1. Humidity The relative measure of the amount of water vapor in the air
Psychrometer
Water vapor affects the density of the air.
Cold air is heavier than warm air.

2.
Air Masses

3. A body of air that has the same temperature and humidity throughout.
What is an air mass?

4. If a large body of air sits over an area of land or water for a long period of time, it will take on the characteristics of the land or water beneath it.
Temperature
Humidity
How do air masses form?

5. Location, Location, Location…
Air masses over the equator will have high temperatures.
Air masses over polar regions will have low temperatures.
Air masses over water (maritime) will have high humidity (moisture content).
Air masses over land (continental) will have low humidity (moisture content).
Location, Location, Location…

6. Where do air masses form?
Air masses tend to form in areas with little wind.
Remember, they sit over an area for a long period of time without moving.
Where do air masses form?

7. Air masses that form over water are called maritime.
Air masses that form over land are called continental.
Labeling Air Masses

8. Classification of Air Masses
mT – maritime tropical
cT – continental tropical
mP – maritime polar
cP – continental polar
cA – continental arctic
Classification of Air Masses

9.
Location of Air Masses

10. Characteristics of Air Masses
mT – warm, moist air
cT – warm, dry air
mP – cold, moist air
cP – cold, dry air
cA – super cold, dry air
Characteristics of Air Masses

11. How do air masses move? Convection!
How do air masses move?

12. Convection Warm air rises, and cold air moves in to replace it.
A circulation pattern is formed.
Causes air and water currents to form
Convection

13. How does convection work?
Density!
Warm air rises.
Cool air sinks.
How does convection work?

14. How do different air masses form?
Reflection Question

15.
Hurricanes 15

16. What is a hurricane? Hurricanes are tropical cyclones.
They form in the southern Atlantic Ocean, Caribbean, Gulf of Mexico, and eastern Pacific Ocean.
Their winds spiral outward in a counterclockwise, circulation pattern.

17. What conditions must exist for a hurricane to form?
Low to medium winds blowing in the same direction
5–30 degrees north of the equator in the ocean
Ocean surface temperature of greater than 80 F that extends down to about 150 feet deep (50 m)
Lower atmosphere must be moist

18. How do hurricanes form?
The air mass above the tropical waters takes on the temperature and humidity of the water beneath it.
Incoming winds force the air upward.
The warm, moist air rises, forming water vapor and clouds.
Above the storm, the winds flow outward.
Outside winds blow inward, and the cycle repeats.

19. How do hurricanes move?
Hurricanes turn to the right, away from the equator, because of the Coriolis Effect caused by Earth’s rotation.
You will learn about this phenomenon later in the lesson.

20. Where does the energy for a hurricane originate?
The Sun heats the oceans.
Warm air rises, and as it cools, it releases energy, fueling the hurricane.

21. Why don’t hurricanes form in higher latitudes?
The temperature of the oceans is not warm enough.
The distance is too far from the equator.

22. Hurricane Katrina 22

23. Reflective Question
How do oceans play a role in the development of weather systems including hurricanes? 23

24. Winds 24

25. The movement of air in a horizontal direction
What is wind?

26. The uneven heating of the Earth causes differences in air pressure.
What causes wind? 26

27. The Sun’s energy is more concentrated at the Equator and spread out more over the poles.
Air over the equator is warm and less dense and has lower pressure.
Air over the poles is cold and denser and has higher pressure.
Why does this happen?

28. As warm air at the equator rises, cooler air from the poles will move in and replace it.
Air pressure moves in a pattern from high to low.
Why does this happen?

29. Convection
As warm air at the equator rises, cooler air from the poles will move in and replace it. 29

30. Global Convection Currents
The density changes caused by temperature changes create convection cells.
These cause circular patterns of air that circulate over the whole planet.
Global Convection Currents 30

31. Where the convections cells meet, prevailing winds and jet streams form.
They blow from one direction over a certain area of the Earth’s surface.
Global Wind Belts 31

32. Jet Stream

33. Jet Stream
Forms high in the upper Troposphere between two air masses of different temperatures
Higher temperature difference = faster speed
Due to the Coriolis Effect, it flows around air masses.
Polar Jet:
It dips southward when frigid polar air masses move south.
It tends to stay north in the summer months.

