- 學位論文
熱動力效率與海燕颱風(2013)快速增強之探討
Dynamic Efficiency of Heat and the Rapid Intensification of Typhoon Haiyan (2013)
摘要
海燕颱風(2013)經歷了一段快速增強(Rapid intensification, RI)的過程。根據聯合颱風警報中心(JTWC) 1分鐘平均最大風速的評估，從11月5日0000 UTC至11月6日 0000 UTC之1分鐘平均最大風速增強了30 m s^(-1)，相當於Hendricks et al. (2010) 所定義之RI門檻值19.5 m s^(-1) day^(-1)之約1.5倍。在SSMIS 91 GHz 衛星圖中發現到海燕颱風在RI期間，中心南側的對流逐漸內縮，眼牆建立並軸對稱化的過程。 此研究為了探討海燕颱風RI之過程，而藉由Hack and Schubert (1986) 所提出動力能量效率之概念進行診斷。此物理量能夠定量描述可用位能轉換成動能的能量轉換率，並以加熱為量度基準。 在Hack and Schubert (1986)的實驗設計中，給定理想的渦旋結構與總加熱量以探討其轉換效率；在此研究中，利用全物理雲解析模式CReSS (Cloud-Resolving Storm Simulator)模擬海燕颱風的RI過程，得到較真實的高解析渦旋結構，以診斷模式中海燕颱風在RI期間的動力轉換效率，並探討其結構分布以及隨時間的變化。 結果顯示，模擬的海燕颱風在RI過程中的強度變化同樣達到30 m s^(-1) day^(-1)，且亦有中心南側的對流內縮建立眼牆並對稱化之過程，與觀測相似。於模擬的海燕颱風動力轉換效率分析中，可以發現在其RI初期就擁有較高的動力轉換效率，顯示此時的渦旋結構可以很有效率地將對流的潛熱釋放轉換成動能，使系統劇烈地增強。
並列摘要
Typhoon Haiyan (2013) underwent an extreme rapid intensification (RI) process. According to the Joint Typhoon Warning Center (JTWC), one-minute maximum sustained wind speed increased 30 m s^(-1) from 0000 UTC Nov 5 to 0000 UTC Nov 6, which is about 1.5 times the RI threshold, 19.5 m s^(-1) day^(-1), defined by Hendricks et al. (2010). The SSMIS 91 GHz satellite map reveals the process that the convection on the south side of the eye contracted, and the eyewall was established and was axisymmetrized in RI period. In order to study the RI process of typhoon Haiyan, we apply dynamic efficiency of heat developed by Hack and Schubert (1986) to diagnose. Through this concept, we can examine the effect of heating on the energy conversion rate, converting total potential energy into total kinetic energy. Hack and Schubert (1986) used idealized vortex structure and ideal diabatic heating to examine the dynamic efficiency. However, in this study, we simulate the RI process of typhoon Haiyan by the Cloud-Resolving Storm Simulator (CReSS) and obtain the high-resolution structure of typhoon Haiyan, which are more realistic than idealized vortex structure, to examine the dynamic efficiency and its structural distribution and its changes over time. The results indicate that CReSS model can reproduce the intensity change rate, the contraction of the convection on the south side of the eye, and the establishment and axisymmetrization of the eyewall. The dynamic efficiency analysis suggests there is high efficiency in the early stage of RI, and the vortex structure at this time can efficiently convert the latent heat into kinetic energy, which rapidly enhances system intensity.