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 Mass Source Location Movement Weather
cP Polar regions in Canada
South-southeast
Cold and dry
mP Polar Pacific; polar Atlantic
Southeast; southwest-south
Cold and moist
cT U.S. southwest North-northeast Warm and dry
mT Tropical 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.