1. Daily Weather Information
Date
Current
Temperature
Wind
Speed
Direction
Dew
Point
Relative
Humidity
Barometric
Pressure

2. Lower Layers of the Atmosphere
Earth’s Atmosphere 1
Lower Layers of the Atmosphere
You study, eat, sleep, and play in the troposphere, which is the lowest of Earth’s atmospheric layers.
Earth’s weather occurs in the troposphere.

3. Energy from the Sun 2 The Sun provides most of Earth's energy.
Energy Transfer in the Atmosphere 2
Energy from the Sun
The Sun provides most of Earth's energy.
When Earth receives energy from the Sun, three different things can happen to that energy.

4. Energy from the Sun 2 Some energy is reflected back into space.
Energy Transfer in the Atmosphere 2
Energy from the Sun
Some energy is reflected back into space.
Some is absorbed by the atmosphere.
Some is absorbed by land and water on Earth's surface.

5. Energy Transfer in the Atmosphere2
Heat
Heat is energy that flows from an object with a higher temperature to an object with a lower temperature.
Energy from the Sun reaches Earth's surface and heats it.
Heat is eventually redistributed by air and water currents.

6. Energy Transfer in the Atmosphere2
Heat is transferred through the atmosphere in three ways—radiation, conduction, and convection.

7. Energy Transfer in the Atmosphere2
Radiation
Radiation is energy that is transferred in the form of rays or waves.
Heat from the Sun reaches Earth in the form of radiation.
Heat is transferred from the Sun to the surface of Earth, which warms the surface of Earth.

8. Energy Transfer in the Atmosphere2
Conduction
Conduction is the transfer of energy that occurs when molecules bump into one another. This occurs when two objects are touching.
Heat from the surface of Earth is transferred to the air directly above the surface by conduction, causing the air directly above the surface to become warmer.

9. Energy Transfer in the Atmosphere2
Convection
Convection is the transfer of heat by the flow of material.
Convection currents circulate heat throughout Earth’s atmosphere.

10. Energy Transfer in the Atmosphere2
Convection
When air is warmed, the molecules in it move apart and the air becomes less dense.
Air pressure decreases because fewer molecules are in the same space.
Warm air has low air pressure.

11. Convection 2 In cold air, the molecules move closer together.
Energy Transfer in the Atmosphere 2
Convection
In cold air, the molecules move closer together.
The air becomes denser and air pressure increases.
Cold air has high air pressure.

12. 2 Energy Transfer in the Atmosphere
Heat is transferred through the atmosphere in 3 ways: radiation, conduction, and convection.

13. Air Movement 3
Forming Wind
Because Earth is curved, areas of Earth receive different amounts of radiation from the Sun.

14. Air Movement 3
Forming Wind
The air at the equator is warmer, less dense, and has lower pressure.
The air at the poles is colder, denser, and has higher pressure.
Wind is the movement of air from an area of high pressure to an area of low pressure.
Differences in air pressure is what causes wind to blow.

15. Air Movement 3
Forming Wind
The Sun’s uneven heating of Earth’s surface forms giant convection currents of wind.

16. Air Movement 3
The Coriolis Effect
The rotation of Earth causes moving air and water to turn to the right north of
the equator and to the left south of the equator.
This is called the Coriolis effect.

17. Air Movement 3
Global Winds
Global winds are wind patterns caused by the giant convection currents combined with the Coriolis Effect.

18. Air Movement 3
Global Winds
Early sailors discovered that the wind patterns on Earth helped them navigate the oceans.
Near the equator, sailors sometimes found little or no wind to move their ships, and it rained nearly every afternoon.
The area near the equator where very little wind occurs and daily rain falls is called the doldrums.

19. Global Winds - Surface Winds
Air Movement 3
Global Winds - Surface Winds
Air moving along Earth’s surface between the equator and 30º latitude (north and south) creates steady trade winds that blow to the west.
These are called trade winds because early sailors used their dependability to establish trade routes.

20. Global Winds - Surface Winds
Air Movement 3
Global Winds - Surface Winds
Between 30º and 60º latitude (north and south), winds called the prevailing westerlies blow to the east, in the opposite direction from trade winds.
Prevailing westerlies are responsible for much of the movement of weather across North America.

21. Global Winds - Surface Winds
Air Movement 3
Global Winds - Surface Winds
Polar easterlies are found near the poles.
Near the north pole, easterlies blow from northeast to southwest.
Near the south pole, polar easterlies blow from the southeast to the northwest.

22. Global Winds - Surface Winds
Air Movement 3
Global Winds - Surface Winds

23. Global Winds - Surface Winds
Air Movement 3
Global Winds - Surface Winds

24. Global Winds - Jet Stream
Air Movement 3
Global Winds - Jet Stream
Narrow belts of strong winds, called jet streams, blow near the top of the troposphere.
The jet streams move storm systems across North America from west to east.

25. Air Movement 3
Local Winds
Global wind systems determine the major weather patterns for the entire planet.
Smaller wind systems affect local weather.
If you live near a large body of water, you’re familiar with two such wind systems—sea breezes and land breezes.

26. Local Winds - Sea and Land Breezes
Air Movement 3
Local Winds - Sea and Land Breezes
A sea breeze is a convection current that blows wind from the cooler sea (high pressure) toward the warmer land (low pressure) during the day.

27. Local Winds - Sea and Land Breezes
Air Movement 3
Local Winds - Sea and Land Breezes
At night, the reverse occurs. Air moves off the land toward the water as the land cools more quickly than the water. This is called a land breeze.