Air Masses & Fronts

Air MassesObjective: to identify the different types of

air masses & where they originate from.

Air Mass Defined:

A large body of air found in the lower troposphere that is similar throughout in: humidity (wetness/dryness) and temperature

Air Masses

cA- continental arctic, very cold and dry (from northern Alaska/Canada)

cP- continental polar, cold and dry (from southern Alaska/Canada) (if travels over H2O, can cause snow)

mP- maritime polar, cold and wet (from north pacific/Atlantic ocean)

mT- maritime tropical, warm and wet (from gulf of Mexico)

cT- continental tropical, warm and dry (from Mexico and central America) (since dry=no clouds)

Answer:1. Where do cold & hot air masses originate?

2. Where do moist & dry air masses originate?

Jet StreamsA fast moving stream

of air found in the upper atmosphere (like a “river of air”)

Found at 30 degrees and 60 degrees north and south of the equator (between convection cells where hot and cold air meet)

FrontsObjective: To identify the different types of fronts and how they are

caused

Review: Air MassesAn air mass is a large body of air that has similar

temperature and humidity

If an air mass forms over land (continental) it has low humidity

If an air mass forms over an ocean (maritime) it has high humidity

Air masses are either hot or cold

What happens when air masses run into each

other?FRONTS!

Air masses don’t mix together

The boundary where the air masses meet is called a front

Fronts are common at mid-latitudes, where tropical and polar air masses commonly meet

What happens when air masses run into each

other?Air masses have different temperatures and

humidity levels

When they collide, the more dense air mass goes under the less dense air mass

FrontsA front is a place

where two different air masses meet

4 types of fronts:

Each bring different types of weather

Cold FrontOccurs when a

polar (cold) air mass runs into (& replaces) a tropical (warm) air mass

The warm air is less dense and gets pushed above the cold air mass

http://www.classzone.com/books/earth_science/terc/content/visualizations/es2002/es2002page01.cfm

Cold FrontTemperatures drop, and there is usually

precipitation

Thunderstorms are usually a result of a cold front

Warm FrontWarm front-

when warm (less dense) air moves forward (advances) and replaces cold air: forms a wedge shape. http://www.classzone.com/books/

earth_science/terc/content/visualizations/es2002/es2002page01.cfm

Warm FrontResults in warmer temperatures, often

higher humidity

Usually precipitation for several days

http://www.atmosphere.mpg.de/enid/1__Weather___Fronts/__Worksheet_1_4ap.html

Stationary FrontOccurs when neither the warm air or the

cold air is advancing

The less dense warm air will rise above the cold air

Stationary FrontClouds and precipitation occur

If a stationary front stays for too long, flooding can occur

Occluded FrontOccurs when a cold front catches up with a warm

front

Cold fronts move twice as fast as warm fronts

Occluded FrontCauses cloudiness and precipitation