North-Atlantic surface winds examined as the source of winter warming in Europe

[1] Trajectories traced backward from western Europe point to the warm southwestern North Atlantic as the source region of the warm maritime air brought into Europe by low-level southwesterlies. Over the eastern North Atlantic, patterns of ocean-surface winds in late winter changed during the second half of the 20th century, and the southwesterly direction became even more predominant. In January-to-March, the strength of southwesterlies in this region and in source region increased significantly in the years 1948-1995, and is likely to account for a large part of the observed warming in Europe during this period. For 1996-2001, however, this trend in southwesterlies appears broken, consistent with a downturn of the winter warming reported from central Europe after 1995. Monthly indexes of North Atlantic Oscillation, NAO, show a similar pattern, rising till 1995 and a downturn for the 1996-2002 winters and early spring, indicating that this climate oscillation is associated with the NAO.