Potential impact of tropopause sharpness on the structure and strength of the general circulation

Abstract

The wintertime extratropical general circulation may be viewed as being primarily governed by interactions between Rossby waves and the background flow. These Rossby waves propagate vertically and meridionally away from their sources and amplify within the core of the tropopause-level jet, which acts as a waveguide. The strength of this waveguide is in part controlled by tropopause sharpness, which itself is a function of the strength of tropopause inversion layer (TIL), a layer of enhanced static stability just above the tropopause. Here, we report a strong relation between interannual-to-multidecadal variations in the strength of the mid-latitude TIL and features of the general circulation (e.g., jet latitude, strength of the Hadley cell) in a reanalysis and climate models. Similar relationships hold for the variability across climate models. Experiments with a mechanistic model show that a sharper tropopause promotes an intensified general circulation and an equatorward shifted jet.