Northern Hemisphere storm tracks and teleconnection patterns in primitive equation and quasigeostrophic models

Abstract

January 1979 was a period of frequent and severe storm activity in the Northern Hemisphere and a time of transition from high-latitude blocking over northwestern Canada and the Beaufort Sea area to persistent and large-scale blocking in the North Atlantic region. It is found that the inclusion of a horizontally varying static stability and nongeostrophic effects influence the structure of the cyclogenesis modes and lead to significant changes in the geographical locations of some of the prefered regions of cyclogenesis in situations of large-scale anomalous flow, such as occurred during January 1979. It is shown that this result can be understood from a consideration of Phillips' criterion for instability generalized to primitive equation and quasigeostrophic models in spherical geometry. In contrast, for more normal climatological flows there is a close correspondence between primitive equation and quasigeostrophic dominant storm track modes, instability criteria, and observations. We have found few differences in the structures of the larger-scale onset-of-blocking, intermediate, and mature anomaly modes that result from the primitive equation and quasigeostrophic instability calculations. -from Authors