Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: WEDNESDAY, February 1, 1995 TAG: 9502010044
SECTION: VIRGINIA PAGE: C-5 EDITION: STATE
SOURCE: Associated Press
DATELINE: CHARLOTTESVILLE LENGTH: Medium
The number of good-visibility days from May through October increased 7 percent from 1993 to 1994, Julie Thomas, the park's air quality program manager, said Monday.
A good-visibility day is when visitors can see more than 30 miles; fair visibility is between 11 and 30 miles; and poor is zero to 10 miles.
In 1994, 23 percent of the days monitored were good, 38 percent offered fair visibility, and 32 percent were poor. The remaining days were classified as foggy. In 1993, the numbers were: good, 16 percent; fair, 41 percent; poor, 36 percent; and foggy, 7 percent.
Air quality specialists are studying the data to determine why 1994 offered better views than 1993.
``It could be a really good trend, and that's what we want to find out,'' Thomas said. ``It could be just that the weather patterns were coming from clean-air areas, or it could be that there really are fewer sulfates in the air.''
The haze that often plagues the park is generally thought to be made up of pollutants emitted by power stations and industrial smokestacks hundreds of miles to the west and from local sources such as cars.
Among national parks, Shenandoah's pollution is the worst, in part because about 2 million visitors drive the scenic Skyline Drive through the mountains each year, park officials say.
As for ozone pollution trends, Thomas said park scientists have not yet studied the raw data to determine why there continues to be so much ground-level ozone.
Tropospheric ozone, or ozone in the atmosphere near the Earth's surface, is a gas formed by the reaction of nitrogen oxides with byproducts from burning fossil fuels, such as coal.
Thomas said 1994 saw more days with moderate levels of ozone and fewer days with low levels of ozone than in the three previous years.
``We really don't know why,'' she said.
by CNB