Rain shadow deserts are formed because tall mountain ranges prevent
moisture-rich clouds from reaching areas on the lee, or protected side,
of the range. As air rises over the mountain, water is precipitated and
the air loses its moisture content. A desert is formed in the leeside
“shadow” of the range.
[Illustration: The Sahara of Africa is the world’s largest desert. It
contains complex linear dunes that are separated by almost 6 kilometers
(Skylab photograph).]
[Illustration: A rare rain in the Tengger, a midlatitude desert of
China, exposes ripples and a small blowout on the left. Winds will
shortly cover or remove these features.]
[Illustration: This Landsat image shows the Turpan Depression in the
rain shadow desert of the Tian Shan of China. A sand sea is in the lower
center on the right, but desert pavement, gray in color, dominates this
desert. The few oases in the desert and the vegetation in the mountains
at the top are in red. A blanket of snow separates the vegetation in the
Tian Shan from the rain shadow desert.]