Air pressure is a measure of the force of air pressing down on the Earth's surface. It can vary depending on factors like temperature, water vapor content, and elevation. Higher elevations have lower air pressure since the atmosphere exerts less force the further one is from sea level.

1. Air Pressure

2. Air Pressure
• Air Pressure is a
measure of the force
of the air pressing
down on the earth’s
surface

3. http://www.youtube.com/watch?v=OHY9fFQhX6
8 Marshmallows

4. Air Pressure can vary at any particular
point on the Earth depending on the
density of the air
Density = mass / volume

5. Where is air
pressure
higher, up in the
mountains or
down in the
valley?

6. http://www.youtube.com/watch?v=GWEyFbyv
Elc&feature=related
Air Pressure and Altitude

7. This bottle was
photographed at 3600m
(left) then again at sea
level (right)
At sea level, because air
is compressible, the
weight of all that air
above us compresses the
air around us, making it
denser.
We all live underneath a huge ocean of
air that is several miles deep: the
atmosphere.
The pressure on our bodies is about the
same as ten meters of sea water
pressing down on us all the time.

8. Density = Mass / Volume
 Warm air is less dense than cool
air. Warm air rises. Cool air sinks.
 Air at high altitudes is less
dense than air at lower altitudes.

9. Factors that affect Air
Pressure
Temperature
Water Vapor
Elevation

10. TEMPERATURE AND AIR PRESSURE
Molecules
HEAT move faster
LESS AIR Move
PRESSURE apart, become
fewer and
weigh less

11. HIGH
TEMPERATURE, LOW AIR
PRESSURE
LOW
TEMPERATURE, HIGH AIR
PRESSURE

12. AMOUNT OF WATER VAPOR
consists of
air and
water
molecules

13. More water vapor means
less air molecules (more
water molecules)
LOW AIR PRESSURE
DRY AIR = HIGH AIR PRESSURE

14. Air Pressure & Weather

15. High pressure generally
means fair weather
Air mass in upper
atmosphere
No clouds
Warm, moi
st air
Layer of Air
cannot rise

16. Low pressure generally
means cloudy, rainy
weather
Warm air
Air masses rises, clouds
move apart form

17. High Pressure System: Indicates clear, calm
Weather map conditions with reduced chance of
precipitation. Drier air usually results in a
greater range of high and low temperatures.
Low pressure system: Increased
cloudiness, winds, temperatures, and chance
of precipitation.

19. Measuring Air Pressure
Types of
Barometer
Air Mercury
Barometer
Pressure Aneroid
is measured
by an
instrument

20. Air pressure
increases, colu
mn of mercury
rises
Air pressure
decreases, colu
mn of mercury
drops

21. High Pressure:
Rising or steady - Continued fair
Slowing falling - Fair
Rapidly falling - Cloudy, Warmer
Medium pressure:
Rising or steady - Same as present
Slowing falling - Little change
Rapidly falling - Precipitation likely
Low Pressure:
Rising or steady - Clearing, cooler
Slowing falling - Precipitation
Rapid falling - Storm

22. Factors Affecting Air Pressure
FACTOR Increase/Decrease Air Pressure
Density
Density
Temperature
Temperature
Water Vapor
Water Vapor
Altitude
Altitude

23. At the top of a mountain How does air pressure
you drank a bottle of affect scuba diving?
water, sealed it, but imploded on your
way down. Why?
A rising barometer A series of hot, humid
indicates a spell of days is preceded by a
cool dry weather. falling barometer.
A southern, coastal areas tend to have Rapidly dropping
lower air pressure than an inland area temperatures are
farther north. accompanied by a
rising barometer.
You are planning a Why would a serious
Picnic and check the athlete decide to train
barometer, which is at a high altitude?
falling. Why should you
cancel the picnic?
You are hiking Mount Everest How does a hot air
and find it hard to breathe at balloon work?
a high altitude.