Download AIR MASSES AND FRONTS WebQuest

AIR PRESSURE, AIR MASSES
AND FRONTS
Earth Science
Air Pressure

Air Pressure: The weight of the air pushing down on the
surface of earth.
Barometer:
•The tool that measures air
pressure.
High and Low Pressure Systems

High pressure is caused by Cool, Dry air SINKING.
Low pressure is caused by Warm, Moist air RISING.

Cool, Dry Air



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= High Pressure
= Clear Skies
Warm, Moist Air
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
= Low Pressure
= Cloudy Skies
ISOTHERMS
Isotherms: Lines connecting place of equal temperature
Pressure Centers

Isobars: Lines on a map connecting places with equal
pressure. This shows you the area of High and Low
Pressure.

Arrows show direction of wind.
DRAWING ISOBARS
•000
•
Global Winds


Global Winds: the global circulation of air from HIGH
pressure to LOW pressure.
THE WINDS WILL BLOW FROM HIGH TO LOW

The winds would go either North or South except for the
Coriolis Effect causes the wind to curve to the RIGHT

What Global Winds affect
North America?
Prevailing Westerlies
Coriolis Effect

The apparent curve of the wind to the right in the
Northern Hemisphere.


Caused by Earth’s Rotation
http://www.wiley.com/college/strahler/0471480533/animations/ch07_a
nimations/animation2.html
Pressure Systems

Surface winds:

High = Move OUT of the center
Low = Move IN toward the center

Add the Coriolis effect (curve to the right)



Motion around a High = Clockwise
Motion around a Low = Counter Clockwise
AntiCyclone
Cyclone
AIR MASSES

Air Mass: A large volume of air defined by its
TEMPERATURE and WATER VAPOR.

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c = Continental = Dry
m = Maritime = Moist
P = Polar = Cold
T = Tropical = Warm
cP = Continental Polar air = Cold, Dry air from Canada
mP = Maritime Polar air = Cold, Moist air from N. Atlantic
cT = Continental Tropical = Warm, Dry air from Mexico
mT = Maritime Tropical = Warm, Moist air from Gulf of Mexico
Frontal Boundaries


Frontal Boundary = Where two different air masses
collide.
Cool, Dry air collides with Warm, Moist air.
Cold Front


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Cold Front = Where a cP air mass collides with a mT air
mass.
cP air is doing the pushing.
mT air is rising UP creating vertical clouds.

Cumulonimbus clouds

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Thunderstorm
What is the weather at A?
What is the weather at B?
What is the weather at C?
C
B
A
Warm Front



Warm Front = When a mT air mass collides with a cP air
mass.
mT air mass is doing the pushing.
As mT air pushes, it rises over the cP air creating low
horizontal clouds.

Stratus, nimbostratus, cirrus

What is the weather at A?
What is the weather at B?
What is the weather at C?


C
B
A
Weather Map Symbols

Identify the weather map symbols to determine weather
in your area.
Cold Front =

Warm Front =

cP
mT
Weather Forecasting
cP
NW
mT
SW
Current U.S. Weather Map

May 24, 2011
Friday’s Weather Map
mP
mT
Mid-Latitude Cyclone
Hurricanes

3 things needed to form a hurricane



Low Pressure
Warm ocean temperatures
High humidity
Hurricane

Where are hurricanes located when at their strongest?

Winds over 76 mph
Hurricanes

What happens when the hurricane hits land?
Weather Station Model

Used to deliver a lot of information in a small space
Weather Map