Does vertical temperature gradient of the atmosphere matter for El Niño development?
Does vertical temperature gradient of the atmosphere matter for El Niño development?
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DOI：
10.1007/s00382-016-3149-9
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发表时间：
2017-03
期刊：
影响因子：
4.6
通讯作者：
Zeng‐Zhen Hu;Bohua Huang;Y. Tseng;Wanqiu Wang;Arun Kumar;Jieshun Zhu;B. Jha
中科院分区：
文献类型：
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作者：
Zeng‐Zhen Hu;Bohua Huang;Y. Tseng;Wanqiu Wang;Arun Kumar;Jieshun Zhu;B. Jha
本文研究了对流层大气沿着赤道的垂直温度梯度与厄尔尼诺-南方涛动（ENSO）的关系以及温度梯度长期变化的可能影响。这表明，当对流层下部的温度异常比对流层上部的温度异常相对较暖（较冷）时，大气不太（更）稳定，有利于厄尔尼诺（拉尼娜）事件的发展。1997-1998年和2014-2015年的厄尔尼诺/南方涛动事件就是这种关系的很好例子。它们始于1997年和2014年春季的类似海洋异常状态，但在1997-1998年发展为极端厄尔尼诺，在2014-2015年发展为边界厄尔尼诺。这可能是由于对流层垂直温度距平梯度演变的差异造成的。因此，除了大气对ENSO的显著响应外，大气内部过程对对流层温度垂直梯度的预处理也在一定程度上对ENSO的演变起着积极的影响作用。对流层上部比对流层下部变暖更明显的长期趋势导致对流层垂直温度梯度减小。此外，与对流层上层几乎同质的暖异常不同，对流层下层在1979-2014年期间沿赤道沿着表现出明显的区域性特征，即中太平洋和东太平洋的冷异常趋势与所谓的间断有关，而其东西两侧的暖异常也存在。太平洋对流层气温的这种垂直和纬向分布趋势与2000年以来中太平洋对流的抑制是一致的，意味着海气耦合的减弱。
In this work, we examine the connection of vertical temperature gradient of the tropospheric atmosphere along the equator with El Niño–Southern Oscillation (ENSO) and the possible impact of the long-term change of the gradient. It is suggested that when the temperature anomalies in the lower troposphere are relatively warmer (cooler) than in the upper troposphere, the atmosphere is less (more) stable and favors an El Niño (a La Niña) event to develop. ENSO evolutions in 1997–1998 and 2014–2015 events are good examples of this relationship. They started from similar ocean anomaly states in the springs of 1997 and 2014, but developed into an extreme El Niño in 1997–1998 and a borderline El Niño in 2014–2015. That may be partially due to differences in the evolutions of the vertical temperature anomaly gradient in troposphere. Thus, in addition to the significant atmospheric response to ENSO, the preconditioning of vertical gradient of the tropospheric temperature due to internal atmospheric processes to some extent may play an active role in affecting ENSO evolution. The long-term trend with more pronounced warming in the upper troposphere than in the lower troposphere causes a reduction in the vertical temperature gradient in the troposphere. Moreover, unlike almost homogenous warm anomalies in the upper troposphere, the lower troposphere shows remarkable regional features along the equator during 1979–2014, with cold anomaly trends over the central and eastern Pacific Ocean associated with the so-called hiatus and some warm anomalies on its two sides in the east and west. This vertical and zonal distribution of the air temperature trends in the troposphere over the Pacific Ocean is consistent with the convection suppression over the central Pacific since 2000, implying a weakening of atmosphere and ocean coupling.