Mediterranean climate

For the influence of Mediterranean climates on viticulture, see Mediterranean climate (wine).

  Areas with Mediterranean climate

A Mediterranean climate is the climate typical of most of the lands in the Mediterranean Basin as part of subtropical climate. Worldwide, this is where the largest area of this climate type is found. Beyond the Mediterranean area, this climatic type prevails in much of California, in parts of Western and South Australia, in southwestern South Africa, in isolated sections of Central Asia and in parts of central Chile.

Characteristics

The climate is characterised by warm to hot, dry summers and mild to cool, wet winters. Mediterranean climate zones are associated with the five large subtropical high pressure cells of the oceans, the Azores High, South Atlantic High, North Pacific High, South Pacific High, and Indian Ocean High. These high pressure cells shift polarward in the summer and equatorward in the winter, playing a major role in the formation of the world's tropical deserts and the zones of Mediterranean climate polarward of the deserts. For example, the Azores High is associated with the Sahara Desert and the Mediterranean Basin's climate. The South Atlantic High is similarly associated with the Namib Desert and the Mediterranean climate of the western part of South Africa. The North Pacific High is related to the Sonoran Desert and California's climate, while the South Pacific High is related to the Atacama Desert and central Chile's climate, and the Indian Ocean High is related to the deserts of western Australia (Great Sandy Desert, Great Victoria Desert, and Gibson Desert) and the Mediterranean climate of southwest and south-central Australia.

Most large, historic cities of the Mediterranean basin, including Athens, Barcelona, Beirut, Jerusalem, Marseille and Rome, lie within Mediterranean climatic zones, as do major cities outside of the Mediterranean, such as Cape Town, Los Angeles, Adelaide, Perth, San Francisco and Santiago de Chile.

Köppen climate classification

  Areas with Köppen-Geiger Csa, Csb, Csc classifications

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°C (64°F) and −3°C. (26.6°F) (or, in some applications, between 18°C and 0°C (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 precipitations in a summer month. But ulterior updates will rather use a 40 mm level . 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 four months averaging above 10°C.

Under this classification, dry-summer subtropical climates (Csa, Csb) usually occur on the western sides of continents, and Csb zones include additional areas such as much of the Pacific Northwest, much of southern Chile, parts of west-central Argentina, and northern Spain and Portugal. Many of these areas would be Oceanic (Cfb) did not their dry-summer patterns meet Koeppen's Cs thresholds, and cities such as Seattle, Portland, and Victoria can be classified as Csb. Additional highland areas in the subtropics also meet Cs requirements, though they, too, are not normally associated with Mediterranean climates.

Under Trewartha's modified Koeppen 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 mm. (35 inches). Thus, under this system, many Csb zones (including the Pacific Northwest), become DO Oceanic.

Precipitation

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 yearly rainfall during their winter season, and may go anywhere from 4 to 6 months during the summer without having any significant precipitation.

Toward the equatorial latitudes, winter precipitation increases as a share of annual precipitation as the climate grades equatorward into the steppe climate usually characterized as BSHs normally too dry to support unirrigated agriculture. Toward the polar latitudes, total moisture usually increases; in Europe there is more summer rain further north while along the American west coast the winters become more intensely wet and the dry seasons shorter as one moves north. In the Pacific Ocean adjacent Mediterranean climate regions the El Niño-Southern Oscillation affects annual precipitation over a given decade.

Temperature

Mediterranean Climate Distribution in the Americas

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. In the case of winters for instance, Lisbon experiences very mild temperatures in the winter, with frost and snow practically unknown, whereas Thessaloniki has colder winters with annual frosts and snowfall. In the case of summers for instance, Athens experiences rather high temperatures in the summer (48.0°C has been measured in nearby Eleusina), whereas San Francisco has cool, mild summers due to the upwelling of cold subsurface waters along the coast producing regular summer fog.

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 reach freezing and snow occurs only rarely at sea level, but often in surrounding mountains because of wet conditions. In the summer, the temperatures range from mild to very warm, depending on distance from the open ocean, 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.

Inland locations sheltered from or distant from sea breezes can experience severe heat during the summer. For example the northern Sacramento Valley and southern San Joaquin Valley regions of the Central Valley of California can experience summer temperatures characteristic of a hot desert (i.e.: 40°C/104°F) because of high temperature and very low humidity, although their winters are very rainy and foggy enough to allow lusher vegetation than is typical in deserts; the vegetation becomes a fire risk in the dry summers. However the middle region of the Central Valley receives an ocean influence from the San Francisco Bay, due west, known as the "Delta Breeze" which reduces the summer heat. It can even carry coastal fog into the area, with cooler temperatures and higher humidity. Meanwhile more southern coastal cities, such as Los Angeles and San Diego, California exhibit drier borderline semiarid climate conditions within the Mediterranean climate. While the wet-winter, dry-summer precipitation pattern prevails in these cities, winters there are relatively dry by overall Mediterranean climate standards. Coastal climates are normally designated as Csb in the Köppen climate classification as they are characterized by an average temperature of the warmest month below 21.8°C (72°F); the hotter, typically inland areas are classified as Csa, which indicates a hot summer with the average temperature of the warmest month being above 21.8°C (72°F). Csb climates are found in northwestern Iberia, coastal California and parts of the Pacific Northwest, central Chile and parts of southern Australia while Csa climates are mainly found around the Mediterranean Sea, southwestern Australia (including the city of Perth), southwestern South Africa and in the interior of California. In the northwestern Mediterranean Basin, the rainiest season is divided into a primary maximum during the autumn and a secondary in spring, making for a shorter dry season than in the classic Mediterranean climate as in Barcelona and with some cold days in winter, when the northern winds often bring cool or freezing air from central and northern Europe (usually accompanied by lower temperatures, high pressure and clear skies) but also with some snowstorms. This northern Mediterranean coasts is close to the Cfa Köppen classified humid subtropical climates of the Danube, Po.

