||Physical and Chemical Indicators of Urban Visual Air Quality Judgments.
Middleton, P. ;
Stewart, T. R. ;
Ely, D. ;
Lewis, C. W. ;
||National Center for Atmospheric Research, Boulder, CO.;Environmental Protection Agency, Research Triangle Park, NC. Atmospheric Sciences Research Lab.
Visual perception ;
Air quality ;
Urban areas ;
Air pollution effects(Humans)
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Key issues in the selection of physical/chemical measures of atmospheric properties as indicators of visual air quality, defined as a human judgment, are addressed. The relations between judgments and measures are examined experimentally over a wide variety of atmospheric and observational conditions. Light scattering extinction measured throughout the day at a site characterized by high pollution concentrations was the single measure most strongly related to judgments of visual air quality. Total light extinction measured by a telephotometer is strongly related to midday visual air quality. The 4-hour averaged fine particle sulfur and 12-hour averaged fine particle sulfur, sulfate, nitrate, and ammonium are all strongly related to the corresponding mean visual air quality. The application of the method and findings to understanding visual air quality in other urban areas is discussed.