Deserts occupy 20 percent of Earth’s land surface and are characterized by annual rainfall of less than 250 mm (9.84 inches). Conventional classifications are: hot and dry, semi-arid, coastal and cold.
Hot and Dry
Hot and dry deserts, such as the Sonoran Desert of Arizona and northwestern Mexico, are warm year-round with an extreme range of diurnal (daily) temperatures because of low humidity. Brief but heavy storms may occur seasonally. Soil is hard and rocky. Burrowing mammals, insects and reptiles are the main fauna. The Great Sandy Desert of Australia and the Sahara of north Africa fall under this category.
Semi-arid deserts, such as the Great Basin of Nevada and western Utah, have long dry summers plus winter rainfall. Dew fall may exceed rainfall. Soil is sandy and rocky, and may include “caliche” (pans of calcium carbonate). Fauna is consistent with hot and dry deserts.
Coastal deserts, such as the Pacific coast of Baja California, have brief cool seasons and long summers. Rainfall may be as much as 13 cm a year. Coastal deserts support larger mammals such as coyotes, as well as amphibians, owls, eagles and reptiles.
Cold deserts, such as Greenland, have long cold winters and brief, barely warm summers. Soils are infertile, salty, alluvial silt. High cold deserts in Utah support a variety of burrowing mammals, coyotes, lizards and foxes. The Gobi in northern China and southern Mongolia falls under this category.
NASA and USGS
NASA and the U.S. Geologic Survey recognize eight types of deserts classified by weather patterns: trade winds, midlatitude, rain shadow, coastal, monsoon, polar, paleodeserts and extraterrestrial.