Air pressure is caused by the weight of the atmosphere pressing down on Earth. It changes with altitude and temperature. Low pressure occurs when air rises, leaving an area where it is pressing down less. Low pressure brings thunderstorms in warm, humid places. High pressure occurs where air is sinking, pressing down harder and usually bringing sunny weather, such as in cold places. Differences in heating cause uneven patterns of high and low pressure that drive wind as air moves from high to low pressure areas. Air pressure is measured using a barometer and is influenced by temperature, humidity, and altitude.

1. Air Pressure

2. Can you feel air
pressure?
When you take off or land in an aircraft, your
ears may hurt or feel uncomfortable. This is
because your eardrums can feel changes in air
pressure as the aircraft moves quickly up and
down.
But what is air pressure?

3. What is Air Pressure?
• It is caused by the weight of
all the air in the atmosphere
pressing down on Earth.
• Air pressure changes with
the height and also when air
warms up or cools down.
• Changes in air pressure
cause changes in the
weather.

4. Differences in Air
Pressure
Low PressureLow Pressure
• When air rises, it leaves behind
an area of lower pressure,
because when air moves up it
is not pressing down so hard
on the surface.
• Low pressure brings
thunderstorms.
• Air with a lot of water (humid)
is heavy so low pressure is
found in warm humid places.

5. High Pressure
• Areas of high pressure
are formed where air
is sinking back down,
and so pushing down
harder.
• High pressure brings
sunny weather.
• Cold air is lighter than
warm air. This means
air pressure is high in
cold places.

6. • The sun heats the
earth in an uneven
way. This causes
different areas of
high and low
pressure.
• When air moves
from high
pressure to low
pressure winds are
formed.
What Causes
Wind?

7. How To Measure Air
Pressure?
• Air pressure is measured by
a barometer.

8. What Affects (influences)
Air Pressure?
• Three things affects or influences air pressure:
– Temperature (how hot or cold it is)
– Humidity (how much water vapor is in the air)
– Distance above sea level ( how far above the sea)