SIMULATION OF MODERN CLIMATE CIRCULATION FEATURES BY ATMOSPHERIC GENERAL CIRCULATION MODELS

G. V. Surkova and D. Yu. Gushchina

The circulation index proposed by M. A. Petrosyants and D. Yu. Gushchina, the integral of the zonal wind velocity along latitude circles, is used to compare the modern atmospheric circulation reproduced by 17 atmospheric general circulation models (AGCM) participating in the Paleoclimate Modeling Intercomparison Project (PMIP). Monthly mean values of zonal wind velocity for 1948–1997 at 200 and 850 hPa from the NCEP/NCAR objective analysis were used as the actual data. A comparison of the actual and model data showed that the models adequately reproduce the circulation intensity and localization of the axis of maximum values in the zone of midlatitude westerlies. Among the shortcoming of the models it is worthwhile to note that practically all of them yield the location of the axis of maximum westerly winds closer to the poles than in reality and overestimate the intensity of westerlies in the lower troposphere, particularly in the Southern Hemisphere. Models that have 12 or more vertical levels reproduce a real picture better, while 9–12-level models have a greater inconsistency with observations in the midlatitudes. The location, intensity, and width of the easterly circulation zone in the lower troposphere are reproduced by the models more successfully than in the upper troposphere, the best agreement with reanalysis data in equatorial regions being demonstrated by the models with a low vertical resolution.