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Air Masses

  • By: David L. Arnold
  • In: Encyclopedia of Geography
  • Edited by: Barney Warf
  • Subject:General Geography, Earth & Environmental Science

The most common definition of an air mass is a large body of air, relatively homogeneous with respect to temperature, humidity, and vertical lapse rates. While this definition is generally valid, it is true only for air masses that remain within their source regions. Once in motion, air masses begin to modify, in some cases quickly, especially if they move significant latitudinal distances. Eventually, modification renders the air mass unrecognizable with respect to its source region.

Source Regions

Air masses form in regions of generally uniform surfaces where winds are typically light for extended periods of time, usually days to weeks. Over periods of time, the overlying air takes on the properties of the underlying surface through radiative and convective processes. These regions tend to be ...

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