Comment: 05:45 - 07:05 (01:20)
Source: Annenberg/CPB Resources - Earth Revealed - 22. Wind, Dust and Deserts
Keywords: "Art Montana", desert, subtropic, "rain shadow", "Pacific Ocean", air, coast, mountain, cloud, rainfall, snow, "Sierra Nevada", California, "Mojave Desert", "United States", Gobi, Asia, "South America", Andes
Our transcription: A few deserts occur outside these subtropical latitudes in the rain shadows of mountains such as California's Sierra Nevada.
The "rain shadow effect" works as follows:
Warm, moist air moves east across the Pacific.
It hits the coast and is forced upwards to get over the mountains.
As it rises, it expands and cools, and its moisture turns into clouds, rain, and sometimes snow.
This leaves the air dry.
As this cool, dry air moves down on the leeward side of the mountains, it is compressed and heats up again.
The air, now warm as well as dry, sucks up what little moisture may be available form the land below creating deserts as it continues its journey east of the Sierra Nevada.
Many of the world's most prominent deserts, well-known deserts are the result of this rain shadow effect.
The Mojave in the United States, for example, the Gobi Desert in Central Asia.
Western South America has a similar situation.
We have a chain of mountains down the west coast, the Andes, which serve as a barrier forming this rain shadow.
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