2. What is the approximate air pressure at 5 miles above sea level?
(1) 1.0 atmospheres (3) 0.4 atmospheres
(2)0.7 atmospheres (4) 0.2 atmospheres

4. Air Pressure Is measured with a barometer.
Uses millibars (mb) or inches (in) as unit.
Will change with altitude (where more? less?)
Is a result of the density (weight) of air.

5. Can we change air’s density?
heat

6. How DOES a thermometer work?
Add HEAT energy,
so molecules
move more!
Cool, so liquid is compact.
Hotter, so liquid expands.

9. Increasing temperature
Increasing Volume
Increasing temperature
and heat energy

11. Air’s density (pressure) tends to increase as
(1) temperature increases
(2) temperature decreases
(3) weather becomes wetter
(4) temperature varies

12. Air Pressure Differences

14. Moist Air (more H2O less N2)
Dry Air (mostly N2 & O2)
Moist Air (more H2O less N2)
Which weighs more?
Which is less dense?

19. A barometric pressure of 1021
A barometric pressure of millibars is equal to how many inches of mercury?
(1) (3) 30.25
(2) (4) 30.50

22. COLD AIR! DRY AIR! Dense
WARM AIR!
MOIST AIR!
Less dense

23. Let air cool
Heat air

24. COLD AIR! DRY AIR! Dense Tends to sink
WARM AIR!
MOIST AIR!
Less dense
Tends to rise

25. Do you remember how to boil water?
Cold, more dense, sinks
Hot, less dense, rises

27. Convection in the Atmosphere
Sinking
Current
Rising
Current H L ?

28. Air not only rises or sinks, it also moves naturally from where there is more (H) to where there is less (L).

29. H L WIND No vapor up here, so sinking air tends to be dry!
Vapor comes from water on surface, so rising air is moist!
Sinking
Current
Rising
Current H L
WIND

31. Low Pressure:
Air enters (converges)
Warm
Moist/Humid
Low density
Rises/Floats
BAD WEATHER!
High Pressure:
Air Leaves (diverges)
Cold
Dry
High density
Sinks
NICE WEATHER!

33. Air pressure is usually lowest when the air is
(1) warm and dry
(2) warm and humid
(3) cool and dry
(4) cool and humid

37. (1) Earth’s rotation and unequal heating of Earth’s surface
The planetary wind belts in the troposphere are primarily caused by the
(1) Earth’s rotation and unequal heating of
Earth’s surface
(2) Earth’s revolution and unequal heating of
(3) Earth’s rotation and Sun’s gravitational
attraction on Earth’s atmosphere
(4) Earth’s revolution and Sun’s gravitational

38. Foucault’s pendulum
Or…how to kill lots of people

39. Coriolis Effect
Objects moving on Earth’s surface rotate with the Earth.
Objects not “attached” to the Earth will not rotate with the Earth.
These objects will be deflected from their intended path.
In the Northern Hemisphere, wind and water deflect to the right!

42. The diagram shows a box used to demonstrate the process of convection in the atmosphere.
Which diagram has arrows that show the direction of airflow that occurs when the
candle is burning?

44. Hurricanes

45. Tornadoes

48. A Foucault pendulum appears to change its direction of swing over a period of several hours because of Earth’s
(1) rotation
(2) tilted axis
(3) revolution
(4) gravity

50. Low Pressure
Air is rising, converging and rotating counter-clockwise

51. Actual Low Pressure Systems

52. High Pressure
High Pressure air is sinking, diverging and rotating clockwise

53. Which is Which? 2) 1)

54. Which map best represents the surface wind pattern around a Northern Hemisphere LOW pressure center?

56. Earth rotates below, so by the time the cannonball hits the ground the target has moved!

59. The diagram shows
weather instruments
A and B.
Which table correctly indicates the name of the weather instrument and the weather variable that it measures?

60. What is the approximate air pressure at 5 miles above sea level?
(1) 1.0 atmospheres (3) 0.5 atmospheres
(2)0.7 atmospheres (4) 0.2 atmospheres

62. Air pressure is usually highest when the air is
(1) cool and humid
(2) cool and dry
(3) warm and humid
(4) warm and dry

63. Let’s go
measure!

65. Still confused?

66. Dry Air (mostly N2 & O2)

67. Moist Air (more H2O less N2)
What happens to the density of air as it gets more humid?
Moist Air (more H2O less N2)
It decreases! (water vapor weighs less than Oxygen & Nitrogen)

69. It decreases! What happens to the density of air as it gets hotter?
(heat increases volume, decreases density)

70. Air pressure (density) can change!
Hot air is lower density Cold air is higher density
Wet air is lower density Dry air is higher density
Hot air is low pressure
Cold air is high pressure
Wet air is low pressure
Dry air is high pressure

71. What air pressure is “normal” for a
Hot summer day?
Low Pressure
Sunny (dry) day?
High Pressure
Cold winter day?
Rainy day?

73. How can I make a barometer?
Water
Air
Pressure
How can I make a barometer?
Too high!
Too Poison!

74. Just right!
Aneroid barometer

75. What will happen to “reading” from
to here?
What will happen to “reading” from
here