We show that over the Tibetan Plateau on 21 March 2001 (spring equinox), the largest deviations in the direct flux with reference to plane-parallel results are about −200 and 200 W/m2 on the shaded and sunward sides of the mountains, respectively. Over high-albedo snow-covered areas, the largest deviations in the direct-reflected- and coupled fluxes are about 200 and 40 W/m2 , respectively. Combining all five components, deviations in the net surface solar flux range from −150 to 180 W/m2 over the Tibetan Plateau. The local deviation in the solar flux could lead to earlier onset of convection and more small-scale circulation. The domain averaged deviations in surface solar fluxes over the whole Tibetan Plateau is on the order of 14 W/m2 at noon of spring equinox, in which the dominant term is the direct-reflected flux, while the contribution of other components is almost 0. This shows that the surface receives more solar energy than the results calculated from conventional 1-D models, which could lead to stronger convection and enhanced snowmelt rate. While the deviations discussed above are based on the grid size of 10×10 km2, significant deviations on the order of 20 W/m2 can be found even at a resolution of 100×100 km2.
Finally, while the current parameterization approach has been developed for clear sky surface solar flux, it should be noted that because the direct- and direct-reflected fluxes do not encounter atmospheric multiple scattering, the regression equations for these fluxes remain unchanged in cloudy conditions. As a first approximation, the coefficients obtained for clear sky conditions can be applied directly to cloudy conditions. In mountainous areas, however, cloud issues are more complex and require further research and analysis.