Effect of ground-based environmental conditions on the level of dangerous ultraviolet solar radiation

Abstract

An analytical model is suggested to determine the contribution of solar radiation scattered by dispersed layers of weakly absorbing highly-porous media on the surface of the earth to the local UV-index, which characterizes harmful ultraviolet irradiation. The transport approximation for the single-scattering phase function and the two-flux method for approximate radiative transfer calculations were used to calculate an additional UV irradiance due to multiple scattering in the layer of a substrate medium. Three important environment conditions are considered in the case problems: the snowpack in a mountain ski resort of Provo (Utah), the salt layer in the Great Salt Lake desert, and the layers of sand typical of sand resorts and beaches. The optical properties of the media were calculated using the data for spectral optical constants of substances in the near-ultraviolet and analytical geometrical optics solution for large spherical particles of a weakly absorbing material. The resulting spectral single-scattering transport albedo of the medium was used to determine an additional harmful UV radiation. It was found that corrected values of the UV-index in all three cases are substantially higher than those calculated without account for the light reflected from a scattering medium on the earth surface. The model of the present paper can be used for different dispersed media in a wide range of physical parameters.