On transport across a barotropic shear flow by breaking inertia-gravity waves

We investigate the interaction of an inertia-gravity wave packet with a barotropic dynamical barrier, by means of three-dimensional direct numerical simulations of the Boussinesq equations in a rotating reference frame. A simple model is used for the barrier, namely a barotropic shear layer with a horizontal shear. We show that the increase of the intrinsic frequency Omega of the wave packet by Doppler shifting may result in the breaking of the wave packet, in the neighborhood of a trapping plane where Omega=N(N is the Brunt-Vaisala frequency of the fluid and is constant in the present study). The breaking process triggers a turbulent diffusive transport of mass and momentum across the barrier, with a turbulent Prandtl number of order 1. (C) 2002 American Institute of Physics.