Transcript air masses and fronts

AIR MASSES AND
FRONTS
Chapter 16 Section 2
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Humidity
• the amount of water vapor in the air
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Air Mass- A large body of air with the same temperature and moisture that
forms over certain areas of our planet.
Air mass temperature and moisture are consistent throughout.
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Air masses take on the characteristics of the area where they form.
Air mass temperature and moisture are consistent throughout.
•
Warm air forms over tropical regions near the equator.
T- Tropical
•
Cold air forms over polar regions.
P- Polar
•
Wet air masses form over water
m- maritime
•
Dry air masses from over land.
c- continental
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• Moisture content is noted by the first
letter.
m – maritime – wet
c – continental – dry
• Temperature is noted by the second
letter.
P – polar – cool
T – tropical - warm
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Description of air masses:
– Continental polar (cP)- cool and dry
• Continental arctic-type of continental polar mass that is
much colder-forms in the arctic circle
– Continental tropical (cT)- warm (hot)
and dry
– Maritime polar (mP)- humid (wet) and
cold; unstable
Maritime tropical (mT)- humid (wet)
and warm; unstable
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• mP- maritime polar air mass
• cP – continental polar air mass
• mT – maritime tropical air mass
• cT – continental polar air mass
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Maritime Tropical
• Warm humid air masses from
oceans near the tropics.
• They form over the Gulf of
Mexico and the Atlantic
Ocean.
• In the summer time maritime
tropical usually bring hot
humid weather.
• In winter, a humid air mass
can bring heavy rain or snow.
Maritime Polar
 Cool humid air masses form
over the icy cold North
Pacific and North Atlantic
oceans.
 The air masses affect the
west coast more than the east
coast.
 In the summer they often
bring rain, fog, and cool
temperatures to the west
coast.
Continental Polar
 Form over central and
northern Canada and Alaska.
 Bring cool and cold air.
 In winter they bring clear,
cool, and dry air to most of
northern America.
 In the summer, storms may
occur when continental air
masses move south and meet
maritime tropical that move
north.
Continental Tropical
 Hot dry air masses form only
in the summer over dry areas
of southwestern and
northern Mexico.
 Cover a smaller area than
other air masses.
 Bring hot, dry weather to the
south.
An air mass is a large body of air that has similar
temperature and moisture properties
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•
A front is a boundary between air
masses.
•
Four types of fronts and map symbols
1.
2.
3.
4.
Cold front
Warm front
Occluded front
Stationary front
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WARM FRONT
• Warm air mass meets a cold air mass
and pushes the cold air mass out of the
way.
• Brings drizzly precipitation.
• Followed by clear warm weather.
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Symbol:
A warm front occurs when a
less dense air mass rides up
over a more dense air mass.
Clouds, Storms,
and rain accompany
warm fronts.
Moving warm air
mass collides with
a slowly moving
cold air mass
• Warm Front Animation:
– http://ww2010.atmos.uiuc.edu/(Gl)/guides/crclm/act/gifs/fpr
4.gif
– http://earthsci.org/processes/weather/weaimages/2e.gif
COLD FRONT
• Cold air mass meets a warm air mass and
pushes the warm air mass out of its way.
• Bring thunderstorms, rain or snow.
• Most tornadoes develop from
• thunderstorms on the edge of a cold front.
• Cold front followed by cooler drier air.
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Symbol:
A cold front occurs when a more
dense air mass pushes under a
less dense air mass.
Cold Fronts can
cause heavy
snow or ice if
there is enough
water vapor in
the air.
STATIONARY FRONT
• Cold air meets warm air.
• Not enough force to move either front.
• Many days of cloudy, wet weather.
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Symbol:
• Warm air mass and cold
air mass meet
• Neither has enough force
to move the other so they
just stay in the same
place.
• Where they meet, water
vapor in the warm air
condenses into rain,
snow, fog or clouds
• Can stall out for days
Stationary Fronts:
•
Stationary Front Animation:
–
http://www.usatoday.com/weather/tg/wsfront/wsfront.htm
Unlike a fast-moving front,
Stationary fronts often
bring several days of cloudy,
wet weather that can last a
week or more.
OCCLUDED FRONT
• Warm air caught between two cold air
masses.
• Brings cool temperatures with large
amounts of rain or snow
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Occcluded Fronts:
The two cooler air masses
meet in the middle and
may mix.
The warm air mass is cut
off (or occluded) from the
ground.
•
http://www.uwsp.edu/geo/f
aculty/ritter/images/atmos
phere/weather/cold_occlus
ion.gif
Symbol:
A warm air mass is
caught between two
cooler air masses
Cold Front, Warm Front and
Occluded Front Animation
• http://www.3villagecsd.k12.ny.us/Murphy/me
dina/weather.html
• http://www.classzone.com/books/earth_scien
ce/terc/content/visualizations/es2002/es2002
page01.cfm?chapter_no=visualization
• Click on the above links.
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