Skitka, J., Arbic, B.K., Ma, Y., Momeni, K., Peltier, W.R., Menemenlis, D., Pan, Y., and Thakur, R. (2024)
Presented at:
Ocean Sciences Meeting 2024Vertical profiles of internal-wave (IW) dissipation are diagnosed in a regional ocean model and compared against observations. Different numerical implementations of dissipation mechanisms are also studied and adapted to improve their handling of IWs. The model is of a region north of the Hawaiian archipelago. It has frequently updated wind stresses, astronomical forcing, and rigidly imposed nested boundary conditions from a similarly forced global ocean model. Previous work has shown that this model partially resolves the internal-wave spectrum and the nonlinear interactions that give rise to it. Results suggest that realistic vertical profiles of IW dissipation are achievable in IW models with 2km horizontal resolution if care is taken with dissipation and other modeling decisions. Specifically, it is found that turning off the horizontal viscosity used by this model (a version of Leith LES) so that it does not act on the horizontally divergent IW continuum improves vertical dissipation profiles of IWs versus observations. In these relatively low-resolution simulations, most IW kinetic energy is dissipated by a combination of the background vertical viscosity and the remaining horizontal viscosity scheme acting on rotational modes. In the relatively high-resolution simulations (256-meter horizontal grid spacing), a shear-instability parameterization becomes significant and can be used as the basis of an accurate IW dissipation diagnosis while also suggesting avenues for further IW-specific dissipation schemes.
