Air Masses

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.

Geographic areas where an air mass originates.

Gives the air mass its characteristics (dry, moist, cool, warm)

Source Regions

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

Classifications:

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

Combinations of the classifications can be used to describe various types of air masses.:

The boundary between contrasting air masses

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

4 types of fronts

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

3.Stationary Front – No movement of surface position

◦Almost parallel air movement to the line of front

◦Possible light precipitation

cold airair

movementwarm air

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

Warm front

Cold Front

Occluded front