Lee-Wave Energy Sinks in Bottom-Intensified Flow: Reabsorption, Dissipation and Nonlinear Spectral Transfer

Abstract

Idealized numerical simulation is used to explore energy sinks for lee waves trapped in their bottom-intensified generating flow. In addition to the loss to explicit dissipation and reabsorption predicted by linear wave action conservation, indirect dissipation due to a nonlinear forward cascade by parametric subharmonic instability represents a significant sink that substantially reduces reabsorption. The partition of lee-wave energy loss between reabsorption and (explicit plus indirect) dissipation is independent of subgridscale damping parameterization. Remote dissipation of freely propagating internal waves generated by shear instability at the lee-wave critical layer proves to be small. A general parameterization for lee-wave dissipation of the balanced flow requires a more complete exploration of the parameter space.