  The meridional temperature profile of the upper layers of planetary
atmospheres is set through a balance between differential radiative heating by
a nearby star, or by intrinsic heat fluxes emanating from the deep interior,
and the redistribution of that heat across latitudes by turbulent flows. These
flows spontaneously arise through baroclinic instability of the meridional
temperature gradients maintained by the forcing. When planetary curvature is
neglected, this turbulence takes the form of coherent vortices that mix the
meridional temperature profiles. However, the curvature of the planet favors
the emergence of Rossby waves and zonal jets that restrict the meridional
wandering of the fluid columns, thereby reducing the mixing efficiency across
latitudes. A similar situation arises in the ocean, where the baroclinic
instability of zonal currents leads to enhanced meridional heat transport by a
turbulent flow consisting of vortices and zonal jets. A recent scaling theory
for the turbulent heat transport by vortices is extended to include the impact
of planetary curvature, in the framework of the two-layer quasigeostrophic
beta-plane model. This leads to a quantitative parameterization providing the
meridional temperature profile in terms of the externally imposed heat flux in
an idealized model of planetary atmospheres and oceans. In addition, it
provides a quantitative prediction for the emergent criticality, i.e., the
degree of instability in a canonical model of planetary atmosphere or ocean.
