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Section 1: The Causes of Weather
Air masses have different temperatures and amounts of moisture
because of the uneven heating of Earth’s surface.
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What I Know
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What I Want to Find Out
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What I Learned
Essential Questions
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What is the difference between weather and climate?
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How do imbalances in the heating of Earth’s surface create weather?
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How do air masses form?
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What are the five types of air masses?
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The Causes of Weather
Vocabulary
Review
New
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heat
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weather
climate
air mass
source region
The Causes of Weather
What is meteorology?
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Meteorology is the study of atmospheric phenomena.
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The root word of meteorology is the Greek word meteoros, which means
high in the air.
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The Causes of Weather
What is meteorology?
Weather versus climate
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Short-term variations in atmospheric phenomena that interact and affect
the environment and life on Earth are called weather.
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Climate is the long-term average of variations in weather for a particular
area.
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The Causes of Weather
Heating Earth’s Surface
Imbalanced heating
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One reason that temperatures may vary from location to location at a
certain time of year is that Earth’s axis of rotation is tilted relative to the
plane of Earth’s orbit.
• Example: In January Miami FL is warmer than Detroit
MI. The # of hours of daylight and amount of solar
radiation is greater in Miami.
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The Causes of Weather
Heating Earth’s Surface
Imbalanced heating
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Solar radiation is unequal partly due to the changing angle of incidence of
the sunlight. The greater the area covered by solar radiation, the smaller
the amount of heat per unit of area.
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The Causes of Weather
Heating Earth’s Surface
Thermal energy redistribution
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The constant movement of air and water among Earth’s surfaces, oceans,
and atmosphere redistributes thermal energy around the world.
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Weather—from thunderstorms to large-scale weather systems—is part of
the constant redistribution of Earth’s thermal energy.
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The Causes of Weather
Air Masses
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An air mass is a large volume of air that has the same characteristics, such
as humidity and temperature, as its source region.
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A source region is the area over which an air mass forms.
• 5 types of air masses (See table 1 p. 316 in book)
– Artic
– Continental polar
– Continental tropical
– Maritime polar
– Maritime tropical
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The Causes of Weather
Air Masses
Types of air masses
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The origins of maritime tropical air are tropical bodies of water.
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The southwestern United States and Mexico are the source regions of
continental tropical air, which is hot and dry, especially in summer.
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The Causes of Weather
Air Masses
Types of air masses
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Maritime polar air masses form over the cold waters of the North Atlantic
and North Pacific.
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Continental polar air masses form over the interior of Canada and Alaska,
and carry frigid air southward in the winter.
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Earth’s ice- and snow-covered surfaces above 60° N latitude in Siberia
and the Arctic Basin are the source regions of arctic air masses.
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https://www.youtube.com/watch?v=tkK4_F0VKhM
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The Causes of Weather
Air Mass Characteristics
https://www.youtube.com/watch?v=tkK4_F0VKhMhttps://www.youtube.com
/watch?v=tkK4_F0VKhM
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The Causes of Weather
Air Masses
Air mass modification
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When an air mass travels over land or water that has characteristics
different from those of its source region, the air mass can acquire some of
the characteristics of that land or water and undergo modification.
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Ex: Lake effect snow from continental polar air mass
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The Causes of Weather
Air Masses
Air mass modification
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As the cold, continental polar air moves over the warmer Great Lakes, the
air gains thermal energy and moisture. This modified air cools as it is
uplifted and produces lake-effect snows.
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The Causes of Weather
Review
Essential Questions
•
What is the difference between weather and climate?
•
How do imbalances in the heating of Earth’s surface create weather?
•
How do air masses form?
•
What are the five types of air masses?
Vocabulary
• weather
• climate
Copyright © McGraw-Hill Education
• air mass
• source region
The Causes of Weather
Classwork/Homework Assignment
• Pick 2 different cities in the US and track the
weather daily
• Write high and low, also precipitation
• Humidity and Dewpoint
• Compare the 2 cities and look for weather
trends
• Present of Friday