ABSTRACT
This chapter outlines the three visual air quality (VAQ) assessment methods and compares the methods with respect to objectives, conceptual framework, study design and data analysis. The major goal of the National Center for Atmospheric Research (NCAR) research effort is to develop a VAQ index that is based upon human judgments of visual air quality, and can be used in forecasting levels of VAQ expected from alternative air quality management plans. The relationship between emissions and pollutant concentrations are described with a three dimensional dispersion model. Environmental Protection Agency/National Park Service approach focuses on the examination of the relationship between properties of the visual environment and human judgments of VAQ. The NCAR method attempts explicitly to link emission changes to measurable properties of the visual environment and then to link these variables to human judgments of VAQ. The comparison of existing pristine area studies with the NCAR approach suggests several considerations for pristine area assessments.
