Quasi-stationarity of centennial Northern Hemisphere midlatitude winter storm tracks.

The winter storm activity on the Northern Hemisphere during the last one thousand years in a global climate simulation was analyzed by determining all midlatitude storms and their tracks, then consecutively clustering them for hundred years' segments. Storm track clusters with longest lifetime and largest deepening rates are found over the oceans. The numbers of extratropical winter storms exhibit notable yearly variability but hardly any variability on centennial time scales. The clusters of these storm tracks also show only small differences between the centuries. The numbers of members in neighboring oceanic clusters are negatively correlated. A linear relationship was found between the numbers of members per storm track clusters over the Pacific or Atlantic Ocean and seasonal mean atmospheric circulation patterns by a canonical correlation analysis. [ABSTRACT FROM AUTHOR]