Mediterranean climate

From Wikipedia, the free encyclopedia
  (Redirected from Mediterranean climates)
Jump to: navigation, search
For the influence of Mediterranean climates on viticulture, see Mediterranean climate (wine).
  Areas with a Mediterranean climate

A Mediterranean climate /ˌmɛdɪtəˈrniən/ is the climate typical of the Mediterranean Basin, and is a particular variety of subtropical climate. The lands around the Mediterranean Sea form the largest area where this climate type is found, but it also prevails in much of California, in parts of Western and South Australia, in southwestern South Africa, sections of Central Asia, and in central Chile.

Köppen climate classification[edit]

Under the Köppen climate classification, "dry-summer subtropical" climates (classified as Csa and Csb) are often referred to as "Mediterranean". Under the Köppen-Geiger system, "C" zones have an average temperature above 10 °C (50 °F) in their warmest months, and an average in the coldest between 18 to −3 °C (64 to 27 °F) (or, in some applications, between 20 to 0 °C (68 to 32 °F)). The second letter indicates the precipitation pattern: "s" represents dry summers: first, Köppen has defined a dry month as a month with less than one-third that of the wettest winter month, and with less than 30 mm of precipitation in a summer month. Some, however, use a 40 mm level.[1][2] The third letter indicates the degree of summer heat: "a" represents an average temperature in the warmest month above 22 °C (72 °F), with at least four months averaging above 10 °C (50 °F); "b", an average temperature in the warmest month below 22 °C, and again with at least two months averaging above 10 °C.

Under this classification, dry-summer subtropical climates (Csa, Csb) usually occur on the western sides of continents. Csb zones include areas normally associated with Oceanic climates, not Mediterranean, such as much of the Pacific Northwest, much of southern Chile, parts of west-central Argentina, Portugal and Spain.[3] Additional highland areas in the subtropics also meet Cs requirements, though they, too, are not normally associated with Mediterranean climates, as do a number of oceanic islands such as Madeira, the Juan Fernández Islands, the western part of the Canary Islands and the eastern part of the Azores.

Under Trewartha's modified Köppen climate classification, the two major requirements for a Cs climate are revised. Under Trewartha's system, at least eight months must have average temperatures of at least 10 °C, and the average annual precipitation must not exceed 900 millimetres (35 in). Thus, under this system, many Csb zones (including the Pacific Northwest) become DO Oceanic. However Trewartha's 900mm threshold also disqualifies some locations generally considered to have a "classic" Mediterranean climate, notably Naples, which it classes as "humid subtropical" despite its hot, dry summers.

Precipitation[edit]

It [Chile] has four months of winter, no more, and in them, except when there is a quarter moon, when it rains one or two days, all the other days have such beautiful suns...

Pedro de Valdivia to Charles V, Holy Roman Emperor

During summer, regions of Mediterranean climate are dominated by subtropical high pressure cells, with dry sinking air capping a surface marine layer of varying humidity and making rainfall impossible or unlikely except for the occasional thunderstorm, while during winter the polar jet stream and associated periodic storms reach into the lower latitudes of the Mediterranean zones, bringing rain, with snow at higher elevations. As a result, areas with this climate receive almost all of their precipitation during their winter, autumn and spring seasons, and may go anywhere from 4 to 6 months during the summer without having any significant precipitation.

Temperature[edit]

Mediterranean climate distribution in the Americas

The majority of the regions with Mediterranean climates have relatively mild and wet winters and very hot and dry summers. However winter and summer temperatures can vary greatly between different regions with a Mediterranean climate. In the case of winters for instance, Lisbon experiences very mild temperatures in the winter, with frost and snow practically unknown, whereas Madrid has colder winters with annual frosts and snowfall. In the case of summers for instance, Athens experiences rather high temperatures in the summer (48 °C (118 °F) has been measured in nearby Eleusina). In contrast, San Francisco and Los Angeles both have mid-warm summers but warmer than summers in most Temperate Maritime climate zones due to the gentle upwelling of cold subsurface waters along the coast producing regular summer fog that does not reach far inland.

