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Key Idea 3
Temperature of the Atmosphere
Concept Question: How does the temperature in the different layers of the atmosphere relate to the chemical composition of the atmosphere?

What do we know?

In Key Idea 1, you learned about the gases that are present in Earth’s atmosphere and their role in regulating the temperature of the atmosphere. How do the various atmospheric gases affect the temperature profile of Earth’s atmosphere? The answer to this question is complicated. The temperature profile in the atmosphere is due to the compressible nature of the gases in the atmosphere as well the amount of water vapour present in the atmosphere. The natural tendency is a decrease in air temperature with increasing height above the Earth's surface.

Scientists divide the atmosphere into four “layers” that have different densities and molecular compositions. Work through the Earth's Atmosphere learning tool to learn about these different layers. When you have finished, be sure you can answer the following questions


How is the mass of Earth’s atmosphere distributed?

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The vast majority of the mass of the atmosphere is concentrated near Earth’s surface. 85% of the mass of the atmosphere is found in the first 15 km above Earth’s surface.


What are the layers of the atmosphere called?

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The layers of the atmosphere are the troposphere, stratosphere, mesosphere and thermosphere.


What determines the boundaries between the layers of the atmosphere?

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The layers of the atmosphere are defined by reversals in the temperature profile of the atmosphere. A new layer is present when the atmospheric temperature changes from increasing to decreasing, or vice versa, as altitude increases.