Distinct large parcels of air moving in one direction

– Originate from areas of uniform weather and topography from where they derive their characteristics e.g. flat areas, forests, deserts, and snow covered areas.

Characteristics of Air Masses

  • A large volume of air.
  • Covers an extensive area.
  • Has uniform temperature and humidity.
  • Distinct from the surrounding air.
  • Retains its characteristics when it moves away.

Types of Air Masses

  1. Equatorial Air Mass
  • Originate from equatorial oceans.
  • It’s hot and unstable.
  1. Sub-tropical Air Mass
  • Forms near sub-tropical high pressure belt.
  1. Polar Air Mass
  • Forms near the poles or temperate low pressure zone.
  • It’s cool.
  1. Arctic and Antarctic air Masses
  • Forms over the ice sheets of Greenland and Antarctica respectively.
  1. Effect of air masses on Weather
  • When warm moist air mass and cool air mass meet cyclonic rainfall is formed e.g. tropical maritime and polar maritime.
  • Cool air masses take cooling effect to the areas they move to e.g. polar continental.
  • If they are warm they take warming influence to the area they move to e.g. tropical continental.
See also  FIELD WORK

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