 
Summary: 15 DECEMBER 1999 4167A L E X A N D E R A N D D U N K E R T O N
1999 American Meteorological Society
A Spectral Parameterization of MeanFlow Forcing due to Breaking Gravity Waves
M. J. ALEXANDER
Colorado Research Associates, Boulder, Colorado
T. J. DUNKERTON
NorthWest Research Associates, Bellevue, Washington
(Manuscript received 8 June 1998, in final form 18 March 1999)
ABSTRACT
A spectral parameterization of meanflow forcing due to breaking gravity waves is described for application
in the equations of motion in atmospheric models. The parameterization is based on linear theory and adheres
closely to fundamental principles of conservation of wave action flux, linear stability, and wavemeanflow
interaction. Because the details of wave breakdown and nonlinear interactions are known to be very complex
and are still poorly understood, only the simplest possible assumption is made: that the momentum fluxes carried
by the waves are deposited locally and entirely at the altitude of linear wave breaking. This simple assumption
allows a straightforward mapping of the momentum flux spectrum, input at a specified source altitude, into
vertical profiles of meanflow force. A coefficient of eddy diffusion can also be estimated. The parameterization
can be used with any desired input spectrum of momentum flux. The results are sensitive to the details of this
spectrum and also realistically sensitive to the background vertical shear and stability profiles. These sensitivities
make the parameterization ideally suited for studying both the effects of gravity waves from unique sources
