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Desert Diary
Climate/Winter Rain


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Climate, with its temporary persona of weather, is intimately connected with physics. It's a fact of nature, for example, that cold air is heavier than hot air and thus tends to be drawn downward by the force of gravity, displacing warmer air upwards. This has all sorts of consequences in shaping our weather.

In the Chihuahuan Desert, we're all aware of the towering clouds that mark the sometimes vicious thunderstorms of summer; these clouds form as turbulent columns of over-heated air hurl themselves skyward through the surrounding cooler air. But what about those winter storms, where drizzle or snow fall lightly upon the ground from overcast skies far different from those of summer? Heavy air, like syrup on pancakes, spreads slowly out from its center. Picture a cold—and thus heavy—wedge of air flowing into our area, its leading edge slipping beneath the warmer desert air. As the warmer air is slowly forced upward, it cools and drops its moisture—a gentle wringing of water from moist air instead of the rambunctious turmoil of the summer tempest.
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Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.