1989 Volume 40 Issue 2 Pages 83-101
The persistence of the Northern Hemisphere planetary-scale circulation in a 12-year simulation of the Meteorological Research Institute atmospheric general circulation model is investigated, based on the daily 500 mb height field. Forty-three quasi-stationary events are identified by the use of a subjectively defined criterion as used by Horel. Twenty-seven of them are classified into five distinct types by cluster analysis. They are compared with the observed persistence and the twenty-five quasi-stationary events for the 8-year period of 1980-1987.
Asymmetry in seasonal variation of the simulated persistence is found. It is high in late winter months, and low in fall, not in summer. It is also found that the model atmosphere is more persistent in the Atlantic sector than in the Pacific. They are different from the observation where the seasonal variation of the persistence is not so large as in the model, the persistence is low in summer and there are no distinct differences in the persistence between the Atlantic and the Pacific sectors.