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 Form 1 Geography Online Lessons on Weather

In this class we are going to learn about the different air masses of the world and their effect on weather

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Answer Text:
Air Masses
- 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.
2. Sub-tropical Air Mass
• Forms near sub-tropical high pressure belt.
3. Polar Air Mass
• Forms near the poles or temperate low pressure zone.
• It’s cool.
4. 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.


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