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Air masses

Air masses . Characteristics Large body of air with similar temperature, pressure, humidity, & density. Move and affect a large portion of a continent . Air masses . Source region – the area where an air mass acquires its properties Two criteria used to classify an air mass

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Air masses

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  1. Air masses • Characteristics • Large body of air with similar temperature, pressure, humidity, & density. • Move and affect a large portion of a continent

  2. Air masses • Source region – the area where an air mass acquires its properties • Two criteria used to classify an air mass • 1) By the latitude of the source region: • Polar (P) • High latitudes • Cold • Tropical (T) • Low latitudes • Warm

  3. Air masses • 2) By the nature of the surface in the source region • Continental (c) • Form over land • Likely to be dry • Maritime (m) • Form over water • Humid air

  4. Air masses • Four basic types of air masses • Continental polar (cP) • Continental tropical (cT) • Maritime polar (mP) • Maritime tropical (mT)

  5. Fronts • Boundary that separates air masses of different densities • Air masses retain their identities • Warmer, less dense air forced to move up • Cooler, denser air acts as wedge, moving downward

  6. Types of Fronts • Warm front • Warm air replaces cooler air • Shown on a map by a line with semicircles • Clouds become lower as the front nears • Moves into an area slowly • Light-to-moderate precipitation

  7. Warm front

  8. Types of Fronts • Cold front • Cold air replaces warm air • Shown on a map by a line with triangles • Twice as steep as warm fronts • Advances faster than a warm front • Associated weather is more violent than a warm front • Intensity of precipitation is greater • Duration of precipitation is shorter

  9. Types of Fronts Cold front • Weather behind the front is dominated by • Cold air mass • Subsiding air • Clearing conditions

  10. Cold front

  11. Types of Fronts Stationary front • Flow of air on both sides of the front is parallel to the line of the front • Position of the front does not move • Occluded front • Active cold front overtakes a warm front • Cold air wedges the warm air upward • Weather is often complex • Precipitation is associated with warm air being forced aloft

  12. Formation of an occluded front

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