Air Masses Reading Packet
High School Earth Science • Reading Series
Air Masses: Giants of the Sky
Lexile Level: ~600L
Reading Passage • Page 1 of 3
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1
What Is an Air Mass?
Look up at the sky. The air above you is not empty. Earth is wrapped in a thick ocean of air called the atmosphere. Sometimes, a huge amount of this air gathers together. Scientists call this an air mass.
An air mass is a giant body of air. It can spread across thousands of miles. It is so big that it can cover several states or even whole countries! Everywhere inside one air mass, the air feels very similar. It has almost the same temperature (how warm or cold it is). It also has the same amount of humidity (how much moisture or water vapor is in the air).
2
Where Do Air Masses Form?
Air masses do not form while rushing quickly across the globe. Instead, air must stay in one place for days or weeks. When air rests over a large area of land or water, it slowly changes. It begins to match the surface underneath it.
The area where an air mass forms is called its source region. If the air sits over cold snow and ice, the air turns cold and dry. If the air sits over a warm ocean, the air turns warm and filled with moisture. The ground or water acts like a mold, shaping the air above it.
Vocabulary Spotlight
- • Air Mass: A very large body of air that has similar temperature and moisture throughout.
- • Humidity: The amount of invisible water vapor held in the air.
- • Source Region: The flat land or ocean region where an air mass sits and forms.
Unit: Weather Systems & Meteorology Continue to Page 2 →
High School Earth Science • Reading Series
Types of Air Masses
Lexile Level: ~600L
Reading Passage • Page 2 of 3
3
Two Big Clues: Moisture and Temperature
Scientists give each air mass a two-part name. The name tells you two things: where it formed and what kind of weather it brings.
Clue 1: Moisture (First Word)
Continental (c): Forms over dry land. This air has very little moisture. It is dry.
Maritime (m): Forms over oceans. Water evaporates into the air. It is moist and humid.
Clue 2: Temperature (Second Word)
Polar (P): Forms near cold regions far from the equator. The air is cold or chilly.
Tropical (T): Forms near the warm equator. The air is warm or hot.
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The Four Main Air Masses in North America
When we combine these clues, we get four major types of air masses. Each one shapes our everyday weather in a different way:
| Code | Full Name | Traits (Weather) | Where It Forms |
|---|
| cP | Continental Polar | Cold and Dry | Northern Canada & Alaska |
| mP | Maritime Polar | Cold and Humid (Moist) | North Pacific & North Atlantic Oceans |
| cT | Continental Tropical | Warm and Dry | Deserts of Mexico & Southwest US |
| mT | Maritime Tropical | Warm and Humid (Moist) | Gulf of Mexico & Atlantic Ocean |
• Bonus Type — Continental Arctic (cA): In the dead of winter, an air mass can form over the frozen Arctic ice cap. This air is bitterly cold and bone dry. When it sweeps south, temperatures plunge below zero!
Unit: Weather Systems & Meteorology Continue to Page 3 →
High School Earth Science • Reading Series
Air Masses on the Move
Lexile Level: ~600L
Reading Passage • Page 3 of 3
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Pushing the Giants: How Air Masses Move
Air masses do not stay over their source regions forever. High above the ground, powerful rivers of wind flow around the Earth. The fastest of these winds is called the jet stream.
The jet stream pushes air masses across North America from west to east. As an air mass travels, it brings its weather with it. A cold mass from Canada makes cities in the Midwest freeze. A warm, humid mass from the Gulf of Mexico makes the East Coast muggy and sticky.
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When Air Masses Collide: Weather Fronts
When two different air masses bump into each other, they do not easily mix together. Cold air is heavy and dense. Warm air is light and less dense.
The border where two different air masses meet is called a front. Most storms happen right along fronts:
- • Cold Front: Cold air moves in fast and digs under warm air. The warm air gets shoved up quickly. This creates tall clouds, sudden heavy downpours, and thunderstorms. Cooler air follows behind.
- • Warm Front: Warm air slides gently up and over cold air. It forms wide, flat sheets of gray clouds. It brings gentle, steady rain that can last for hours or even days.
- • Stationary Front: Two air masses push against each other, but neither one moves. Weather stays cloudy and wet for a long time.
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Why Tracking Air Masses Matters
Meteorologists (weather scientists) track air masses using radar, satellites, and weather balloons. By knowing which air mass is coming your way, forecasters can tell you if you need a winter coat, an umbrella, or sunglasses.
Unit: Weather Systems & Meteorology Turn to Page 4 for Comprehension Questions →
Reading Comprehension • Part 1
Fill in the Blank Questions
Questions 1–10
Student Worksheet • Page 4 of 5
Name:
Date:
Score: / 10
Directions: Read each sentence carefully. Choose the correct scientific term from the word bank to complete each blank. Each term is used exactly once.
Word Bank:
Air Mass Source Region Humidity Continental Maritime Polar Tropical Jet Stream Front Cold Front
A very large body of air that has similar temperature and moisture throughout is called an .
The amount of invisible water vapor or moisture contained in the air is known as .
The flat land or body of water where an air mass sits and forms is called its .
An air mass that forms over dry land and contains very little moisture is labeled .
An air mass that forms over the ocean and holds lots of moisture is labeled .
Air that forms in cold regions near the North or South poles is classified as .
Air that forms near the warm equator and brings warm or hot temperatures is called .
The high-altitude band of fast winds that pushes air masses from west to east is the .
The boundary where two different air masses meet and clash is called a weather .
When cold, dense air moves in quickly and pushes warm air up to create thunderstorms, it is a .
Air Masses Reading Comprehension Turn to Page 5 for Multiple Choice Questions →
Reading Comprehension • Part 2
Multiple Choice Questions
Questions 11–20
Student Worksheet • Page 5 of 5
Directions: Circle the letter (A, B, C, or D) of the best answer for each question.
Score: _____ / 10
11. What must air do to become an air mass?
A) Spin in circles very quickly
B) Stay over one large area for days
C) Freeze into solid ice pellets
D) Travel around the world in hours
16. What direction do air masses usually move across the U.S.?
A) From east to west
B) From south to north only
C) From west to east
D) They never move at all
12. Which traits describe a Continental Polar (cP) air mass?
A) Cold and dry
B) Warm and humid
C) Hot and dry
D) Cold and humid
17. Why do cold and warm air masses not easily mix?
A) They have different densities
B) Both air masses are dry
C) Wind stops blowing between them
D) The sun warms them both equally
13. Where does a Maritime Tropical (mT) air mass form?
A) Northern Canada
B) Cold Arctic ice caps
C) Warm Gulf of Mexico
D) Deserts of the Southwest
18. What kind of weather does a fast-moving cold front often bring?
A) Days of warm, gentle drizzle
B) Hot, cloudless sunshine
C) Sudden heavy rain and thunderstorms
D) No change in the weather
14. What letter symbol stands for Maritime Polar?
A) cP
B) mP
C) cT
D) mT
19. What weather is typical when a warm front passes over an area?
A) Bitter freezing blizzards
B) Steady, gentle rain and flat clouds
C) Instant drop in temperature
D) Severe flash tornadoes
15. A Continental Tropical (cT) air mass brings weather that is:
A) Wet and freezing cold
B) Warm and very dry
C) Cool with dense fog
D) Moist and stormy
20. Why do weather scientists track air masses?
A) To stop the wind from blowing
B) To change the seasons faster
C) To forecast upcoming weather
D) To measure the depth of the ocean
Air Masses Reading Comprehension • End of Questions Total Score: _____ / 20
