Semi-arid climate

A semi-arid climate or steppe climate describes climatic regions that receive precipitation below potential evapotranspiration, but not extremely so. A more precise definition is given by the Köppen climate classification that treats steppe climates (BSk and BSh) as intermediates between desert climates (BW) and humid climates in ecological characteristics and agricultural potential. Semi-arid climates tend to support short or scrubby vegetation, with semi-arid areas usually being dominated by either grasses or shrubs.

To determine if a location has a semi-arid climate, the precipitation threshold must first be determined. Finding the precipitation threshold (in millimeters) 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 half of the year (April through September in the Northern Hemisphere, 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. If the area's annual precipitation is less than the threshold but more than half the threshold, it is classified as a BS (steppe climate). Furthermore, to delineate "hot semi-arid climates" from "cold semi-arid climates", there are three widely used isotherms: Either a mean annual temperature of 18°C, or a mean temperature of 0°C or -3°C in the coldest month, so that a location with a "BS" type climate with the appropriate temperature above whichever isotherm is being used is classified as "hot semi-arid" (BSh), and a location with the appropriate temperature below the given isotherm is classified as "cold semi-arid" (BSk).

Hot Semi-arid climates

Hot semi-arid climates (type "BSh") tend to be located in the tropics and subtropics. These climates tend to have hot, sometimes extremely hot, summers and mild to warm winters. Snow rarely (if ever) falls in these regions. Hot semi-arid climates are most commonly found around the fringes of subtropical deserts. At higher latitudes, hot semi-arid climates typically feature a Mediterranean precipitation pattern, with dry summers and wetter winters, while hot semi-arid climates at lower latitudes typically feature precipitation patterns more like those of tropical savanna climates, with warmer wet seasons and cooler dry seasons. Hot semi-arid climate zones in regions such as West Africa, India and Pakistan will experience the seasonal effects of monsoons, being extremely wet during the monsoon months, and extremely dry in the rest of the year, with few or no months bringing moderate levels of precipitation.

Notable Cities with Hot Semi-arid climates

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Luanda, Angola

Dakar, Senegal

Gaborone, Botswana

Mogadishu, Somalia

N'Djamena, Chad

Niamey, Niger

Kano, Nigeria

Bloemfontein, South Africa

Lahore, Pakistan

Ahmedabad, India

Jaipur, India

Nicosia, Cyprus

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Beersheba, Israel

Amman, Jordan

Damascus, Syria

Mosul, Iraq

Willemstad, Curaçao

Maracaibo, Venezuela

Petrolina, Brazil

Laredo, USA

Monterrey, Mexico

Chihuahua, Mexico

Almería, Spain

Murcia, Spain

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Cold Semi-arid climates

Cold semi-arid climates (type "BSk") tend to be located in temperate zones. They are typically found in continental interiors some distance from large bodies of water. Cold semi-arid climates usually feature hot and dry (often exceptionally hot) summers, though their summers are typically not quite as hot as those of hot semi-arid climates. Unlike hot semi-arid climates, areas with cold semi-arid climates tend to have cold winters. These areas usually see some snowfall during the winter, though snowfall is much lower than locations at similar latitudes with more humid climates. Areas featuring cold semi-arid climates tend to have higher elevations than areas with hot semi-arid climates, and are sometimes subject to major temperature swings between day and night, sometimes by as much as 30°C/55°F in that time frame. These temperature swings are seldom seen in hot semi-arid climates. Cold semi-arid climates at higher latitudes tend to have dry winters and wetter summers, while cold semi-arid climates at lower latitudes tend to have precipitation patterns more akin to Mediterranean climates, with dry summers, relatively wet winters, and even wetter springs and autumns.

