I discuss a parameterization for upper tropospheric, transient eddy momentum fluxes. The momentum fluxes are derived from the linear response of a randomly excited, nondivergent, barotropic, vorticity model. The basic state is the zonal mean, monthly mean, zonal flow at 200mb, and the dissipation is vorticity diffusion. The crucial part of this parameterization is the random forcing, the magnitude of which is chosen so as to produce the observed wave activity flux divergence between 400-200mb. The resulting stochastic model is tantamount to a parameterization relating the eddy momentum fluxes to a combined function of the mean flow and eddy heat fluxes. Only two tunable parameters are involved in the stochastic model: a coefficient of diffusion and a characteristic decorrelation length of the random forcing. For a fixed set of parameters, the parameterization produces a realistic annual cycle for the momentum fluxes but a weak annual cycle for the eddy kinetic energy.
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12th Conference on Atmospheric and Oceanic Fluid Dynamics