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Extreme Weather in the Southeast Pacific - Windows to the Universe

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This image shows a fog bank in a valley of the Atacama Desert, along the coast of northern Chile. These fog banks are called "las camanchacas."
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Image Courtesy of Darryl Scott

Extreme Weather in the Southeast Pacific

The weather in the Southeast Pacific region can be considered extreme, in the sense that it receives very little rainfall and is extremely dry. For example, some places in the Atacama Desert in Chile receive an average of less than one millimeter (0.04 inches) of rain a year. Sometimes this region doesn't receive any rain at all for many years in a row.

There are several reasons why this region is so dry. The Chilean Coastal Range and the Andes mountains block this area from receiving moisture. In addition, a large wind current called the Pacific Anticyclone blows dry air into the region. Finally, an ocean current called the Humboldt Current brings cool water up the coast of Chile, which cools the air above it and forms clouds that tend not to produce precipitation.

Over the Southeast Pacific Ocean the clouds do produce drizzle, but this doesn't usually happen over the land. Instead, fog sometimes forms along the coast. People who live in this region call this fog "camanchacas," and it can support life. Even though it doesn't actually rain, algae, lichen, and some cacti are able to capture enough moisture from the fog in order to survive. In a village in northern Chile called Chunungo, people use nets to capture water from the fog.

Last modified September 18, 2008 by Becca Hatheway.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF