Mediterranean climate
This article possibly contains original research. (May 2022) |
A Mediterranean climate (/ˌmɛdɪtəˈreɪniən/ MED-ih-tə-RAY-nee-ən), also called a dry summer climate, described by Köppen as Cs, is a temperate climate type that occurs in the lower mid-latitudes (normally 30 to 44 north and south latitude). Such climates typically have dry summers and wet winters, with summer conditions ranging from warm to hot and winter conditions typically being mild to cool. These weather conditions are typically experienced in the majority of Mediterranean-climate regions and countries, but remain highly dependent on proximity to the ocean, altitude and geographical location.
The dry summer climate is found throughout the warmer
Mediterranean climate zones are typically located along the western coasts of landmasses, between roughly 30 and 45 degrees north or south of the equator. The main cause of Mediterranean, or dry summer, climate is the subtropical ridge, which extends towards the pole of the hemisphere in question during the summer and migrates towards the equator during the winter. This is due to the seasonal poleward-equatorward variations of temperatures.[1]
The resulting vegetation of Mediterranean climates are the garrigue or maquis in the European Mediterranean Basin, the chaparral in California, the fynbos in South Africa, the mallee in Australia, and the matorral in Chile. Areas with this climate are also where the so-called "Mediterranean trinity" of major agricultural crops have traditionally been successfully grown (wheat, grapes and olives). As a result, these regions are notable for their high-quality wines, grapeseed/olive oils, and bread products.[2]
Most of the historically iconic cities and regions of the Mediterranean Basin lie within the Mediterranean climatic zone, including Algiers, Antalya, Athens, Barcelona, Beirut, Dubrovnik, İzmir, Jerusalem, Tel Aviv, Limassol, Marseille, Monaco, Nice, Naples, Rome, Tunis and Valletta. Locations with Mediterranean climates outside of the Mediterranean Basin include Adelaide, Cape Town, Casablanca, Dushanbe, Lisbon, Los Angeles, Perth, Porto, San Francisco, Santiago, Tashkent, Victoria and Viña del Mar.[3]
Köppen climate classification
Under the Köppen climate classification, "hot dry-summer" climates (classified as Csa) and "cool dry-summer" climates (classified as Csb) are often referred to as just "Mediterranean". Under the Köppen climate system, the first letter indicates the climate group (in this case temperate climates). Temperate climates or "C" zones average temperature above 0 °C (32 °F) (or −3 °C (27 °F)), but below 18 °C (64 °F), in their coolest months. The second letter indicates the precipitation pattern ("s" represents dry summers). Köppen has defined a dry summer month as a month with less than 30 mm (1.2 in) of precipitation and as a month within the high-sun months of April to September, in the case of the Northern Hemisphere and October to March, in the case of the Southern Hemisphere, and it also must contain exactly or less than one-third that of the wettest winter month. Some, however, use a 40 mm (1.6 in) level.[4][5] The third letter indicates the degree of summer heat: "a" represents an average temperature in the warmest month above 22 °C (72 °F), while "b" indicates the average temperature in the warmest month below 22 °C (72 °F). There is a "c" with 3 or less months' average temperature above 10 °C (50 °F), but this climate is rare and is very isolated.
Under the Köppen classification, dry-summer climates (Csa, Csb) usually occur on the western sides of continents. Csb zones in the Köppen system include areas normally not associated with Mediterranean climates but with
Under
Precipitation
This Section needs additional citations for verification. (August 2023) |
[Chile] has six, 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...
Poleward extension and expansion of the subtropical
During summer, regions of the Mediterranean climate are strongly influenced by the subtropical ridge which keeps atmospheric conditions very dry with minimal cloud coverage. In some areas, such as coastal
In winter, the subtropical ridge migrates towards the equator and leaves the area, making rainfall much more likely. As a result, areas with this climate receive almost all of their precipitation during their winter and spring seasons, and may go anywhere from four to six months during the summer and early fall without having any significant
Irregularity of the rainfall, which can vary considerably from year to year, accentuates the droughts of the Mediterranean climate. Rain does not fall evenly, nor does the rain arrive at the same time or within the same intervals. In Gibraltar, for instance, rain starts falling nearly half a season earlier than at the Dead Sea. In the Holy Land no rain at all falls in summer but early rains may come in autumn.[8]
Temperature
The majority of the regions with Mediterranean climates have relatively mild winters and very warm summers. However, winter and summer temperatures can vary greatly between different regions with a Mediterranean climate. For instance, in the case of winters, Los Angeles experiences mild to warm temperatures in the winter, with frost and snowfall almost unknown, whereas Tashkent has cold winters with annual frosts and snowfall; or, to consider summer, Seville experiences rather high temperatures in that season. In contrast, San Francisco has cool summers with daily highs around 21 °C (70 °F) due to the continuous upwelling of cold subsurface waters along the coast.
