Vertical velocity in the interaction between inertia‐gravity waves and submesoscale baroclinic vortical structures

Abstract

The interaction between submesoscale baroclinic vortical structures and large amplitude inertia‐gravity waves (IGWs), with emphasis on the vertical velocity, is numerically investigated using a high‐resolution three‐dimensional non‐hydrostatic model. A rich variety of vortex‐wave interactions are possible depending on the potential vorticity (PV) content and length scale of the submesoscale monopoles or dipoles, and on the amplitude and wave number of the IGWs. On the one hand, large amplitude IGWs cause horizontal and vertical advection of the vortices, which conserve their stability though their geometry is largely modified by the wave motion. On the other hand, the horizontal vortical motion Doppler shifts the local frequency of IGWs. The vortical angular velocity and vortex density stratification lead to a wave dispersion relation involving the effective Coriolis frequency (Coriolis frequency plus the vortical angular velocity) and the total Brunt‐Väisälä frequency. This inhomogeneous change in the local wave frequency causes IGWs to depart from their initial plane geometry. In the particular case of inertial waves, the nonlinear vortex‐wave interaction generates spiral IGWs, having vertical velocities one order of magnitude larger than the submesoscale vortical flow in the absence of waves.