Clear Sky Spatial Distribution of Solar Ultraviolet-B Radiance

Spatial distribution of sky radiance needs to be measured to understand the exact influence of solar ultraviolet-B (UV B: 290320nm) radiation on humans, animals, plants, and materials. For this purpose, a solar UV-B sky radiance meter was developed and has been used since August 1996. The spatial distribution of solar UV-B sky radiance under clear skies showed quite different patterns from those of solar total (TOTAL: 300-3000nm) sky radiance, being more uniform. From the measured data, an empirical formula for the spatial distribution of solar UV-B sky radiance under clear skies was derived using three parameters: solar elevation ranging from 28° to 72°, angle of sky location from the horizon, and scattering angle between sky location and the sun.