Subgrid parameterisation of the eddy-meanfield interactions in a baroclinic quasi-geostrophic ocean

Abstract

We present parameterisations of the subgrid eddy-eddy and eddy-meanfield interactions in a baroclinic ocean representative of the Antarctic Circumpolar Current. Benchmark direct numerical simulations were undertaken using a quasi-geostrophic spectral spherical harmonic code of maximum zonal and total truncation wavenumber of $T=252\,$. The eddy-eddy interactions are represented by both stochastic and deterministic parameterisations, with model coefficients determined from the direct numerical simulations truncated back to the large eddy simulation truncation wavenumber $T_R$ less than $T$. Coefficients of the deterministic eddy-meanfield model are determined by a new least squares regression method. Truncations were repeated for various $T_R$, with the dependence of the coefficients on $T_R$ identified. Kinetic energy spectra from the large eddy simulations using these coefficients agree with the direct numerical simulations. References

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