1. Convection in Our Atmosphere
Credit to:
Burnett Middle School
8th Grade Science

2. Previous Knowledge
What do you already know about convection?

3. Vocabulary
Convection and Winds Vocabulary - give as notes.

4. CONVECTION
is the transfer of heat by the movement of warmed matter (air or liquid)

5. The Sun provides the energy that drives convection within the atmosphere and oceans, producing winds and ocean currents.

6. Hot Air is Less Dense!

7. What is most dense SINKS!
Atmospheric Density
What is most dense SINKS!

8. CONVECTION

9. CONVECTION

10. CONVECTION CURRENTS move the air in our atmosphere!
We have global winds that blow because of these large convection currents

11. CONVECTION
Wind over the shore changes direction because of EARTH’S UNEVEN WARMING & COOLING! We can these local winds

12. Click the Video button to watch a movie about convection currents.
- Winds
Convection Currents
Click the Video button to watch a movie about convection currents.

13. CONVECTION DEMOS! Tea bag http://www.youtube.com/watch?v=7xWWowXtuvA
Colored Water

14. Why does hot air rise and cold air sink?
Cool air is more dense than warm air, so the cool air ‘falls through’ the warm air.
Why are the heating elements placed beneath hot water tanks in people’s homes?
Hot water rises.
So when the element heats the water, and the hot water rises, the water tank is filled with hot water.

15. Wind

16. Wind is the movement of air from an area of high pressure to an area of low pressure.
This is caused by the unequal heating of the Earth’s surface.
As air is heated, it becomes less dense and rises. The air pressure is also lower .
Cooler, more dense air, has a higher pressure, and moves under the warmer air.
This causes a convection current,
creating wind
The greater the pressure
difference, the faster the air
moves, and the stronger the
wind blows.

17. How is Wind Measured?
Wind direction is measured with a wind vane, which points in the direction the wind is coming from.
This is how the wind is named.
A western wind is blowing from the west.
This means a northern wind actually blows toward the south.
Wind speed is measured with an instrument called an anemometer.

18. Why We have Global Winds
Since the air near the equator is less dense, it rises forming areas of low pressure.
The cold air near the poles sinks because it is more dense, forming areas of high pressure.
The air moves in large circular patterns called convection currents.
The change in density is due to the unequal heating of Earth’s
surface

19. L H 90 30 60 Cold Moist Air Rises Cool Dry Air Sinks60 90
Warm Moist Air Rises
Very Cold Air Sinks
Cold Moist Air Rises
Cool Dry Air Sinks
Cool Dry Air Sinks
Cold Moist Air Rises
Very Cold Air Sinks

20. Wind Moves from HIGH to LOW30 60 90
Wind Moves from HIGH to LOW

21. Objects are deflected to the RIGHT in the Northern Hemisphere30 60 90
Objects are deflected to the
RIGHT in the Northern Hemisphere
But why?

22. The Coriolis Effect
As Earth rotates, the Coriolis effect turns winds in the Northern Hemisphere toward the right.

23. Northern Global Wind Patterns
Polar Easterlies
90 – 60 latitude from the east
Prevailing Westerlies
60 – 30 latitude from the west
Trade winds
30 – 0 latitude from the East

24. Global Winds
Polar Easterlies are the wind belts that extend from the poles to 60° latitude in both hemispheres. They form as cold, sinking air moves away from the poles. They can carry cold arctic air over the U.S. which can produce snow and freezing weather.
Westerlies are the wind belts found between 30° and 60° latitude in both hemispheres. They blow toward the poles from west to east. These winds can carry moist air of the U.S. producing rain and snow.
Trade Winds are the winds that blow from 30° latitude almost to the equator in both hemispheres. They curve to the West as they blow toward the equator.

25. Global Winds, continued
The Doldrums The trade winds of the Northern and Southern Hemispheres meet in an area around the equator called the doldrums. there is very little wind because the warm, rising air creates an area of low pressure. The name doldrums means “dull” or “sluggish.”

26. Global Winds
Sailing the global winds activity

27. Jet Streams
Narrow belts of high-speed winds that blow in the upper troposphere and lower stratosphere. Knowing the path of a jet stream is important not only to pilots but also to meteorologists. Because jet streams affect the movement of storms, meteorologists can track a storm if they know the location of a jet stream.

28. Jet Streams
Jet Streams form at latitudes where wind systems come together
High speed westerly winds form high above the surface

29. Local Winds Sea Breeze Land Breeze
Local winds move over a short distance
Caused by the heating of a small area of Earth’s surface
Sea Breeze
The sun warms the land faster than the water, so the air above
the land becomes warmer.
The cooler air over the water moves inland
Land Breeze
At night, the land cools faster than the water, so the air above
the land becomes cooler.
The cooler air over the land moves out to the water.

30. Local Winds
Local winds generally move short distances and can blow from any direction.
Mountain and valley breezes are examples of local winds caused by an area’s geography.
Sea and land breezes are affected by temperature.

32. Air Currents
United streaming video – 11 minutes

33. Ocean Currents

34. Major Ocean Currents
An Ocean Current is a large volume of water flowing in a certain direction.
Wind-driven currents are called surface currents.
Surface currents carry warm or cold water horizontally across the ocean’s surface

35. Major Ocean Currents
Surface currents extend to about 400 m below the surface, and they move as fast as 100 km/day.
Earth’s major wind belts, called prevailing winds, influence the formation of ocean currents and the direction they move.

36. Coriolis Effect
The Coriolis Effect is the movement of wind and water to the right or left that is caused by Earth’s rotation.
It causes fluids such as air and water to curve to the right in the Northern hemisphere, in a clockwise direction.
The Coriolis effect also cases fluids to curve to the left in the southern hemisphere, in a counterclockwise direction.

37. Coriolis Effect
The shapes of continents and other land masses affect the flow and speed of currents.
Currents form small or large loops and move at different speeds, depending on the land masses they contact.

38. Impacts of Weather and Climate
Warm-water currents and cold-water currents affect weather and climate in different ways
Regions near warm-water currents are often warmer and wetter than regions near cold-water currents

39. Impacts on Weather and Climate
The Gulf Stream is a warm-water current that affects coastal areas of the southwestern United States by transferring lots of thermal energy and moisture to the surrounding air.
The cold California Current affects coastal areas of the southwestern United States.

40. Video Ocean Currents and weather
You can show whole video (27 minutes) or just the section on ocean currents (5ish minutes)
Planet Water – Water cycle, oceans, and weather – 20 minutes

41. Puff Mobile

42. Answer the following questions using complete sentences.
Explain in detail how the wind affected the movement of your car. Incorporate factors such as intensity, duration, and direction in your explanation.
Using the same factors, explain how wind affects air masses which in turn impact our weather.