Sack Lunch Seminar (SLS)

Finite-Amplitude Equilibration of Baroclinic Waves on a Jet







A two-layer quasi-geostrophic model is used to study the equilibration of baroclinic waves. In this model, if the background flow is relaxed toward a jet-like profile, a finite amplitude baroclinic wave solution can be realized in both supercritical and subcritical regions of the model's parameter space. Analyses of the model equations and numerical model calculations indicate
that the finite amplitude wave equilibration hinges on the breaking of Rossby waves before they reach their critical latitude. This `jet-ward' wave breaking results in an increase in the upper layer wave generation and a reduction in the vertical phase tilt. This change in the phase tilt has a substantial impact on the Ekman pumping, as it weakens the damping on the lower-layer wave for some parameter settings, and enables the Ekman pumping to serve as a source of wave growth at other settings. Together, these processes can account for the O(1) amplitude wave equilibration.