Structure of Atmosphere – Layers, Diagram, Definition

By BYJU'S Exam Prep

Updated on: November 14th, 2023

Structure of Atmosphere is usually defined into five layers based on temperature and density. It is segregated into different layers such as the troposphere, stratosphere, ozonosphere, mesosphere, thermosphere, and exosphere. The structure of atmosphere protects us from harmful ultraviolet rays and in a way regulates the entry of solar radiation into the earth’s atmosphere.

The structure of atmosphere also keeps the temperature over the earth’s surface within certain limits and in absence of the atmosphere, extremes of temperature would exist between day and night. To comprehend the concept of the structure of atmosphere for the upcoming UPSC exam, aspirants must understand the composition and layers of the atmosphere. The aspirants can download the structure of atmosphere UPSC notes to get complete ideation of the topic.

Definition Of Atmosphere

The atmosphere is a mixture of different types of gases such as nitrogen, oxygen, carbon dioxide, hydrogen, helium, etc. It also includes water vapour and dust particles. The atmosphere is mainly made up of two gases, Nitrogen, and Oxygen. Other gases like oxygen, carbon dioxide, hydrogen, helium, etc. form the remaining part of the atmosphere.

The atmosphere, in addition, contains huge numbers of solid and liquid particles, collectively called aerosols. The proportion of gases changes in the higher layers of the atmosphere. Carbon Dioxide and water vapor are found only up to 90 km from the surface of the earth and oxygen will be almost in negligible quantity at the height of 120 km.

Structure Of Atmosphere

The structure of atmosphere is divided into different layers according to its composition, density, pressure, and temperature variations. According to its composition, the structure of the atmosphere is divided into two layers- homosphere and heterosphere. Mostly, the segregation of the layers of the Atmosphere is done on the basis of varying temperatures and density. The structure of atmosphere is basically made up of 5 layers, which are mentioned below.

  • The homosphere is the lower segment of the atmosphere and consists of three regions namely troposphere, stratosphere, and mesosphere, and extends from the earth’s surface up to an altitude of 80km.
  • Whereas, the heterosphere is where the gases are separated out by molecular diffusion with increasing altitude such that lighter species become more abundant relative to heavier species. It begins over 80km and extends up to 10,000 km and includes the Thermosphere and the Exosphere.

Structure of Atmosphere Diagram

The diagram for the structure of atmosphere has been elaborated here. This will assist the candidates in visualizing the layers, composition and structure of atmosphere in great detail.

Layers of the Atmosphere

Layers Of Atmosphere

The structure of atmosphere consists of different layers with varying temperatures and densities. The density of air is highest near the surface of the earth and decreases with increasing altitude. The layers of the Atmosphere include:

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Ionosphere
  • Exosphere

Read More –

Troposphere – 1st Layer Of Atmosphere

It is the lowermost layer of the atmosphere which contains dust particles and water vapors. The troposphere extends up to the height of 10 km from the earth’s surface. Certain facts have been mentioned here about the first layer of the structure of atmosphere, get in touch with complete details.

  • The height of the Troposphere is about 18 km on the equator and 8 km on the poles. The thickness of this layer is greatest at the equator because heat is transported to great heights by strong convectional currents.
  • Meteorologically, Troposphere is the most significant zone in the entire atmosphere because all weather conditions, such as temperature inversion, turbulence, and eddies take place in this layer.
  • The air never remains static in this layer, and therefore, the troposphere is also known as the ‘changing sphere’.
  • The troposphere is also called the convective region since all convection stops here.
  • The air temperature at the tropopause is about –80 degrees Celsius over the equator and about –45 degrees Celsius over the poles. The temperature here is nearly constant, and hence, it is called tropopause.
  • The zone separating the troposphere from the stratosphere is known as the tropopause.
  • The troposphere is influenced by seasons and jet streams.

Stratosphere – 2nd Layer Of Atmosphere

The stratosphere is the second layer constituting the structure of atmosphere. It is just above the troposphere. It extends up to 50km from the surface of the earth. Walk through the under-noted points to gain complete knowledge of the second layer of the structure of atmosphere.

  • The stratosphere is considered ideal for flying aircraft because the air blows horizontally here.
  • This layer is almost free from clouds
  • The temperature remains almost the same in the lower part of the stratosphere up to the height of 20km. After 20km, the temperature increases slowly with the increase in height. This rise is due to the presence of ozone.
  • The cirrus clouds are present at lower levels of the stratosphere.


