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

TL;DR

This study uses idealized simulations to analyze energy sinks of lee waves in bottom-intensified flows, highlighting the roles of reabsorption, dissipation, and nonlinear spectral transfer, with implications for understanding internal wave energy budgets.

Contribution

It reveals that nonlinear cascade processes significantly reduce reabsorption and that energy loss partitioning is independent of damping parameterization, advancing understanding of lee-wave energy dynamics.

Findings

Nonlinear forward cascade reduces reabsorption significantly.

Partition of energy loss is independent of damping parameterization.

Remote dissipation of internal waves is minimal.

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.