Attenuation of Light in the Lower Atmosphere*

Abstract

Researches on the attenuation of light in the lower atmosphere permit the conclusions:(a) From 3500 to 5400A in distances up to 6 km the attenuation of pure air and water vapor is due to molecular scattering with negligible true absorption; (b) from 3000 to 2000A pure air possesses an absorption in addition to molecular scattering, probably due to oxygen, which increases rapidly with decreasing wavelength; (c) the degradation of visible light in normally clear air at sea, probably due to prevalent haze, is such as to reduce light to 1/10 in 10 nautical miles; (d) natural fog degrades visible light either equally across the spectrum or slightly less for red than for blue light but not enough to redden appreciably white or yellow lights.