A simple model for cloud radiative forcing

Abstract. We present a simple model for the longwave and shortwave cloud radiative forcing based on the evaluation of extensive radiative transfer calculations, covering a global range of conditions. The simplicity of the model equations fosters the understanding on how clouds affect the Earth's energy balance. In comparison with results from a comprehensive radiative transfer model, the accuracy of our parameterization is typically better than 20%. We demonstrate the usefulness of our model using the example of tropical cirrus clouds. We conclude that possible applications for the model include the convenient estimate of cloud radiative forcing for a wide range of conditions, the evaluation of the sensitivity to changes in environmental conditions, and as a tool in education. An online version of the model is available at http://www.iac.ethz.ch/url/crf.