Rain Shadow Range
Date: Fall 2011
The "rain shadow" effect of mountains causes dry climates on the leeward side of mountains. About how far does that "rain shadow" extend? Less than 100 miles? Hundreds of miles? I am sure it depends on the size of the mountain range. How about the Rockies? The Himalayas?
The rain shadow extends until the air encounters a source of moisture. In North America, for instance, air that passes over the Rocky Mountains is quite dry; precipitation in the Midwest tends to come from moisture carried.from the Gulf of Mexico.
Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming
An excellent example of an active rain shadows in the prevailing westerlies is the Coast Range followed by Sierra Nevada chain. The California Coast ranges create a rain shadow (hence the need to irrigate crops in the "Valley" and the existence of temperate rain forests) and the Sierras complete the job and create the Nevada desert.
This should spark a discussion on the effect of elevation on the drying effect, and prepare students to understand the wetter parts of the Colorado plateau and why the Western Slope is the source of water for Denver.
R. W. "Mr. A." Avakian
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Update: June 2012