Subsidence (atmosphere)

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Subsidence, in the Earth's atmosphere, is most commonly caused by a low temperature. As the air cools, it becomes denser and moves towards the ground, as warm air becomes less dense and moves upwards. Subsiding air, when cool, is subject to adiabatic warming, which tends to cause the evaporation of any clouds that might be present.

Subsidence generally causes high barometric pressure as more air moves into the same space: the polar highs are areas of almost constant subsidence, as are the horse latitudes, and the areas of subsidence are the sources of much of the world's prevailing wind.

Subsidence also causes many smaller-scale weather phenomena, such as morning fog. An extreme form of subsidence is a downburst, which can result in damage similar to that produced by a tornado. A milder form of subsidence is referred to as downdraft.