Distinct large parcels of air moving in one direction
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– 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
- Equatorial Air Mass
- Originate from equatorial oceans.
- It’s hot and unstable.
- Sub-tropical Air Mass
- Forms near sub-tropical high pressure belt.
- Polar Air Mass
- Forms near the poles or temperate low pressure zone.
- It’s cool.
- Arctic and Antarctic air Masses
- Forms over the ice sheets of Greenland and Antarctica respectively.
- 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.