Because most regions with a Mediterranean climate are near large bodies of water, temperatures are generally moderate with a comparatively small range of temperatures between the winter low and summer high (although the daily range of temperature during the summer is large due to dry and clear conditions, except along the immediate coasts). Temperatures during winter only occasionally fall below the freezing point and snow is generally seldom seen. In the summer, the temperatures range from mild to very hot, depending on distance from a large body of water, elevation, and latitude. Even in the warmest locations with a Mediterranean-type climate, however, temperatures usually do not reach the highest readings found in adjacent desert regions because of cooling from water bodies, although strong winds from inland desert regions can sometimes boost summer temperatures, quickly increasing the risk of wildfires.

As in every climatologic domain, the highland locations of the Mediterranean domain can present cooler temperatures in winter than the lowland areas, temperatures which can sometimes prohibit the growth of typical Mediterranean plants. Some Spanish authors opt to use the term "Continental Mediterranean climate" for some regions with lower temperature in winter than the coastal areas[4] (direct translation from Clima Mediterráneo Continentalizado), but most climate classifications (including Köppen's Cs zones) show no distinction.

Additionally, the temperature and rainfall pattern for a Csa or even a Csb climate can exist as a microclimate in some high-altitude locations adjacent to a rare tropical As (summer-drought tropical climate, typically in a rainshadow region).

Mediterranean biome[edit]

The Mediterranean forests, woodlands, and scrub biome is closely associated with Mediterranean climate zones, as are unique freshwater communities. Particularly distinctive of the climate are sclerophyll shrublands, called maquis in the Mediterranean Basin, chaparral in California, matorral in Chile, fynbos in South Africa, and mallee and kwongan shrublands in Australia. Aquatic communities in Mediterranean climate regions are adapted to a yearly cycle in which abiotic (environmental) controls of stream populations and community structure dominate during floods, biotic components (e.g. competition and predation) controls become increasingly important as the discharge declines, and environmental controls regain dominance as environmental conditions become very harsh (i.e. hot and dry); as a result, these communities are well suited to recover from droughts, floods, and fires.[5] Aquatic organisms in these regions show distinct long-term patterns in structure and function,[6] and are also highly sensitive to the effects of climate change.[7][8]

Natural vegetation[edit]

The native vegetation of Mediterranean climate lands must be adapted to survive long, hot summer droughts and prolonged wet periods in winter. Mediterranean vegetation examples include the following:[9]

Much native vegetation in Mediterranean climate area valleys have been cleared for agriculture. In places such as the Sacramento Valley and Oxnard Plain in California, draining marshes and estuaries combined with supplemental irrigation has led to a century of intensive agriculture. Much of the Overberg in the southern Cape of South Africa, once covered with renosterveld, has likewise been largely converted to agriculture, mainly wheat. In hillside and mountainous areas, away from urban sprawl, ecosystems and habitats of native vegetation are more sustained.

The fynbos vegetation in the South-western Cape in South Africa is famed for its high floral diversity, and includes such plant types as members of the Restionaceae, Ericas (Heaths) and Proteas. Representatives of the Proteaceae also grow in Australia, such as Banksias. The palette of California native plants is also renowned for its species and cultivar diversity.

Hot-summer Mediterranean climate[edit]

  Hot-summer Mediterranean climate (Csa)

This subtype of the Mediterranean climate (Csa) is the most common form of the Mediterranean climate, therefore it is also known as a “typical Mediterranean climate”. As stated earlier, regions with this form of a Mediterranean climate experience average monthly temperatures in excess of 22.0 °C (71.6 °F) during its warmest month and an average in the coldest month between 18 to −3 °C (64 to 27 °F) or, in some applications, between 18 to 0 °C (64 to 32 °F). Also, at least four months must average above 10 °C (50 °F). Regions with this form of the Mediterranean climate typically experience hot, sometimes very hot and dry summers and mild, wet winters. In a number of instances, summers here can closely resemble summers seen in arid and semiarid climates. However, high temperatures during summers are generally not quite as high as those in arid or semiarid climates due to the presence of a large body of water. All areas with this subtype have wet winters. On the other hand, some areas with a hot Mediterranean subtype can actually experience very chilly winters, with occasional snowfall. Precipitation is heavier during the colder months. However, there are a number of clear, sunny days during the wetter months.

