Wu and Cheng (1999)使用ECMWF/TOGA (European Center for Medium-Range Weather Forecasts / Tropical Ocean Global Atmosphere)分析資料研究颱風Flo(1990)的增強機制，結果顯示，包括增強的外流、增加的EFC ( eddy flux convergence of relative angular momentum )、低垂直風切(在風速增加率最大時，垂直風切約3 m/s)及暖洋面溫度(約27.5-27.8℃) ，皆為其迅速增強的有利因素。但定量上，這些因子如何交互影響，則仍無清楚的瞭解。此外，因芙蘿(Flo) 颱風的生成、發展及迅速增強皆發生於海洋，且有突然轉向的情況發生，因此亦被選為COMPARE (Comparison Of Mesoscale Prediction And Research Experiment) 計畫之測試個案。綜合上述，本研究選擇芙蘿颱風做為我們進行MM5（Fifth-generation Penn. State/NCAR Mesoscale Model）數值模擬之研究個案，初期一方面探討不同初始資料及初始化過程對模擬結果的影響，一方面則希望未來能夠與Wu and Cheng (1999)之分析結果比對，並利用模式高解析度模擬的特色進行颱風結構的詳細分析，以及經由控制實驗瞭解影響颱風強度演變的主要物理機制。
本研究以美國國家大氣科學研究中心與賓州大學合作發展的第五代中尺度靜力/非靜力模式MM5為模擬工具，模擬時採用不同來源的初始資料，包括JMA (Japan Meteorological Agency) 、NCEP (National Centers for Environmental Prediction) 及ECMWF/TOGA 的網格分析資料，但由於全球分析資料所解析的颱風範圍過大且強度太弱，須使用初始化方法植入渦旋。在此採用不同初始化方法，包括: GFDL (Geophysical Fluid Dynamics Laboratory) 颱風模式初始化方法 (Kurihara et al., 1995) 、Kuo植入方法 (Kuo et al., 1997) ，前者的優點在於定義較佳的環境場，後者的優點在於由結構簡單的渦旋經預先模擬而產生與模式動力一致的渦旋。 本研究結合前兩者優點而發展一系列新方法，針對不同資料、不同初始化方法及不同初始時間做模擬測試，以瞭解這些不確定因素對模擬結果的影響。
模擬結果在路徑方面，於不同初始資料及初始化方法所得之模擬結果有明顯的差異性存在，其中採用不同初始資料(JMA與ECMWF/TOGA) ，因模擬時對太平洋副高的趨勢掌握不同，故導致對Flo颱風路徑的模擬有較大的差異。而使用相同初始資料(ECMWF/TOGA)並採用不同的初始化方法，因初始時間採用不同的渦旋植入過程，於颱風中心附近流場造成改變，模擬的路徑亦有相當程度的差別存在。大部分的模擬結果顯示，因事先已濾除分析場中之不正確颱風訊息，故以結合渦旋與經濾除颱風分量的環境場之模擬結果較佳。又所植入渦旋必須經由預先模擬過程而產生，否則開始模擬時會因渦旋結構與模式動力不一致而需一段調整期，導致模擬結果不佳。有關不同初始化過程造成不同模擬結果之原因，我們未來將使用片段位渦反求(Wu and Emanuel, 1995)方法進行量化之探討。
至於強度模擬方面，雖然模擬實驗可以掌握高層TUTT(tropical upper tropospheric trough)接近Flo颱風的過程，並與Wu and Cheng (1999)的分析結果相似。但是各模擬實驗皆無法反映Flo颱風迅速增強的情況，此結果凸顯出現階段模式掌握颱風強度演變所面臨的難題。
研究結果顯示，模擬結果對於不同初始資料及初始化方法有相當程度的敏感性，故模擬時需採用適當的初始化方法，才能得到合理的初始場，在此以初始化方法的改進做為日後繼續研究的基礎。至於造成模擬結果不佳可能的原因，包括初始資料是否掌握正確訊息、初始化作用是否適當、解析度的設定是否可解析颱風結構，亦或是模式本身物理過程所導致，都是值得未來更深入討論的問題。此外，於模擬時加入四維資料同化過程以及納入海洋回饋機制，更是將來值得探討的重點，如能發展一大氣-海洋偶合之颱風模式，對於颱風強度模擬的掌握可能有正面的影響(Ginis and Shen, 1999)。

摘要 Ⅰ
致謝 Ⅲ
目錄 Ⅳ
圖表說明 Ⅵ
第一章 前言 1
1.1 研究背景 1
1.1.1 MM5模擬回顧 3
1.1.2 超級颱風芙蘿(Flo)研究回顧 5
1.1.3 初始化方法研究回顧 7
1.1.3.1 Kuo 渦旋植入方法回顧 7
1.1.3.2 GFDL颱風模式初始化方法回顧 8
1.2 研究動機與目的 11
第二章 實驗設計 13
2.1 MM5模式簡介 13
2.1.1 動力及物理過程之處理 16
2.2 模式設定 18
2.3 模擬個案:超級颱風芙蘿(Flo)簡介 18
2.4 初始資料與初始化方法 19
第三章 模擬結果 24
3.1 渦旋植入結果的探討 24
3.1.1 海平面氣壓之比較 24
3.1.2 位渦垂直結構之比較 24
3.1.3 緯向_垂直速度垂直結構之比較 25
3.1.4 位溫垂直結構之比較 25
3.1.5 相對濕度垂直結構之比較 25
3.2 路徑 26
3.3 強度 28
3.4 垂直結構 29
3.4.1 位渦與緯向-垂直(u-w)風場之垂直剖面分布 29
3.4.2 位溫之垂直剖面分布 30
3.5 擴大邊界範圍模擬測試 31
3.5.1 實驗EW2_14擴大邊界範圍模擬測試 31
3.5.2 實驗J擴大邊界範圍模擬測試 32
第四章 結果分析與討論 33
4.1 路徑模擬結果討論33
4.1.1 實驗J與實驗EW2_14之500 mb 高度場分析 33
4.1.2 實驗J濾除颱風之環境場模擬測試 34
4.1.3 實驗EK_14與實驗EW2_14之駛流分析 35
4.2 高層355K的位渦與風場分析 37
4.3 分析結果討論 39
第五章 結語42
附錄一、Kurihara et al. (1995) 初始化方法簡介 45
附錄二、Kuo渦旋植入方法 49
附錄三、Kurihara et al. (1995)分離基本場與擾動場之平滑運算子(smoothing operator ) 54
附錄四、Kurihara et al. (1995)選定濾除範圍初始半徑之決定方法 55
附錄五、Kurihara et al. (1995)建構非颱風分量最佳內插法之應用 56
參考文獻 58
附圖 65

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