Global atmospheric angular momentum and Earth-atmosphere exchange of angular momentum simulated in a general circulation model

Abstract

The atmospheric angular momentum budget as described by the National Center for Atmospheric Research community climate model has been studied. Model data from a 20-year climate simulation have been used to study 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 the model were compared with observed values already published in the literature, as well as with values based on data obtained from the National Center for Environmental Prediction. Computed values of gravity wave drag torques are also presented. These values cannot be directly compared with observational data, but they give some idea of the possible role of wave drag on the angular momentum budget. A detailed comparison shows that the general circulation model simulates the seasonal variation of the angular momentum and frictional and mountain torques reasonably well. We also found that the model simulates the seasonal global atmospheric pressure variations owing to global redistributions of mass in a realistic way.