Parameterisation of meso-scale mixing in the ocean
Final Report Abstract
In ocean climate models which do not explicitly resolve meso-scale eddies because of too coarse resolution, the eddy effect on the large-scale circulation must be parameterized. Instead of a previously proposed mixing length appoach to predict the lateral diffusivity appropriate to the parameterisation by Gent et al. (1995), eddy fluxes and diffusivities calculated from the polarisation of the most unstable Rossby wave given by linear stability analysis have been used for eddy parameterisations, following a suggestions by Stone (1972) and Killworth (1997). This approach allows for (in principle non-diffusive) closures which also include the prediction of eddy momentum fluxes, which are not included in the parameterisation by Gent et al. (1995). Successful application of the approach to idealized ocean models included the parameterisation of eddy buoyancy fluxes and also the eddy momentum fluxes in the framework of potential vorticity mixing. Both versions did not show large differences in the simulation, but the latter approach also allows for the parameterisation of along isopycnal mixing of properties other than density. A difficulty in the approach by Stone and Killworth is the specification of the amplitude of the eddy fluxes which is not predicted by linear theory. Ways to combine the prediction from linear theory with eddy energy predicted by an additional energy equation co-integrated in the coarse model have been explored and will be combined with upcoming ideas and implemented and tested in ocean climate models in the future.
Publications
- (2020) A wind-driven model of the ocean surface layer with wave radiation physics. Ocean Dynamics 70 (8) 1067–1088
Olbers, Dirk; Jurgenowski, Philipp; Eden, Carsten
(See online at https://doi.org/10.1007/s10236-020-01376-2) - (2011): A closure for meso-scale eddy fluxes based on linear instability theory. Ocean Modeling 39, 362-369
Eden, C.
- (2012): Implementing diffusivities from linear stability analysis in a threedimensional general circulation ocean model. Ocean Modelling 57, 15-28
Eden, C.
(See online at https://doi.org/10.1016/j.ocemod.2012.08.001) - (2013): A global map of meso-scale eddy diffusivities based on linear stability analysis. Ocean Modelling 72, 198-209
Vollmer, L. and Eden, C.
- (2015): Comparing isopycnal eddy diffusivities in the Southern Ocean with predictions from linear theory. Ocean Modelling 94, 33-45
Griesel, A., Eden, C., Koopmann, N. and Yulaeva, E.
(See online at https://doi.org/10.1016/j.ocemod.2015.08.001)
