Change in the Atmosphere with Altitude

Air pressure changes with altitude.

This line graphs shows that both air pressure and air density decrease with increasing altitude. The y-axis shows the altitude in kilometers from 0 to 500 in 100 kilometer increments.  The x-axis is labeled with low pressure and density on the left increasing to high pressure and density on the right. The trend lines for both air pressure and air density are low at the highest altitude and are both high at the lowest altitude.

Air is all around us, but we cannot see it. Gravity from the Earth pulls air down - this is called air pressure. We don't feel this pressure because our bodies push an equal amount of pressure outward. This graph shows how air density and air pressure changes with altitude (the distance above sea level). Barometers are used to measure air pressure in millibars.