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. 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
middle latitudes, affecting almost exclusively the western portions of continents in relative proximity to the coast. The
climate type's name is in reference to the coastal regions of the
Mediterranean Sea, which mostly share this type of climate, but it can also be found in the Atlantic portions of
Iberia and Northwest Africa, the Pacific portions of the United States and Chile, extreme west areas of
Argentina, around
Cape Town, South Africa, parts of
Southwest and
South Australia and parts of Central Asia.
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, extending towards the hemisphere in question's pole during the summer and migrating 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,
Athens,
Barcelona,
Beirut,
İzmir,
Jerusalem,
Marseille,
Monaco,
Naples,
Rome,
Tunis,
Valencia, 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]
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
California, the cold
current has a stabilizing effect on the surrounding air, further reducing the chances for rain, but often causing thick layers of marine
fog that usually evaporates by mid-day. Similar to
desert climates, in many Mediterranean climates there is a strong
diurnal character to daily temperatures in the warm summer months due to strong solar heating during the day from sunlight and rapid cooling at night.
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
precipitation. In the lower latitudes, precipitation usually decreases in both the winter and summer due to higher
evapotranspiration. Toward the polar latitudes, total moisture usually increases; for instance, the Mediterranean climate in
Southern Europe has more rain. The rainfall also tends to be more evenly distributed throughout the year in Southern Europe, while in places such as the
Eastern Mediterranean, or in
Southern California, the summer is nearly or completely dry. In places where
evapotranspiration is higher, steppe climates tend to prevail, but still follow the basic pattern of the Mediterranean climates.
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,
temperatures are generally moderate, with a comparatively small range of temperatures between the winter low and summer high unlike dry-summer
humid continental climates (although the daily diurnal range of temperature during the summer is large due to dry and clear conditions, except along the immediate coastlines). Temperatures during winter only occasionally fall below the freezing point and
snow is generally seldom seen. Summer temperatures can be cool to very hot, depending on the distance from a large body of water, elevation, and latitude, among other factors. Strong winds from inland desert regions can sometimes boost summer temperatures up, quickly increasing the risk of
wildfires. Notable exceptions to the usual proximity from bodies of water, thus featuring extremely high summer temperatures and cooler winters, include south-eastern Turkey and northern Iraq (
Urfa,
Erbil), surrounded by hot deserts to the south and mountains to the north. Those places routinely experience summer daily means of over 30 °C (86 °F), while receiving enough rainfall in winter not to fall into
arid or
semi-arid classifications.
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
[7] (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.
