Coarse Graining the Vorticity Equation in the ECMWF Integrated Forecasting System: The Search for Kinetic Energy Backscatter

AbstractStochastic kinetic energy backscatter parameterization schemes are now widely used in ensemble prediction systems to account for random error associated with excessive dissipation and unrepresented energy backscatter in numerical weather prediction models. This dissipation arises from numerical advection schemes and explicit diffusion terms and is also implicit in some parameterization schemes. In the absence of a backscatter theory applicable to the convective scale and mesoscale, current parameterization methods are based on simple heuristic models designed to scale the energy input in proportion to a suitable measure of net energy dissipation rate. Free parameters in the formulation of backscatter tend to be tuned for the optimal performance of ensemble prediction systems, yet other forms of uncertainty represented in these forecasting systems make that task harder. Results are presented here from a study that aims to characterize the form and magnitude of kinetic energy backscatter within a gl...