南太平洋年代際變化與熱帶大西洋間的關聯性

Abstract

Hsu and Chen (2011)發現西太平洋沿岸降雨的年代際變異與西南太平洋的海溫變化有關，並將此海溫結構命名為SPDO。將SPDO指數和全球海溫進行相關分析所得的結果，高相關的區域除了西南太平洋之外，熱帶大西洋亦有不錯的相關性，且在時間序列上，1975-1994年熱帶大西洋領先西南太平洋大約一年的時間。熱帶大西洋與SPDO時間序列上的延遲關係，是否意味著熱帶大西洋會透過類似大氣橋(Alexander 1992)的過程影響到西南太平洋?因此，本研究透過延遲迴歸的分析方法並使用模試驗證，以了解熱帶大西洋及西南太平洋之間是否存在關聯性，以及西南太平洋海溫年代際變異的成因。 綜合觀測資料分析及耦合模式模擬的結果，熱帶大西洋的暖海溫所造成的低層輻合，引發垂直環流在南半球120oW附近地區下沉，透過西南太平洋地區的海氣交互作用，在西南太平洋形成反氣旋式的環流場。觀測分析的結果，西南太平洋的反氣旋透過大氣潛熱通量及海洋Ekman pumping的作用，可使西南太平洋海溫增暖，逐漸形成SPDO的海溫結構。由此可知，熱帶大西洋及西南太平洋之間確實存在海氣交互作用的關聯性。

Hsu and Chen (2011) suggested that the decadal rainfall variability along the Western Pacific coast during July-October was found associated with the SST variability in the Western South Pacific, which is called the SPDO. The SPDO index is highly correlated with SST not only in Western South Pacific but also in other ocean basins such as the tropical Atlantic. Tropical Atlantic was about one year ahead of Western South Pacific in 1975-1994. Does “tropical Atlantic leading Western South Pacific” imply that tropical Atlantic will impact Western South Pacific through a process similar to Atmosphere Bridge? This study applied the regression analysis and verified with couple model, to understand the relationship between tropical Atlantic and Western South Pacific, and the reason can lead to the SST decadal variability in Western South Pacific. Combine the results of observation data analysis and model simulation. The low-level convergence anomaly occurred over the positive SSTA in tropic Atlantic and divergence anomaly occurred at about 120oW in Southern Hemisphere through an east-west vertically overturning circulation, and then the air-sea interaction caused anticyclone in the Western South Pacific. Concluding remarks from observation data analysis: The anticyclone in the Western South Pacific caused the Western South Pacific warm through the joint process of latent heat flux and ocean Ekman pumping. Therefore, the Western South Pacific was connected to the tropical Atlantic by atmospheric-ocean coupling process in these two regions.