Diffuse transmissions through atmospheres of haze and clouds were measured over slant ranges from 0.5 to 9.0 kilometers. The modification of the transmissions when the source was near a diffusely reflecting surface was also measured. The transmissions are presented as curves representing the least squares fit to the experimental data for general weather conditions.
RALPH G. ELDRIDGE and JOHN C. JOHNSON, "Diffuse Transmission through Real Atmospheres," J. Opt. Soc. Am. 48, 463-468 (1958)