Wave-mean flow interactions in the upper atmosphere

Abstract

The nature of internal gravity waves is described with special emphasis on their ability to transport energy and momentum. The conditions under which these fluxes interact with the mean state of the atmosphere are described and the results are applied to various problems of the upper atmosphere, including the quasi-biennial oscillation, the heat budget of the thermosphere, the general circulation of the mesosphere, turbulence in the mesosphere, and even the ‘4-day’ circulation of the Venusian stratosphere. Gravity waves have long been recognized as an important element in the dynamics of the upper atmosphere - largely due to their very large amplitudes in this region. It is the implied purpose of this paper to convey some of the thinking that has gone on about the role of gravity waves in the large-scale circulation of the upper atmosphere. Insofar as gravity waves are now being identified as important entities in the lower atmosphere as well, it is possible that mechanisms identified in the upper atmosphere will prove relevant to the troposphere.