ABSTRACT

Calculations of the radiative transfers in the atmosphere represent one of the most important points in numerical weather prediction. The radiative heating constitutes an essential element for the maintenance of the global atmospheric heat budget and contributes an important part to the total energy driving the earth climate. The solar energy at the top of the atmosphere undergoes many alterations before it finally reaches the earth's surface. Part of this solar radiance is reflected on the ground defining the surface albedo. The remaining part, together with the net downward longwave irradiance emanating from the atmosphere, constitutes the net radiation absorbed at the surface. The bulk of the absorbed energy is redistributed to the atmosphere via eddy fluxes of sensible and latent heat, while a small fraction is exchanged with the ground superficial layers. The method uses an emissivity tabulation for the longwave or infrared radiation and an absorptivity function to define the shortwave radiative transfer.