Transmission and Scattering Properties of a Nevada Desert Atmosphere under Cloudy Conditions

The angular scattering diagram of a Nevada desert atmosphere has been measured under clear sky and cloudy conditions for radiation of 0.40-, 0.45-, 0.50-, and 0.55-μ wavelengths, and attenuation coefficients for scattering and absorption have been determined for radiation of 0.40-, 0.50-, 0.70-, and 0.83-μ wavelengths. The ratio R of scattered-in to direct radiation received from a 4-π source by a flat receiver facing the source was also determined for the latter wavelengths, both with and without cloud cover. Source-receiver distances D of from 1.07 to 17.15 miles were used. Plots of R vs D are presented which show that under conditions of little or no cloud cover, R for each of the four wavelengths increases monotonically with D out to a distance of 17.15 miles, whereas for the case of full overcast at 4000 ft above ground, R increases with D for distances up to about 10 miles and then decreases with increasing distance at least for the next few miles. For lower cloud heights, the maximum in R appears to move to smaller distances, approximately in proportion to cloud height.