learn how air masses change weather patterns
TRANSCRIPT
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Warm-Up Air Masses and Fronts
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Words to Know
Fill in this table as you work through the lesson. You may also use the glossary to help you.
air mass a large of air with generally uniform
temperature, humidity, and air pressure
anticyclonea system of winds rotating around a center of
pressure
cyclonea system of winds rotating around a center of
pressure
front the boundary between di�erent air
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Lesson Goals
Learn how air masses change weather patterns.
Identify the major types of
air masses.
.
Explain how air masses
Differentiate the four
main types of
.
Lesson Question
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Warm-Up Air Masses and Fronts
Global Winds
Unequal of Earth’s surface causes global winds.
• They flow constantly from poles toward the .
• They are a�ected by e�ect, which causes global wind patterns.
• The three main wind belts are:
• polar .
• prevailing westerlies.
• easterlies.
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Air Masses and Fronts
Air Masses
An air mass is a body of air with the following uniform characteristics:
• temperature.
• .
• air .
• .
As wind carries air masses over Earth’s surface, the air masses directly influence weather in the regions over which they move.
Classification of Air Masses
The four classifications of air masses are based on where they originate.
• Warm or hot
• Originate over the lower latitudes
• Cold
• Originate over higher latitudes
• Humid
• Originate over the oceans
• Dry
• Originate over land
Tropical Continental
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Instruction
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Major Types of Air Masses
Scientists have paired the classifications to identify four major types of air masses.
Air Mass Symbol Form Over
tropical mT warm water
continental cT warm land
maritime mP cold water
polar cP cold land
Principal World Air Masses
• Continental tropical air masses form over land at low .
• Continental polar air masses form over land at latitudes.
Instruction
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Principal World Air Masses
• Maritime tropical air masses form over water at latitudes and are
closer to the .
• Lastly, we have maritime polar air masses, which form over cold water closer to
the .
MARITIME TROPICAL AIR MASS
Maritime tropical air masses develop over
warm, areas.
• Have warm, air
• Bring showers and
in the
summer
• Bring heavy rain and snow in
the
Instruction
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Air Masses and Fronts
MARITIME POLAR AIR MASS
Maritime polar air masses form over water in polar areas.
• Have , moist air
• Have more
than air masses that form over
• Bring cool, wet weather including
Instruction
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CONTINENTAL TROPICAL AIR MASS
Continental tropical air masses form over
dry regions in the or lower latitudes.
• Have warm, air
• Form principally during
• Bring , dry weather
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CONTINENTAL POLAR AIR MASS
Continental polar air masses form over land
near the poles of the Hemisphere.
• Form over central and northern Canada and Alaska
• Bring cold, dry to
central and eastern United States
How Air Masses Move
In the United States, two natural wind patterns move air masses.
• Prevailing
• Jet streams
• Long, narrow bands of strong wind in the upper
• Usually blow west to east but may
• Stronger the farther they are from the
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Instruction Air Masses and Fronts
Fronts
When air masses move and collide, they
create a weather called a front.
A front often exhibits:
• rapid changes in conditions.
• and unsettled
weather.
• and air
di�erences on
either side.
Types of Fronts
Cold front Warm front
Occludedfront
Types ofFronts
front
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COLD FRONTS AND WEATHER PATTERNS
Cold fronts can cause rapid changes in weather.
• in summer
• Snow in winter
COLD FRONT
A cold front forms when a cold air mass advances against a warmer air mass.
• The cold air mass is moving quickly,
and the air mass is
moving slowly.
• The dense, cold air mass pushes
the warm air mass .
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Instruction Air Masses and Fronts
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STATIONARY FRONT
A stationary front forms between a warm air mass and a cold air mass.
• Neither air mass moves much.
• The water vapor in warm air
into rain,
, , or clouds.
• It can stay in the area for several days,
causing clouds and .
WARM FRONT
A warm front occurs when a warm air mass moves over a cold air mass.
• The warm air mass is moving
than the cold air
mass.
• If the warm air is humid, rain or
may fall.
• If the warm air is dry, may form.
• Warm fronts move slowly, causing
days of cloudy or weather.
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Cyclones
Sometimes the boundary between
is distorted by mountains
or strong winds.
• This causes a bend to form along the front.
• A cyclone is a swirling center
of air.
• Cyclones bring winds, clouds,
, and
violent .
OCCLUDED FRONT
An occluded front is when a warm air mass
is caught between two air masses.
• Warm air is pushed up, and cool air masses meet and may mix.
• The warm air is cut o� from the
.
• The ground gets cooler.
• This may result in widespread clouds, rain, or snow.
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Anticyclones
An anticyclone is the of a cyclone.
• An anticyclone is a high-pressure center of dry air.
• The wind rotates from the center.
• Anticyclones bring dry, clear weather.
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Summary Air Masses and Fronts
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Review: Key Concepts
The movements and interactions of air masses cause changes in weather.
•
tropical
• Continental tropical
• Maritime polar
• Continental polar
• Prevailing
• Jet streams
• Fronts
• Cold fronts
• fronts
• Stationary fronts
• Occluded fronts
Types of Air Masses
How Air Masses Move
Types of Fronts
Answer
Lesson Question
How do the movements and interactions of air masses cause changes in weather?
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