Are Hydrostatic Models Still Capable of Simulating Oceanic Fronts

: Sub-mesoscale structures such as oceanic fronts can play a very important role in the transfer of properties, tracers, momentum and energy between the surface ocean and the upper thermocline. The ability to correctly represent the fronts in ocean circulation models is important for mixed layer and thermocline simulations as well as large scale circulations. Numerical experiments are conducted using hydrostatic (HY) and nonhydrostatic (NH) models to address the relevance of NH effects on the evolution of density fronts and the development of meso- and submeso-scale vertical motions. Model results indicate that even though the NH simulations give stronger upwelling/downwelling than the HY simulations, the characteristics of submesoscale structures are very similar between them, suggesting that the HY model are capable to produce correct dynamical response for oceanic fronts. Model resolution is found to be critical for frontal simulations for both hydrostatic and nonhydrostatic models, and 100 meter resolution is adequate for frontal simulations.