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.