1. Air Pressure
Chapter 2, Section 1

2. Air Pressure The force of air molecules pushing on an area.
Depends on the weight of the air above it
The greater the force, the greater the pressure.
Molecules push in all directions

3. Air Pressure and Altitude
Air pressure decreases as altitude increases
With less air above you (i.e. at the top of a mountain), the pressure is lower.

4. Air Pressure and Density
Remember, density is the mass of an object divided by its volume.
Since the pressure is greater nearer to sea level, the air’s density is also greater.
More pressure = tightly packed air molecules

5. Air Pressure and Air Motion
Air moves from areas of higher air pressure to lower air pressure

6. Air Pressure and Barometers
A barometer is any instrument that measures air pressure.

7. Air Pressure and Weather
If a high pressure system is on its way, often you can expect cooler temperatures and clear skies. H
If a low pressure system is coming, then look for warmer weather, storms and rain. L

8. Wind
Chapter 2, Section 2

9. Brain Break
Seat mix up.
2 minutes to find a new seat for the day… make smart choices!

10. Wind and Weather
Weather: the condition of Earth’s atmosphere at a certain time or place
Wind: the air that moves parallel to the ground
Wind moves from high pressure to low pressure

11. Wind Movement
Sun heats ground, ground heats air. Warm air rises, low pressure forms.
Sun heats new ground less strongly. Cold air is more dense, sinks, and a high pressure forms.
Air moves from the high pressure to the low pressure.

12. Wind Movement Some winds die quickly.
Some winds travel thousands of kilometers in patterns
Global winds
They last for weeks.
Caused by uneven heating between the poles (cooler) and the equator (warmer).

13. Earth’s Rotation and Wind
The Coriolis effect causes global winds to curve as they move from the poles to the equator.
They move in three curved paths, called the global wind belts.

14. Calm Regions The Doldrums The Horse Latitudes
Low pressure zone near the equator
Warm air rises and spreads out to poles, causing clouds and heavy rain
The Horse Latitudes
high pressure zones located 30 degrees north and south of the equator
Warm air traveling from equator cools and sinks

15. Wind Belts 3. The Trade Winds 4. The Westerlies 5. The Easterlies
Blow from the east toward the equator
Die out as they come near equator
4. The Westerlies
Blow from the west toward the poles
Bring storms across the US
5. The Easterlies
Blow from the east, moving from the poles to the mid-latitudes
Stormy weather occurs when they meet the westerlies

19. Eye Witness Part 1
Eye Witness Part 2

20. Chapter 2, Notes 3
Clouds

21. What is a cloud?
A cloud is a large group of water droplets that join together during the process of condensation.
You can write:
cloud = group of droplets joined by condensation

22. Types of Clouds
There are three main categories that clouds are grouped into:
High clouds = cirrus
Middle clouds = alto
Low clouds = stratus

23. Cirrus clouds Cirrus means “curl of hair”. thin and wispy.
high clouds mostly made of ice crystals.
found above 18,000 feet.
indicate fair/pleasant weather.

24. Altostratus clouds A type of alto cloud. Gray or blue colored cloud.
Made of ice crystals.
Usually form before a rain or snow storm.

25. Altocumulus clouds A type of alto cloud. Gray puffy masses.
Can indicate thunderstorms.

26. Stratus clouds Gray clouds that usually cover the entire sky.
Looks like fog.
Sometimes a light precipitation comes from them.

27. Nimbostratus clouds Dark gray, wet looking clouds
Light to moderate continuous rain fall or snow.

28. Note Break!
5 minute vocab review

29. Cumulus clouds White, puffy clouds that look like cotton.
“fair-weather clouds”
Flat bottoms with rounded tops.

30. Cumulonimbus clouds Thunderstorm clouds High winds flatten the clouds
Heavy rain, snow, hail, lightning, and tornadoes.

31. Fog
Cloud on the ground.

32. Contrails Trails left behind jet aircrafts.
Hot air from exhaust mixes with cold atmosphere.

33. Green Clouds Severe weather likely to produce hail and tornadoes.
The green color is not understood yet.

34. Brain Break!
3 minute break.

35. Chapter 2, Notes 4
Precipitation

36. How it forms… By several water droplets combining
About 1 million
By growth of ice crystals

37. How is it measured?
Rain: we use a rain gauge to collect the rain and it has measurements on the side.
Snow: ruler or a special type of gauge

38. Types of Precipitation
Rain/drizzle
Most common type
Drizzle: light rain from stratus clouds

39. Types of Precipitation
Freezing Rain
Freezes when it lands on Earth’s surface

40. Types of Precipitation
Sleet
Freezes in the air and turns into small pellets of ice.

41. Types of Precipitation
Snow
Ice crystals grow and combine in the clouds
They have 6 sides

42. Types of Precipitation
Hail
Lumps of ice fall from cumulonimbus clouds

43. Acid Rain
Rain that mixes with sulfur and nitrogen in the air to form acid.
Dangerous to living organisms.