Semiarid climate ( Latin semi - semi and aridus - dry) (in the classification of Köppen’s climates is denoted by a combination of Latin letters BSk / BSh ) - a semi-dry climate with precipitation that does not ensure the growth of trees on watershed spaces, and often does not ensure the normal development of crops . A climate in which artificial irrigation of fields is mostly necessary. The semiarid climate is the main factor in the formation of landscapes of semi-deserts , steppes , and partly forest-steppes of a moderate geographical zone [1] .
To classify the climate as semi-arid, it is necessary to determine the average annual rainfall. The threshold allowing to distinguish between humid and semi-arid climate is calculated by the following formula: the average annual air temperature in ° C must be multiplied by 20, and then add 280, if 70% of the annual rainfall or more falls on the hot half of the year (from April to September for the northern hemisphere and from October to March for the southern one), or 140 if from 30% to 70% of the annual rainfall falls on the corresponding period, or 0 if less than 30% of the annual rainfall falls in the hot season. If the annual rainfall is less than the specified threshold, then the climate is classified as semi-arid BS (climate of the steppes) [2]
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Types of semi-arid climate
Depending on the temperature regime of the area, the semi-arid climate is subdivided into the semi-arid climate of temperate latitudes (or the steppe climate ) and the semi-arid climate of low latitudes [3] .
Temperate semi-arid climate
The semi-arid climate of temperate latitudes (BSk is a cold semi-arid climate) is characteristic of the temperate zone . As a rule, such a climate is typical for areas remote from the ocean and large seas and usually separated from them by high mountains. This type of climate is characterized by hot (often extremely hot) and arid summers and rather cold winters [3] . As a rule, snow falls in such regions in winter, but to a lesser extent than in areas with humid climates located in the same latitudes. The semi-arid climate of temperate latitudes is characterized by significant temperature differences during the day (up to 20 and more ° C). For a semi-arid climate at low latitudes, such significant differences in air temperatures are uncharacteristic. The temperature regime is highly dependent on latitude [3] .
| Climate Astrakhan , Russia | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Indicator | Jan | Feb | March | Apr | May | June | July | Aug | Sep | Oct | Nov | Dec | Year |
| Absolute maximum, ° C | 14.0 | 16.9 | 24.0 | 32,0 | 36.8 | 39.9 | 41.0 | 40.8 | 38,0 | 29.9 | 21.6 | 16,4 | 41.0 |
| Average maximum, ° C | −0.1 | 0.7 | 7.8 | 17.4 | 23.8 | 29.3 | 32,0 | 30.7 | 24.3 | 16.3 | 7.4 | 1,2 | 15.9 |
| Average temperature, ° C | −3.6 | −3.7 | 2,3 | 11.1 | 17.7 | 23.1 | 25.6 | 24.0 | 17.7 | 10,4 | 3,1 | −1.9 | 10.5 |
| Average minimum ° C | −6.5 | −7.1 | −1.9 | 5.9 | 12.1 | 17.4 | 19.6 | 18.0 | 12.3 | 5.9 | 0.3 | −4.6 | 6.0 |
| Absolute minimum, ° C | −31.8 | −33.6 | −26.9 | −8.9 | −1.1 | 6.1 | 10.1 | 6.1 | −2 | −10.5 | −25.8 | −29.9 | −33.6 |
| Precipitation rate, mm | sixteen | 12 | sixteen | 23 | 28 | 25 | 24 | 20 | 17 | 18 | 18 | sixteen | 233 |
| Source: Weather and Climate | |||||||||||||
Low latitude semi-arid climate
The semi-arid climate of low latitudes (BSh - a hot semi-arid climate) is typical for the regions located in the subtropical and tropical zones. This subspecies of the semiarid climate is characterized by hot, sometimes extremely hot, summers and mild winters [3] . Snow falls not everywhere and very rarely. The semi-arid climate of low latitudes is characteristic of many regions of West Africa , India , Mexico , and Southern California . Some areas with a semi-arid climate of low latitudes ( India , Pakistan ) are characterized by a short but pronounced rainy season, but their total number is insufficient to classify the climate of the area as the tropical savannah climate. In Australia, a hot semi-arid climate is typical for most of the outback [4] .
| Climate Dakar , Senegal (1961−1990) | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Indicator | Jan | Feb | March | Apr | May | June | July | Aug | Sep | Oct | Nov | Dec | Year |
| Absolute maximum, ° C | 39.6 | 38.7 | 40,4 | 38,4 | 36,2 | 36.6 | 36.9 | 35.0 | 36,2 | 39.3 | 40.3 | 39.5 | 40,4 |
| Average maximum, ° C | 25.3 | 25,2 | 25,4 | 25.0 | 26.0 | 28.6 | 30,0 | 30.3 | 30.7 | 31,0 | 29.8 | 27.4 | 27.9 |
| Average temperature, ° C | 20.9 | 20.6 | 21.1 | 21.5 | 22.8 | 25.6 | 27,2 | 27.5 | 27.7 | 27.7 | 25.9 | 23,4 | 26,4 |
| Average minimum ° C | 18.3 | 18.0 | 18.5 | 19.2 | 20.7 | 23.5 | 25.1 | 25.3 | 25,2 | 25.3 | 23.3 | 21.0 | 23.8 |
| Absolute minimum, ° C | 11.0 | 10.7 | 10.9 | 14.0 | 15.4 | 17.0 | 17,2 | 20,0 | 20,0 | 17,2 | 17.0 | 12,4 | 10.7 |
| Precipitation rate, mm | 1,0 | 2.0 | 0.3 | 0,0 | 0.1 | 14.0 | 51.0 | 154.0 | 133.0 | 26.0 | 0.2 | 1,0 | 382.0 |
| Source: Weather and Climate | |||||||||||||
Notes
Links
- Arid climate
- Steppe
- Semi desert