Mediterranean Climates

Mary Sue Ittner
Mon, 17 Mar 2003 10:44:32 PST
Dear All,

In preparation for the introduction to the topic of the week I will post 
today I am posting some background information on Mediterranean climates. I 
am borrowing heavily from Plant Life in the World's Mediterranean Climates: 
California, Chile, South Africa, Australia, and the Mediterranean Basin by 
Peter R. Dallman.

The regions of the world with this climate are found in California, Chile, 
South Africa, Australia, and the Mediterranean Basin. These areas lie 
between 30 degrees and 45 degrees of latitude with California and the 
Mediterranean Basin being in the Northern Hemisphere and central Chile, the 
western Cape and Southwest and South Australia being in the Southern 

What these areas have in common is dry summers with sunshine and clear 
skies. Rainfall is concentrated during the mild, winter half of the year 
and averages 10-40 inches (25-100 cm) annually. Snow is rare except for 
high elevations. Rainfall is variable every year and usually comes in 
storms that may last a few days. Areas closer to the equator are drier and 
those farther away get more rainfall. For example Southern California is 
much drier than Northern California and the southwestern part of the Cape 
much wetter than the areas farther north. Rainfall is typically greater 
with increased elevation, especially on western slopes that face the ocean. 
For example, Adelaide, the capital of South Australia near sea level 
averages 21 inches (53 cm) of rain yearly and Mt Lofty nearby at 2400 foot 
(727 m) elevation gets twice as much. Between storms the weather in crisp 
and clear. Summer rains are rare but only two of the regions have areas 
that are completely dry: California and Chile. Other regions have 
occasional rainfall even though they get most of their rain in winter. The 
valleys between the mountains are much drier. The Biedouw Valley in South 
Africa is quite dry whereas the Cederberg Ranges above it get significantly 
more rainfall.

All of these regions are located on the western or southwestern coasts of 
continents where there are cold, offshore ocean currents. These oceans have 
a moderating effect on summer temperatures. But there are exceptions here 
as well. Southwestern Australia has southward-pflowing offshore currents 
that are warm and a warmer summer climate. The Mediterranean Sea because it 
is enclosed by land warms up more so the lands that border it have hotter 
summers. Lauw spoke of areas that can grow citrus versus areas that are 
good for olive trees. Areas closer to the oceans are cooler and often have 
very little variation between summer and winter temperatures. The coastal 
areas of California experience summer cooling fogs that also provide 
moisture. In Cape Town the "tablecloth" on table mountain provides cooling 
temperatures and mists and I believe the same kind of thing happens in the 
Stirlings in Western Australia. The moderating maritime influence of most 
of these climate areas give them mild winter temperatures well above 
freezing even during the coldest month of the year.

Geophytes because of their underground food and water storage organs that 
allow them to cope with the long period of drought are one of the plant 
adaptations of these climates so a large number are usually found in these 

Mary Sue
PBS List Administrator and TOW Coordinator

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