• An air mass is a large body of air that has about the same conditions throughout.
  • The characteristics of an air mass depend on where the air mass formed.
  • Most air masses form over polar or tropical regions.
  • They may form over continents or oceans.
  • Air masses move when they are pushed by high level winds.
  • Many air masses move toward the northeast over the U.S.
  • This is the same direction that global winds blow.
  • Moving air masses cause the weather to change.
  • For example, a warm air mass moving over cold ground may cause an inversion.
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