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Origin and predictability of the extreme negative NAO winter of 2009/10
Author(s) -
Jung T.,
Vitart F.,
Ferranti L.,
Morcrette J.J.
Publication year - 2011
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl046786
Subject(s) - predictability , climatology , north atlantic oscillation , polar vortex , environmental science , proxy (statistics) , sea surface temperature , anomaly (physics) , atmospheric circulation , snow , atmospheric sciences , stratosphere , geology , physics , condensed matter physics , quantum mechanics , machine learning , geomorphology , computer science
The winter of 2009/2010 was one of the most negative winters of the North Atlantic Oscillation (NAO) during the last 150 years. While most operational extended‐range forecasting systems had difficulties in predicting the onset of the negative NAO phase, once established, extended‐range forecasts were relatively skilful in predicting its persistence. Here, the origin and predictability of the unusual winter of 2009/10 are explored through numerical experimentation with the ECMWF Monthly forecasting system. More specifically, the role of anomalies in sea surface temperature (SST) and sea ice, the tropical atmospheric circulation, the stratospheric polar vortex, solar insolation and near surface temperature (proxy for snow cover) are examined. None of these anomalies is capable of producing the observed NAO anomaly, especially in terms of its magnitude. The results of this study support the hypothesis that internal atmospheric dynamical processes were responsible for the onset and persistence of the negative NAO phase during the 2009/10 winter.

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