Eastward shift of the Pacific/North American pattern on an interdecadal time scale and an associated synoptic eddy feedback

Abstract

In this study, we investigate the interdecadal changes in the Pacific/North American (PNA) pattern during the winter season (NovemberFebruary) that accompanies the global-scale climate shift in the late 1970s. In the Empirical Orthogonal Function (EOF) analysis, the PNA pattern shows three distinctive features during the period of 19832002 in contrast with that of the previous decades (19591977): the extension of the central North Pacific cell into the Gulf of Alaska, the eastward shift of the action centre of the Canadian cell, and weakening of the North America cell. Pacific/North American structural changes are closely related to the southeastward shift of the storm track that causes the vigorous synoptic eddy feedback region to move farther east. Eddy activity feeds the cyclonic flow at the eastern part of conventional central North Pacific cell, following the pattern change of storm track. Copyright (c) 2011 Royal Meteorological Society