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 (direct translation from Clima Mediterráneo Continentalizado) ,but most climate classifications (including Köppen's Cs zones) show no distinction.

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

The Mediterranean forests, woodlands, and scrub biome is closely associated with Mediterranean climate zones. 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 component (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.

Natural vegetation

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:

• Evergreen trees: such as Pines, Cypress, and Oaks
• Deciduous trees: such as Sycamores, Oaks, and Buckeyes
• Fruit trees such as Olives, Figs, Citrus, Walnuts and Grapes
• Shrubs: Bay laurel and California laurel, Manzanitas, and Chamise
• Sub-shrubs: such as Sages, Artemisias, and Sagebrush
• Grasses: Grassland types, Bunchgrasses; Sedges, and Rushes
• Herbs: such as fragrant Rosemary, Basil, Thyme, and Lavender

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. 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

This subtype of the Mediterranean climate (Csa) is the most common form of the Mediterranean climate. As stated earlier, regions with this form of a Mediterranean climate experiences average monthly temperatures in excess of 21.8°C (72°F) during its warmest month and an average in the coldest month between 18°C (64°F) and −3°C (26.6°F) or, in some applications, between 18°C and 0°C (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 seen in arid or semiarid climates due to the presence of a large body of water. All areas with this subtype have wet winters. However, some areas with a hot Mediterranean subtype can actually experience very chilly winters, complete with occasional snowfall. Precipitation is heavier during the colder months. However, there are a number of clear, sunny days during the wetter months.

Notable Cities with Hot-summer Mediterranean climate

Adelaide, Australia Al Bayda, Libya Algiers, Algeria Antalya, Turkey Athens, Greece (Borderline BSh hot semi-arid climate) Barcelona, Spain Madrid, Spain Beirut, Lebanon Beja, Portugal (Borderline BSh hot semi-arid climate) Casablanca, Morocco (Borderline BSh hot semi-arid climate) Dubrovnik, Croatia Dushanbe, Tajikistan Funchal, Portugal Gaza, Gaza Strip Haifa, Israel Heraklion, Greece Izmir, Turkey Jerusalem, Israel Latakia, Syria Limassol, Cyprus Lisbon, Portugal Los Angeles, United States (Borderline BSh hot semi-arid climate)

Marseille, France Monaco, Monaco Mostar, Bosnia and Herzegovina Naples, Italy Nice, France Palermo, Italy Perth, Australia Podgorica, Montenegro Rabat, Morocco Ramallah, West Bank Rome, Italy San Diego, United States (Borderline BSh hot semi-arid climate) San Jose, United States Sevilla, Spain Split, Croatia Tel Aviv, Israel Thessaloniki, Greece Tirana, Albania Tripoli, Libya Tunis, Tunisia Valencia, Spain Valletta, Malta

Warm-summer Mediterranean climate

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 experiences warm (but not hot) and dry summers, with no average monthly temperatures above 21.8°C (72°F) during its warmest month and an average in the coldest month between 18°C (64°F) and −3°C (26.6°F) or, in some applications, between 18°C and 0°C (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 is heavier during the colder months, but there are a number of clear sunny days even during the wetter seasons.

In some instances, regions with this subtype of the Mediterranean climate closely resembles an Oceanic climate. However during the summer months, these regions experiences sunny, dry and warm conditions, where almost no rain falls, hence forest fires like in Galicia in 2006, and the Spanish classification in the risk-zones areas . Despite the fact that these climates are technically Csb climates, a number of scientists (and others) do not consider the climate “Mediterranean”. They are instead categorized as a form of an oceanic climate.

