Desert (geography)

A dry region where evaporation usually exceeds precipitation and vegetation is sparse. Deserts can be hot or cold and include both sandy landscapes and rocky or gravel plains.

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Hadley cell: A tropical atmospheric circulation pattern in which air rises near the equator and descends in the subtropics. Descending dry air helps form many of the world's subtropical deserts.
Precipitation: Water released from the atmosphere as rain, snow, sleet, or hail. Its low and irregular supply is the defining climatic constraint in deserts.
Sahara: The vast subtropical desert covering much of North Africa. Its immense area and varied terrain illustrate the scale of a major hot desert.
Semi-arid climate: A climate with limited rainfall, more than a desert climate but less than a humid climate. It lies near the dry margin of desert classifications and often grades into desert.
Rain shadow: A dry region on the leeward side of a mountain range, where descending air has lost much of its moisture. Mountain barriers create deserts far from subtropical high-pressure belts.
Evapotranspiration: The transfer of water from land to the atmosphere through evaporation and plant transpiration. Its high potential relative to rainfall leaves little water available to ecosystems.
Gobi Desert: A cold desert spanning parts of northern China and southern Mongolia. It shows that deserts need not be hot or dominated by sand dunes.
Steppe: A semi-arid grassland with too little rainfall to support forests but enough for continuous grasses. Its greater plant cover distinguishes it from most deserts.
Cold ocean current: A flow of relatively cold seawater that can cool the air above it and suppress rainfall along nearby coasts. Cold currents help explain coastal deserts such as the Atacama.
Xerophyte: A plant adapted to survive with little available water. Desert vegetation consists largely of species with water-saving adaptations.