Semi-arid climate

A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on variables such as temperature, and they give rise to different biomes.

Regions with semi-arid climates
  BSh
  BSk

Defining attributes of semi-arid climates

A more precise definition is given by the Köppen climate classification, which treats steppe climates (BSk and BSh) as intermediates between desert climates (BW) and humid climates (A, C, D) in ecological characteristics and agricultural potential. Semi-arid climates tend to support short, thorny or scrubby vegetation and are usually dominated by either grasses or shrubs as it usually can't support forests.

Sahel region of Mali

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):

  • 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 a BS (steppe or semi-arid climate).[1]

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 (64.4 °F), a mean temperature of 0 °C (32.0 °F) in the coldest month, or a mean temperature of −3 °C (26.6 °F) in the coldest month. A location with a BS-type climate is classified as hot semi-arid (BSh) if its appropriate mean temperature is above whichever isotherm is being used, and a location with temperature below the given isotherm is classified as cold semi-arid (BSk).

Hot semi-arid climates

Regions with hot semi-arid climates

Hot semi-arid climates (type "BSh") tend to be located in the 20s and 30s latitudes of the tropics and subtropics, typically in proximity to regions with a tropical savanna or a humid subtropical climate. These climates tend to have hot, 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.

Hot semi-arid climates are most commonly found in Africa, Australia and South Asia. In Australia, a large portion of the Outback surrounding the central desert regions lies within the hot semi-arid climate region.[2] In South Asia, both India and sections of Pakistan experience the seasonal effects of monsoons and feature short but well-defined wet seasons, but are not sufficiently wet overall to qualify as a tropical savanna climate.

Hot semi-arid climates can also be found in Europe, primarily in southeast Spain[3][4] and parts of Greece,[5] Italy, Portugal and Cyprus. They are also found in parts of North America, such as Mexico, the ABC Islands, and areas of the Southwestern United States, and sections of South America such as the sertão, the Gran Chaco, and the poleward side of the arid deserts, where they typically feature a Mediterranean precipitation pattern, with generally rainless summers and wetter winters.

Cold semi-arid climates

Regions with cold semi-arid climates

Cold semi-arid climates (type "BSk") tend to be located in elevated portions of temperate zones, typically bordering a humid continental climate or a Mediterranean 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 some snowfall during the winter, though snowfall is much lower than at 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 tend to feature major temperature swings between day and night, sometimes by as much as 20 °C (36 °F) or more. These large diurnal temperature variations 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 subtropical climates, with dry summers, relatively wet winters, and even wetter springs and autumns.

Cold semi-arid climates are most commonly found in Mongolia, the Middle East and other parts of Asia and Western North America. However, they can also be found in Northern Africa, South Africa, Europe, sections of South America and sections of interior southern Australia (e.g. Kalgoorlie and Mildura) and New Zealand (around Alexandra).

Regions of varying classification

In climate classification, any one of three isotherms may be used to delineate hot from cold semi-arid climates — that of 18 °C (64 °F) average annual temperature; or that of the coldest month, either 0 °C (32 °F) or −3 °C (27 °F). The warm side of the isotherm of choice is classified as BSh, the cooler side as BSk. As a result of these differing definitions, some areas can have climates that are classified as either hot or cold semi-arid, depending on the isotherm used. One such location is San Diego, California (at its main airport). The city has cool summers for its latitude, due to prevailing winds off the ocean, so the average annual temperature is below 18 °C (64 °F)); however, winters are mild, with an average January temperature of 14 °C (57 °F), much closer to the 18.0 °C (64.4 °F) coldest-month isotherm that separates tropical and subtropical climates than to the 0 or −3 °C (32 or 27 °F) coldest-month isotherm that separates temperate and continental climates.

