GLOBAL ATMOSPHERIC ANGULAR-MOMENTUM AND EARTH-ATMOSPHERE EXCHANGE OF ANGULAR-MOMENTUM SIMULATED IN A GENERAL-CIRCULATION MODEL

The atmospheric angular momentum budget as described by the National C enter for Atmospheric Research community climate model has been studie d. Model data from a 20-year climate simulation have been used to stud y time variations of atmospheric angular momentum and Earth-atmosphere exchange of angular momentum. Computed values of frictional torques, mountain torques, and atmospheric angular momentum as determined by th e model were compared with observed values already published in the li terature, as well as with values based on data obtained from the Natio nal Center for Environmental Prediction. Computed values of gravity wa ve drag torques are also presented. These values cannot be directly co mpared with observational data, but they give some idea of the possibl e role of wave drag on the angular momentum budget. A detailed compari son shows that the general circulation model simulates the seasonal va riation of the angular momentum and frictional and mountain torques re asonably well. We also found that the model simulates the seasonal glo bal atmospheric pressure variations owing to global redistributions of mass in a realistic way.