Persistent anomalies of the extratropical Northern Hemisphere wintertime circulation: structure.

Abstract

The present study identifies the typical structures of persistent anomalies, focusing on whether persistent anomalies that occur in certain key regions (the central North Pacific (PAC), the eastern North Atlantic (ATL) and the northern Soviet Union (NSU)) are related to recurrent large-scale flow patterns. For each region, detailed comparisons are provided of the flow patterns associated with persistent positive and negative anomaly cases, and with the patterns obtained in other observational and theoretical studies of persistent phenomena. The majority of the persistent anomaly cases in each region are related to episodes of unusually large amplification of the primary patterns, with one phase frequently associated with blocking and the other with an abnormally strong zonal flow. -from Author