The regime shift in the 1960s and associated atmospheric change over the southern Indian Ocean
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摘要: 本文基于海气再分析和模式资料,研究了近60年来南印度洋的海表面温度的变化特征。结果表明,南印度洋在上世纪60年代期间的年代际转变与70年代之后的持续增暖在数值上有相同的量级,而关于前者的研究尚不充分。分析结果表明南印度洋的年代际转变伴随着天气要素变化如西风带的减弱。其内在动力机制为当西风减弱时,西风带与信风带之间的反气旋环流则随之减弱,进而冷却海表面温度。值得注意的是,60年代的年代际转变不仅发生在南印度洋,也发生在整个南半球,体现在副热带低压和整个高纬度西风带的变化,这种南半球大规模的激变与南极环状模的调整密切相关。Abstract: The change of sea surface temperature (SST) in the southern Indian Ocean (SIO) during the recent six decades has been analyzed based on oceanic reanalysis and model, as well as atmospheric data. The results show that a thermal regime shift in SIO during the 1960s, which is not caught enough attentions, has been of equal magnitude to the linear warming since 1970. Empirical Orthogonal Function (EOF) analyses reveal that a thermal shift is combined with atmospheric changes such as the weakening of westerly during the period of 1960-1967. Inner dynamic connections can be defined that when the westerly winds turn weak, the anticyclonic wind circulation between westerly winds and the trade winds decreases, which further reduces the SST to a negative peak in this period. It is noted that the shifts in the 1960s are also evident for Southern Hemisphere. For example, subtropical high and the entire westerly winds belt at high latitudes both change dramatically in the 1960s. This large-scaled process maybe link to the change of southern annular mode (SAM).
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