Learn how air masses change weather patterns

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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

WK2

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


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.


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.

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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

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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


Instruction Air Masses and Fronts

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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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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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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.


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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Summary Air Masses and Fronts

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Learn how air masses change weather patterns