1. Define the following vocabulary words: can be found in ch. 16 - 18
Air pressure
Barometer
Temperature
Convection currents
Wind
Anemometer
Wind-chill factor
Local winds
Sea breeze
Land breeze
Global winds
Coriolis effect
Latitude
Jet stream
Water cycle
Evaporation
Humidity
Relative humidity
Dew point
Precipitation
Air mass
Tropical
Polar
Maritime
Continental
Front
Occluded
Thermal energy
Trade winds
Prevailing westerlies
Polar easterlies
Wind vane

2. Classwork Assignment 2/18
You will make an outline for chapter 16 section 3:Layers of the Atmosphere.
Make sure you get any important information for each layer of the atmosphere.

3. Weather Patterns & Forecasting

4. Layers of the Earth’s Atmosphere

5. 1. Troposphere
0-12km
Rain, snow, storms, and most clouds occur in the troposphere
Changes more than any other layer
Layer of the Earth’s atmosphere in which Earth’s weather occurs
Greatest atmospheric pressure occurs here

6. 2. Stratosphere 12-50km Contains the ozone layer
Absorbs UV radiation
Upper stratosphere is warmer than the lower stratosphere

7. 3. Mesosphere
50-80km
Layer of the atmosphere that protects Earth’s surface from being hit by most meteoroids

8. 4. Thermosphere
Above 80km
Extends above Earth’s surface outward into space
Has no definite outer limit
Very hot because sunlight strikes here first
Nitrogen and Oxygen molecules convert this energy into heat

9. What is Weather? Who does the weather affect? What professions?
What types of weather can you describe?
Can you explain how it happens?

10. Weather
Refers to the state of the atmosphere at a specific time and place
Describes conditions such as:
Air pressure
Wind
Temperature
Amount of moisture in the air

11. What provides the energy that drives Earth’s weather?
The Sun

12. Earth’s Energy The sun provides almost all of Earth’s energy
Sun’s energy evaporates water into the atmosphere
Eventually, the water falls back to Earth as rain or snow
The sun is also a source of heat energy
Heat from the sun is absorbed by Earth’s surface, which then heats the air above it
Differences in Earth’s surface leads to uneven heating of Earth’s atmosphere

13. Weather Factors
Air temperature
Wind
Humidity
Relative humidity

14. 1. Air Temperature
The temperature of air influences your daily activities
Air is made up of molecules that are always moving randomly
Even when there’s no wind
Temperature is a measure of the average amount of motion of molecules
When the temperature is high:
Molecules in air move rapidly and it feels warm
When the temperature is low:
Molecules in air move less rapidly and it feels cold

15. 2. Wind Air moving in a specific direction is called wind
Wind results because air moves from areas of high pressure to areas of low pressure
Cold air sinks:
High pressure
Warm air rises
Low pressure
Wind must have a speed and a direction

16. Wind Direction can be measured using a wind vane
Speed can be measured using an anemometer

17. 3. Humidity Amount of water vapor present in the air
Heat evaporates water into the atmosphere
More water vapor can be present when the air is warm than when it is cold

18. 4. Relative Humidity
A measure of the amount of water vapor present in the air compared to the amount needed for saturation at a specific temperature
Saturation: when enough water vapor is present in the air for condensation
USUALLY INCREASES BEFORE PRECIPITATION
If you hear a forecaster say that the relative humidity is 50%, it means that the air contains 50% of the water needed for the air to be saturated

19. Dew Point Temperature at which condensation begins
Changes with the amount of water vapor in the air
When air near the ground cools to its dew point, water vapor condenses and forms dew

20. Forming Clouds
Clouds form as warm air is forced upward, expands, and cools
As the air cools, the amount of water vapor needed for saturation decreases and the relative humidity increases
When relative humidity reaches 100%, the air is saturated
Water vapor soon begins to condense in tiny droplets around small particles such as dust and salt
Billions of these droplets form a cloud

21. Forming Clouds
AIR TEMPERATURE AT ITS DEW POINT LEADS TO THE FORMATION OF A CLOUD AT THE EARTH’S SURFACE

22. Precipitation Water falling from clouds
Occurs when cloud droplets combine and grow large enough to fall to Earth
AIR TEMPERATURE DETERMINES WHETHER WATER FORMS RAIN, SNOW, SLEET, OR HAIL (4 TYPES OF PRECIPITATION)

23. Weather Patterns

24. Weather Changes
Because of the movement of air and moisture in the atmosphere, weather constantly changes

25. Air Masses
Large body of air that has properties similar to the part of Earth’s surface over which it develops
An air mass that develops over land is dry compared with one that develops over water
An air mass that develops over the tropics is warmer than one that develops over northern regions
An air mass can cover thousands of square kilometers