Notable Cities with Cold Semi-arid climates

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Kabul, Afghanistan

Yerevan, Armenia

Lethbridge, Canada

Medicine Hat, Canada

Kamloops, Canada

Tabriz, Iran

Urmia, Iran

Astana, Kazakhstan

Ulan Bator, Mongolia

Lanzhou, China

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Lhasa, China

Ürümqi, China

Ulan-Ude, Russia

Volgograd, Russia

Astrakhan, Russia

Sutherland, South Africa

Denver, USA

Salt Lake City, USA

Boise, USA

Samarkand, Uzbekistan

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Regions of varying classification

As stated previously, there are three isotherms used to delineate between hot and cold semi-arid climates. As a result of this, some areas can have climates that are classified as hot or cold semi-arid depending on the isotherm used. Such locations include:

Baku, Azerbaijan

Xi'an, China

Tehran, Iran

Ankara, Turkey

Eskişehir, Turkey

Konya, Turkey

Zaragoza, Spain

Comodoro Rivadavia, Argentina

Examples of regions with semi-arid climates

Oceania Australia: a large portion of the Outback, surrounding the central desert regions, including the following areas:

* MacDonnell Ranges, not including Alice Springs.

* Southern Kimberley, including Broome

* Central part of the WA Goldfields, including Kalgoorlie

* Western Pilbara, including Karratha

* Eastern Riverland, northern Victorian Mallee and Sunraysia, including Mildura

* Central North West Queensland, including Mount Isa

* Coastal part of the Far North region of South Australia, including Port Augusta

* See Goyder's Line which delineates the northern limit of land suitable for agriculture in South Australia

South America

Argentina: parts of Patagonia and western side of the pampas and Chaco region.

Brazil: the North-eastern Sertão or Caatinga

Paraguay: west of the country, in the dry Chaco.

Venezuela: the upper north-west zone Zulia and Falcón.

North America

Caribbean: the Leeward Antilles.

Canada:

* Palliser's Triangle, a region in the southern Prairie Provinces including central and southern Alberta, southern Saskatchewan and extreme southwestern Manitoba. The interior of the Triangle is semi-arid, the fringes are not;

* Parts of the British Columbia interior including the Cariboo plateau and the Okanagan Valley

United States: the western interior and western Great Plains, including the following states (except in montane areas and higher, as well as some other small areas):

* Western parts of the Dakotas

* Western Nebraska

* Western Kansas

* Western Oklahoma

* Western Texas

* Most of New Mexico

* Colorado

* Montana

* Wyoming

* Most of Utah

* Northeastern Arizona

* Northern Nevada

* Southern Idaho

* California's Central Valley

* Eastern Oregon

* Eastern Washington

Mexico:

* Parts of Eastern Sonora

* Parts of Southern Chihuahua

* Parts of Coahuila

* Most of Nuevo León

* Northern San Luis Potosí

Asia

Cyprus: Mesaoria plain

Israel: shrub steppe (Batha) of the Shfela

Much of Mongolia

Kazakhstan: Steppe

Pakistan: Hot semi-arid in western part of Pakistan (Balochistan) and few parts of Sindh.

India: Hot semi arid in western parts of India and cold semi arid in parts of northwestern India, the Deccan Plateau

Turkey: the Steppe of Central Anatolia, East Anatolia and Southeast Anatolia in the interior part of Turkey.

China: Much of the northwest and north-central regions, parts of Tibet, low elevations in some river valleys of Yunnan

Most of Iran

Large areas of Afghanistan

Portions of Kyrgyzstan, Uzbekistan

Most of lowland Azerbaijan

Africa

North Africa: The region between the Tell Atlas and the Saharan Atlas; and the Sahel on the southern edge of the Sahara

Southern Africa: wetter parts of the Karoo and Kalahari regions in the western interior of South Africa and Botswana, also bordering the Namib Desert to the north and west.

Southwestern Madagascar

Europe

Russia: Southwestern Russia, around the Caspian Sea

Greece: most of the southern Athens area

Spain: most of Canary Islands, the north-east peninsular zone in province of Zaragoza and the south-east peninsular zone in province of Alicante, province of Almeria and Region of Murcia.

Charts of Selected Cities

Hot Semi-arid climates

Cold Semi-arid climates

Cities of varying classification

See also

Continental climate

Goyder's Line and Palliser's Triangle - lands with unreliable rainfall were used for intensive agriculture, against climate advice.

Köppen climate classification

References

Category:Climate Category:Köppen climate classifications Category:Grasslands Category:Plains Category:Prairies