Stratospheric Communication of El Nino Teleconnections to European Winter
Stratospheric Communication of El Nino Teleconnections to European Winter
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DOI：
10.1175/2009jcli2717.1
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发表时间：
2009-08-01
影响因子：
4.9
通讯作者：
Scaife, A. A.
中科院分区：
文献类型：
--
作者：
Bell, C. J.;Gray, L. J.;Scaife, A. A.
使用具有良好解析平流层的中间大气环流模型，研究了平流层在欧洲冬季表面气候对厄尔尼诺-南方涛动海面温度强迫的响应中的作用。在厄尔尼诺条件下，模拟的对流层和平流层平均状态环流变化分别与观测到的冬末负北大西洋涛动和强烈减弱的极地涡旋的“典型”响应非常吻合。极地涡旋的变化受到整个冬季平流层突然变暖事件频率增加的调节。通过敏感性实验研究了这种平流层响应在热带太平洋-欧洲遥相关中的潜在作用，其中平流层的平均状态和变化性被降低。结果，观测到的平流层对厄尔尼诺的响应受到抑制，平均海平面压力响应无法与观测的时间和空间演变相似。结果表明，平流层在欧洲对厄尔尼诺的反应中发挥着积极作用。建议采用饱和机制，对于最强的厄尔尼诺事件，对流层强迫主导欧洲的响应。通过敏感性测试对此进行了检验，结果表明，在大厄尔尼诺现象的强迫下，欧洲的反应对平流层的代表性不敏感。
The stratospheric role in the European winter surface climate response to El Nino-Southern Oscillation sea surface temperature forcing is investigated using an intermediate general circulation model with a well-resolved stratosphere. Under El Nino conditions, both the modeled tropospheric and stratospheric mean-state circulation changes correspond well to the observed "canonical" responses of a late winter negative North Atlantic Oscillation and a strongly weakened polar vortex, respectively. The variability of the polar vortex is modulated by an increase in frequency of stratospheric sudden warming events throughout all winter months. The potential role of this stratospheric response in the tropical Pacific-European teleconnection is investigated by sensitivity experiments in which the mean state and variability of the stratosphere are degraded. As a result, the observed stratospheric response to El Nino is suppressed and the mean sea level pressure response fails to resemble the temporal and spatial evolution of the observations. The results suggest that the stratosphere plays an active role in the European response to El Nino. A saturation mechanism whereby for the strongest El Nino events tropospheric forcing dominates the European response is suggested. This is examined by means of a sensitivity test and it is shown that under large El Nino forcing the European response is insensitive to stratospheric representation.