Air Masses & Fronts

What is an air mass?

a giant bubble of air with the same temperature and humidity throughout

Earth’s surface. . . . . . . .100’s of miles . . . . . . . . .

Air masses are named according to…

____________________________

known as their ____________ .

the area over which they form

source region

What is an air mass?

a giant bubble of air with the same temperature and humidity throughout

Earth’s surface. . . . . . . .100’s of miles . . . . . . . . .

Compare the air conditions in the Arizona Desert and the Florida coast.

How would the temperature compare? Why?

How would the humidity compare? Why?

Does the air mass form over…

land or water?land = continental air mass (dry)

ocean = maritime air mass (moist)

a warm area or a cold one?warm area = tropical air mass (warm)

cold area = polar air mass (cool)

There are four types of air masses:

• mT – maritime tropical – warm, moist air

• mP – maritime polar – cold, moist air

• cT – continental tropical – warm, dry air

• cP – continental polar – cool, dry air

1

2

3

4 5

Name the type of air mass that is shown at each of the following locations:

Location 1: mP

Location 2: mT

Location 3:

Location 4:

Location 5:

cP

cT

mT

Air masses get their characteristics from the location where they form, called their

source region.

How does a source region affect an air mass?

The source region determines the temperature and humidity of the

air mass.

Which two air masses affect Michigan the

most?

cP

mT

Why does the weather change so often in

Michigan?

cP

mT

Two very different air masses meet right over our state!

Air Mass Review

Air Mass Conditions

Name an air mass!

Air Mass Review

• Which air mass is the lightest?• Which air mass is the heaviest?

mT (least dense)

cP (most dense)

Air Mass Conditions

cT warm, dry

mT warm, moist

mP cool, moist

cP cool, dry

What is a front?

the boundary between 2 different air masses

front

Earth’ surface

warm, moist mT air cool, dry cP air

How are fronts named?

• If a warm air mass is blowing in, we call it a warm front.

• If a cold air mass is blowing in, we call it a cold front.

Fronts are named according to the type of air mass blowing into an area.

What type of front is shown here?

front

Earth’ surface

warm, moist mT air cool, dry cP air

W I N D

Warm Front

Warm Fronts

Warm fronts occur when warm, moist mT air blows over colder and more dense cP air. The warm air cools and the moisture condenses to

form horizontal layers of clouds.

mT air

cP air

nimbostratus cloud

Warm Fronts = overcast skies

• Hours or days of gray, overcast (cloudy) skies• On and off gentle rain (nimbostratus clouds)• Pass slowly• Bring warm, humid air• NO SEVERE WEATHER!!!

What type of front is shown here?

front

Earth’ surface

cool, dry cP air warm, moist mT air

W I N D

Cold Front

Cold Fronts

Cold fronts occur when cooler, drier cP air scoops up the less dense mT air and forces it to rise straight up. The mT cools and the moisture

condenses to form very tall cumulonimbus clouds .

cP air

mT aircumulonimbus

Cold Fronts

Cold fronts produce cumulonimbus clouds, storms, and severe weather!

Cold Fronts = storms

• thunderstorms, lightning, and severe weather

• cumulonimbus clouds and heavy rainfall

• bring cooler, less humid air

• pass quickly

• hail, high winds, and/or tornadoes possible

After a cold front passes you can expect…

• Cooler temperatures

• Clearer skies

• Fair weather

• Drier air – lower humidity

• Higher pressure

• Rising barometer

Warm Fronts on a Weather Map

warm, moist

mT air

cool, dry cP air

In which direction is this front moving?

Warm Fronts

Cold Fronts on a Weather Map

cool, dry

cP air

warm, moist

mT air

In which direction is this front moving?

Cold Fronts on the Weather Map

A

B

•What are the sky and temperature conditions like at city A?

•What are the sky and temperature conditions like at city B?

Main Types of Fronts:

• warm front – warm air blows in bringing overcast skies, gentle rain

• cold front – cold air blows in, overcast skies, thunderstorms, severe weather

Stationary Fronts

Resources• http://www.uwsp.edu/geo/faculty/ritter/images/atmosphere/pressure_wind/lo

w_pressure_small.jpg

• http://www.traveleye.com/northamerica/images/map.jpeg

• http://www.islandnet.com/~see/weather/graphics/photos/naairmass2.jpg

• http://members.aol.com/pakulda/images/stpptam.gif

• http://www.rvstogophx.com/images/arizona_desert_lg.jpg

• http://www.florida-gulf-villa.co.uk/Florida-beach.jpg

• http://recomb04.sdsc.edu/images/north_america.jpg• http://www.ecn.ac.uk/Education/cold_fronts.htm

• http://www.atmosphere.mpg.de/media/archive/1822.gif

• www.photolib.noaa.gov

• http://ww2010.atmos.uiuc.edu/guides/mtr/af/frnts/wfrnt/gifs/def1.gif

• http://www.atmosphere.mpg.de/media/archive/1824.gif

http://www.newmediastudio.org/DataDiscovery/Hurr_ED_Center/Easterly_Waves/Geostrophic_Wind/Geostrophic_Wind_fig05.jpg

http://www2.cet.edu/weather/images/coldfront.gif