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From Wikipedia, the free
encyclopedia
A Mediterranean climate is a climate that resembles
those of the lands bordering the Mediterranean Sea.
These climates generally occur on the western coasts of
continental landmasses, roughly between the latitudes of
30° and 45° north and south of the equator.
Location of Mediterranean Climates
Besides the Mediterranean Basin, regions which have a
Mediterranean climate include much of California between
Cape Mendocino and greater Los Angeles, the Western Cape
in South Africa, central Chile, the coastal areas of
southern Western Australia and western South Australia.
Isolated examples of microclimates which approximate
the Mediterranean climate may occur outside the
Mediterranean climate zones, but these generally are a
result of localized processes that are not
characteristic of the Mediterranean climate regime.
Mediterranean climates on land tend to grade off
poleward toward zones of oceanic or maritime climate in
which summer rains are significant and equatorward into
dry-summer steppes where the winter rains are inadequate
(an example of such a steppe climate is to be found in
San Diego, California).
Mediterranean Climates Precipitation
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 but making rainfall impossible or unlikely,
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 the winter
season, and may go anywhere from 2-5 months during the
summer without having any significant precipitation.
As an example, San Francisco in California, USA,
receives an average of 448 mm (17.6 in.) of rain from
November through April each year, but averages only 52
mm (2 in.) of rain for the rest of the year, and
receives almost no precipitation at all during the
months of July and August.
Mediterranean Climates Temperatures
All regions with Mediterranean climates have
relatively mild winters, but summer temperatures are
variable depending on the region. For instance, Athens,
Greece experiences rather high temperatures in the
summer, while San Francisco, California has cool, mild
summers due to the upwelling of cold subsurface waters
along the coast. Because all 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 temperatures
during the summer is large, except along the immediate
coasts). Temperatures during winter only occasionally
reach freezing and snow only rarely occurs at sea level.
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 don't reach the highest readings found in
adjacent desert regions.
Inland locations sheltered from or distant from sea
breezes can experience severe heat during the summer.
Locations inside the Sacramento Valley of northern
California, for example, are subject to summer
temperatures characteristic of hot deserts (often around
40°C/100°F), although winters are rainy enough to allow
lusher vegetation than is typical in deserts. In Perth,
Australia hot, dry summers (frequently exceeding
35°C/95°F) and cool, wet winters (with a daily
temperature range usually within 10-15°C/50-60°F) are a
perfect example of a Mediterranean climate. Unlike the
coastal climates that are designated Csb in the Köppen
climate classification—characteristic of places with
cooler summers—the hotter, typically inland areas have
the Csa classification that indicates a hot summer.
Areas that experience the typical Mediterranean pattern
of cool, rainy winters and very dry summers, but which
experience milder average summer temperatures include,
Porto, in Portugal and San Francisco, in California.
Likewise, locations that are slightly higher latitude
and cut off from milder ocean winds may have somewhat
colder winters and more distinct seasons. This
"temperate Mediterranean" climate is most noticeable in
northern Italy and northern Greece, as well as southern
Oregon. In these areas, plants that are commonly
associated with milder Mediterranean climates, such as
citrus, date palm, olive, oleander and eucalyptus, can
be frozen to death in the occasional severe winter.
Areas of high altitude adjacent to locations with
Mediterranean climates may have the cold winters that
are characteristic of a continental climate; under
Köppen's scheme such places might earn the designation
Dsa, Dsb or even Dsc. |
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