On the potential of regional-scale emissions zoning as an air quality management tool for the grand canyon

Abstract

Air arriving at the Grand Canyon of the Colorado River during 1988-1989 is attributed to one of four geographic quadrants--NE, SE, SW, NW--on the basis of routinely calculated back-trajectories. Most of the haze observed at the Canyon is attributed to the SW quadrant, which contains the populous and industrialized areas of southern California. Air from either northern quadrant tends to be significantly clearer than air from either southern quadrant. Clear northern air is most common during the winter, and is rarely observed during the summer tourist season, when steady flow from the southwest is the norm. Various possible interpretations of these empirical results are discussed, with varying implications for emissions management policy.