Hadley cell
Rainfall at the ALMA site averages annually. The dry climate of Llano de Chajnantor is due to three factors: the rain shadows created by the Andes and the Chilean Coastal Range, the inversion created by the Humboldt Current off the coast of Chile, and dry air descending between the Hadley cell and the Ferrel cell, which forms the South Pacific High. While the site is generally viewed as being in the Atacama Desert, in terms of ecoregions it is in the Central Andean dry puna. Llano de Chajnantor is at the same latitude as deserts in southern Africa and central Australia.