Notable Cities with Warm-summer Mediterranean Climates

• Cape Town, South Africa
• Porto, Portugal
• San Francisco, United States
• Santiago, Chile
• Valparaiso, Chile
• Viña del Mar, Chile

Notable Cities with Csb Climates under the Koeppen-Geiger system, but are sometimes considered Oceanic climates

• Portland, United States
• Puerto Montt, Chile
• Seattle, United States
• Viana do Castelo, Portugal
• Victoria, Canada
• Coruna, Spain

Charts of selected cities

Hot-summer Mediterranean climate

Barcelona
Climate chart (explanation)
J F M A M J J A S O N D     41     13 4     29     15 5     42     16 7     49     18 9     59     21 12     42     24 16     20     28 19     61     28 19     85     26 17     91     22 13     58     17 8     51     14 6 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: WMO
Imperial conversion J F M A M J J A S O N D     1.6     56 40     1.1     58 42     1.7     61 44     1.9     64 47     2.3     69 54     1.7     76 60     0.8     82 65     2.4     82 67     3.3     78 62     3.6     71 55     2.3     63 47     2     58 42 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

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
Imperial conversion J F M A M J J A S O N D     3.3     68 49     3.7     70 50     3.1     70 52     0.8     73 54     0.3     74 58     0.1     80 61     0     84 65     0.1     85 66     0.3     83 65     0.4     79 60     1.1     73 53     1.9     69 48 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

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: [1]
Imperial conversion J F M A M J J A S O N D     4.1     53 37     3.9     55 38     2.7     59 41     2.6     65 46     1.9     73 52     1.3     81 58     0.9     87 63     1.3     87 64     2.7     80 59     3.7     71 51     5.1     61 44     4.4     55 39 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Madrid
Climate chart (explanation)
J F M A M J J A S O N D     37     10 3     35     12 4     26     16 6     47     18 7     52     21 11     25     27 15     15     31 18     10     31 18     28     26 15     49     19 10     56     13 6     56     10 4 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: WMO
Imperial conversion J F M A M J J A S O N D     1.5     49 37     1.4     54 39     1     60 42     1.9     64 45     2     71 51     1     80 59     0.6     88 65     0.4     87 65     1.1     79 59     1.9     66 50     2.2     56 43     2.2     50 39 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Lisbon
Climate chart (explanation)
J F M A M J J A S O N D     97     15 8     90     16 9     51     18 10     65     19 12     56     21 13     17     25 16     6.1     28 18     6.8     28 18     29     26 17     80     22 15     107     18 12     122     15 10 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: Instituto de Meteorologia (1971-2000) Template:Pt icon
Imperial conversion J F M A M J J A S O N D     3.8     58 47     3.6     61 49     2     65 51     2.5     67 53     2.2     71 56     0.7     77 61     0.2     82 64     0.3     82 65     1.1     79 63     3.1     72 58     4.2     64 53     4.8     59 49 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Adelaide
Climate chart (explanation)
J F M A M J J A S O N D     20     29 17     13     29 17     25     26 15     40     23 12     60     19 10     81     16 8     75     15 7     67     17 8     60     19 10     46     22 11     32     25 14     28     27 16 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: Australia Bureau of Meteorology
Imperial conversion J F M A M J J A S O N D     0.8     84 63     0.5     85 63     1     79 59     1.6     73 54     2.4     66 50     3.2     61 47     3     60 45     2.6     62 47     2.4     66 49     1.8     71 53     1.3     77 57     1.1     81 60 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Perth (AUS)
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: Australia Bureau of Meteorology
Imperial conversion J F M A M J J A S O N D     0.4     87 64     0.5     88 64     0.8     85 62     1.7     78 56     4.6     72 51     7     67 47     6.7     65 46     5.3     66 46     3.2     68 49     2.1     73 52     0.9     79 57     0.5     84 61 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Santiago (Chile)
Climate chart (explanation)
J F M A M J J A S O N D     0.4     30 13     0.6     29 12     3.2     27 11     10     23 8     42     19 6     70     15 4     87     15 4     52     17 5     22     19 6     13     22 8     9.2     25 10     2.1     28 12 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: WMO
Imperial conversion J F M A M J J A S O N D     0     85 55     0     84 54     0.1     80 51     0.4     74 46     1.7     66 43     2.8     59 40     3.4     59 39     2     62 41     0.9     66 43     0.5     72 47     0.4     78 50     0.1     83 54 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

Warm-summer Mediterranean climate

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
Imperial conversion J F M A M J J A S O N D     0.6     79 60     0.7     80 60     0.8     78 58     1.6     73 53     2.7     69 49     3.7     65 46     3.2     64 45     3     64 46     1.6     67 48     1.2     70 51     0.6     74 56     0.7     77 59 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

León
Climate chart (explanation)
J F M A M J J A S O N D     58     7 −1     46     10 0     29     13 2     50     14 3     58     18 6     39     23 10     28     27 12     24     27 12     39     23 10     56     16 6     58     11 3     70     8 1 █ Average max. and min. temperatures in °C █ Precipitation totals in mm Source: Agencia Estatal de Meteorología Template:Es icon
Imperial conversion J F M A M J J A S O N D     2.3     45 31     1.8     49 33     1.1     55 35     2     58 37     2.3     64 43     1.5     74 49     1.1     81 54     0.9     80 54     1.5     73 50     2.2     62 44     2.3     52 37     2.8     46 33 █ Average max. and min. temperatures in °F █ Precipitation totals in inches

See also

• Mediterranean climate (wine)

External links

• Explanation of Mediterranean Climate (University of Wisconsin)