Six USGS groups
Types of desert
USGS classifies deserts by geographical location and dominant weather pattern as trade wind, midlatitude, rain shadow, coastal, monsoon, or polar deserts. USGS
Trade wind deserts
The trade winds in two belts on the equatorial sides of the Horse Latitudes heat up as they move toward the Equator. USGS These dry winds dissipate cloud cover, allowing more sunlight to heat the land. USGS Most of the major deserts of the world lie in areas crossed by the trade winds. USGS The Sahara of North Africa has experienced temperatures as high as 57 degrees C, and is a trade wind desert. USGS The Sahara of Africa is the world's largest desert, in USGS wording. USGS
Midlatitude deserts
Midlatitude deserts occur between 30 and 50 degrees north and south, poleward of the subtropical high-pressure zones. USGS These midlatitude deserts are in interior drainage basins far from oceans and have a wide range of annual temperatures. USGS
Rain shadow deserts
Rain shadow deserts are formed because tall mountain ranges prevent moisture-rich clouds from reaching areas on the lee, or protected side, of the range. USGS As air rises over the mountain, water is precipitated and the air loses its moisture content. USGS
Coastal deserts
Coastal deserts generally are found on the western edges of continents near the Tropics of Cancer and Capricorn. USGS A coastal desert, the Atacama of South America, is the Earth's driest desert, according to USGS. USGS In the Atacama, measurable rainfall of 1 millimeter or more may occur as infrequently as once every 5-20 years. USGS Crescent-shaped dunes are common in coastal deserts such as the Namib, Africa. USGS
Monsoon deserts
"Monsoon," derived from an Arabic word for "season," refers to a wind system with pronounced seasonal reversal. USGS
Polar deserts
Polar deserts are given a mean annual precipitation less than 250 millimeters and a mean temperature during the warmest month of less than 10 degrees C. USGS Polar deserts on the Earth cover nearly 5 million square kilometers and are mostly bedrock or gravel plains. USGS Though normally associated with hot, sandy environments, cold deserts are also widespread. Met Office The Gobi Desert of east Asia is one example, where annual average temperatures can be below 0 degrees C. Met Office
Are polar deserts "deserts"?
USGS includes polar deserts, giving them a mean annual precipitation less than 250 millimeters and a mean temperature during the warmest month of less than 10 degrees C, and says they cover nearly 5 million square kilometers. Britannica notes that some definitions include "frigid deserts," but the account we checked restricts the term to hot and temperate deserts. We report both approaches.
Three named places, and the disagreements around them, are on the places page.