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Computation of solar radiation flux within a fog layer is essential during the dissipation stage. A new parameterization of the asymmetry factor g and of the single scattering albedo ω allows the use of a monospectral model (FB), already designed for cloudy layer by Fouquart and Bonnel (1980). This new parameterization is necessary because of the different droplet size distributions existing in clouds and fogs. A calculation method of new g and ω values, in function of the optical thickness δ and of the effective radius re of droplet size distribution is proposed.

A method is given for calculating the absorption coefficient spectra k ( v ) from experimental data in a real atmosphere for narrow spectral intervals centered in a CO 2 absorption band (λ = 740 cm −1 ). The results have been compared with radiometric data and are useful for calculating emission and absorption in the atmosphere.

The radiative effects are essential among the processes that govern the evolution of a fog layer, especially during the initial and dissipation phases. The study presented here includes a numerical simulation dealing with radiative cooling (or warming up) and surface radiative flux values, in function of the fog layer characteristics. The results of the numerical simulation allow to deduce the optical thickness of the fog layer from the data obtained during the “Valladolid 85” experiment.