颱風路徑的低頻變化常受到北太平洋副熱帶高壓與夏季季風所影響的導引氣流而改變。然而，研究證據顯示黑潮對大氣環流也存在強烈的影響。我們的研究顯示自1980年以來，日本東部外海黑潮延伸流區域的海表面溫度鋒面在緯向上的擺盪與在六至十月登陸於東亞區域的颱風頻率有高達70%的顯著相關性[第一年研究所發表的期刊: Huang, S-M and L.-Y. Oey, 2018: Land-falling typhoons are controlled by the meridional oscillation of the Kuroshio Extension. Climate Dyn., 50(320), 1-13. https://doi.org/10.1007/s00382-018-4295-z]。透過觀測資料和理想化數值模式，我們證明當海表面溫度鋒面往極區(赤道)移動時，黑潮南邊的海表面溫度梯度與對流層的西風將會減弱(增強)，驅使更多颱風轉向(遠離)東亞大陸。我們的研究結果也顯示海表面溫度梯度與西風的減弱趨勢，似乎與前人研究的全球暖化而導致的黑潮北偏有著密不可分的關係。這也顯示在將來會有更多的颱風登陸東亞大陸地區。在第2年，我們尋求研究資金來繼續支持這項研究，但我們將著重於數值模式的模擬實驗，以支持我們在觀測分析上黑潮與颱風的關係，期望能更理解黑潮和颱風路徑之間動力的耦合反應過程。 ;Low-frequency variations of typhoon paths are often attributed to changes in the North Pacific subtropical high and monsoon through influences on the steering wind. Evidence indicates however a strong imprint of the Kuroshio on the atmosphere. Year-1 research has resulted in a paper: Huang, S-M and L.-Y. Oey, 2018: Land-falling typhoons are controlled by the meridional oscillation of the Kuroshio Extension. Climate Dyn., 50(320), 1-13. https://doi.org/10.1007/s00382-018-4295-z. There we show that the meridional oscillation of sea surface temperature (SST) front over the Kuroshio Extension east of Japan significantly correlates with the frequency of land-falling typhoons along East Asia from June to October, accounting for 70% of the low-frequency variance since 1980. We used observations and an idealized model to show that when the SST front shifts poleward (equatorward), SST gradient south of the current and westerly tropospheric wind weaken (strengthen), steering more typhoons to veer toward (away from) the East Asian continent. Our analysis also shows that long-term weakening of SST gradient and westerly wind appears to be concomitant with poleward shifting of the Kuroshio, attributed to global warming in some studies, and suggests the potential for more land-falling typhoons in East Asia in the coming decades. In year 2, we request funding to continue our research, but instead of observational analysis and analytical modeling, we propose to focus on numerical modeling to support the observational analysis result and to better understand the coupled dynamical response between the Kuroshio and typhoon paths.
