photo #5267906

The mountains of Chile affect the country’s clouds and the climate in profound ways, as revealed by this image looking north-east over the Pacific coast by an astronaut aboard the International Space Station. The Andean Mountain Range running north to south separates the cloud-filled region of Bolivia to the east from Chile’s completely cloudless Atacama Desert region to the west. The prevailing winds of this region blow from east to west (top right in the image to bottom left). Though they can carry moisture from the Amazon basin in Brazil, off in the distance, the winds only reach the Atacama after flowing up over the Andes. As the air lifts, it cools, which encourages clouds to form and shed precipitation on the eastern slopes of the Andes. The air is dry by the time it sinks back down on the west to reach the Atacama. When winds do blow inland from the Pacific, another mountain range, the Chilean Coastal Range, visible here along the coast, performs a similar cloud-busting role. This range strips the air of moisture on its coastal slopes before reaching the Atacama. Sandwiched between two mountain ranges like this, this part of Chile is in a double rain shadow. As a result, the Atacama is one of the driest places on Earth, where it rains here no more than a handful of times a century.