颱風通過臺灣於其東南角離岸生成冷舌之數值研究

Abstract

2009年莫拉克颱風通過臺灣，在臺灣東南角海域生成獨特的冷舌現象，為了釐清冷舌生成的主導因素，本研究使用區域海洋模式系統（ROMS），模擬2005年至2013年之17個颱風案例；與有限的現場觀測資料，進行系統性的分析，並對這17個通過台灣軌跡的颱風路徑進行研究探討。結果顯示，颱風的行進軌跡分布與冷舌生成之間有密切關聯。而後，在此研究，為了更加瞭解冷舌與軌跡之間的關係，我們進行三個理想化實驗，評估其他因素是否影響冷舌之生成，結果顯示，颱風強度與颱風移度速度皆會影響冷舌的溫降幅度：一般情況下，移動速度越慢，強度越強的颱風，冷舌造成的溫降幅度就越強。我們根據這些系統性的分析結果，能夠預估冷舌的生成，並且預防夏季時，冷舌受黑潮傳輸對沿途周遭之生態環境所造成的影響。With the passage of a westward impinging typhoon Morakot (2009) directly through Kuroshio and mid Taiwan, a distinct cool jet generated at the southeast corner off Taiwan and extended toward Kuroshio downstream region. In order to clarify the dominant factor infuencing cool jet, in this study, systematical analyses based on Regional Oceanic Modeling System (ROMS), and limited in-situ measurements with a focus on all tropical cyclones with similar tracks as Morakot from 2003 to 2013 were conducted to elucidate the generations of those cool jets. The results show that the generations of those cool jets are highly sensitive to moving tracks of individual typhoons. Subsequently, three suites of idealized experiments were conducted to provide a more comprehensive view on the contributions from other factors. It shows that including tropical cyclone intensities, translation speed also influence the magnitude of cool jet. Generally, the moving and intensity of typhoon is slower and stronger, the cool jet is stronger. Finally, outline of the impact region was sketched based on the systematic results. With those results, it becomes possible to prevent from cold shock generating in summer time triggered by those cool jets in response to typhoons westward impinging through Taiwan.