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.