34. http://www.pbs.org/wgbh/nova/vanished/jetstr_five. html
Jet Stream Animation

35. Prevailing Winds Named for the direction from which they blow:
Polar Easterlies – High latitudes blow east to west toward the equator
Westerlies – Mid latitudes blow west to east toward the poles
Easterlies (Trade Winds) – Low latitudes blow east to west toward the Equator

36. Prevailing Winds

37. Prevailing Winds
Pressure belts form in between the wind belts.

38. MoreDirect Sun Hot 0 o Equator 30 o S 60 o S 90 o S 30 o N 60 o N

39. Global Wind Belts The winds from the poles blow toward the equator.
The winds from the equator blow toward the poles. 39

40. If wind is moving north and south, …
…then why is it defined as the horizontal movement of air? Does the Earth stand still?

41. The Coriolis Effect
As the Earth rotates counterclockwise, the winds bend and curve around the Earth.
Gustave-Gaspard Coriolis, an engineer and mathematician, described this effect as an inertial force in 1835.

42. The Coriolis Effect
In the Northern Hemisphere, winds bend to the right of their direction of travel.
In the Southern Hemisphere, winds bend to the left of their direction of travel.
Let’s try a little investigation to see how this works.
At this point, stop and allow students to investigate. See the Handout: Coriolis Effect and Teacher Resource: Coriolis Effect KEY. 42

43. Weather patterns and systems move in a circular motion due to the bending of the winds caused by the Earth’s rotation.
The Coriolis Effect

44. Equilibrium Our Earth is always seeking balance.
In an effort to find balance, there is a continuous cycle of patterns.
What is the driving force behind the changes that create these patterns?

45. How are winds produced?
Reflection Question

46. Ocean Currents 46

47. Ocean Currents Warm currents flow away from the equator.
Cold currents flow toward the equator.
Ocean Currents

48. Factors Influencing Currents
Sun
Wind
Coriolis
Gravity

49. Sun Energy from the Sun heats the water.
Warm water is less dense that cold water.
Warm water rises, and cold water sinks.
As warm water rises, cold water moves it to replace it.

50. Convection Cycle 50

51. Wind
Just as wind moves from high pressure to low pressure areas, so does the water.
Winds blow across the surface of the water, causing friction.
The water piles up because the surface currents flow slower than the winds.

52. Wind 52

53. Gravity
As water piles up and flows from high pressure to low pressure, gravity will pull down on the water.
This forms vertical columns or mounds of water.
The Coriolis Effect causes the water to curve.

54. The Coriolis Effect
Causes water to move to the right in the Northern Hemisphere
Causes water to move to the left in the Southern Hemisphere

55. The Coriolis Effect 55

56. Surface Currents Make up 10% of oceans’ water
Up to maximum depth of 400 m
Surface ocean currents are caused by the surface wind patterns.
Surface Currents

57. http://upload. wikimedia
Surface Currents 57

58. Gyres
Vertical columns or mounds of water at the surface and flow around them
Produce enormous circular currents
Five major locations:
North Pacific - clockwise
South Pacific - counterclockwise
Indian Ocean - counterclockwise
South Atlantic - counterclockwise
North Atlantic - clockwise

59. Oceanic Gyres http://commons.wikimedia.org/wiki/File:Oceanic_gyres.png59

60. Gulf Stream A strong surface current Begins at the tip of Florida
Flows up the eastern coastline of the U.S.
Crosses the Atlantic Ocean
Causes warmer climate in NW Europe

61. Upwelling Surface waters blow to the right of the wind.
As less dense, surface water moves off shore, cold, deep, denser waters come to the surface to replace them.

62. Upwelling 62

63. The Great Ocean Conveyor: Helps maintain Earth’s Balance
The Great Ocean Conveyor: Helps maintain Earth’s Balance 63

64. Deep Water Currents Make up about 90% of oceans’ water
Differences in density cause them to move.
Differences in density are related to temperature and salinity.
At high latitudes, they sink deep into the ocean basins.
Temperatures are so cold, they cause the density to increase.

65. How are ocean currents produced?
Reflective Question

66. El Nino
Abnormally high surface ocean temperatures off the coast of South America
Causes unusual weather patterns across
the globe

67. El Nino
Starts because the easterly trade winds weaken and allow the warm waters in the Western Pacific to move east toward South America
This changes where the convection current occurs.
Causing rain where it usually doesn't occur and drought where it usually rains

68. El Nino Winter 68

69. El Nino Summer 69

70. La Nina
Abnormally low surface ocean temperatures off the coast of South America
Causes unusual weather patterns across
the globe

71. Ocean’s Effect on Climate
Ocean currents move more slowly than winds.
Oceans hold more heat than the atmosphere and land.
Cold currents will cause nearby coastlines to be cooler.
Warm currents will cause nearby coastlines to be warmer.
Where do the cold currents come from? The warm currents?

72. Predictable Patterns How do these currents affect the climate of the coastline? 72

73. Reflection Questions
How do our oceans impact climate?