Abstract
It is shown that in the absence of dissipation or of critical levels where the mean zonal flow vanishes the forcing of the mean zonal flow by linearized, quasi-static, stationary long waves is proportional to the Jacobian of the mean zonal flow and the eddy meridional heat flux. However, if the Richardson number for the mean zonal flow is large, this eddy forcing is exactly balanced everywhere by the zonal momentum advection of the mean meridional circulation. Therefore, the local acceleration of the mean zonal flow vanishes. This theorem provides a generalization of the results obtained by Charney and Drazin for quasi-geostrophic perturbations.
