Indian Ocean Capacitor Effect on Indo–Western Pacific Climate during the Summer following El Niño
Indian Ocean Capacitor Effect on Indo–Western Pacific Climate during the Summer following El Niño
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DOI：
10.1175/2008jcli2544.1
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发表时间：
2009-02
影响因子：
4.9
通讯作者：
S. Xie;Kaiming Hu;J. Hafner;H. Tokinaga;Yan Du;G. Huang;T. Sampe
中科院分区：
文献类型：
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作者：
S. Xie;Kaiming Hu;J. Hafner;H. Tokinaga;Yan Du;G. Huang;T. Sampe
在春季厄尔尼诺现象在赤道太平洋消散后，显著的气候异常持续到整个夏季（6月至8月）。它们包括热带印度洋（TIO）海表温度（SST）变暖，热带对流层温度升高，副热带西北太平洋的异常反气旋，东亚梅雨增雨。这些挥之不去的厄尔尼诺效应在夏季的原因进行了调查使用的观测和大气环流模式（GCM）。本文的结果表明，TIO变暖的行为就像一个电容器锚定大气异常的印度西太平洋。它导致对流层温度升高，通过深层对流的绝热调整，向太平洋发出斜压开尔文波。在西北太平洋，这种赤道开尔文波引起东北风地面风异常，并在副热带辐散触发抑制对流和异常反气旋。大气环流模式的结果支持这种Kelvin波引起的Ekman发散机制。在TIO上空设定SST升高，模式模拟了赤道低压Kelvin波、西北太平洋副热带地区对流受抑制和反气旋异常。另一项实验进一步表明，北印度洋变暖对开尔文波和西北太平洋反气旋的影响最为重要，这一结果得到了观测的证实。这些结果对印度西太平洋夏季气候的可预测性具有重要意义：TIO变暖的空间分布和幅度，而不仅仅是前一个冬天是否有厄尔尼诺现象，影响印度西太平洋和东亚夏季气候异常。
Significant climate anomalies persist through the summer (June-August) after El Nino dissipates in spring over the equatorial Pacific. They include the tropical Indian Ocean (TIO) sea surface temperature (SST) warming, increased tropical tropospheric temperature, an anomalous anticyclone over the subtropical northwest Pacific, and increased mei-yu-baiu rainfall over East Asia. The cause of these lingering El Nino effects during summer is investigated using observations and an atmospheric general circulation model (GCM). The results herein indicate that the TIO warming acts like a capacitor anchoring atmospheric anomalies over the Indo-western Pacific Oceans. It causes tropospheric temperature to increase by a moist-adiabatic adjustment in deep convection, emanating a baroclinic Kelvin wave into the Pacific. In the northwest Pacific, this equatorial Kelvin wave induces northeasterly surface wind anomalies, and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone. The GCM results support this Kelvin wave-induced Ekman divergence mechanism. In response to a prescribed SST increase over the TIO, the model simulates the Kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest Pacific. An additional experiment further indicates that the north Indian Ocean warming is most important for the Kelvin wave and northwest Pacific anticyclone, a result corroborated by observations. These results have important implications for the predictability of Indo-western Pacific summer climate: the spatial distribution and magnitude of the TIO warming, rather than simply whether there is an El Nino in the preceding winter, affect summer climate anomalies over the Indo-western Pacific and East Asia.