A theoretical study of waves forced by isolated topography

In this study, analytical and numerical methods are used to examine the nonlinear dynamics of gravity waves forced by an isolated mountain. The topographic gravity waves take the form of a packet, localized in the horizontal direction and comprising a continuous spectrum of horizontal wavenumbers centered at zero. The wave packet propagates upwards in a density-stratified shear flow and reaches a critical level, where the horizontal mean wind is the same as the wave phase speed. The governing nonlinear time-dependent equations are solved to study the nonlinear interactions that take place between the wave packet and the mean wind in the vicinity of the critical level. The phenomena studied include the transfer of momentum to the mean flow by the packet, wave reflection and overturning isopycnals and, eventually, wave breaking leading to turbulence.