Why does the temperature of the atmosphere vary?

Most people know that it is colder on top of a mountain compared to the ground, but few actually know why. And even less know that the atmosphere actually warms up again! The true temperature profile of the atmosphere is shown in the image.

The air at the surface up to around 10 kilometers is called the troposphere. The reason it is warmer at the surface is simple. The air is warmed by heat given off by the Earth! The farther away from the surface the air moves, the less heat there is to absorb.

From 10 to 20 kilometers the atmosphere is stable. This region is called the tropopause. From 20 to about 50 kilometers is the stratosphere. In this region the air actually warms with height! Ozone is concentrated in this part of the atmosphere and it absorbs ultraviolet light from the Sun. More light is absorbed at higher altitudes compared to the lower stratosphere, so the temperature increases.

But at 50 kilometers, the temperature levels out again in a region called the stratopause. At about 55 km, the mesosphere begins. In the mesosphere, the temperature decreases with height again, because there is very little ozone to warm up the air.

Finally, the mesopause divides the mesosphere from the thermosphere, which is the section of the atmosphere higher than 90 km. In this region, the temperature increases again! This time, it is molecular oxygen (O2) that causes the temperature increase. The oxygen absorbs light from the Sun, and since there is very little air in the thermosphere, just a little absorption can go a long way!

Submitted by Kenneth Loose (Medicine Hat, AB Canada)
(January 6, 2000)

You might also be interested in:

Science, Evolution, and Creationism

How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable....more

The Troposphere

The troposphere is the lowest layer of Earth's atmosphere. The troposphere starts at Earth's surface and goes up to a height of 7 to 20 km (4 to 12 miles, or 23,000 to 65,000 feet) above sea level. Most...more

The Stratosphere

The stratosphere is a layer of Earth's atmosphere. The stratosphere is the second layer, as one moves upward from Earth's surface, of the atmosphere. The stratosphere is above the troposphere and below...more

The Mesosphere

The mesosphere is a layer of Earth's atmosphere. The mesosphere is above the stratosphere layer. The layer above the mesosphere is called the thermosphere. The mesosphere starts at 50 km (31 miles) above...more

Me and my boyfriend are arguing over whether or not the Moon is round (circular like Earth). I say it is and he says it's not.

What is the diameter of the Moon in Kilometers? By how much is the Earth heavier than the Moon? How far is the Moon from the Earth? How old is the Moon? What is the internal structure of the Moon? I was...more

What Role Have Women Played in the History of the Space Program

*Please note that this page is a student project written by Nicole Turner. It was not written or edited by Windows to the Universe scientists.* From Harriet Quimby (the first licensed woman pilot,) to...more

Does wind have an effect on radio waves?

Wind does not have an effect on radio waves. Radio waves have a long wavelength. Wind cannot affect radio waves because the air particles associated with wind are far too small for the radio wave to bounce...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA