副熱帶東北太平洋海溫年際及年代際變化以及其對亞洲-太平洋之影響

Abstract

觀測發現，副熱帶東北太平洋的暖海溫從2013年開始出現持續增暖的現象，近期研究發現此暖海溫對短期天氣或長期氣候變異颱風都有顯著的影響。然而相較於赤道東太平洋海溫, 有關副熱帶東北太平洋海溫的時空特徵之相關研究仍相當有限. 本研究主要探討副熱帶東北太平洋的特徵, 增暖的物理機制, 以及對天氣與氣候的可能影響 分析顯示，此區域之海溫變異與太平洋經向模態密切相關。除此之外，亦受到暖化趨勢的影響（約貢獻15%之海溫變異）。小波分析進一步發現此區域海溫包含了年際及年代際變化。在年際尺度，副熱帶東北太平洋海溫增暖同時，赤道太平洋亦同時有一類似聖嬰結構之海溫增暖現象。而在年代際尺度，太平洋年代際震盪、北太平洋環流震盪以及大西洋多重年代際震盪對此區域海溫變化皆有顯著的影響。 海洋混合層熱量收支得知，此海溫近期之增暖，主要透過風－蒸發－海溫(wind－evaporation－SST, WES) 之正回饋機制。除此之外，本研究也藉由兩個個案，討論此海溫對聖嬰現象以及西北太平洋颱風活動之影響。

The subtropical Eastern North Pacific (SENP) sea surface temperature (SST) is persistent warming from 2013. Notably, the impactof the SENP SST on weather and climate are also significant and demonstrated in several recent studies. Compare to the equatorial eastern Pacific SST, the characteristics of SENP SST are less discussed. In this study, we aired to diagnose the characteristics, warming mechanism, and possible impact of SENP SST. It reveals that the SENP SST is associated with Pacific meridional mode (PMM) and global warming. The warming trend contributes approximately 15% to the variability of SENP SST. Wavelet analysis further shows that SENP SST exhibits the interannual and interdecadal variations. The regression analysis shows that SENP and ENSO-like (El Niño–Southern oscillation) SST warm simultaneously in the interannual time scale. The Pacific decadal oscillation (PDO), North Pacific gyre oscillation (NPGO), Atlantic multi-decadal oscillation (AMO) have an impact on SENP SST variation in the interdecadal time scale. The mixed layer heat budget analysis suggested that the SENP SST is warming through wind–evaporation–SST mechanism. Furthermore, the impact of SENP SST on ENSO and tropical cyclone (TC) activity are also showed in the two case studies, which hinders the development of 2014 El Niño and enhances the 2016 TC activity in western North Pacific.