Because most regions with a Mediterranean climate are near large bodies of water,
As in every climatologic domain, the highland locations of the Mediterranean domain can present cooler temperatures in the summer and winter than the lowland areas, temperatures which can sometimes prohibit the growth of typical cold-sensitive Mediterranean plants. Some Spanish authors opt in to use the term 'continental Mediterranean climate' for some regions with lower temperatures in winter than the coastal areas[9] (direct translation from Clima Mediterráneo Continentalizado), but most climate classifications (including Köppen's Cs zones) show no distinction as long as winter temperature means stay above freezing.
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 (tropical savanna climate with dry summers, typically in a rainshadow region, as in Hawaii). These have a favourable climate, with mild wet winters and fairly warm, dry summers.
Mediterranean biome
The
Mediterranean vegetation shows a number of adaptations to
Aquatic communities in Mediterranean climate regions are adapted to a yearly cycle in which
Natural vegetation
The native vegetation of Mediterranean climate lands must be adapted to survive long, hot summer droughts in summer and prolonged wet periods in winter. Mediterranean vegetation examples include the following:[11]
- Evergreen trees: eucalyptus,casuarina, melaleuca, pine, and cypress
- Deciduous trees: sycamore and some types of oak
- Fruit trees: grapes
- Shrubs: oaks.
- Sub-shrubs: sagebrush
- Grasses:
- Herbs: Achillea, Dietes, Helichrysum and Penstemon
Many native vegetations in Mediterranean climate area valleys have been cleared for agriculture and farming. 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, was once covered with renosterveld, but has likewise been largely converted to agriculture, mainly for wheat. In hillside and mountainous areas, away from the urban sprawls, ecosystems and habitats of native vegetation are more sustained and undisturbed.
The
diversity.Hot-summer Mediterranean climate
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 and −3 °C (64 and 27 °F) or, in some applications, between 18 and 0 °C (64 and 32 °F). Also, at least four months must average above 10 °C (50 °F) to avoid becoming a cold-summer Mediterranean subtype. Regions with this form of the Mediterranean climate typically experience hot, sometimes very hot and dry summers. Winters can be mild, cool or chilly, and some cities in this region receive some snowfall while others do not.
Csa climates are mainly found around the
Los Angeles, United States
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Perth, Australia
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Warm-summer Mediterranean climate
Occasionally also termed the "Cool-summer Mediterranean climate", this subtype of the Mediterranean climate (Csb) is less common and experience warm (but not hot) and dry summers, with no average monthly temperatures above 22 °C (72 °F) during its warmest month and as usual an average in the coldest month between 18 and −3 °C (64 and 27 °F) or,[citation needed] in some applications, between 18 and 0 °C (64 and 32 °F).[citation needed]
Also, at least four months must average above 10 °C (50 °F) once again.
Cool ocean currents, upwelling and higher latitudes are often the reason for this cooler type of Mediterranean climate.
The other main reason for this cooler type is the altitude. For instance, Menton on the French coast has a Csa climate while Castellar, Alpes-Maritimes, the adjacent town just north of Menton, with an altitude between 100 and 1,382 m (328 and 4,534 ft), has a Csb climate instead.[15]
Winters are rainy and can be mild to chilly. In some instances, snow can fall on these areas.
Precipitation occurs often in the colder seasons, but there are a number of clear sunny days even during the wetter seasons.
Csb climates are found in northwestern
Porto, Portugal
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Victoria, Canada
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Cape Town, South Africa
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Cold-summer Mediterranean climate
The cold-summer subtype of the Mediterranean climate (Csc) is rare and predominantly found at scattered high-altitude locations along the west coasts of North and South America having a similar climate.[citation needed] This type is characterized by cool, dry summers, with less than four months with a mean temperature at or above 10 °C (50 °F), as well as with cool, wet winters, with no winter month having a mean temperature below 0 °C (32 °F) (or −3 °C [27 °F]), depending on the isotherm used).[citation needed] Regions with this climate are influenced by the dry-summer trend (though briefly) that extends considerably poleward along the west coast of the Americas, as well as the moderating influences of high altitude and relative proximity to the Pacific Ocean. These conditions maintain an unusually narrow temperature range through the year for climate zones at such distances from coasts.
In North America, areas with Csc climate can be found in the
In South America, Csc regions can be found along the Andes in Chile and Argentina. The town of Balmaceda, Chile is one of the few towns confirmed to have this climate.
Small areas with a Csc climate can be found at high elevations in Corsica.[25]
In Norway, the small fishing village of Røst above the Arctic Circle has a climate bordering on Csc and is known as a "climatic anomaly" due to abnormally warm temperatures despite its latitude located above 67°N latitude.[26]
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Liawenee, Tasmania
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External links
Media related to Mediterranean climate at Wikimedia Commons