天；之後桔梗颱風初始渦旋之低層環流在此地區形成。本研究之目的在探討上述中層環流對桔梗颱風形成過程之影響，及其中之重要機制。
本研究採用片段位渦反演方法，診斷中層氣旋式環流在準平衡條件下對低層風場的貢獻，並進行移除不同倍率中層環流之數值敏感度實驗。片段位渦反演結果顯示，在桔梗颱風初始渦旋之低層環流形成前，中層正位渦距平對低層正渦度有最大的貢獻。移除部分中層環流的敏感度實驗結果顯示，隨著移除倍率的增加，模擬的低層擾動強度有系統性減弱的現象，且伴隨中層環流區域的對流強度亦有減弱並延遲發生的現象。而在完全移除中層環流之模擬實驗中，皆無顯著對流系統發展，因此無低層擾動形成。綜合分析結果顯示，中層渦旋能提供適合對流發展的環境，促使桔梗颱風形成；因此，中層環流在桔梗颱風的形成過程中，扮演關鍵角色。

Tropical Storm Toraji (2013) is a rare case that formed near Taiwan and is involved with a mid-level cyclonic circulation which is a remnant of Tropical Storm Kong-Rey (2013). When Kong-Rey (2013) was moving northward to the offshore of the eastern Taiwan on Aug 28, 2013, its low- and mid-level cyclonic circulation decoupled due to the strong vertical wind shear. The low-level circulation kept moving northward, while the mid-level circulation moved west-northward and across the central mountain range of Taiwan. The mid-level circulation moved to the northern Taiwan Strait and had become stationary for 1 to 2 days. After then, the incipient vortex of Tropical Storm Toraji formed in the region. The major purpose of this study is to disuss the influence of the mid-level circulation on the formation of Tropical Strom Toraji and the mechanism.
The piecewise potential vorticity inversion (PPVI) method was applied to figure out the contribution of the mid-level cyclonic circulation to the low-level wind field under quasi-balanced condition. In addition, sensitivity numerical experiments designed to remove the mid-level circulation by different removing factors had also been conducted. The results of PPVI showed that the mid-level positive PV anomalies had the most contribution to the low-level positive vorticity before the formation of the low-level circulation of Toraji’s incipient vortex. Besides, the sensitivity experiments showed that when the removing factor was increased, there was a declining trend of the intensity of low-level perturbation, and the intensity of convection systems in the region of the mid-level circulation also became weaker and developed late. Moreover, the simulations whose the mid-level circulation was totally removed showed that no significant convection system developed, so that no low-level perturbation formed. The analyses showed that the mid-level circulation provided a favorable environment for convection and led to the formatio of Toraji. As a result, the mid-level circulation played a critical role in the formation of Toraji.

致謝 i
摘要 ii
Abstract iii
圖目錄 vi
第一章 前言 1
1.1 文獻回顧 1
1.2 研究動機與目的 5
第二章 資料來源、分析方法及實驗設計 6
2.1 資料來源與分析方法 6
2.2 實驗設計 8
第三章 臺灣海峽中北部片段位渦反演診斷分析 12
3.1 綜觀分析 12
3.2 位渦距平分布分析 14
3.3 各層位渦距平之反演結果比較與分析 15
3.4 小結 17
第四章 移除中層渦旋之桔梗颱風形成過程之模擬與分析 18
4.1 控制組實驗中之重要現象 18
4.2 實驗組實驗結果 20
4.3 各組實驗關鍵對流形成之差異與機制 24
4.4 各組實驗結果轉變點之討論 29
4.5 小結 31
第五章 討論與總結 32
參考文獻 35
圖 39
附錄一 78
附錄二 81

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