26. Air Masses
WHEN YOU OBSERVE A CHANGE IN THE WEATHER FROM ONE DAY TO THE NEXT, IT IS DUE TO THE MOVEMENT OF AIR MASSES
THEY GENERALLY MOVE FROM WEST TO EAST OVER THE CONTINENTAL UNITED STATES
PROVIDED THE BASIS FOR DAILY WEATHER FORECASTS

27. High and Low Pressure Systems
Remember that winds blow from areas of high pressure to areas of low pressure
Cold air sinking: high pressure
Warm air rising: low pressure

28. Types of winds
Local winds
Global winds

29. 1. Local winds Winds that blow over short distances
Caused by the unequal heating of Earth’s surface within a small area
Only form when large-scale winds are weak

30. 2 types of local winds
Sea breeze
Land breeze

31. a. Sea breeze
Unequal heating often occurs along the shore of a large body of water
It takes more energy to warm up a body of water than it does to warm up an equal area of land
Land warms up faster than water
This causes the air over the land to become warmer than air over water
This warm air expands and rises
Low pressure area
Cool air blows inland and moves underneath the warm air

32. Sea breeze – draw this picture

33. b. Land breeze At night, the process is reversed
Land cools more quickly than water, so the air over the land becomes cooler than the air over the water
As the warmer air over the water expands and rises, cooler air from the land moves beneath it

34. Land breeze – draw this picture

35. 2. Global winds
Winds that blow steadily from specific directions over long distances
Created by the unequal heating of Earth’s surface over a large area

36. Global winds

37. Global Convection Currents
How do global winds develop?
Temperature differences between the equator and the poles produce giant convection currents in the atmosphere
Warm air the equator and cold air the poles
Pressure is equator
Pressure is greater near poles
Warm air: low pressure
Cold air: high pressure

38. Global Convection Currents
The differences in pressure causes winds at Earth’s surface to blow from the poles toward the equator
Winds move from areas of high pressure to areas of low pressure
However, higher in the atmosphere, air flows away from the equator toward the poles
Those air movements produce global winds

39. The Coriolis Effect
If Earth did not rotate, global winds would blow in a straight line from the pole toward the equator
Because Earth rotates, global winds don’t follow a straight path
As the wind blows, Earth rotates from west to east underneath them
Making it seem as if the winds have curved
The way Earth’s rotation makes winds curve is called the Coriolis effect

40. The Coriolis Effect Because of the Coriolis effect:
1. global winds in the Northern Hemisphere gradually turn toward the right
2. global winds in the Southern Hemisphere curve toward the left

41. Coriolis effect – draw this picture

42. Path of winds without Coriolis effect

43. Global wind belts
The Coriolis effect and other factors combine to produce a pattern of calm areas and wind belts around Earth
Calm areas:
1. doldrums
2. horse latitudes
Wind belts:
1. trade winds
2. polar easterlies
3. prevailing westerlies

44. Calm areas: Doldrums
Regions near the equator with little or no wind

45. Calm areas: horse latitudes
Latitude: distance from the equator
Warm air that rises to the equator divides and flows both north and south
Horse latitudes: 30°N & S of the equator
Air stops moving toward the poles and sinks

46. Horse Latitudes

47. Wind belts: Trade winds
Steadily easterly winds
The cold air over the horse latitudes sinks and produces a region of high pressure
The high pressure causes surface winds to blow both toward the equator and away from it
The winds that blow toward the equator are turned west by the Coriolis effect

48. Trade Winds
As a result, winds in the Northern Hemisphere between 30°N latitudes and the equator generally blow from the northeast
In the Southern Hemisphere, between 30°S latitudes and the equator, the winds blow from the southeast

49. Trade winds

50. Wind belts: prevailing westerlies
In the mid latitudes, between 30° & 60° N & S, winds that blow toward the poles are turned toward the east by the Coriolis effect
Because they blow from the west to the east, they are called prevailing westerlies
Generally blow from the southwest in northern latitudes and from the northwest in southern latitudes
Play an important part in the weather of the U.S.

51. Prevailing westerlies

52. Wind belts: polar easterlies
Cold air near the poles sinks and flows back toward lower latitudes
The Coriolis effect shifts these polar winds to the west, producing polar easterlies
Polar easterlies meet the prevailing about 60°N and 60°S latitudes
Region called the polar front
The mixing of warm and cold air along the polar front has a major effect on weather in the U.S.

53. Draw this picture. Make sure you include the arrows and the latitude.

54. Jet Streams About 10km above surface Bands of high speed winds
Generally blow from west to speeds of 200 to 400km per hour
As jet streams travel around Earth they wander N and S along a wavy path

55. Jet Streams – draw this picture