Charts of selected cities

Patos, Paraíba, Brazil
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
66
 
 
32
22
 
 
139
 
 
32
22
 
 
213
 
 
31
22
 
 
177
 
 
30
22
 
 
55
 
 
29
21
 
 
28
 
 
27
21
 
 
12
 
 
27
20
 
 
3
 
 
28
20
 
 
1
 
 
30
20
 
 
4
 
 
31
21
 
 
8
 
 
32
21
 
 
22
 
 
32
21
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: [6]
Imperial conversion
JFMAMJJASOND
 
 
2.6
 
 
90
71
 
 
5.5
 
 
89
71
 
 
8.4
 
 
88
71
 
 
7
 
 
86
71
 
 
2.2
 
 
84
71
 
 
1.1
 
 
81
69
 
 
0.5
 
 
81
67
 
 
0.1
 
 
82
67
 
 
0
 
 
85
69
 
 
0.2
 
 
88
69
 
 
0.3
 
 
89
70
 
 
0.9
 
 
90
71
Average max. and min. temperatures in °F
Precipitation totals in inches
Kalgoorlie, Australia
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
27
 
 
34
18
 
 
32
 
 
32
18
 
 
25
 
 
30
16
 
 
20
 
 
25
13
 
 
25
 
 
21
9
 
 
27
 
 
18
6
 
 
24
 
 
17
5
 
 
21
 
 
19
6
 
 
14
 
 
22
8
 
 
16
 
 
26
11
 
 
19
 
 
29
14
 
 
16
 
 
32
17
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: [7]
Imperial conversion
JFMAMJJASOND
 
 
1.1
 
 
92
65
 
 
1.3
 
 
90
64
 
 
1
 
 
85
61
 
 
0.8
 
 
78
55
 
 
1
 
 
69
48
 
 
1.1
 
 
64
43
 
 
1
 
 
62
41
 
 
0.8
 
 
66
42
 
 
0.5
 
 
72
47
 
 
0.6
 
 
79
52
 
 
0.7
 
 
84
58
 
 
0.6
 
 
90
62
Average max. and min. temperatures in °F
Precipitation totals in inches
Jaipur (Sanganer), India
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
8
 
 
19
4
 
 
12
 
 
22
7
 
 
6
 
 
29
12
 
 
4
 
 
34
17
 
 
16
 
 
38
21
 
 
66
 
 
38
23
 
 
216
 
 
31
22
 
 
231
 
 
29
20
 
 
80
 
 
30
19
 
 
23
 
 
30
15
 
 
3
 
 
25
9
 
 
3
 
 
20
5
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: India Weather On Web
Imperial conversion
JFMAMJJASOND
 
 
0.3
 
 
66
39
 
 
0.5
 
 
72
45
 
 
0.2
 
 
84
54
 
 
0.2
 
 
93
63
 
 
0.6
 
 
100
70
 
 
2.6
 
 
100
73
 
 
8.5
 
 
88
72
 
 
9.1
 
 
84
68
 
 
3.1
 
 
86
66
 
 
0.9
 
 
86
59
 
 
0.1
 
 
77
48
 
 
0.1
 
 
68
41
Average max. and min. temperatures in °F
Precipitation totals in inches
Niamey, Niger
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
0
 
 
33
16
 
 
0
 
 
36
19
 
 
3.9
 
 
39
23
 
 
5.7
 
 
41
27
 
 
35
 
 
40
28
 
 
69
 
 
37
26
 
 
154
 
 
34
24
 
 
171
 
 
33
23
 
 
92
 
 
34
24
 
 
9.7
 
 
38
24
 
 
0.7
 
 
36
20
 
 
0
 
 
33
17
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: Deutscher Wetterdienst[8]
Imperial conversion
JFMAMJJASOND
 
 
0
 
 
91
61
 
 
0
 
 
96
66
 
 
0.2
 
 
102
73
 
 
0.2
 
 
106
80
 
 
1.4
 
 
104
82
 
 
2.7
 
 
99
78
 
 
6.1
 
 
93
75
 
 
6.7
 
 
91
74
 
 
3.6
 
 
94
74
 
 
0.4
 
 
100
76
 
 
0
 
 
97
67
 
 
0
 
 
92
62
Average max. and min. temperatures in °F
Precipitation totals in inches
Murcia, Spain
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
25
 
