Haze in the Grand Canyon An Evaluation of the Winter Haze Intensive Tracer Experiment (1990) / Chapter Skim
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Appendix 1: Nature of the Visibility Problem
Appendix 1: Nature of the Visibility Problem
Pages 43-44
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Visibility can be quantified directly in terms of human judgments or in terms of indices, such as light extinction, that can be related to judgments. Visibility can be Ascribed quantitatively in terms of the following indices: · Contrast the relative brightness of various features in a scene; · Discoloration—shifts in the wavelength distribution of light as it moves through the atmosphere; · Visual range—the farthest distance at which an observer is able to distinguish a large black object against the horizon sky; and · .Extinctton coefficient- the fraction of light that is attenuated per unit of distance as a light beam traverses the atmosphere.
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From page 44... ...
Accordingly, pollution aerosols from all sources have on the average resulted In about a 50% increase in light extinction above natural conditions. During haze episodes, pollution aerosols can produce extinction values 2 or more times higher than natural levels (Trijonis et al., 1989)
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