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Desert Diary
Climate/Cold Air


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Like water, dense air sinks to the lowest available point. In mountainous arid regions, this propensity leads to some interesting phenomena. In winter, along the major rivers and basins of the Chihuahuan Desert, rivers and pools of cold, dense air collect in low-lying areas during windless hours of night and early morning. With no forces acting on them except gravity, they resist mixing with the overlying, less dense, warmer air. Pollutants, trapped within the cold air, collect in this temperature inversion until the sun warms the air to the temperature of the warm-air cap. Only then can cities emerge from their cocoons of smog.

But where does the cold air come from? In the dry, night air, bare, rocky mountainsides radiate heat rapidly, cooling a thin layer of air immediately above them. This air slowly flows down slopes and arroyos, to be replaced by warmer air that, in turn, cools and flows away. Like guerillas infiltrating enemy territory, these tendrils steal into the lowlands, there to join and conquer.
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Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


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.



Phillips, S. J., and P. W. Comus. 2000. A Natural History of the Sonoran Desert. Arizona-Sonora Desert Museum Press, Tucson, 628 pp (see pp. 58-59).