Air Pressure

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?

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.

Differences in Air PressureLow 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.

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.

• 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?

How To Measure Air Pressure?

• Air pressure is measured by a barometer.

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)