Air Masses cont. A large body of air with the same temperature and moisture content When air is stationary or moves slowly it takes on uniform characteristics Classified by source region, temperature and humidity Polar regions=cold, dry air Tropical regions=warm, moist air
Types of Air Masses Continental Form over large landmasses Northern Canada, southwestern USA Low humidity Why?? Two types Continental polar (cP): cold and dry Continental Tropical (cT): warm and dry
Types of Air Masses Maritime Form over oceans or large bodies of water High humidity Commonly bring rain or fog Two types Maritime polar (mP): moist and cold Maritime tropical (mT): moist and warm
North American Air Masses Air MassSource LocationMovementWeather cPPolar regions in Canada South-southeastCold and dry mPPolar Pacific; polar Atlantic Southeast; southwest-south Cold and moist cTU.S. southwestNorth-northeastWarm and dry mTTropical Pacific; tropical Atlantic Northeast; north- northwest Warm and moist
FRONTS When two air masses with different properties meet, density differences keep them separate. A front is a boundary that forms between two air masses. Four types: cold fronts, warm fronts, occluded fronts, stationary fronts
Cold Fronts Forms when a cold air mass meets and pushes under a warm air mass As warm air is lifted, cumulonimbus clouds form Typically produces storms Followed by cooler air
Warm Fronts Forms when a warm air mass overtakes a cold air mass and moves over it. Warm air rises over cooler air and causes slight to moderate precipitation. Followed by warmer air
Occluded Front Forms when a cold air mass quickly overtakes a warm front, and completely lifts the warm air off the ground. Precipitation usually follows
Stationary Front A front where no movement occurs. Precipitation may occur for several days.