1. Unequal Heating, Air Pressure and Winds

2. It is caused by the uneven heating of the Earth's surface by the sun
It is caused by the uneven heating of the Earth's surface by the sun. Because the Earth's surface is made of very different types of land and water, it absorbs the sun's heat at different rates.

3. Air Pressure Review Air has mass. Air takes up space. Air has density.
Air pressure is the weight of a column of air pressing down on an area.

4. Atmosphere/Pressure Atmosphere held in place by gravity
Pressure strongest at surface-more air above you
*as altitude increases, air pressure decreases
Stack of books

5. Air Pressure
As Air Pressure decreases, so does density.

6. Atmosphere
Atmosphere: a mixture of gases that surrounds Earth: acts like a blanket
Contains oxygen
Protects from sun

7. Layers of the Atmosphere
Troposphere: all weather happens here
Stratosphere: ozone layer-protects us
Mesosphere: middle layer
Thermosphere: hottest layer

8. Atmosphere

9. Composition of Troposphere
Nitrogen=78%
Oxygen=21%
Other 1%=water vapor, CO2 and other

10. Weather Factors
Sun’s energy travels to earth as Electromagnetic waves.
What type of heat transfer is this?

11. Weather Factors Scattering: Reflections of light in all directions.
Why is the sky blue?

12. Radiation
Ever feel the heat of the sun on your face or the heat from standing by a campfire? That is radiation.
It is the direct transfer of energy by electromagnetic waves through space.

13. Conduction
Have you walked barefoot on the sand at the beach and the sand burned your feet? That is conduction.
It is the direct transfer of heat from one substance to another through direct contact.

14. Convection
Did you come in after the snow with wet shoes on and your mother told you to put them over the heating vent to dry? How does this dry them even though the actual furnace is in the attic? That is convection.
The transfer of heat by the movement of fluid or air. Hot air rises, cold air sinks.

15. How is Earth heated?
Light/heat from the sun RADIATES through the atmosphere, hits the Earth where it is absorbed.
This heats the air above it by CONDUCTION.
This heat rises up to the greenhouse gases where it is trapped, cools, sinks and heats at the surface again.-CONVECTION.

16. Weather Factors

17. Greenhouse Effect
These gases absorb the heat and act as a “blanket” to keep Earth warm.
Some greenhouse gases: water, methane, carbon dioxide.

18. Greenhouse Effect Roleplay
Sun
Gases
Sun’s Rays

19. Hot Air Rises… But how does the ground get hotter
Hot Air Rises… But how does the ground get hotter??? … It is farther from the sun!
Air in the atmosphere acts as a fluid (water vapor). The sun's radiation strikes the ground = warming the rocks/ground. As the ground’s temperature rises due to conduction, heat energy is released into the atmosphere, forming a “bubble” of air which is warmer than the surrounding air. This “bubble” of air rises into the atmosphere. As it rises, the air in the “bubble” cools and becomes more dense. The movement of the air creates wind. Convection currents are responsible for many weather patterns in the troposphere.

20. Convection
Currents!

21. Winds

22. What causes winds? Lots of difference Differences in air pressure
More of a difference in pressure = faster winds
Lots of difference

23. Air Rises @ Equator Air Sinks @ Poles
You know…
Warm air rises = less dense
Cool air sinks = more dense
Now understand…
Warm air = less dense
= low pressure
Cool air = more dense
= high pressure

24. Global Winds
Created by unequal heating of Earth’s surface.

25. Global Winds… cont…
The movement of air between the poles and the equator produces global winds.
Coriolis effect produces patterns of air circulation called global winds.

27. Global Wind Belts Major global wind systems:
Polar easterlies, westerlies, and trade winds.

28. Doldrums Where the trade winds meet around the equator
Very little wind because the warm air rising = low pressure

29. Horse Latitudes
High pressure areas… 300N and 300S
Very week winds

30. Jet Streams Bands of high speed winds
Upper troposphere and lower stratosphere
Blow from west to east at speeds of km/hr.
Help airplanes save fuel and time when traveling east.

31. Local Winds Local winds are winds that blow over short distances.
Have you ever flown a kite at the beach on a hot summer day? Even if there is no wind inland, there may be a cool breeze blowing in from the water toward the beach. This breeze is an example of local winds!
Local winds are winds that blow over short distances.
They are caused by unequal heating of Earth’s surface within a small area.
Types:
sea breezes and land breezes
Mountain breeze and valley breeze

32. Sea Breeze (Day)
Land heats up faster than water. Hot air over land rises (Low Pressure), cool air over water falls (High Pressure). Winds move from the water (High Pressure) to the land (Low Pressure).

33. Land Breeze (Evening)
Land cools off faster than water. Cool air over land falls (High Pressure), warm air over water rises (Low Pressure). Winds move from the land (High Pressure) to the water (Low Pressure).

34. Valley Breeze (Day)
During the day the sun warms the air slopes, creating a valley breeze…
at nightfall, the air along the mountain slopes cools…

35. Mountain Breeze (Night)
This cool air moves down the slopes into the valley, producing a mountain breeze!

36. Measuring Wind Winds are described by their direction and speed.
Wind Vane
Measuring Wind
Anemometer – The cups catch the wind, turning faster when the wind blows faster.
Winds are described by their direction and speed.
Wind direction is determined with a wind vane – points in the direction the wind is moving!
Wind speed is measured with an anemometer.
The increased cooling that a wind can cause is called the wind chill factor.