ON THE ROLE OF AN ANISOTROPIC GRAVITY-WAVE SPECTRUM IN MAINTAINING THE CIRCULATION OF THE MIDDLE ATMOSPHERE

The spectral parameterization of gravity wave momentum deposition prop osed by Medvedev and Klaassen has been incorporated into the Canadian Middle Atmosphere Model.Numerical experiments show that an anisotropic gravity wave source significantly improves the middle atmosphere circ ulation compared to an isotropic source. These results suggest that, a t least in midlatitudes, the gravity waves primarily responsible for t he momentum deposition at mesospheric heights are launched with observ ed phase velocities which are primarily in the same direction as the m ean wind at tropospheric (source) heights.