MEAN FLOWS INDUCED BY INTERNAL GRAVITY-WAVE PACKETS PROPAGATING IN A SHEAR-FLOW

An inviscid, incompressible, stably stratified fluid occupies a horizontal channel, along which an internal gravity wave packet is propagating in the presence of a basic shear flow. By using a generalized Langrangian mean formulation, the equation for wave action conservation is derived to describe the manner in which the basic flow affects the waves. Equations describing the second order (in amplitude) wave induced Lagrangian mean flows are obtained. Two kinds of applications are discussed: (i) steady mean flows, due to waves encountering an inhomogeneity in their environment, such as varying channel depth; (ii) mean flows induced by modulations in the wave amplitude. (A)