Download air masses and fronts

AIR MASSES AND
FRONTS
Chapter 16 Section 2
1
•
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
2
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.
3
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.
6
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.
9
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
12
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.
15
Humidity
• the amount of water vapor in the air
16
An air mass is an extremely large body of air whose
properties of temperature, moisture content (humidity) and
air pressure are similar throughout . Air masses can cover
hundreds of thousands of square miles.
•
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)- cold and dryforms over land, High Pressure
– Continental tropical (cT)- warm (hot)
and dry- forms over land (Low
Pressure)
– Maritime polar (mP)- Cold and Humid
(wet); Forms over cold water (High
Pressure)
– Maritime tropical (mT)- Warm and
humid(wet); Forms over warm water
19
(Low Pressure)
• mP- maritime polar air mass
• cP – continental polar air mass
• mT – maritime tropical air mass
• cT – continental polar air mass
20
An air mass is a large body of air that has similar
temperature and moisture properties
22