1. Air Pressure
 The pressure
exerted on an
object by the air.
– Occurs in all
directions  up,
down, sideways

2. Air Pressure
 A barometer is used
to measure the
amount of pressure
in the air.
– Units = mmHg
(millimeters of
Mercury) or atm
(atmospheres)

3. Barometers
 Rapidly falling pressure almost always
means an approaching storm system.
 Rapidly rising pressure almost always
means clearing and cooler weather is
ahead.

4. Winds
 Winds are created
by horizontal air
pressure
differences –
pressure gradients
 Uneven heating of
the Earth creates
pressure
differences

5. What affects wind?
 Pressure differences- Cause air to
move
 The Coriolis Effect- causes global
winds to be deflected
 Friction- slows down air, which
changes wind direction

6. Measuring Pressure
 Isobars- lines of equal pressure
– Much like contour lines, but instead of
elevation, they are lines of equal pressure
– Are used to predict where weather is
moving

7. Jet Stream
 Fast flowing,
relatively narrow
air currents found
just under the
tropopause
 Form at the
boundaries of
adjacent global
wind belts

8. Global Winds
 Global winds are
created by the
unequal heating of
Earth.
 The equator is
much hotter than
the rest of Earth,
causing an
extremely low
pressure.

9. Global Winds
 This causes air from
adjacent areas to
move towards the
equator.
 This movement
begins a chain
reaction of air
movement
throughout Earth,
creating 6 wind
belts.

10. High Pressure Zone/Cyclone
 Occurs when
temperatures are cold
 Little or no moisture
(humidity)
– The air is heavy and sinks
towards Earth’s surface
 Winds move outward and
clockwise around the
center of a cyclone

11. Low Pressure Zone/Anticyclone
 Occurs when
temperatures are warm
 Can have large amounts of
moisture (humidity)
– The air is light and rises
upward into the atmosphere
 Winds move outward and
counterclockwise around
the center of the
anticyclone

12. The Coriolis Effect
 The Coriolis effect is a
result of the spinning of
Earth.
 As Earth spins, anything
moving in a straight line
from North to South will
be deflected sideways.
– In the Northern
Hemisphere, winds,
water, and other fluids
will be deflected to the
right at a 90o angle.
– In the Southern
Hemisphere, everything
will be deflected to the
left at a 90o angle.

13. Assignment
 Complete procedure questions for “Air Pressure
Demonstration”
 Identify Types of Energy Transfers Worksheet