Wanderlust World Wanderlust World Deserts—areas receiving less than 250 mm (10 in) of annual precipitation—are shaped by large-scale atmospheric and geographic patterns. Two fundamental factors drive their formation:
At roughly 30° north and south latitude, descending air from the Hadley circulation creates persistent high-pressure zones. This sinking air warms adiabatically, inhibiting cloud formation and precipitation. The result: the world's great subtropical deserts—Sahara, Arabian, Sonoran, Kalahari, Australian Outback—all straddle these latitudes. The mechanism is global atmospheric circulation, not local geography alone.
Oceans are the primary source of atmospheric moisture. As air masses travel inland, they lose humidity through precipitation. Deep continental interiors—far from oceans—receive little residual moisture. This explains deserts like the Gobi (central Asia), Great Basin (western USA), and Patagonian Desert (rain shadow + continentality). Mountain ranges can intensify this by blocking maritime winds (rain shadow effect).
Many deserts arise from a combination: subtropical highs plus continentality (Sahara), or rain shadows plus cold offshore currents (Atacama, Namib). Understanding these drivers is key to predicting desertification and climate change impacts.