SNOW AND CLOUD FEEDBACKS MODELED BY AN ATMOSPHERIC GENERAL-CIRCULATION MODEL

One of the most important parametrizations in general circulation mode ls used for climate change experiments is that of the surface albedo. The results of an albedo feedback experiment carried out under the aus pices of the US Department of Energy are presented. An analysis of lon g and short wave components of the model response shows that short wav e response dominates changes in fixed to variable albedo experiments, but that long wave response dominates in clear to cloudy sky changes. Cloud distribution changes are also discussed and are related to chang es in global sensitivity. At the surface, the heat balance change for perturbed sea surface temperatures is dominated by changes in latent h eat flux and downward long wave radiation. If albedo is freed up howev er, the major contrast lies in the change in surface reflected short w ave radiation, amplified by changes in downward short wave radiation c aused by cloud amount changes.