Coastal deserts generally are found on the western edges of continents
near the Tropics of Cancer and Capricorn. They are affected by cold
ocean currents that parallel the coast. Because local wind systems
dominate the trade winds, these deserts are less stable than other
deserts. Winter fogs, produced by upwelling cold currents, frequently
blanket coastal deserts and block solar radiation. Coastal deserts are
relatively complex because they are at the juncture of terrestrial,
oceanic, and atmospheric systems. A coastal desert, the Atacama of South
America, is the Earth’s driest desert. In the Atacama, measurable
rainfall—1 millimeter or more of rain—may occur as infrequently as once
every 5-20 years.
[Illustration: Crescent-shaped dunes are common in coastal deserts such
as the Namib, Africa, with prevailing onshore winds. Low clouds cover
parts of the Namib in this space shuttle photo.]
[Illustration: High dunes of the Namib Desert near Sossus Vlei
(photograph by Georg Gerster).]
[Illustration: Morning fog moistens the dunes of the Namib coastal
desert (photograph by Georg Gerster).]