How Well Are Clouds Represented In Climate Models?
Stratocumulus clouds (low, lumpy, gray clouds found from earth’s surface to 2000 meters) strongly influence the global climate because of their radiative properties. These clouds are highly reflective, i.e., they decrease the amount of solar radiation that reaches Earth’s surface, and, because of their large optical thickness, they emit infrared radiation like a blackbody. Thus, it is important that their effects on earth’s radiation balance be accurately represented in climate models. An international team, including DOE-funded scientists, used observational data to determine how accurately forecasts from several models represented a region with persistent stratocumulus clouds. The results, reported in a recent paper in the Journal of Climate, suggest that although significant progress has been made in the development of parameters used to represent these clouds in climate models, there are still significant differences between models and observations. These results also demonstrate the value of field campaigns for model validation.
C. Hannay, Williamson, D.L., Hack, J.J., Kiehl, J.T., Olson, J.G., Klein, S., Bretherton, C.S., and Kohler M., 2009: Evaluation of Forecasted Southeast Pacific Stratocumulus in the NCAR, GFDL, and ECMWF Models. J. Climate, 22, 2871-2889.