The structure of an eddy-driven jet within a broad baroclinic region is determined by positive and negative feedbacks involving the generation of baroclinic eddies and the influence of these eddies on the zonal mean flow. A positive feedback results when baroclinic eddies propagate from their source latitudes to neighboring latitudes where they are absorbed. The secondary circulations induced by eddy absorption enhances the mean-flow baroclinicity at the eddy source latitude.

Negative feedbacks limit the strength of jets. As the jet, which includes both baroclinic and barotropic components, strengthens, baroclinic eddies lose energy propagating down the barotropic shear. If this barotropic shear is too strong, the eddies can no longer be sustained against dissipation. This is the barotropic governor. Strictly energetic considerations, however, appear to be insufficient to constrain the strength of jets, in comparison with observations. Increased barotropic shear also shifts eddy critical lines, presumed regions of eddy absorption, towards the jet center, narrowing the width of the region of enhanced baroclinicity.

Using simple and heuristic “parameterizations” of eddy generation and absorption, we explore the role of these feedbacks in determining the structures of eddy-driven jets and their variability.