2009.04.27 17:49
Death Valley National Park
The Lost '49ers
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Death Valley National Park is an excellent place for stargazing, the darkest out of all National Parks. Low light pollution levels and frequently cloudless skies allow professionals and amateurs to see many heavenly bodies after dark. Although the skies are fairly dark compared to skies in more populated areas of the United States, they are affected by a noticeable glows from Las Vegas and the central valley.
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One might think that the air would be pristine at Death Valley National Park due to its remote location. However, pollutants can be carried great distances on the wind. The general trend in upper air movement brings pollutants from metropolitan areas, industrial areas, and transportation corridors from the west. In summer, surface winds come from the southwest, where major population centers, industrial areas, and a dry lakebed are located. In winter, surface winds come from the northeast. Since these winds bring an air mass that originates in less developed areas, our air quality is better in the winter.
Pollutants carried in from other areas usually change form by the time they reach Death Valley. For example, sulfur dioxide and nitrogen dioxide emitted by power plants and cars react with other molecules to form sulfates and nitrates, which interfere with visibility and contribute to acid rain. Similarly, ozone is formed by nitrogen dioxide and volatile organic carbons. Pollutants such as nitrogen dioxide that are directly emitted into the air are called primary pollutants, whereas the pollutants these are converted into are called secondary pollutants. During the summer months, more sunlight and higher temperatures speed up these conversion reactions.
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