A unique climate called the warm temperate western margin climate or Mediterranean climate can be seen on the western portion of continental masses between 30 and 45 degrees north and south of the earth.
The transitional nature, with part of the year with a tropical climate and another part with a temperate climate, makes it unique.
MEDITERRANEAN CLIMATE DEFINITION
In simple terms, it has a dry and hot summer and a cool, rainy winter.
WHY IS THE MEDITERRANEAN CLIMATE NAMED AFTER THE MEDITERRANEAN REGION?
The area around the Mediterranean Sea is situated in the latitude of the oscillating front of divergence. This front divides the sphere of influence of westerlies and tradewinds, which results in a winter rain climate. Due to this reason, the popular Mediterranean is used for this peculiar climate type.
Even though named after the Mediterranean region, the best-developed form of this climate type is found in central Chile.
CHARACTERISTICS OF MEDITERRANEAN CLIMATE
The Mediterranean climate, or the warm temperate western margin climate type, is characterised by the following distinctive climatic features.
- Dry, warm summers (warmest month usually above 70 Fahrenheit) with offshore trade winds.
- Incidence of winter rainfall with on-shore westerlies and mild winters (coldest mount usually above 43 Fahrenheit).
- Bright sunny weather with a more or less complete summer drought (no rain during summer).
- The prominence of local winds around the Mediterranean Sea (common around the Mediterranean region).
DISTRIBUTION
The warm, temperate western margin climate can be seen in the following regions that receive influence from the West:
- The region in Central Chile
- San Francisco region in California
- South-West tip of South Africa ( including Cape Town)
- Mediterranean region
- South Australia(Victoria and Adelaide) and south-west Australia (Swanland).
This climatic type has only a limited extension on the western margins of continents except in Europe.
In Europe, the Mediterranean Sea extends its range 200 miles into the heat of the land.
Depending on location, this climatic type spans from arid to humid. Due to the strong influence of subtropical high pressure, the climate is drier in an area closer to the tropics.
If we move eastward, there will be a rapid change into steppes and deserts. This is due to the progressive reduction of winter rainfall.
In other parts like Australia and South Africa, the land is too narrow to support an interior steppe climate, so the Mediterranean climate changes directly into the eastern margin variety by a gradual increase of summer rain.
SUMMER SEASON IN THE MEDITERRANEAN CLIMATE
The summer season in warm temperate western margin climate is usually hot, with the highest range of 70 to 80 Farenheat and the mean annual range being about 30 Farenheat. This range is greater than the tropics but less than most cool temperate climates.
This range will increase with the increase in distance from the sea. For example, if the temperature in Naples is 30 degrees Celsius, then in Rome, it is 33 degrees Celsius. The highest temperature will be recorded at places located at the continental eastern margin of the Mediterranean. This change in temperature is due to the distance of location from the Mediterranean, which limits the Atlantic influence.
Locations at ocean margins will show low summer temperatures due to cold currents, which set equatorward along the western coats in these latitudes.
In summer, the westerlies will be shifted a little poleward and rain bearings will not likely reach this region. So, due to offshore trade winds, there will be no rain, which may result in drought.
AUTUMN IN THE MEDITERRANEAN CLIMATE
Dew and mist are frequent in late autumn. The moist air from the Atlantic Ocean and the rapid fall in temperatures result in frequent dew and mist.
The highly humid autumn makes the season unpleasant.
SPRING IN THE MEDITERRANEAN CLIMATE
Spring in regions with this climate type will bring warm and fresh air. It is the most pleasant season. During spring, flowers blossom and bring prosperity to the agriculture field.
WINTER IN THE MEDITERRANEAN CLIMATE
In warm temperate types, the winter season will bring the most rain due to the presence of on-shore westerlies.
Snow really occurs in lowlands and coastal districts.
Insular locations usually have remarkably warm winters because they are unaffected by cold currents. For example, Las Palmas of Grand Canary has a minimum temperature of 59 to 63 Fahrenheit.
RAIN
The presence of on-shore westerlies brings much precipitation. These westerlies usually bring cyclonic storms from the Atlantic to the countries on the Mediterranean coast.
The seasonal incidence of cyclonic rains corresponds to the migration of westerlies towards the equator during the winter season.
Mountains will intercept the moist winds blowing in the winter season, resulting in orographic rain and sometimes snow. Snow-covered peaks of Sierra Nevada are an example.
Another factor for winter rain is cool land. It acts as a precipitating agent on moist winter winds.
Rain in Mediterranean Europe typically begins in September and will reach its peak in October. Sometimes, heavy downpours result in catastrophic floods—for example, the 1967 floods in Lisbon.
Normally, the following reasons will result in a reduction in rainfall.
- The rain decreases when moving eastwards
- The precipitation decreases when moving away from the oceans.
