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The desert climate or arid climate (in the
Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, nota ...
''BWh'' and ''BWk''), is a dry climate sub-type in which there is a severe excess of
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when hu ...
over precipitation. The typically bald, rocky, or sandy surfaces in desert climates are dry and hold little moisture, quickly evaporating the already little rainfall they receive. Covering 14.2% of earth's land area, hot deserts are the second most common type of climate on earth after the
polar climate The polar climate regions are characterized by a lack of warm summers but with varying winters. Every month in a polar climate has an average temperature of less than . Regions with polar climate cover more than 20% of the Earth's area. Most of ...
. There are two variations of a
desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About o ...
climate according to the
Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, nota ...
: a hot desert climate (''BWh''), and a cold desert climate (''BWk''). To delineate "hot desert climates" from "cold desert climates", there are three widely used
isotherms A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve along which the function has a constant value, so that the curve joins points of equal value. It is a plane section of the three-dimensional grap ...
: most commonly a mean annual temperature of , or sometimes the coldest month's mean temperature of , so that a location with a ''BW'' type climate with the appropriate temperature above whichever isotherm is being used is classified as "hot arid subtype" (''BWh''), and a location with the appropriate temperature below the given isotherm is classified as "cold arid subtype" (''BWk''). Most desert/arid climates receive between of rainfall annually, although some of the most consistently hot areas of
Central Australia Central Australia, also sometimes referred to as the Red Centre, is an inexactly defined region associated with the geographic centre of Australia. In its narrowest sense it describes a region that is limited to the town of Alice Springs and i ...
, the
Sahel The Sahel (; ar, ساحل ' , "coast, shore") is a region in North Africa. It is defined as the ecoclimatic and biogeographic realm of transition between the Sahara to the north and the Sudanian savanna to the south. Having a hot semi-arid c ...
and Guajira Peninsula can be, due to extreme potential evapotranspiration, classed as arid with the annual rainfall as high as .


Precipitation

Although no part of Earth is known for certain to be absolutely rainless ever, in the Atacama Desert of northern Chile, the average annual rainfall over a period of 17 years was only just . Some locations in the Sahara Desert such as Kufra, Libya record an even drier of rainfall annually. The official weather station in
Death Valley Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. During summer, it is the hottest place on Earth. Death Valley's Badwater Basin is the point of lowest elevation in North Am ...
, United States reports annually, but in a 40-month period between 1931 and 1934 a total of just of rainfall was measured. To determine whether a location has an arid climate, the precipitation threshold is determined. The precipitation threshold (in millimetres) involves first multiplying the average annual temperature in °C by 20, then adding 280 if 70% or more of the total precipitation is in the high-sun summer half of the year (April through September in the
Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...
, or October through March in the Southern), or 140 if 30–70% of the total precipitation is received during the applicable period, or 0 if less than 30% of the total precipitation is so received there. If the area's annual precipitation is less than half the threshold (50%), it is classified as a ''BW'' (desert climate), while 50-100% the threshold results in a semi-arid climate.


