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Cold, dry air affecting the northern
United States in winter comes from
what kind of air mass?
a. Continental tropical air masses
b. Continental polar air massess
c. Maritime polar air masses
d. Maritime tropical air masses
Project Work time
You have 20 minutes to get
your project together!!!!!!
What effects air pressure?
How does air temperature effect the air
pressure?
Air masses and fronts
 Types of air masses (large body of air with
similar properties)
 Tropical – forms over the high latitudes / Polar
– forms in low latitudes
 Maritime – forms over water and are moist
 Continental – forms over land and are dry.
 This results in four main types




Maritime polar
Maritime tropical
Continental polar
Continental tropical
 Air masses move because global winds move
the air masses
An air mass is a large (usually thousands of miles across) volume of air that
has the same temperature and humidity.
Air masses get their properties from spending days to weeks over the same
part of the Earth
Examples: over central Canada, the North Pole, the tropical Pacific Ocean.
Describe what the air would be like in each of these places. Warm? Cold?
Wet? Dry?
If the air mass sits over the ocean
for a while, it becomes humid (wet)
and is called maritime.
The air will have high humidity.
If the air mass sits over land for a
while, it becomes dry and is called
continental.
The air will have low humidity.
If the air mass sits near the equator
for a while, it becomes warm and is
called tropical.
If the air mass sits near the poles
for a while, it becomes cold and is
called polar.
This means there are 4 combinations:
What do you think they will be?
Maritime tropical = wet & warm
Continental tropical = dry & warm
Maritime polar = wet & cold
Continental polar = dry & cold
Our weather constantly changes
because different kinds of air masses
are being pushed around the Earth.
Front
Fronts occur where two air masses with
different properties touch each other.
Four types of fronts
Cold Front
The air mass doing the pushing is cooler and
more dense that the air mass it is pushing
Move quickly and can produce severe weather
After it moves through, clear skies, cooler
temperatures
Warm Front
The air mass doing the pushing is warmer and less
dense than the air mass it is pushing
Bring humid weather, sometimes rainy for several
days
After it moves through, temperatures are warmer
Stationary front
Two air masses next to each other. Neither mass is
moving the other
Weather remains the same for several days
Occluded front
Warm air mass is caught between two cold air
masses
A weather front is a “battle” between two different
air masses that are touching.
Imagine two water balloons that are filled with
water of different temperatures. If you hold
one in each hand and push them together, the
places the balloons touch is the boundary
between the two balloons. This would be the
balloon “front.”
Notice the symbol for a cold front!
.
Notice that the colder (blue) air is pushing the other
air out of the way. It is “winning the pushing battle.”
Notice the kinds of clouds at a cold front.
Cold front facts to know:
1. Moves quickly
2. Rapid “uplift” of air occurs due to the
cold air lifting the warm air.
3. Produces cumulus first.
4. Often produces severe weather
(tornadoes, hail, lightning).
5. Cooler, drier air follows.
Cold front
Drier,
cooler air
mass
Warm Front
• A warm front occurs when a less dense air mass
rides up over a more dense air mass.
Notice the symbol for a warm front!
A warmer air mass is pushing into a cooler air mass.
Because warm air is less dense, it gets pushed over the
cooler air mass.
Notice the kinds of clouds at a warm front.
Facts to know about warm fronts!
1. Warm air moves over cold
2. Often begins with cirrus clouds
followed by stratus.
3. Produces light to moderate rain.
4. After it passes, warmer
weather.
Stationary Front
• A stationary front occurs when the air masses on
either side of the front are not moving toward each
other. On surface maps, a stationary front is
indicated by alternating the cold/warm symbols as
shown.
Sometimes is you are observant, you can see the front!
H stands for a high pressure
air mass
L means low pressure.
Isotherm map – these lines are isotherms
Iso = equal therm = temperature
Wind map – these lines are isobars
Doppler radar map of a hurricane crossing Florida.
Doppler radar
sends out
microwaves
that bounce
back to a
receiver
according to
how much
precipitation
gets in the
way.
Combination map used for TV and internet
Another combination map – Can you read it?
Classwork Activity
Due Friday
Choices
1. Brochure for the weather channel
2. Weather Skit
Must Include: (10 Pts. Each)
• Air masses (Maritime, continental, tropical and Polar)
• Cloud Types (cumulous, stratus, and cirrus)
• Cold Fronts
• Warm Fronts
• Stationary fronts
• Pressure (high and low)
• Temperature
• Jet Stream
• Weather Map
• Occluded Front