Atmospheric Vacillations in a General Circulation Model. III: Analysis using Transformed Eulerian-Mean Diagnostics

Abstract

The vacillatory behavior of the general circulation model described by Hunt (1978a,b) is analyzed using transformed Eulerian-mean diagnostics. This model was shown by Hunt to have large time variations in the troposphere and stratosphere with a period of ?20 days. These diagnostics are used to show the coupling between the troposphere and the stratosphere and the forcing of mean state changes during the vacillation cycle. The time variations of the wave-induced form on the mean flow and the Coriolis torque are in approximate balance throughout the vacillation cycle. Thus mean flow changes are small and the effect of the mean state on wave propagation is approximately constant. The vacillation cycle in the model is apparently due to variations in baroclinic wave activity in the troposphere and not to wave, mean flow interaction in the upper troposphere and stratosphere.