Asemi-arid climate,semi-desert climate,orsteppe climateis adry climatesub-type. It is located on regions that receiveprecipitationbelowpotential evapotranspiration,but not as low as adesert climate.There are different kinds of semi-arid climates, depending on variables such as temperature, and they give rise to differentbiomes.
A more precise definition is given by theKöppen climate classification,which treatssteppeclimates (BShandBSk) as intermediates betweendesert climates(BW) and humid climates (A, C, D) inecologicalcharacteristics and agricultural potential. Semi-arid climates tend to support short, thorny or scrubby vegetation and are usually dominated by eithergrassesorshrubsas they usually cannot support forests.
To determine if a location has a semi-arid climate, the precipitation threshold must first be determined. The method used to find the precipitation threshold (in millimeters):[citation needed]
multiply by 20 the average annual temperature in degrees Celsius and then
add 280 if at least 70% of the total precipitation falls in the summer half of the year (April–September in the northern hemisphere, October–March in the southern hemisphere)
add 140 if 30–70% of the total precipitation falls in the summer half of the year
add nothing if less than 30% of the total precipitation falls in the summer half of the year
If the area's annual precipitation in millimeters is less than the threshold but more than half or 50% the threshold, it is classified as aBS(steppe, semi-desert, or semi-arid climate).[1]
Furthermore, to delineate hot semi-arid climates from cold semi-arid climates, a mean annual temperature of 18 °C (64.4 °F) is used as an isotherm. A location with aBS-type climate is classified as hot semi-arid (BSh) if its mean temperature is above this isotherm, and cold semi-arid (BSk) if not.
Regions with hot semi-arid climatesSemi-arid climate inQueensland,Australia.
Hot semi-arid climates (type "BSh" ) tend to be located from the high teens to mid-30s latitudes of thetropicsandsubtropics,typically in proximity to regions with atropical savanna climateor ahumid subtropical climate.These climates tend to have hot, or sometimes extremely hot, summers and warm to cool winters, with some to minimal precipitation. Hot semi-arid climates are most commonly found around the fringes of subtropical deserts.[citation needed]
Regions with cold semi-arid climatesSemi-arid climate inMontana,USA.
Cold semi-arid climates (type "BSk" ) tend to be located in elevated portions oftemperate zonesgenerally from the mid-30s to low 50s latitudes, typically bordering ahumid continental climateor aMediterranean climate.They are also typically found in continental interiors some distance from large bodies of water. Cold semi-arid climates usually feature warm to hot dry 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 and possibly freezing winters. These areas usually see somesnowfallduring the winter, though snowfall is much lower than at locations at similar latitudes with more humid climates.[citation needed]
Areas featuring cold semi-arid climates tend to have higher elevations than areas with hot semi-arid climates, and tend to feature major temperature swings between day and night, sometimes by as much as 20 °C (36 °F) or more. These largediurnal temperature variationsare 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 toMediterranean climates,with dry summers, relatively wet winters, and even wetter springs and autumns.[citation needed]
Cold semi-arid climates are most commonly found in central Asia and the western US, as well as the Middle East and other parts of Asia. However, they can also be found in Northern Africa, South Africa, sections of South America, sections of interior southern Australia (e.g.KalgoorlieandMildura) and southern New Zealand (Alexandra) and sections of Europe.[citation needed]
