The Stochastic GM+E closure: A framework for coupling stochastic backscatter with the Gent and McWilliams parameterization

Non-eddying models lack variability. They lack variability on small scales that cannot be represented on the grid; this cannot be fixed without going to higher resolution. But they also lack variability on the large, resolved scales, variability that is dynamically driven by the unresolved mesoscales. This can be fixed without going to higher resolution, by introducing appropriate subgrid-scale parameterizations. This research develops a new stochastic subgrid-scale parameterization of a transfer of kinetic energy from unresolved scales. The rate of transfer is proportional to the rate at which the Gent-McWilliams (GM) parameterization removes resolved potential energy. The parameterization induces significantly increased (improved) variability in SST and SSH in a non-eddying global configuration of the MOM6 ocean model.