Role of the eastern subtropical North Pacific Ocean on the El Niño’s transition processes
Role of the eastern subtropical North Pacific Ocean on the El Niño’s transition processes
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DOI：
10.1007/s00382-020-05530-w
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发表时间：
2021-01
期刊：
影响因子：
4.6
通讯作者：
S. Yeh;H. Jo;S. Hyun;W. Cai;Y. Ham
中科院分区：
文献类型：
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作者：
S. Yeh;H. Jo;S. Hyun;W. Cai;Y. Ham
本文利用观测、多世纪模式模拟和大气环流模式(AGCM)实验，研究了厄尔尼诺在一年内发生的转换过程。一种是厄尔尼诺事件在次年冬季迅速转变为拉尼娜事件，另一种是缓慢衰变到近中性状态或持续的厄尔尼诺事件。虽然印度洋和大西洋都对厄尔尼诺的转换过程作出了贡献，但我们进一步发现，东副热带北太平洋的海面温度(SST)条件和与之相关的地面风异常在通过海-气耦合过程决定不同类型的厄尔尼诺转换过程中起着重要作用。特别是，由于海气耦合作用，早春副热带北太平洋中部的东北风异常有助于热带太平洋中部海洋热含量(OHC)异常的减少和东风异常的加强。这些异常导致在接下来的冬天转变为拉尼娜事件。反之，早春副热带北太平洋东部海温异常偏暖和东北风减弱，有利于次年冬季进入中性状态或持续发生厄尔尼诺事件。在一个多世纪的模型模拟中也发现了类似的转变过程。通过理想的大气环流模式试验，我们还发现厄尔尼诺高峰期副热带北太平洋东部海温异常可能导致厄尔尼诺爆发季节热带中太平洋地面风异常。这些结果为预测厄尔尼诺事件发生一年后的拉尼娜事件、中性态和厄尔尼诺事件的发生提供了潜在的前兆。
We examine the transition processes of El Niño occurring in 1 year after using observations, a multi-century model simulation and atmospheric general circulation model (AGCM) experiments. One type is characterized by a quick transition from an El Niño event into a La Niña event in the following winter, and the other type involves a slow decay to an almost neutral state or a continuous El Niño event. While both the Indian and the Atlantic Oceans contribute to the El Niño’s transition processes, we further find that sea surface temperature (SST) conditions in the eastern subtropical North Pacific and the associated surface wind anomalies play important roles in determining the different types of El Niño’s transition processes through atmosphere–ocean coupled processes. In particular, northeasterly wind anomalies in the central subtropical North Pacific during the early spring, which is in consequence of atmosphere–ocean coupled processes, contribute to decreasing ocean heat content (OHC) anomalies and strengthening easterly wind anomalies in the central tropical Pacific. These anomalies lead up to a transition into a La Niña event in the following winter. On the contrary, weakening of the northeasterly wind and warm SST anomalies in the eastern subtropical North Pacific during the early spring are conducive to a neutral state or a continuous El Niño event in the subsequent winter. Similar transition processes are also found in a multi-century model simulation. By conducting idealized AGCM experiments, we also show that the anomalous SST in the eastern subtropical North Pacific during El Niño peak season may induce surface wind anomalies in the central tropical Pacific during El Niño onset season. These results provide potential precursors for predicting the occurrence of a La Niña event, a neutral state and an El Niño event 1 year after the occurrence of an El Niño event.