Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 2 2009 10.5194/acpd-9-8541-2009 http://www.atmos-chem-phys-discuss.net/9/8541/2009/ http://www.atmos-chem-phys-discuss.net/9/8541/2009/acpd-9-8541-2009.html http://www.atmos-chem-phys-discuss.net/9/8541/2009/acpd-9-8541-2009.pdf 8541 8560 2009-03-31 A simple model for cloud radiative forcing T. Corti thierry.corti@env.ethz.ch T. Peter Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland We present a simple model for the longwave and shortwave cloud radiative forcing based on the evaluation of extensive radiative transfer calculations. 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 fast estimate of cloud radiative forcing, the evaluation of the sensitivity to changes in environmental conditions, and as a tool in education. Allan, R P., Shine, K P., Slingo, A., and Pamment, J A.: The dependence of clear-sky outgoing long-wave radiation on surface temperature and relative humidity, Q. J. R. Meteorol. Soc., 125, 2103–2126, 1999. Baker, M B.: Cloud microphysics and climate, Science, 276, 1072–1078, 1997. Barkstrom, B R.: The Earth Radiation Budget Experiment (Erbe), B. Am. Meteorol. Soc., 65, 1170–1185, 1984. Carlin, B., Fu, Q., Lohmann, U., Mace, G G., Sassen, K., and Comstock, J M.: High-cloud horizontal inhomogeneity and solar albedo bias, J. Clim., 15, 2321–2339, 2002. Chen, T., Rossow, W B., and Zhang, Y C.: Radiative effects of cloud-type variations, J. Clim., 13, 264–286, 2000. Chylek, P. and Wong, J. G D.: Cloud radiative forcing ratio~– an analytical model, Tellus Ser. A-Dyn. Meteorol. Oceanol., 50, 259–264, 1998. Coakley, J A. and Chylek, P.: The 2-stream approximation in radiative transfer~– including angle of incident radiation, J. Atmos. Sci., 32, 409–418, 1975. Corti, T., Luo, B P., Peter, T., Vomel, H., and Fu, Q.: Mean radiative energy balance and vertical mass fluxes in the equatorial upper troposphere and lower stratosphere, Geophys. Res. Lett., 32, L06802, doi:10.1029/2004GL021889, 2005. Fu, Q. and Liou, K N.: On the correlated K-distribution method for radiative-transfer in nonhomogeneous atmospheres, J. Atmos. Sci., 49, 2139–2156, 1992. Fu, Q. and Liou, K N.: Parameterization of the radiative properties of cirrus clouds, J. Atmos. Sci., 50, 2008–2025, 1993. Glickman, T S.: Glossary Of Meteorology, 2nd ed., American Meteorological Society, Cambridge, Massachusetts, USA, 2000. Hartmann, D L., Ockertbell, M E., and Michelsen, M L.: The effect of cloud type on earths energy-balance~– global analysis, J. Clim., 5, 1281–1304, 1992. Hartmann, D L., Holton, J R., and Fu, Q.: The heat balance of the tropical tropopause, cirrus, and stratospheric dehydration, Geophys. Res. Lett., 28, 1969–1972, 2001. Heymsfield, A J. and Platt, C. M R.: A~parameterization of the particle-size spectrum of ice clouds in terms of the ambient-temperature and the ice water-content, J. Atmos. Sci., 41, 846–855, 1984. IPCC: Climate Change 2007~– The Physical Science Basis, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 2007. Johnson, R H., Rickenbach, T M., Rutledge, S A., Ciesielski, P E., and Schubert, W H.: Trimodal characteristics of tropical convection, J. Clim., 12, 2397–2418, 1999. Liou, K.: Radiation and Cloud Processes in the Atmosphere, Oxford University Press, Oxford, United Kingdom, 1992. Raval, A., Oort, A H., and Ramaswamy, V.: Observed dependence of outgoing longwave radiation on sea-surface temperature and moisture, J. Clim., 7, 807–821, 1994. Rossow, W B. and Lacis, A A.: Global, seasonal cloud variations from satellite radiance measurements. 2. Cloud properties and radiative effects, J. Clim., 3, 1204–1253, 1990. Sassen, K.: Cirrus Clouds, in: Cirrus, edited by: Lynch, D K., Sassen, K., Starr, D O., and Stephens, G., Oxford University Press, 231–255, Oxford, United Kingdom, 2002. Stephens, G L., Tsay, S C., Stackhouse, P W., and Flatau, P J.: The relevance of the microphysical and radiative properties of cirrus clouds to climate and climatic feedback, J. Atmos. Sci., 47, 1742–1753, 1990.