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Annular modes and apparent eddy feedbacks in the Southern Hemisphere

Byrne, N. J., Shepherd, T. G., Woollings, T. and Plumb, R. A. (2016) Annular modes and apparent eddy feedbacks in the Southern Hemisphere. Geophysical Research Letters, 43 (8). pp. 3897-3902. ISSN 0094-8276

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To link to this item DOI: 10.1002/2016GL068851

Abstract/Summary

Lagged correlation analysis is often used to infer intraseasonal dynamical effects but is known to be affected by non-stationarity. We highlight a pronounced quasi-two-year peak in the anomalous zonal wind and eddy momentum flux convergence power spectra in the Southern Hemisphere, which is prima facie evidence for non-stationarity. We then investigate the consequences of this non-stationarity 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 non-stationary interannual variability external to any potential feedback process in the mid-latitude troposphere. The findings have implications for the diagnosis of feedbacks in both models and re-analysis data as well as for understanding the mechanisms underlying variations in the zonal wind.

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:63813
Publisher:American Geophysical Union

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