  • The Ozonosphere lies between 30 km and 60 km altitude from the earth’s surface. The temperature rises at a rate of 5°C per kilometer through the ozonosphere.
  • The ozonosphere is also known as the chemosphere because a lot of chemical activity takes place in this layer. This layer reflects the harmful ultraviolet radiation due to the presence of the ozone molecules.

Mesosphere- 3rd Layer Of Atmosphere

The Mesosphere is the third layer of the atmosphere, which is above the stratosphere and extends up to the height of 80km from the Earth’s surface. The mesosphere is the layer that is found between the thermosphere and stratosphere, as the name suggests “meso” means middle.

  • The temperature reaches up to – 100 degrees Celsius at the height of 80 km due to the fact that temperature starts to decrease with an increase in altitude.
  • The meteorites burn up in this layer and the falling star phenomenon occurs in this layer only.
  • The upper limit of the mesosphere is known as mesopause.

Thermosphere- 4th Layer Of Atmosphere

The thermosphere is located above the Mesopause, at a height of between 80km- 400km. The ionosphere is a part of this layer. It contains electrically charged particles. Check the complete details of the 4th layer constituting the structure of the atmosphere.

  • In the thermosphere, the temperature rises very rapidly with an increase in height, but a person would not feel warm because of the thermosphere’s extremely low pressure.
  • The radio waves transmitted from the earth are reflected back to the earth by this thermosphere, which makes radio transmission possible.
  • The International Space Station and satellites orbit in this layer. The siting of Aurora’s is also observed in the lower parts of this layer.

Exosphere- 5th Layer Of Atmosphere

The Exosphere is the uppermost layer of the atmosphere above 400km and coincides with space. As the name suggests “exo” meaning outer, it is the uppermost layer which further merges with outer space.

  • The density of gases is very sparse here due to the lack of gravitational force. Light gases such as helium and hydrogen float into space from here.
  • As Exosphere is exposed to direct sunlight, the temperature gradually increases through the layer.

Composition Of Atmosphere

The structure of atmosphere is made up of a mixture of many gases that vary across the structure of the atmosphere. The gases in the atmosphere are composed of neutral, uncharged particles. The proportion of gas changes in the higher layers of the atmosphere, such as oxygen is negligible at the height of approx 120km. Carbon Dioxide and water vapour are found only up to the height of 90 km from the surface of the earth.

Nitrogen and Oxygen constitute about 99% of the clean dry air. The remaining gases are mostly inert and constitute about 1% of the atmosphere. Besides these gases, large quantities of water vapour and dust particles are also present in the atmosphere.

Gases Of Atmosphere

The table below represents the gases of the atmosphere in volume by their percentage. The gases are also constituents of the structure of atmosphere. They are in the neutral state, check here the percentage of the volume of the gases present in the atmosphere.

Constituent % by Volume
Nitrogen 78.08
Oxygen 20.95
Argon 0.93
Carbon dioxide 0.036
Neon 0.002
Helium 0.0005
Krypton 0.001
Xenon 0.00009
Hydrogen 0.00005

Structure Of Atmosphere UPSC

Get in-depth knowledge of the structure of atmosphere to be able to score well and crack the exam in the stipulated time period. The compilation of notes will assist the candidates in moving further in all the stages of the recruitment process. Along with composition and structure of atmosphere UPSC notes, read through the Class 11 and Class 12 NCERT Geography. You can also go through the Geography Book for UPSC to ensure that no point is missed.

The candidates can get themselves acquainted with all the parameters of this crucial and pivotal topic to be able to crack the exam and score well in it. The notes have been curated by the experts that will lead the candidates toward the way to accomplishing success.

Structure Of Atmosphere Questions

The structure of Atmosphere along with its layers, and composition is an essential part of the Geography part of the UPSC Syllabus. The topic is asked both in the Prelims and in the UPSC Mains GS-Paper 2. The topic can be covered through the NCERT Books for UPSC and sufficing with the recommended books. The aspirants can solve numerous questions on the structure of the atmosphere to get in touch with the concept and the pattern of questions in the exam. Several questions have been asked in the UPSC Previous Year Question Papers in both Prelims and Mains. One example of MCQ is:

Find the wrong pair?

I. The home of humankind-Troposphere

II.Ozone layer-Stratosphere

III.Meteor shower region-Stratosphere

IV.Long-distance broadcasting of radio programs-Mesosphere

A – I&II




Correct Answer – Option C

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