Decay and return of internal solitary waves with rotation

The effect of rotation on the propagation of internal solitary waves is examined. Wave evolution is followed using a new rotating extension of a fully nonlinear, weakly nonhydrostatic theory for waves in a two-layer system. When a solitary wave solution of the nonrotating equations is used as the initial condition, the wave initially decays by radiation of longer inertia-gravity waves. The radiated inertia-gravity wave always steepens, leading to the formation a secondary solitary-like wave. This decay and reemergence process then repeats. Eventually, a nearly localized wave packet emerges. It consists of a long-wave envelope and shorter, faster solitary-like waves that propagate through the envelope. The radiation from this mature state is very weak, leading to a robust, long-lived structure that may contain as much as 50% of the energy in the initial solitary wave. Interacting packets may either pass through one another, or merge to form a longer packet. The packets appear to be modulated, fully nonlinear versions of the steadily translating quasi-cnoidal waves. (c) 2007 American Institute of Physics.