SEMIDIURNAL VARIATIONS IN THE BUDGET OF ANGULAR-MOMENTUM IN A GENERAL-CIRCULATION MODEL AND IN THE REAL ATMOSPHERE

Diurnal and semidiurnal variations in the budget of atmospheric angula r momentum are evident in a simulation by the NCAR Community Climate M odel (CCM2). These variations depicted with 20-min time resolution tea ch time step) are used as guides to study similar variations determine d from 6-hourly NCEP/NCAR Reanalysis data. A semidiurnal variation in relative angular momentum and in angular momentum related to solid bod y rotation of the atmosphere is found in the reanalysis. Although ther e is evidence that both frictional and gravity-wave drag torques play roles, the effects of semidiurnal variations in mountain torque, resul ting from the migrating semidiurnal pressure wave, are most thoroughly documented.