The shortwave algorithm was developed at NASA LaRC by W. F. Staylor. The current model is a modified version of an earlier model by Darnell et al. A recent application of the method is given in Darnell et al. The shortwave algorithm was developed at NASA LaRC by W. F. Staylor. Downward SW flux at the surface is the product of insolation at the TOA, clear-sky atmospheric transmittance and cloud transmittance.
Daily insolation requires time integration of the instantaneous values from sunrise to sunset.
Atmospheric transmittance is a function of surface pressure, surface albedo, aerosols, and the effective clear-sky atmospheric optical depth. The first three terms account for the atmospheric backscatter of surface reflected rays. The effective clear-sky atmospheric optical depth is a vertical attenuation factor for solar energy and it is the sum of all absorption and scattering processes. These processes include absorption and scattering due to gases and aerosols. Clear-sky reflectances are determined by one of several methods depending on the snow cover and surface type.