Csa climates are mainly found around the Mediterranean Sea, southwestern Australia, southwestern South Africa, sections of Central Asia and in the interior of California. Southern California's coasts also experience hot summers due to the shielding effect of the Channel Islands.

Rome
Climate chart (explanation)
J F M A M J J A S O N D
 
 
103
 
12
3
 
 
99
 
13
4
 
 
68
 
15
5
 
 
65
 
18
8
 
 
48
 
23
11
 
 
34
 
27
15
 
 
23
 
30
17
 
 
33
 
30
18
 
 
68
 
27
15
 
 
94
 
22
11
 
 
130
 
16
7
 
 
111
 
13
4
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: [10]
Los Angeles
Climate chart (explanation)
J F M A M J J A S O N D
 
 
85
 
20
9
 
 
94
 
21
10
 
 
80
 
21
11
 
 
21
 
23
12
 
 
7.9
 
24
14
 
 
1.5
 
26
16
 
 
0.3
 
29
18
 
 
3.3
 
29
19
 
 
8.1
 
29
18
 
 
9.4
 
26
16
 
 
27
 
23
11
 
 
49
 
20
9
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: NOAA
Perth
Climate chart (explanation)
J F M A M J J A S O N D
 
 
9.5
 
31
18
 
 
13
 
31
18
 
 
19
 
30
16
 
 
44
 
26
14
 
 
118
 
22
11
 
 
177
 
19
9
 
 
170
 
18
8
 
 
134
 
19
8
 
 
81
 
20
10
 
 
52
 
23
11
 
 
22
 
26
14
 
 
13
 
29
16
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: BoM[11]

Warm-summer Mediterranean climate[edit]

  Warm-summer Mediterranean climate (Csb)

Occasionally also termed “Cool-summer Mediterranean climate”, this subtype of the Mediterranean climate (Csb) is the less common form of the Mediterranean climate. As stated earlier, regions with this subtype of the Mediterranean climate experience warm (but not hot) and dry summers, with no average monthly temperatures above 22 °C (72 °F) during its warmest month and an average in the coldest month between 18 to −3 °C (64 to 27 °F) or, in some applications, between 18 to 0 °C (64 to 32 °F). Also, at least four months must average above 10 °C (50 °F). Winters are rainy and can be mild to chilly. In a few instances, snow can fall on these areas. precipitation can appear in the colder seasons in Mediterranean, but there are a number of clear sunny days even during the wetter seasons which makes it a Mediterranean climate.

As stated earlier, in some instances, regions with this subtype of the Mediterranean climate closely resemble an oceanic climate. Unlike typical Mediterranean climates, for the majority of the year, these regions experience generally cloudier and damper conditions. However, sunshine duration remains higher than in the Cfb areas, and during the summer months, these regions experience sunny, dry and warm conditions, where almost no rain falls. There is the legitimate threat of forest fires in these areas, in regions such as Galicia[12] and the Pacific Northwest.[13] Despite the fact that these climates are technically Csb climates, a number of scientists (and others) do not consider the climate “Mediterranean”, primarily because of the predominantly oceanic characteristics that these places exhibit. They are instead categorized as a form of oceanic climate.

Csb climates are found in northwestern Iberia, coastal California and parts of the Pacific Northwest, central Chile, parts of southern Australia and sections of southwestern South Africa.

Porto
Climate chart (explanation)
J F M A M J J A S O N D
 
 
158
 
14
5
 
 
140
 
15
6
 
 
90
 
17
7
 
 
116
 
18
9
 
 
98
 
20
11
 
 
46
 
23
14
 
 
18
 
25
16
 
 
27
 
25
15
 
 
71
 
24
15
 
 
138
 
20
12
 
 
158
 
17
8
 
 
195
 
15
7
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: Instituto de Meteorologia[14]
San Francisco
Climate chart (explanation)
J F M A M J J A S O N D
 
 
120
 
15
8
 
 
105
 
16
9
 
 
86
 
17
10
 
 
32
 
18
10
 
 
14
 
19
11
 
 
3.3
 
20
12
 
 
1
 
20
12
 
 
2.3
 
21
13
 
 
7.1
 
22
13
 
 
30
 
21
13
 
 
84
 
18
10
 
 
81
 
15
8
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: NOAA[15]
Cape Town
Climate chart (explanation)
J F M A M J J A S O N D
 
