The Influence of Wave Damping on the Winter Lower Stratosphere

Abstract

The mean circulation of the winter stratosphere depends strongly on the interaction between the planetary waves and the zonally averaged flow. The theory of wave-mean flow interactions is used to determine the acceleration of the mean zonal flow by linear stationary waves as a function of the wave's amplitude, vertical structure and damping rate. The theory can be used to determine the expected response to changes in wave damping processes and mean drag. Sensitivity experiments in which the above terms are modified in a version of the NCAR Community Climate Model are used to show that the model responds as expected from the theory. Different forms of wave damping are shown to have similar effects on the mean flow as long as their time scales are comparable. Wave damping significantly in excess of the internally determined relative damping of the model is required in order to produce a reasonable simulation of the lower winter stratosphere. In the context of this study it cannot be determined whether this damping is required because of inadequate tropospheric forcing top boundary effects or missing damping or drag terms which are present in the atmosphere.