Asymmetry and nonlinearity of the influence of ENSO on the northern winter stratosphere: 1. Observations

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• 作者：Jian Rao ; Rongcai Ren
• 刊名：Journal of Geophysical Research: Atmospheres
• 出版年：2016
• 出版时间：16 August 2016
• 年：2016
• 卷：121
• 期：15
• 页码：9000-9016
• 全文大小：9.8MB
• ISSN：2169-8996

文摘

The El Niño–Southern Oscillation (ENSO) has significant effects on the extratropical stratosphere. This study explores the nonlinearity and the asymmetry of these influences by distinguishing the different effects of four types of ENSO: “moderate El Niño,” “strong El Niño,” “moderate La Niña,” and “strong La Niña.” It is revealed that the moderate El Niño and the strong La Niña are much more efficient than the strong El Niño and the moderate La Niña, respectively, in modulating the northern winter stratospheric variability, resulting in significant nonlinearity and asymmetry. The tropical rainfall anomalies induced by a moderate El Niño or a strong La Niña are centered over the central equatorial Pacific region near the dateline, while the convection responses to a strong El Niño or a moderate La Niña are centered farther eastward. Accordingly, the anomalous Pacific-North America wave train pattern is modulated by ENSO in a nonlinear and asymmetric way, which leads to the large nonlinear and asymmetric components of the vertical Eliassen-Palm (E-P) flux responses to ENSO. The increase of planetary wave activity in the extratropical stratosphere in moderate El Niño winters is thus greater than in strong El Niño winters, whereas a strong La Niña gives a larger decrease in propagation than a moderate La Niña. The relatively strong (weak) E-P flux responses to moderate (strong), El Niño and strong (moderate) La Niña explains the remarkable nonlinearity and asymmetry in the response of the extratropical stratosphere to ENSO.