Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 3 1 1999 10.5194/hess-3-15-1999 http://www.hydrol-earth-syst-sci.net/3/15/1999/ http://www.hydrol-earth-syst-sci.net/3/15/1999/hess-3-15-1999.html http://www.hydrol-earth-syst-sci.net/3/15/1999/hess-3-15-1999.pdf 15 30 0000-00-00 Combined modelling of shortwave and thermal radiation for one-imensional SVATs D. Pearson C. C. Daamen R. J. Gurney L. P. Simmonds Environmental Systems Science Centre, Harry Pitt Building, Whiteknights, PO Box 238, Reading RG6 6AL, UK. Kerikeri Research Centre, PO Box 23, Kerikeri, Bay of Islands, New Zealand. Department of Soil Science, University of Reading, Whiteknights, PO Box 233, Reading RG6 6DW, UK. Expressions for the upwelling and downwelling fluxes of optical and thermal radiation between soil, vegetation and the sky are derived, under certain simple assumptions. These are that interception of radiation by the vegetation is a purely geometric effect, while scattering is isotropic, with a strength given by a single-scattering albedo in the optical part of the spectrum, and by Kirchhoff's Law in the thermal. The soil is assumed to be a lambertian reflector, also scattering according to an albedo and Kirchhoff's Law. The model, called RM, conserves energy exactly. As part of a SVAT, it is driven by measured insolation instead of radiation, with little increase in computational cost and number of parameters.