Atmosphere Contents

1. Structure And Composition

Conclusions

The Earth's atmosphere has changed over millions of years from one of little oxygen to one where oxygen, nitrogen, argon and carbon dioxide are the predominant gases. The atmosphere has a clearly defined vertical profile of layers: troposphere, stratosphere, mesosphere, thermosphere, exosphere and magnetosphere, with the troposphere and stratosphere containing most of the weather elements affecting the Earth. Carbon dioxide plays a particularly active role in the atmosphere having a big impact on global climate, notably by contributing to climate change. Carbon dioxide and oxygen are essential elements for life and should remain in balance in the atmosphere.

Question and answers

1. What was the principal change in atmospheric composition from the early Earth to the present day?

question 1 answers

2. What are the three main atmospheric gases, and what are their average proportions near the Earth's surface?

question 2 answers

3. At what altitude is ozone (O3) predominantly found?

question 3 answers

4. What are the four vertical layers of the atmosphere nearest to the Earth's surface, and at what altitudes do they occur?

question 4 answers

5. i) What is the 'atmospheric lapse rate' of the troposphere, and ii) What is the predominant motion that takes place?

question 5 answers

6. What is the profile of temperature in the stratosphere?

question 6 answers

7. At what position are interactions likely to take place between the stratosphere and the troposphere?

question 7 answers

8. What is the most active part of the carbon cycle?

question 8 answers

Question 1 answer

For the first billion or so years the Earth had an atmosphere with little oxygen and larger concentrations of gases such as methane. Owing to the release of oxygen by the earliest life forms, the composition evolved over hundreds of millions of years to something similar to that which we find today.

Question 2 answer

Nitrogen (N) = 78%

Oxygen (O2) = 21%

Argon (Ar) = 0.9%

Question 3 answer

15 km to 40 km. Most other gases are fairly constant up to 80km.

Question 4 answer

Troposphere = Surface to 10-15 km

Stratosphere = Troposphere to 50 km

Mesosphere = Stratosphere to 80 km

Thermosphere = Mesosphere to 100 km

Question 5 answer

i) - 6.5 K/km as height increases.

ii) There is a constant overturning of the air by convective motions due to the thermodynamic nature of warmer air rising into the colder air above.

Question 6 answer

Temperature, in general, increases with height.

Question 7 answer

Interactions occur when there are breaks in the tropopause; this mostly occurs at the position of the jet streams.

Question 8 answer

Atmospheric carbon dioxide (although only present in small quantities 0.03%) is the most active part of the carbon cycle.