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 MassesAir 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 drymT Tropical Pacific;
tropical AtlanticNortheast; 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.