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Why do Mediterranean climates have dry summers and wet winters?
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Köppen climate classification
The major climatic types are based on patterns of average precipitation, average temperature, and natural vegetation. This map depicts the world distribution of climate types based on the classification originally invented by Wladimir Köppen in 1900.
The Mediterranean climate, a major type within the Köppen climate classification, is defined by its distinct seasonal precipitation patterns caused by the shifting influence of subtropical anticyclones.1
During the summer, these regions are dominated by the poleward expansion of subtropical anticyclones over the oceans. This movement brings subsiding air to the region, which suppresses vertical convection and results in clear skies, high temperatures, and dry conditions.12
In the winter, the subtropical anticyclone shifts toward the Equator. This movement allows the region to be influenced by traveling, frontal cyclones, which bring the characteristic cool, wet weather associated with the Mediterranean climate.1