Dynamics of the middle atmosphere

Observational evidence for the broad spectrum of motions in the middle atmosphere (defined as that region between the tropopause and 100 km) are presented. These include zonal mean motions, planetary waves (both extratropical and tropical), tides, gravity waves, synoptic scale motions, and turbulence. The present status of our understanding of the sources and sinks for these motions, as well as the wave propagation properties of the middle atmosphere, are reviewed. The problems involved in numerically modelling the general circulation in the middle atmosphere are contrasted with the analogous problem in the troposphere. Finally, some remarks are made about the promise of new observational techniques for giving improved data on the dynamics of the middle atmosphere.