On the vertical structure of the extratropical circulation response to global warming and of the annular modes

The simulated response of the zonal-mean Southern-Hemisphere extratropical circulation to greenhouse warming in climate models resembles observed trends. A simple diffusive quasi-geostrophic theory, similar to the model of J. Green, is presented to account for the vertical structure of this response. A dynamical connection is made between this structure and the structure of the internal variability of the quasigeostrophic baroclinic turbulence as represented by the annular modes.