Quasi-Stationary Regimes in the Northern Hemisphere of the NCAR Community Climate Model

Abstract

The persistence of the planetary-scale circulation in a perpetual January experiment of the NCAR Community Climate Model is investigated. Pattern correlations between maps of 500 mb geopotential height are used to identify periods in which the large scale flow remains quasi-stationary for periods of a week or longer. Thirty- one distinct periods are dominated by quasi-stationary flow patterns encompassing 22% of the model experiment. The time between quasi-stationary periods is typically longer than their duration. On the basis of subjective similarities among some of these events, we classified many of them into four distinct types. The characteristics of the model quasi-stationary regimes are contrasted with those observed and those found in simpler models.