Low-Latitude Reflection of Rossby Wave Trains

Abstract

The nonlinear reflection of an isolated Rossby wave train at a low-latitude wave-breaking region is contrasted with the more familiar longitudinally periodic case. General theoretical arguments for nonlinear reflection based on absorptivity bounds do not carry over to the case of an isolated wave train, and detailed investigation is needed to determine the absorption-reflection behavior. Numerical experiments in a single-layer shallow-water model show that wave activity is reflected back into midlatitudes (rather than propagating longitudinally at low latitudes). Finite-amplitudes wave activity diagnostics are used to analyze the nonlinear reflection. Further idealized numerical simulations and simple ideas concerning the propagation of Rossby waves in shear flows are used to give insight into the nonlinear reflection.