of Gravity Wave Drag
Introduction of Gravity Wave Drag Parameterization
Gravity waves can be excited when stably stratified air
flows over irregular terrain. Such waves may propagate feely to considerable
altitudes before being significantly dissipated or absorbed. While orographic
excitation is one of the more common sources of vertically propagating gravity
waves they may also occur in association with a number of other processes such
as the onset of shear instabilities and the rapid development of convective
complexes and squall lines.
gravity waves can play a role what transfer momentum from source to sink. Gravity
wave drag process is important to simulate upper atmospheric momentum well, but
the resolution of current GCMs is too sparse to simulate gravity wave by mountains.
So parameterization of wave characteristics in large scale flow is needed. The
parameterization of gravity wave is based on simple linear theory of single retarded
wave having momentum flux divergence by wave breaking. Absorbing waves break
out at a critical altitude where gradient Richardson number is much greater than 0.25.