Spectral Distribution of Radiation from Sun and Sky

Abstract

Measurements of the spectral distribution of the radiation falling on a horizontal plane from sun and sky have been made in various kinds of weather, using the transportable spectrophotometer described by Cooper and Probine. On overcast days the relative-energy/wavelength curve of sun and sky together is nearly the same as on clear days, although the amount of radiation is only about one-fifth. Haze, thin cloud, and mist produce more noticeable changes in distribution. On clear days small amounts of cloud cause large changes in the distribution of radiation from the sky alone. As an example of a simpler method of stating the distribution, which may be suitable where relative-energy/wavelength curves are unnecessarily detailed, the C.I.E. chromaticity co-ordinates and colour temperatures have been calculated for a few days.