 
17
5
 
 
28
 
 
18
6
 
 
30
 
 
21
8
 
 
27
 
 
23
10
 
 
32
 
 
27
13
 
 
20
 
 
31
17
 
 
5
 
 
34
20
 
 
10
 
 
34
21
 
 
27
 
 
30
18
 
 
44
 
 
26
14
 
 
32
 
 
20
9
 
 
21
 
 
17
6
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: Agencia Estatal de Meteorología[9]
Imperial conversion
JFMAMJJASOND
 
 
1
 
 
62
40
 
 
1.1
 
 
65
43
 
 
1.2
 
 
70
46
 
 
1.1
 
 
74
49
 
 
1.3
 
 
80
56
 
 
0.8
 
 
88
63
 
 
0.2
 
 
93
69
 
 
0.4
 
 
94
70
 
 
1.1
 
 
87
64
 
 
1.7
 
 
78
57
 
 
1.3
 
 
69
48
 
 
0.8
 
 
63
42
Average max. and min. temperatures in °F
Precipitation totals in inches
Reno, Nevada, United States
Climate chart (explanation)
J
F
M
A
M
J
J
A
S
O
N
D
 
 
26
 
 
8
−4
 
 
26
 
 
11
−2
 
 
19
 
 
14
1
 
 
12
 
 
18
3
 
 
12
 
 
23
8
 
 
13
 
 
29
11
 
 
4.6
 
 
33
14
 
 
5.8
 
 
33
13
 
 
8.9
 
 
28
9
 
 
13
 
 
21
4
 
 
21
 
 
13
−1
 
 
26
 
 
8
−4
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: NOAA[10]
Imperial conversion
JFMAMJJASOND
 
 
1
 
 
46
25
 
 
1
 
 
51
29
 
 
0.8
 
 
58
33
 
 
0.5
 
 
64
38
 
 
0.5
 
 
74
46
 
 
0.5
 
 
83
52
 
 
0.2
 
 
92
58
 
 
0.2
 
 
91
56
 
 
0.4
 
 
82
49
 
 
0.5
 
 
69
39
 
 
0.8
 
 
55
31
 
 
1
 
 
46
25
Average max. and min. temperatures in °F
Precipitation totals in inches

See also

  • Continental climate
  • Dry climate
  • Desert climate
  • Dust Bowl (an era of devastating dust storms, mostly in the 1930s, in semi-arid areas on the Great Plains of the United States and Prairies of Canada)
  • Goyder's Line (a boundary marking the limit of semi-arid climates in the Australian state of South Australia)
  • Köppen climate classification
  • Palliser's Triangle (semi-arid area of Canada)
  • Ustic (Soil Moisture Regime)
  • Wave height

References

  1. Peel, M. C.; Finlayson, B. L.; McMahon, T. A. (March 1, 2007). "Updated world map of the Koppen-Geiger climate classification" (PDF). hydrol-earth-syst-sci.net. University of Melbourne: Hydrology and Earth System Sciences. pp. 1633–1644. Retrieved May 8, 2017.
  2. Bureau of Meteorology – climate classification maps
  3. "ATLAS CLIMÁTICO IBÉRICO" (PDF). administracion.gob.es/. Instituto de Meteorologia de Portugal. Retrieved May 8, 2017.
  4. http://www.aemet.es/documentos/es/conocermas/recursos_en_linea/publicaciones_y_estudios/publicaciones/2Atlas_climatologico/Atlas_Clima_Macaronesia___Baja.pdf
  5. "Climate Atlas of Greece" (PDF). Hellenic National Meteorological Service. Archived from the original (PDF) on 21 September 2017. Retrieved 30 December 2019.
  6. Climate of Patos Access on January 16th, 2016.
  7. Access on August 14, 2021.
  8. "Klimatafel von Niamey (Aéro) / Niger" (PDF). Federal Ministry of Transport and Digital Infrastructure. Retrieved 14 June 2016.
  9. "Valores Climatológicos Normales. Murcia - Alcantarilla". Aemet.es. Archived from the original on 2009-12-14. Retrieved 2013-09-08.
  10. "NowData – NOAA Online Weather Data". National Oceanic and Atmospheric Administration. Retrieved June 6, 2015.
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