Impact of Parameterized Lee Wave Drag on the Energy Budget of an Eddying Global Ocean Model

We examine the impact of a lee wave drag parameterization on an eddying global ocean model. The wave drag parameterization represents the the momentum transfer associated with the generation of lee waves arising from geostrophic flow impinging upon rough topography. It is included in the online model, thus ensuring that abyssal currents and stratification in the simulation are affected by the presence of the wave drag. The model utilized here is the nominally 1/12th degree Hybrid Coordinate Ocean Model (HYCOM) forced by winds and air-sea buoyancy fluxes. An energy budget including the parameterized wave drag, quadratic bottom boundary layer drag, vertical eddy viscosity, and horizontal eddy viscosity is diagnosed during the model runs and compared with the wind power input and buoyancy fluxes. Wave drag and vertical viscosity are the largest of the mechanical energy dissipation rate terms, each more than half of a terawatt when globally integrated. The sum of all four dissipative terms approximately balances the rate of energy put by the winds and buoyancy fluxes into the ocean. An ad hoc global enhancement of the bottom drag at each grid point by a constant factor cannot serve as a perfect substitute for wave drag, particularly where there is little wave drag. Eddy length scales at the surface, sea surface height variance, surface kinetic energy, and positions of intensified jets in the model are compared with those inferred from altimetric observations. Vertical profiles of kinetic energy from the model are compared with mooring observations to investigate whether the model is improved when wave drag is inserted.; The drag and viscosity terms in our energy budget [log_10(W m^-2)]: (a) quadratic bottom boundary layer drag, (b) parameterized internal lee wave drag, (c) vertical viscosity, and (d) "horizontal" viscosity. Shown is an average of inline estimates over one year of the spin-up phase with wave drag.