Layers of the atmosphere

Earth’s atmosphere is divided in 5 different layers. These layers are troposphere, stratosphere, mesosphere, thermosphere and exosphere. The layers of atmosphere are basically divided on the basis of temperature variation with altitude. Lets dive deep and learn a few things about each layer.

Troposphere

  • It is the lowest and the most dense layer of the atmosphere. Moreover, around 75 percent of all atmospheric mass is present in this part of the atmosphere.
  • All weather phenomena take place inside the troposphere.
  • The width of the troposphere is not constant. It is widest at the equator and thinnest at the poles. Average width is about 8-15 km.
  • Temperature drops with altitude inside the troposphere.
  • The boundary of troposphere and stratosphere is known as tropopause.
Layers of atmosphere

Stratosphere

  • Stratosphere is the second layer from the surface and it extends after the tropopause till about 50 km.
  • Unlike the troposphere, temperatures increases with altitude in stratosphere.
  • Ozone layer is present here which protects us from the harmful ultraviolet radiations of the sun.
  • Stratopause is the boundary between the stratosphere and the mesosphere (the next layer).

Why temperature rises with elevation in stratosphere?

The ozone layer absorbs the ultraviolet radiations of the sun making the stratosphere warmer. The higher stretches of the ozone layer absorb more intense radiations. Thus, temperatures are higher at higher elevations.

Mesosphere

  • Mesosphere starts after the stratopause and extends till about 85 km.
  • Temperature decreases with altitude in mesosphere.
  • It is in the mesosphere that the meteors burn up.
  • Mesopause forms the boundary between mesosphere and thermosphere.

Thermosphere

  • It is that layer of the atmosphere where the International Space Station (ISS) orbits.
  • Thermosphere start just after the mesopause and extends till 600 km.
  • Aurora light display occurs in the thermosphere.
  • Temperature rises with elevation in this part.
  • Thermopause forms the boundary between thermosphere and exosphere.

Quick question

Does hot air rise or sink?


Exosphere

  • Exosphere starts after the thermopause and does not have a definite outer boundary.
  • A rough estimation of the outer boundary is about 10,000 km from the surface.

Ionosphere

  • Ionosphere overlaps parts of mesosphere, thermosphere and exosphere. It exist from 50 km to around 1000 km. However, the total width of ionosphere keeps changing depending on the solar radiations.
  • In ionosphere, the atoms are ionised by the solar radiation and cosmic rays. They become positively charged by stripping electrons.
  • This layer helps in radio communication by acting as a reflector of radio waves.
  • The ionosphere is further divided in D, E and F regions.

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Answer to quick question

Hot air rises and cold air sinks.


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