CHAPTER 1
Introduction
1.1
The Mediterranean Climate
In addition to the regions surrounding Mediterranean Sea, a Mediterranean
climate is also typical of the western coasts of the five continents, i.e. most of
California, central Chile, parts of south-western South Africa and parts of
south -western Australia (Aschman 1973; Daget 1984). According to Aschman,
a Mediterranean climate is characterised by a hot summer with a high rate of
evapotranspiration and a mild winter with rather high precipitation. Aschman defined the Mediterranean climate quantitatively as follows: annual precipitation in the range of 275 to 900 mm with over 65% occurring during the
6 colder months. During this period the monthly average temperature is
below 15°C, while the temperature falls below freezing for less than 3% of the
year.
Regions characterised by a Mediterranean climate occupy less than 5% of
the earth's surface between 25° and 45° latitude north and south (Tsiourlis
1990). Traditionally, most ecological studies in the Mediterranean regions
focus on the structure and function of vegetation. As a consequence, the definit ion of Mediterranean bioclimatic zones is based primarily upon variables
associated with plant growth, such as fluctuating temperature and, most
notably, the amount and seasonal distribution of rainfall. Seasonality in precipitation is higly characteristic of the Mediterranean climate, and Lamotte
and Bladin (1989) contrasted the regularly occurring summer drought in
Mediterranean areas with the irregular distribution of rainfall in temperate
regions, as well as with rainfall occurring during a limited time period in
tropical regions.
Sauvage (1961) and, more recently, Nahal (1981) used Ebergers' index of
drought to subdivide Mediterranean climate into subclasses as follows:
2P
Q=----~
(M+m)(M-m) ,
where P is annual precipitation, M the mean maximum temperature of the
hottest month, and m the mean minimum temperature of the coldest month.
Introduction
1.1
The Mediterranean Climate
In addition to the regions surrounding Mediterranean Sea, a Mediterranean
climate is also typical of the western coasts of the five continents, i.e. most of
California, central Chile, parts of south-western South Africa and parts of
south -western Australia (Aschman 1973; Daget 1984). According to Aschman,
a Mediterranean climate is characterised by a hot summer with a high rate of
evapotranspiration and a mild winter with rather high precipitation. Aschman defined the Mediterranean climate quantitatively as follows: annual precipitation in the range of 275 to 900 mm with over 65% occurring during the
6 colder months. During this period the monthly average temperature is
below 15°C, while the temperature falls below freezing for less than 3% of the
year.
Regions characterised by a Mediterranean climate occupy less than 5% of
the earth's surface between 25° and 45° latitude north and south (Tsiourlis
1990). Traditionally, most ecological studies in the Mediterranean regions
focus on the structure and function of vegetation. As a consequence, the definit ion of Mediterranean bioclimatic zones is based primarily upon variables
associated with plant growth, such as fluctuating temperature and, most
notably, the amount and seasonal distribution of rainfall. Seasonality in precipitation is higly characteristic of the Mediterranean climate, and Lamotte
and Bladin (1989) contrasted the regularly occurring summer drought in
Mediterranean areas with the irregular distribution of rainfall in temperate
regions, as well as with rainfall occurring during a limited time period in
tropical regions.
Sauvage (1961) and, more recently, Nahal (1981) used Ebergers' index of
drought to subdivide Mediterranean climate into subclasses as follows:
2P
Q=----~
(M+m)(M-m) ,
where P is annual precipitation, M the mean maximum temperature of the
hottest month, and m the mean minimum temperature of the coldest month.