CHAOTIC MIXING AND TRANSPORT IN ROSSBY-WAVE CRITICAL LAYERS

A simple, dynamically consistent model of mixing and transport in Ross by-wave critical layers is obtained from the well-known Stewartson-War n-Warn (SWW) solution of Rossby-wave critical-layer theory. The SWW so lution is thought to be a useful conceptual model of Rossby-wave break ing in the stratosphere. Chaotic advection in the model is a consequen ce of the interaction between a stationary and a transient Rossby wave . Mixing and transport are characterized separately with a number of q uantitative diagnostics (e.g. mean-square dispersion, lobe dynamics, a nd spectral moments), and with particular emphasis on the dynamics of the tracer field itself. The parameter dependences of the diagnostics are examined: transport tends to increase monotonically with increasin g perturbation amplitude whereas mixing does not. The robustness of th e results is investigated by stochastically perturbing the transient-w ave phase speed. The two-wave chaotic advection model is contrasted wi th a stochastic single-wave model. It is shown that the effects of cha otic advection cannot be captured by stochasticity alone.