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| 論文分類 | 碩士 |
|---|---|
| 學號 | 108626006 |
| 姓名 | 陳冠呈 Guan-Cheng Chen |
| 標題 | 1999~2018年期間南海沿岸淺水區對颱風登陸時強度變化之影響 Intensification of landfalling typhoons over the shallow South China coast during 1999~2018 |
| 指導教授 | 潘任飛 Iam-Fei Pun |
| 畢業日期 | 2022-01 |
| 附件檔案 | |
| 參考連結 | https://etd.lib.nycu.edu.tw/cgi-bin/gs32/ncugsweb.cgi?o=dncucdr&s=id=%22GC108626006%22.&searchmode=basic |
| 摘要 | 在颱風的生長過程中會從海洋汲取大量的能量，因此海洋對於颱風來說彷彿巨大的能源儲存庫，扮演著非常重要的角色。海表面溫度越高，海氣熱通量會越高，颱風所形成的強度也會越強。此外，颱風與海洋之間的交互關係不僅與海表面有關，海表面底下的溫度結構也至關重要。當颱風經過海洋時，會產生垂直混合作用，將深層較冰冷的海水帶至海洋表面，造成海表溫度下降，稱之為SST Cooling。SST Cooling是颱風本身的負回饋效應的過程。當SST Cooling越強，海表溫度會變得越低溫，海洋可能無法提供更多的能量，進而使颱風強度減弱。 本研究主要分析1999年至2018年在西北太平洋之中，通過南海沿岸的淺海區域並且在登陸前強度增強或是維持的颱風。並研究「淺海」是否為強度增強或維持的關鍵因素。經研究發現到，對於登陸之前強度「增強」的颱風組別來說，如果沒有淺海的存在，SST Cooling會增加142%、海氣熱通量會減少92%。另外，對於登陸之前強度「維持」的颱風組別來說，SST Cooling會增加192%、海氣熱通量會減少75%。這都顯示出了如果沒有淺海的存在，海表溫度冷卻會大幅地增加、海洋供給颱風的能量會大幅地降低。主要原因為颱風在登陸之前所經過的海洋表面之下的冷水較少，再加上深度會受淺海的限制，使海表面至海洋底部的溫度皆能夠維持高溫，導致整層的平均溫度非常溫暖。因此，颱風在登陸之前不管如何攪拌海水，SST Cooling會很微弱，從而使海氣熱通量提高。颱風本身的負回饋效應大幅地受到抑制，使颱風強度在登陸之前增強或維持。 【關鍵字 : 海表面溫度冷卻、颱風負回饋效應、淺海的影響】 The large amount of energy will be transferred from the ocean during the growth of typhoons. Therefore, the ocean is like a huge source of energy for typhoons and plays an important role. The higher sea surface temperature (SST), the higher air-sea enthalpy flux and the stronger the intensity of typhoons. Besides, the interaction between typhoons and ocean is not only related to the sea surface. The thermal structure under the sea surface is important as well. When typhoons pass over the ocean, it will produce the vertical mixing and bring the colder water at the deeper layer to the sea surface. Causing the sea surface temperature decrease which is called SST cooling. SST cooling is the negative feedback effect of typhoon itself. When SST cooling is stronger, the sea surface temperature will get colder. The ocean may not be able to provide more air-sea enthalpy flux, which may weaken the intensity of typhoons. This study mainly analyzes typhoons in the Western North Pacific during 1999 to 2018 that passed over the shallow South China coast and intensified or maintained their intensity before landfalling. And to discuss whether the “shallow water” is a crucial factor for intensification or maintenance. We found that for “Intensification” typhoons, if there is no shallow water, SST cooling will increase by 142% and the air-sea enthalpy flux will decrease by 92%. For “Maintenance” typhoons, SST cooling will increase by 192% and the air-sea enthalpy flux will decrease by 75%. It shows that if there is no shallow water, SST cooling will largely increase, and the air-sea enthalpy flux will largely reduce. The main reason is that there is less cold water under the sea surface where typhoons pass before making landfall. And the depth is limited by the shallow water. So the water temperature from the surface to the bottom could maintain high, resulting in a very warm average temperature of the entire layer. Therefore, no matter how typhoons mix the ocean, SST Cooling will be less. Causing the air-sea enthalpy flux increase. The negative feedback effect of typhoon itself will be largely suppressed, so the intensity of typhoons will intensify or maintain before making landfall. 【Keywords : SST Cooling, the negative feedback effect of typhoon itself, the impact of shallow water】 |
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