- The rain decreases when moving away from the equatorward.
- The precipitation decreases when moving away from the cyclones.
LOCAL WINDS
Hot and cold local winds are common in the Mediterranean region, and orographic factors significantly influence them. Even though influenced by orographic features, these local winds require a surface low-pressure system; later, the airflow will be modified by local orographic features.
The topography of the region, with the Alps mountains in the north, the Sahara desert in the south direction, the Atlantic Ocean in the West and continental interiors in the east, results in differences in temperature, pressure and rain of the region.
The local wind bears a specific name, and the name will be related to the region.
Etesian winds
The summer and autumn pressure gradient between the Azores high and the Persian low results in a wind flow system called Etesian winds.
It blows over the Adriatic, Ionian and Aegean seas from mid-May to mid-September. Its intensity reaches a maximum in the early afternoon, and its intensity will be a minimum at night.
This strong wind is also known as “Meltemia”. The word “Etesian” is derived from the Greek word “Etos“, and it is used to express their annual nature.
The Etesian wind moderates the heat in the area, and this ventilating effect is largely balanced by adiabatic warming created by subsidence. This natural phenomenon restricts cloud formation and creates clear skies.
Sirocco
When the westerly circulation passes from West to East through Gibraltar Strait or Biscay Bay via the Gate of Carcassonne, it results in a hot, dry, red dust, dust-laden wind called Sirocco.
The Sirocco wind originates from the Shara desert or desert of North Africa.
Even though it may occur at any time of the year, it is more common in spring. It usually lasts for only a few days.
When the wind passes across the warm seas, it absorbs the water vapour. High humidity carrying hot winds creates fog, mist and sometimes rain.
Sirocco’s hot air results in dry skin, cracks and considerable difficulty for humans. It damages vegetation, especially when the vines and Olives are in blossom.
The resulting rain may look red in colour due to the red dust. So, it is known as red rain.
This wind is known by many other local names, such as
- Chilli in Tunisia
- Leveche in Spain
- Khamsin in Egypt
- Ghibli in Libya
- Sirocco in Algeria
When the hot wind gets fortified with water vapour from the Adriatic Sea and the Aegean Sea, it is known as Gharbi.
Mistral
When a high pressure over Europe combines with a low pressure in the Ligurian Sea, cold, dry air from the North or Plateau of Cevennes rushes down to the Rhône valley, resulting in a cold wind called Mistral.
It is a strong, cold katabatic wind rushing into the Gulf of Lion. The violent gusts often exceed 40 knots and sometimes reach 100 knots.
Due to its high speed, it is considered dangerous when compared with other Mediterranean local winds.
Mistral is common in winter and in spring. It will be strong in the transition season between winter and spring. Farmers plant Cypress hedges to protect orchards from this freezing wind; otherwise, Mistral wind will cause severe damage to farms.
Bora
Bora is a similar north-easterly windblown along the Adriatic coast during winter.
It is formed due to the difference in pressure between Europe and the Mediterranean.
Bora blows outwards into the Mediterranean.
The word “Bora” came from the Greek Word “Boreas“, meaning northwind.
This wind can reach a maximum speed of more than 100km per hour.
DarkBora: Bora wind sometimes blows with clouds gathering on the hilltops and moving toward the sea with rain or snow. In this situation, Bora is termed Dark Bora.
ClearBora: Bora wind with clear skies is termed as clear Bora.
VEGETATION
Mediterranean evergreen forests are open woodlands with trees like Oaks. Because of their economic value, cork oaks are special, and they are found only in climatically favoured regions with a rainfall of well over 25 inches.
The forest productivity is largely a function of the temperature and water supply. This forest has an excellent variety of species, and around 15 per cent of species are endemic.
In Australia, Eucalyptus is the main tree found in this climatic type, and in California, Gaint Sequoia is the main Mediterranean evergreen forest tree.
Mediterranean forests are less productive than the average world forests. The forest in South France is the most productive among the Mediterranean forests.
The evergreen coniferous trees in this climate type include pines, cedars, and cypresses, which form preforest types of vegetation.
The dry and hot summer gives place to shrubs in some places. The shrublands are usually divided into “Maquis” and “Garrigue”. Maquis means dense vegetation of small trees and bushes with evergreen leaves, occurring mainly on siliceous substrates.
Garrigue means low sparse plant communities on calcareous substrates.
The word Maquis is derived from the Corsican dialect word Macchia, which means mottled. The name Maquis is used in South France, and Macchia is used in Italy.
Spanish word Matorral fails to distinguish between the two main types except that low, poor or degraded Matorral is closer to Garrigue and to the Phrygana of Greece.
In some areas, soil is usually poor, and the topsoil is frequently missing. This leads to the survival of wiry and bunchy grasses.
