OBSERVED DEPENDENCE OF THE WATER-VAPOR AND CLEAR-SKY GREENHOUSE-EFFECT ON SEA-SURFACE TEMPERATURE - COMPARISON WITH CLIMATE WARMING EXPERIMENTS

This study presents a comparison of the water vapor and clear-sky gree nhouse effect dependence on sea surface temperature for climate variat ions of different types. Firstly, coincident satellite observations an d meteorological analyses are used to examine seasonal and interannual variations and to evaluate the performance of a general circulation m odel. Then, this model is used to compare the results inferred from th e analysis of observed climate variability with those derived from glo bal climate warming experiments. One part of the coupling between the surface temperature, the water Vapor and the clear-sky greenhouse effe ct is explained by the dependence of the saturation water vapor pressu re on the atmospheric temperature. However, the analysis of observed a nd simulated fields shows that the coupling is very different accordin g to the type of region under consideration and the type of climate fo rcing that is applied to the Earth-atmosphere system. This difference, due to the variability of the vertical structure of the atmosphere, i s analyzed in detail by considering the temperature lapse rate and the vertical profile of relative humidity. Our results suggest that extra polating the feedbacks inferred from seasonal and short-term interannu al climate variability to longer-term climate changes requires great c aution. It is argued that our confidence in climate models' prediction s would be increased significantly if the basic physical processes tha t govern the variability of the vertical structure of the atmosphere, and its relation to the large-scale circulation, were better understoo d and simulated. For this purpose, combined observational and numerica l studies focusing on physical processes are needed.