Internal solitary waves in a variable medium

In both the ocean and the atmosphere, the interaction of a density stratified flow with topography can generate large-amplitude, horizontally propagating internal solitary waves. Often these waves are observed in regions where the waveguide properties vary in the direction of propagation. In this article we consider nonlinear evolution equations of the Kortewegde Vries type, with variable coefficients, and use these models to review the properties of slowly-varying periodic and solitary waves