An analysis of stabilizing mechanisms in the climate system using a simple atmosphere-ocean box-model

Nearly all simple climate models developed during the past thirty years have been based on the Budyko-Sellers approach, in which surface fluxes are eliminated using an atmospheric energy balance equation. The atmospheric fluxes that need to be parameterized in terms of the surface temperature are then the top of the atmosphere infrared radiative flux and the meridional heat transport. Recently a new approach to simple climate models has been taken (Bates, 1999, Tellus) in which the turbulent surface fluxes are calculated explicitly using surface winds derived from an empirical parameterization of the atmospheric angular momentum transport from the tropics to the extra-tropics. This leads to a negative evaporative feedback on sea surface temperature (SST) perturbations. On the other hand the parameterization of the infrared radiation at the surface in this model gives a positive water vapour/infrared radiation feedback on SST perturbations. A simple atmosphere model based on this new approach is coupled to a simple ocean box-model representing the thermohaline circulation based on Stommel's model (Stommel, 1961, Tellus). The stability of the model's realistic steady state to perturbations along its eigenmodes is analyzed and compared to the stability analysis of box-models using the Budyko-Sellers approach (eg. Marotzke and Stone, 1995, J. Phys. Oceanogr.).