A three-dimensional Monte Carlo code is used to compute the ultraviolet zenith sky radiance; the code is validated by comparison with a successive-orders-of-scattering code. The amplifications of global irradiance, diffuse irradiance, and zenith radiance that are due to multiple reflectances between a snow-covered ground surface and the atmosphere are compared. For an inhomogeneous Lambertian surface, the contribution of the site environment is analyzed; it depends slightly on the atmospheric turbidity and on the surface reflectance distribution. However, in most cases one can expect approximately 12–15% of the reflected photon contribution to come from within 1 km about the observation site, 25–30% come from areas from 1 to 5 km from the site, 43–47% from 5 to 30 km, and still 10–15% reflected at larger distances. An average contribution function is proposed and used to compute an effective reflectance, which permits retrieval of the sky radiance within 2–4% with a one-dimensional model.
© 2000 Optical Society of America
(120.5700) Instrumentation, measurement, and metrology : Reflection
(260.2160) Physical optics : Energy transfer
(260.7190) Physical optics : Ultraviolet
(290.1310) Scattering : Atmospheric scattering
(290.1350) Scattering : Backscattering
Jacqueline Lenoble, "Influence of the Environment Reflectance on the Ultraviolet Zenith Radiance for Cloudless Sky," Appl. Opt. 39, 4247-4254 (2000)