Les climats subtropicaux dits «méditerranéens» et les climats de la Méditerranée (1re partie)

Abstract

At the boundary between temperate and tropical zones, in the subtropical latitudes (at about 40-30 ° N and S), spread the so-called «Mediterranean» climates, with reference to the area of their former definition. These climates are characterized by two well marqued seasons : a cool (even cold) rainy season centered on winter, and a warm (even hot) and rainless (even really dry) season centered on summer. This type of climate owes its features to the dynamics of MPHs (Mobile Polar Highs), responsible for the wintry rains, and to their agglutination in anticyclonic cells (AA), inversely responsible for stability and lack of rain during summertime. This transitional climate is found, in the subtropical latitudes, and in a simple manner, over California, central Chile, Capetown region of South Africa, Southern Australia, ana the Atlantic side of Iberia and Morocco. The Mediterranean offers to MPHs particular dynamic conditions, the four main entrances of polar air being determined by relief. After an accelerated passage through defiles, MPHs form again over the Mediterranean and deviate northwards on their leading edge warm southerly flows, laden with a rich précipitable potential, the same reliefs then organizing the distribution of rains, often violent, junction and facing of the different MPHs paths provoke the high winds, gusts and storms, and thermal and pluviométrie paroxysms, specific features of the mediterranean climate.