Change in the Atmosphere with Altitude

Air pressure changes with 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 milibars.

This graph shows how air pressure changes with altitude (the distance above sea level) as one moves upward in the atmosphere. The density of air is computed based on the mass of air molecules, divided by the volume of air. Density and pressure change similarly with height.

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 50 in 10 kilometer increments.  The x-axis is show pressure in mb from 0 to 1,200 in 200 mb increments. The trend line for air pressure is low at the highest altitude and high at the lowest altitude.

Which of the following statements about the graph are true?

Air pressure is higher at lower altitudes.
Air density is higher at lower altitudes.
There is more space between air molecules at higher altitudes.
There is less oxygen to breathe at the top of a high mountain than there is at sea level.

Temperature changes with altitude

The atmosphere is divided into different layers depending on how temperature changes. Take a look at the graph below to see how temperature changes with altitude.

Vertical profile of the Earth's atmosphere. The diagram depicts altitude on the y-axis.  The altitude increases as you move upward on the y-axis. The x-axis shows lower temperature on the left increasing to higher temperature on the right.  The layers of the atmosphere are labeled by altitiude inside of the graph.  The troposphere goes from 0 to 10,000 meters.  The stratosphere goes from 10,000 to 50,000 meters.  The Mesosphere goes from 50,000 to 85,000 meters. Finally, the Thermosphere and Ionosphere goes from 85,000 to ~500,000 meters.  The data shows that the temperature decreases in the thermosphere, decreases slightly to 20,000 meters in the stratosphere before increasing.  The temperature then decreases significantly in the Mesosphere before increasing slightly to 100,000 meters in the Thermosphere where it then increases rapidly.

Which of the following statements about the graph are true?

If you follow the temperature line in the graph above from the surface of the Earth to the top of the atmosphere, moving to your left represents a decrease in temperature, to your right represents an increase in temperature, and straight up represents a constant temperature.
Temperature increases as you gain altitude in the stratosphere and the thermosphere.
Temperature decreases as you gain altitude in the troposphere and mesosphere.
Air temperature varies in complicated ways with altitude.

Near the Earth's surface, air gets cooler the higher you climb.

As you climb a mountain, you can expect the air temperature to decrease by 6.5° C for every 1000 meters you gain. This is called the standard (average) lapse rate.

Lapse rate: 6.5 degrees Celsius per 1,000 meters. 3.6 degrees Fahrenheit per 1,000 feet.

If air temperature is 27° C at sea level as shown, you can expect it to be around 1° C at air altitude of 4000 meters because of the lapse rate.

Plan an Expedition

You are going to climb Mount Audubon in Colorado today!

Mount Audubon with a lake and dark trees in front of it
When you leave your house at 2000 meters, the air temperature is 15° C. What is the temperature likely to be at the 4000 meter summit?