Solar influence on the spatial structure of the NAO during the winter 1900-1999

The solar influence on the North Atlantic Oscillation (NAO), reported in a previous study based on 39 years of data, was confirmed by using 100 years of historical data. During the low solar activity winters, the NAO signal in the sea level pressure is confined in the Atlantic sector, while, during the high solar activity winters, NAO-related anomalies extend over the northern hemisphere, in particular over the polar region and Eurasian continent. It was also found that the solar influence on the NAO originates from the Eurasian continent in early winter. In addition, two prolonged periods of high NAO index in the early and late 1900s showed spatial structures that were quite different and similar to those that occur during the low and high solar activity winters, respectively.