Annular modes and apparent eddy feedbacks in the Southern Hemisphere

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• 作者：Nicholas J. Byrne ; Theodore G. Shepherd ; Tim Woollings ; R. Alan Plumb
• 刊名：Geophysical Research Letters
• 出版年：2016
• 出版时间：28 April 2016
• 年：2016
• 卷：43
• 期：8
• 页码：3897-3902
• 全文大小：606.0KB
• ISSN：1944-8007

文摘

Lagged correlation analysis is often used to infer intraseasonal dynamical effects but is known to be affected by nonstationarity. We highlight a pronounced quasi 2 year peak in the anomalous zonal wind and eddy momentum flux convergence power spectra in the Southern Hemisphere, which is prima facie evidence for nonstationarity. We then investigate the consequences of this nonstationarity for the Southern Annular Mode and for eddy momentum flux convergence. We argue that positive lagged correlations previously attributed to the existence of an eddy feedback are more plausibly attributed to nonstationary interannual variability external to any potential feedback process in the midlatitude troposphere. The findings have implications for the diagnosis of feedbacks in both models and reanalysis data as well as for understanding the mechanisms underlying variations in the zonal wind.