  A closure model is presented for large-eddy simulation (LES) based on the
three-dimensional variational data assimilation algorithm. The approach aims at
reconstructing high-fidelity kinetic energy spectra in coarse numerical
simulations by including feedback control to represent unresolved dynamics
interactions in the flow as stochastic processes. The forcing uses statistics
obtained from offline high-fidelity data and requires only few parameters
compared to the number of degrees of freedom of LES. This modeling strategy is
applied to geostrophic turbulence on the sphere and enables simulating
indefinitely at reduced costs. It proves to accurately recover the energy
spectra and the zonal velocity profiles in the coarse model, for three generic
situations.