 
15
 
26
16
 
 
17
 
27
16
 
 
20
 
25
14
 
 
41
 
23
12
 
 
69
 
20
9
 
 
93
 
18
8
 
 
82
 
18
7
 
 
77
 
18
8
 
 
40
 
19
9
 
 
30
 
21
11
 
 
14
 
24
13
 
 
17
 
25
15
Average max. and min. temperatures in °C
Precipitation totals in mm
Source: WMO[16]

See also[edit]

References[edit]

  1. ^ Kottek, Markus; Grieser, Jürgen; Beck, Christoph; Rudolf, Bruno; Rube, Franz (June 2006). "World Map of the Köppen-Geiger climate classification updated". Meteorologische Zeitschrift 15 (3): 259–263. doi:10.1127/0941-2948/2006/0130. Retrieved 2011-02-27. 
  2. ^ Peel, M. C.; Finlayson, B. L.; McMahon, T. A. (2007). "Updated world map of the Köppen-Geiger climate classification". Hydrology and Earth System Sciences 4 (2): 439–473. doi:10.5194/hessd-4-439-2007. Retrieved 2011-02-27. 
  3. ^ Peel, M. C.; Finlayson, B. L.; McMahon, T. A. (2007). "Updated world map of the Köppen-Geiger climate classification". Hydrology and Earth System Sciences 11 (5): 1633–1644. doi:10.5194/hess-11-1633-2007. Retrieved 2011-02-27. 
  4. ^ climate of Spain, National Geographic Institute of Spain
  5. ^ Gasith, A. and V.H. Resh (1999). "Streams in Mediterranean Climate Regions: Abiotic Influences and Biotic Responses to Predictable Seasonal Events". Annu. Rev. Ecol. Sys. 30: 51–81. doi:10.1146/annurev.ecolsys.30.1.51. 
  6. ^ Resh, V.H.; L.A. Bêche, J.E. Lawrence, R.D. Mazor, E.P. McElravy, A.H. Purcell, and S.M. Carlson (2013). "Long-term Population and Community Patterns of Benthic Macroinvertebrates and Fishes in Northern California Mediterranean-climate Streams". Journal of the North American Benthological Society 719: 93–118. doi:10.1007/s10750-012-1373-9. Retrieved 10 November 2013. 
  7. ^ Lawrence, J.E.; K.B. Lunde, R.D. Mazor, L.A. Bêche, E.P. McElravy, and V.H. Resh (2010). "Long-Term Macroinvertebrate Responses to Climate Change: Implications for Biological Assessment in Mediterranean-Climate Streams". Journal of the North American Benthological Society 29: 1424–1440. doi:10.1899/09-178.1. Retrieved 10 November 2013. 
  8. ^ Filipe, A.F.; J.E. Lawrence, N. Bonada (November 2013). "Vulnerability of Biota in Mediterranean Streams to Climate Change: A Synthesis of Ecological Responses and Conservation Challenges". Hydrobiologia 719: 331–251. doi:10.1007/s10750-012-1244-4. Retrieved 10 November 2013. 
  9. ^ Dallman, Peter (1998). Plant Life in the World's Mediterranean Climates. Berkeley, CA: University of California Press. ISBN 9780520208094. 
  10. ^ STAZIONE 239 ROMA CIAMPINO at the Wayback Machine (archived December 23, 2009). meteoam.it
  11. ^ "Perth Monthly climate statistics". Australia Bureau of Meteorology. Retrieved 2010-08-02. 
  12. ^ "Forest fires in Spain". Iberianature.com. Retrieved 2011-02-27. 
  13. ^ "IFPL Shutdown Zones". Washington State Department of Natural Resources. November 2006. Retrieved 2011-02-27. 
  14. ^ "Monthly Averages for Porto, Portugal". Instituto de Meteorologia. Retrieved 2010-08-02. 
  15. ^ "Climatography of the United States No. 20 (1971–2000)". National Oceanic and Atmospheric Administration. Retrieved 2010-05-31. 
  16. ^ "Weather Information for Cape Town". World Weather Information Service. Retrieved 2010-08-02. 

External links[edit]