NEW PARAMETERIZATIONS AND SENSITIVITIES FOR SIMPLE CLIMATE MODELS

This paper presents a reexamination of the Earth radiation budget parameterization of energy balance climate models in light of data collected over the last 12 years. The study consists of three parts: (1) an examination of the infrared terrestrial radiation to space and its relationship to the surface temperature field on time scales from 1 month to 10 years; 2) an examination of the albedo of the Earth with special attention to the seasonal cycle of snow and clouds; (3) solutions for the seasonal cycle using the new parameterizations with special attention to changes in sensitivity. While the infrared parameterization is not dramatically different from that used in the past, the albedo in the new data suggest that a stronger latitude dependence be employed. After retuning the diffusion coefficient the simulation results for the present climate generally show only a slight dependence on the new parameters. Also, the sensitivity parameter for the model is still about the same (1.25-degrees-C for a 1% increase of solar constant) for the linear models and for the nonlinear models that include a seasonal snow line albedo feedback (1.34-degrees-C). One interesting feature is that a clear-sky planet with a snow line albedo feedback has a significantly higher sensitivity (2.57-degrees-C) due to the absence of smoothing normally occurring in the presence of average cloud cover.