Geographic variation of surface energy partitioning in the climatic mean predicted from a thermodynamic limit

Abstract:

Convective and longwave radiative cooling are the two principle mechanisms by which the earth's surface transfers heat into the atmosphere and that shape surface temperature. However, this partitioning is not sufficiently constrained by energy and mass balances alone. We use a simple energy balance model in which surface temperatures and convective fluxes are determined with the additional thermodynamic constraint of maximum convective power. We assume that convection acts as a perfect heat engine operating at this limit. Applying our approach at regional scales, we find that the geographic variation of heat fluxes in the climatological mean reproduce ECMWF reanalysis with a high correlation (r² = 0.88) despite a uniform bias.

Our global estimates of the convective flux and surface temperature, with bias correction, is within 4% of satellite based estimates. Our results show that given total surface radiative forcing, the ratio between the surface cooling fluxes remains nearly constant. This provides an insight into surface energy partitioning that could be useful in setting physical limits to equilibrium climate sensitivity.