Air Masses

1. Air Masses

2. Air Mass - an extremely large body of air whose properties of temperature and moisture content (humidity), at any given altitude, are fairly similar in any horizontal direction.

3. Source Regions • Geographic areas where an air mass originates. • Gives the air mass its characteristics (dry, moist, cool, warm)

4. Classifications: • Polar latitudes (P) - located near the poles • Tropical latitudes (T) - located near equator • Continental (c) - located over large land masses--dry • Maritime (m) - located over the oceans ---moist

5. Combinations of the classifications can be used to describe various types of air masses.: • cP continental polar cold, dry, stable • cT continental tropical hot, dry, stable air aloft--unstable surface air • mP maritime polar cool, moist, and unstable • mT maritime tropical warm, moist, usually unstable

8. Fronts: • The boundary between contrasting air masses

9. 4 types of fronts • 1. Warm Front – warm air displaces cooler air • Shallow leading edge • Warm air rides up over the cold, dense air mass • Warmer temps. and light precipitation over large area for an extended period of time • Wind shift from east to southwest cool air air movement warm air

10. 2. Cold Front – cold, dense air displaces warmer air • Steep leading edge • Moves more quickly than warm fronts • Forceful lifting of air • Heavy downpours and gusty winds • Temps. drop and winds shift warm air air movement cool air

11. 3.Stationary Front – No movement of surface position • Almost parallel air movement to the line of front • Possible light precipitation cold air air movement warm air

12. 4. Occluded Front – Occurs cold front overtakes a warm front • Cold front wedges warm front upward • Most precip. formed from rising warm air • Newly formed front can produce precip. air movement

13. Warm front

14. Cold Front

15. Occluded front