The Atacama and American Deserts

Chile's Atacama Desert is widely regarded as the driest nonpolar desert on Earth, with some interior weather stations near Calama and Yungay recording no measurable rainfall across multi-decade stretches of instrumental record. Three reinforcing mechanisms produce this extreme dryness: the cold, northward-flowing Humboldt Current chills the coastal air and suppresses the convection needed to generate rain; a persistent South Pacific subtropical high keeps the region under stable, sinking air; and the Andes to the east block moisture arriving from the Amazon Basin, casting a deep rain shadow. The combined effect leaves parts of the Atacama with average annual rainfall measured in single-digit millimeters.