ABSTRACT
Mediterranean climates like occur around 30° latitude on the western margins of continents around the world: the Mediterranean, Southern California, southern Chile, southwest Australia, and the western cape region of Africa. Mediterranean climates essentially result from (1) a descending air mass drying out the atmosphere and the land below and (2) the adjacent cold water circulating offshore.
During the cool winter months, storm tracks move down the California coast and bring seasonal rains from November to March that account for 85% of the annual total for most of Southern California west of the Transverse and Peninsular Ranges. Farther east in the desert communities, winter rain accounts for only about 50% of the annual total and summer months (June–August) experience a little more than 20% because of monsoonal rain drifting west from Arizona.
Southern California’s climate zones are determined mainly by the relative contribution of maritime versus continental influence. The latter becomes increasingly dominant inland. Broadly, these zones are the Maritime Fringe, Intermediate Valleys, Transitional, Mountain, High Desert, and Low Desert. Climate zones may be parsed even further depending on local topography and the creation of thermal belts, especially west of the deserts.
