The effect of surface reflection function and of atmospheric parameters on the shortwave radiation budget

Errors in the determination of the shortwave radiation budget from broadband satellite measurements at the top and at the bottom of a cloudless atmosphere due to uncertainties of the actual parameters of the atmosphere and the surface are derived by computer modelling. The model uses measured bidirectional reflectance functions and realistic values of the optical parameters of the atmosphere. Examples are presented which show the range of such uncertainties. Neglecting the anisotropy of the reflection function of land surfaces results in high uncertainties of the shortwave radiation budget, both at the top and the bottom of the atmosphere. The uncertainties caused by actual uncertain atmospheric parameters are low if data of the meteorological network are properly used.