Hot desert climates

Hot desert climates (''BWh'') are typically found under the
subtropical ridge The horse latitudes are the latitudes about 30 degrees north and south of the Equator. They are characterized by sunny skies, calm winds, and very little precipitation. They are also known as Subtropics, subtropical ridges, or highs. It is a h ...
in the lower middle latitudes or the
subtropics The subtropical zones or subtropics are geographical and climate zones to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 35° north and ...
, often between 20° and 33° north and south latitudes. In these locations, stable descending air and high pressure aloft clear clouds and create hot, arid conditions with intense sunshine. Hot desert climates are found across vast areas of North Africa, Western Asia, northwestern parts of the Indian Subcontinent, interior Australia, and smaller areas of the
Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...
, and
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...
. This makes hot deserts present in every continent except Antarctica, with Almería in Southern Spain also having this climate. At the time of high sun (summer), scorching, desiccating heat prevails. Hot-month average temperatures are normally between , and midday readings of are common. The world absolute heat records, over , are generally in the hot deserts, where the heat potential can be the highest on the planet. This includes the record of in
Death Valley Death Valley is a desert valley in Eastern California, in the northern Mojave Desert, bordering the Great Basin Desert. During summer, it is the hottest place on Earth. Death Valley's Badwater Basin is the point of lowest elevation in North Am ...
, which is currently considered the highest temperature recorded on Earth. Some desert in the tropics consistently experience very high temperatures all year long, even during wintertime. These locations feature some of the highest annual average temperatures recorded on Earth, exceeding , up to nearly in Dallol, Ethiopia. This last feature is seen in sections of Africa and
Arabia The Arabian Peninsula, (; ar, شِبْهُ الْجَزِيرَةِ الْعَرَبِيَّة, , "Arabian Peninsula" or , , "Island of the Arabs") or Arabia, is a peninsula of Western Asia, situated northeast of Africa on the Arabian Plate. ...
. During colder periods of the year, night-time temperatures can drop to freezing or below due to the exceptional radiation loss under the clear skies. However, very rarely do temperatures drop far below freezing under the cold subtype. Hot desert climates can be found in the deserts of North Africa such as the wide Sahara Desert, the Libyan Desert or the Nubian Desert; deserts of the
Horn of Africa The Horn of Africa (HoA), also known as the Somali Peninsula, is a large peninsula and geopolitical region in East Africa.Robert Stock, ''Africa South of the Sahara, Second Edition: A Geographical Interpretation'', (The Guilford Press; 2004), ...
such as the Danakil Desert or the Grand Bara Desert; deserts of Southern Africa such as the Namib Desert or the Kalahari Desert; deserts of Western Asia such as the Arabian Desert, the
Syrian Desert The Syrian Desert ( ar, بادية الشام ''Bādiyat Ash-Shām''), also known as the North Arabian Desert, the Jordanian steppe, or the Badiya, is a region of desert, semi-desert and steppe covering of the Middle East, including parts of sou ...
or the Dasht-e Lut; deserts of South Asia such as Dasht-e Kavir or the Thar Desert of India and Pakistan; deserts of the United States and Mexico such as the Mojave Desert, the Sonoran Desert or the
Chihuahuan Desert The Chihuahuan Desert ( es, Desierto de Chihuahua, ) is a desert ecoregion designation covering parts of northern Mexico and the southwestern United States. It occupies much of far West Texas, the middle to lower Rio Grande Valley and the lowe ...
; deserts of Australia such as the Simpson Desert or the Great Victoria Desert and many other regions. Hot deserts are lands of extremes: most of them are among the hottest, the driest and the sunniest places on Earth because of nearly constant high pressure; the nearly permanent removal of low-pressure systems, dynamic fronts and atmospheric disturbances; sinking air motion; dry atmosphere near the surface and aloft; the exacerbated exposure to the sun where solar angles are always high makes this desert inhospitable to most species.


Cold desert climates

Cold desert climates (''BWk'') usually feature hot (or warm in a few instances), dry summers, though summers are not typically as hot as hot desert climates. Unlike hot desert climates, cold desert climates tend to feature cold, dry winters. Snow tends to be rare and sporadic in regions with this climate. The
Gobi Desert The Gobi Desert (Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world. Geography The Gobi measures from southwest to northeast an ...
in northern China and Mongolia is one example of cold deserts. Though hot in the summer, it shares the very cold winters of the rest of Inner Asia. Cold desert climates are typically found at higher altitudes than hot desert climates and are usually drier than hot desert climates. Cold desert climates are typically located in temperate zones, usually in the leeward
rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes) is carrie ...
of high mountains, which restricts precipitation from the westerly winds. An example of this is the Patagonian Desert in Argentina bounded by the Andes ranges to its west. In the case of Central Asia, mountains restrict precipitation from the eastern monsoon. The Kyzyl Kum, Taklamakan and
Katpana Desert The Cold Desert, also known as the Katpana Desert or Biama Nakpo, is a high-altitude desert located near Skardu, Gilgit−Baltistan, Pakistan. The desert contains large sand dunes that are sometimes covered in snow during winter. Situated at a ...
deserts of Central Asia are other major examples of ''BWk'' climates. The Ladakh region, and the city of
Leh Leh () ( lbj, ) is the joint capital and largest city of Ladakh, a union territory of India. Leh, located in the Leh district, was also the historical capital of the Kingdom of Ladakh, the seat of which was in the Leh Palace, the former ...
in the Great Himalayas in India also have a cold desert climate. In North America the cold desert climate occurs in the drier parts of the Great Basin Desert and in the Bighorn Basin in Big Horn and Washakie Counties in Wyoming. The Hautes Plaines, located in the northeastern section of Morocco and in
Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , largest_city = capital , religi ...
is another major example of a cold desert climate. The Absheron Peninsula in eastern Azerbaijan is also an example of a cold desert climate. Arctic and Antarctic regions also receive very little precipitation during the year, owing to the exceptionally cold dry air freezing most precipitation ; however, both of them are generally classified as having
polar climate The polar climate regions are characterized by a lack of warm summers but with varying winters. Every month in a polar climate has an average temperature of less than . Regions with polar climate cover more than 20% of the Earth's area. Most of ...
s because they have average summer temperatures below even if they have such desert-like features as intermittent streams, hypersaline lakes, and extremely barren terrain in unglaciated areas such as the McMurdo Dry Valleys of Antarctica.


See also

* List of deserts * Dry climate * Semi-arid *
Desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About o ...


References


External links


Desert climate summary




{{Authority control Climate of Africa Climate of Asia Climate of Australia Climate of North America Climate of South America climate +Climate Köppen climate types