Equilibration of a two-level primitive equation model on the sphere

The equilibration of a two-level primitive equation model forced by relaxation towards a fixed axisymmetric temperature profile is studied as a function of the forcing equator-to-pole temperature difference. We find that the mean equilibrated temperature gradient rises quickly with the forcing. It is found also that the mean eddy momentum flux convergence induces a strong barotropic jet at mid-to-high latitudes. We suggest that, as found in previous work, the barotropic governor effect induced by the jet is responsible for the sensitivity of the equilibrated temperature gradient to the forcing.