Human perception of visual air quality (uniform haze)

Abstract The National Park Service and the U.S. Environmental Protection Agency are cooperatively conducting ongoing studies of human perception of visual air quality. Major objectives of this program include: (1) determination of the relationship between judgments of visual air quality of actual three dimensional scenes and a surrogate slide representation of that scene, (2) examination of the effect of sun angle and meteorological conditions on perceived visual air quality, (3) examination of the effect of demographic background on observer's judgments of visual air quality, (4) establishment of a functional relationship between human perception of visual air quality and various electro-optical parameters for several different scenic vistas and (5) development of a model capable of predicting the sensitivity of a park to visual air pollution impact. Preliminary results of a previous study involving one vista revealed a linear relationship between human perception and apparent vista contrast for constant vista illumination and ground cover. A more general formalism for averaging vista color contrast appeared to account for effects that snow cover and varying illumination have on the sensitivity of perceived visual air quality to air pollution. These functional relationships are re-examined using a number of southwestern vistas. A first order model capable of predicting perceived visual air quality as a function of change in air pollution is developed. In addition, the relationship between perceived visual air quality of actual three dimensional scenes and pictoral surrogates is examined.