This paper considers the interaction of Rossby waves with large-scale flows. We focus on the case of a non-zonal baroclinic plane-parallel flow with vertical shear. We develop short-wave asymptotics for linear waves in the vicinity of the critical layer. Vertical wave modes (eigenfunctions) of the corresponding boundary problem are presented in terms of Hermite polynomials. In addition to the classical case, when the wave modes are focused on the absolute minimum of the vertical profile of the baroclinic flow velocity, we show that there is another option when a mode is formed with focusing not on the minimum, but the absolute maximum of the vertical profile of the background flow velocity. The new option makes it possible to implement new dynamical regimes that are considered in the paper. We obtain a new criterion that limits the number of vertical modes and, thus, determines regimes of the mode localization in depth or its de-localization. Theoretical criteria of different regimes of Rossby wave dynamics in the non-zonal baroclinic are presented in terms of two dimensionless variables: B associated with "an effective β -parameter" and S= N2/ f2 (N is the Brunt–Väisälä frequency, and f is the Coriolis parameter). The analysis of experimental data shows the relevance of theoretically predicted effects.
- barotropic and baroclinic modes
- critical layer
- overshooting phenomenon
- Rossby waves
- WKBJ approximation (geometric optics)
- zonal and non-zonal baroclinic flows