Page 181 - Fundamentals of Air Pollution

III. Effects of Atmospheric Haze 147

Fig. 10-9. The evolution and transport of a large hazy air mass. Contour maps of noon
visibility for June 25-July 5, 1975. Source: Lyons, W. A., and Husar, R. B., Mon. Weather Rev,
104, 1623-1626 (1976).

dresses the problem of visibility degradation by atmospheric haze of anthro-
pogenic origin. This legislation recognizes atmospheric haze as a cause of
degradation in visual air quality.
All nations contain areas of exceptional scenic beauty. The value of these
areas is largely determined by society. Many nations, determined to protect
these areas, have established parks or preserves where only limited devel-
opment can occur, in many instances limited to facilities such as food and
lodging for visitors to the area.
Grand Canyon National Park in the southwestern United States is a
prime example of an area of natural beauty. This park is ~250 km long,
varying in width up to ~45 km. The actual canyon is —10 km at its wid-
est point, with the Colorado River running in the bottom of the canyon,
1600 m below the edge of the outer rim. Visitors go to parks for many
reasons, such as hiking, camping, wildlife, and the enjoyment of solitude,
but the overwhelming majority visit the Grand Canyon to enjoy the mag-
nificent views from its rim. These views have detail in the foreground (0-
5 km), with colored layers of rock strata on canyon walls perhaps 5-25 km
distant and in the far background (25-50 km) additional geologic features
which contribute to the viewers' appreciation of the scene. To enjoy these
views, one must have good visibility over the entire path length from the
details in the foreground to the objects in the distant background.
A survey by national park personnel indicates that large areas of the
United States are subject to varying degrees of visibility degradation (1).
The middle portion of the eastern half of the country and the Florida Gulf
Coast are subject to widespread hazy air masses associated with stagnation
conditions. Large portions of the western half of the country are subject