Surface albedos are specified either as single values for all bands with diagnosed snow albedos or spectral values with prognostic snow albedos.
Bare soil albedos vary geographically with soil colour. Snow aging is represented by reducing the snow albedo when surface temperature exceeds –2 °C
The Sellers (1985) two-stream canopy radiation model is used for vegetation albedos in the optional spectral albedo scheme. Separate direct-beam and diffuse albedos in visible and near-infrared wave bands are calculated for each vegetation type.
Snow albedos are calculated using a simplification of the Marshall (1989) parametrization of the Wiscombe and Warren (1980) spectral snow albedo model. The aging of snow is characterized by introducing a prognostic grain size, set to a minimum value for fresh snow and limited to a maximum value.
Marshall, S. E., 1989: A physical parametrization of snow albedo for use in climate models. NCAR Cooperative Thesis 123, National Center for Atmospheric Research, Boulder, Co.
Sellers, P. J., 1985: Canopy reflectance, photosynthesis and transpiration. Int. J. Remote Sens., 6(8), 1335-1372
Wiscombe, W. J., and S. G. Warren, 1980: A model for the spectral albedo of snow. I. Pure snow. J. Atmos. Sci., 37, 2712-2733. 24