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姓名 洪于珺(Yu-chun Hung) 查詢紙本館藏 畢業系所 大氣物理研究所 論文名稱 颱風辛樂克(2008) WRF模擬及位渦反演之研究 相關論文 檔案 [Endnote RIS 格式]
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摘要(中) 本研究使用WRF 3.1版模擬2008年颱風辛樂克(Sinlaku)，在第一部份的研究中，檢驗加入Tropical Cyclone (TC) bogus scheme對模式初始場颱風強度的改善情況，並測試此方法中給定不同的風速參數值對颱風模擬的影響。模擬結果顯示，在此個案使用TC bogus能有效改善初始場颱風之結構與強度，以及模擬颱風之強度，但加入TC bogus後反而使颱風移速過快且路徑西偏。此外，還測試了兩組不同的domain 1對颱風路徑模擬的敏感度，結果顯示，不同的domain設定對初始場颱風強度及模擬之路徑、強度等皆有很大的影響。
研究的第二部分則延續前人之研究，使用Wang and Zhang (2003)所發展之包含水氣影響的位渦反演法、準平衡ω方程，以及Kieu (2005)所提出的片段位渦反演方法分析模擬颱風之流場，希望藉此瞭解颱風內部結構。位渦反演結果顯示此方法可反演大部分颱風之流場，唯在上層外流、及下層內流區差異較大，高層差異與反演時所做的假設有關，而底層差異則是摩擦力，以及反演時將資料差分至虛高座標而導致誤差，這些差異結果顯示此反演法仍有部分問題需要思考並改善。
將反演的平衡場進一步以準平衡ω方程估計垂直速度，發現ω方程會低估垂直速度量值，但整體結構如下層內流、上層外流等輻合輻散的結構皆良好的被估計出來，這表示颱風流場大部分是準平衡流場。接著將ω方程的各項貢獻分別做討論，發現潛熱釋放是造成颱風眼牆上升運動、眼內下沈運動的主要原因；而摩擦力作用的貢獻則在邊界層下的內流，並類似Ekman pumping的作用使垂直速度能伸展至高度10 km左右，抵銷部分潛熱所造成的下沈運動；乾動力過程則是颱風渦旋與環境水平風之垂直風切交互作用所造成，並可能與颱風流場的不對稱分佈有關。
將流場以高度10公里分為上層外流區及下層區做片段位渦反演，發現壓力擾動的反演結果顯示，上片段及下片段都於底層產生較強的壓力擾動；將潛熱作用分成兩個片段，則上片段的潛熱作用主要影響上對流層的垂直運動、下片段則對應下對流層；乾動力過程則不論是上片段或下片段都會產生一個深厚的順時鐘環流場。
摘要(英) This study uses Weather Research and Forecasting Model (WRF) version 3.1 to simulate Typhoon Sinlaku (2008). The first part of this study is to examine how Tropical Cyclone (TC) bogus scheme modifies the vortex intensity of the first guess field, and try to understand the impact on simulation for different vmax_ratio values used in the TC bogus scheme. The results show that application of the TC bogus scheme can improve the vortex structure and intensity in the first guess field, and can also improve the simulated intensity, but lead to rapid movement and westward deviation in track. It was also found that the track and intensity of the typhoon is somewhat sensitive to different model domains.
The second part applies the potential vorticity (PV) inversion and quasi-balanced ω equation to analyze the simulated typhoon for understanding of the structure of the vortex core. The results show that most characteristics of typhoon structures can be successfully inverted, but exhibiting larger differences at high-level outflow and low-level inflow with the boundary layer. Differences may result at high-level from the assumption of inversion system and at low-level due to the friction. Transferring the data from the model height to the pseudo-height may also introduce inversion errors, especially, for the intense typhoon with a central sea-level pressure as low as 930 mb.
Using quasi-balanced ω equation to calculate the vertical motion induced by the balanced flow, we find that the ω equation tends to underestimate the magnitude of the vertical motion, but the convergence and divergence associated with the lower-level inflow and upper-level outflow can be reasonably derived. Contributions to the vertical motion in the ω equation indicate that latent heating dominates the updraft in the eyewall and the downdraft in the eye. The vertical motion can reach to 10 km, as induced by the friction in the low-level inflow like Ekman pumping. Dry dynamic process is in response to the interaction between the typhoon vortex and the vertical shear of horizontal wind, and may be attributed to the formation of the asymmetric typhoon vortex.
Results from piecewise PV inversion in dry dynamic process indicate that the PV pieces above and below 10 km height both can induce perturbation pressure down to the lower boundary, and produce a deep clockwise vertical circulation. Pieced latent heating at upper and lower levels produces the dominant vertical motion at upper and lower levels, respectively.
關鍵字(中) ★ 颱風
★ 片段位渦反演
★ 準平衡ω方程
★ 位渦反演關鍵字(英) ★ typhoon
★ piecewise potential vorticity inversion
★ quasi-balanced ω equation
★ potential vorticity Inversion論文目次 中文摘要 ···································································································· I
英文摘要 ··································································································· II
致謝 ········································································································ IV
目錄 ········································································································· V
圖表說明 ································································································· VII
符號說明 ································································································ XIII
第一章 緒論 ························································································ 1
1-1 前言 ························································································ 1
1-2 前人研究 ·················································································· 1
1-3 研究動機及目的 ········································································· 3
第二章 位渦反演研究方法 ······································································ 4
2-1 位渦反演方程 ············································································ 4
2-2 準平衡ω 方程 ··········································································· 8
2-3 片段位渦反演 ············································································ 9
第三章 個案簡介及實驗設計 ································································· 13
3-1 WRF 模式介紹 ········································································· 13
3-2 WRF TC bogus 介紹 ·································································· 13
3-3 模式設定 ················································································ 15
3-4 實驗設計 ················································································ 15
第四章 模擬結果 ················································································ 17
4-1 初始場實驗 ············································································· 17
4-2 個案選取 ················································································ 19
第五章 位渦反演分析 ·········································································· 21
5-1 平衡流場分析 ·········································································· 21
VI
5-2 準平衡流場分析 ······································································· 22
5-3 片段位渦反演分析 ···································································· 24
第六章 總結及未來展望 ······································································· 28
參考文獻 ·································································································· 31
附錄一 ····································································································· 34
附錄二 ····································································································· 35
附錄三 ····································································································· 36
附錄四 ····································································································· 37
附表與附圖 ······························································································· 38
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指導教授 黃清勇(Ching-yuang Huang) 審核日期 2010-7-22 推文 plurk
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