Semi-arid climate

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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). http://www.hydrol-earth-syst-sci.net/11/1633/2007/hess-11-1633-2007.pdf 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).

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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

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

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:

Examples of regions with semi-arid climates

Oceania

South America

North America

Asia

Africa

Europe

Hot Semi-arid climates

Gaborone
Climate chart (explanation)
J F M A M J J A S O N D
average max. and min. temperatures in °C
precipitation totals in mm
Monterrey
Climate chart (explanation)
J F M A M J J A S O N D
average max. and min. temperatures in °C
precipitation totals in mm
source: MSN Weather UK (2009-01-07), INEGI, 2006 report

Curaçao
Climate chart (explanation)
J F M A M J J A S O N D
average max. and min. temperatures in °C
precipitation totals in mm
source: Meteorological Service of the Netherlands Antilles and Aruba

Lahore
Climate chart (explanation)
J F M A M J J A S O N D
average max. and min. temperatures in °C
precipitation totals in mm
source: World Weather Information Service[3]

Cold Semi-arid climates

Denver
Climate chart (explanation)
J F M A M J J A S O N D
average max. and min. temperatures in °C
precipitation totals in mm
source: NWS Denver/Boulder, CO

Kabul
Climate chart (explanation)
J F M A M J J A S O N D
average max. and min. temperatures in °C
precipitation totals in mm
source: Weather Underground

Cities of varying classification

Comodoro Rivadavia
Climate chart (explanation)
J F M A M J J A S O N D
average max. and min. temperatures in °C
precipitation totals in mm
source: Weather 2 Travel
Eldorado County Weather

See also

References