Origin and predictability of the extreme negative NAO winter of 2009/10
Article first published online: 9 APR 2011
Copyright 2011 by the American Geophysical Union.
Geophysical Research Letters
Volume 38, Issue 7, April 2011
How to Cite
2011), Origin and predictability of the extreme negative NAO winter of 2009/10, Geophys. Res. Lett., 38, L07701, doi:10.1029/2011GL046786., , , and (
- Issue published online: 9 APR 2011
- Article first published online: 9 APR 2011
- Manuscript Accepted: 2 MAR 2011
- Manuscript Revised: 18 FEB 2011
- Manuscript Received: 17 JAN 2011
- snow cover;
- solar activity;
 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.