This article covers everything you need to know about the structure of atmosphere for IAS Exam.

The Structure of Atmosphere is divided into 5 different layers:

1. Troposphere:

  • It is the lowermost part of the atmosphere.
  • It contains 75% of the total gaseous mass of the atmosphere.
  • Height of troposphere at poles is about 8 km, whereas, at the equator, its height is around 18 km. This is because at the equator, due to intense heating, the air becomes light and rises up, whereas, at the poles due to intense cooling, air is descending in nature which reduces Troposphere’s height.
  • As we go up in the Troposphere, the temperature decreases with height. Earth’s main source of energy is Sun. Sun releases its energy in the form of Short Waves which can easily enter our atmosphere. These Short Waves after reaching the ground are reflected back in the form of Long Waves (also called as Terrestrial Waves). Earth is more heated by Long Waves than the Short Waves. Also, our atmosphere restricts the outgoing of Long Waves. Due to these reasons, temperature decrease with increase in height in Troposphere. Temperature decreases with the rate of 6.5 degree Celsius per kilometre as we move upward in the troposphere. This fall of temperature with increase in height is called “Lapse Rate”.
  • Almost all the weather phenomena like rainfall, fog, hailstorm etc occur in the troposphere.
  • Troposphere ends at Tropopause. Tropopause acts as a boundary between Troposphere and Stratosphere.

2. Stratosphere:

  • It lies beyond Stratosphere up to an altitude of 50 km from the earth’s surface.
  • At Stratosphere, temperature increases with height. This is because of the presence of Ozone layer at in the upper Troposphere, which is also called Ozonosphere. Ozone absorbs Ultra Violet rays present in sunlight.
  • There is no vertical movement of air present in the Stratosphere as it is restricted to Troposphere. This layer is very dry and very little water vapour is present here. Due to this dryness, this layer is free from clouds and the weather is calm. This is the reason jet aircrafts fly easily in lower Stratosphere.

3. Mesosphere:

  • It is an intermediate layer beyond the Ozonosphere and continues up to an altitude of 80 km from the earth’s surface.
  • Due to the absence of greenhouse gases, temperature again decreases with increase in height in Mesosphere.

4. Thermosphere:

  • It extends between 80 to 600 km.
  • In Thermosphere, temperature increases abruptly with increase in altitude. Though the temperature rises to more than 1000 deg Celsius in this layer, a person would not feel warm because of extremely low pressure. This low pressure is due to sparsely located gas molecules in this layer.
  • The lower layer of Thermosphere is called Ionosphere. The ionosphere is responsible for Aurora lights. Aurora is a beautiful light caused by collision between electrically charged particles released from the Sun that enters Earth’s atmosphere. Aurora that occurs in Northern Hemisphere is called “Aurora Borealis” and in Southern Hemisphere, it is known as ‘Aurora Australis’.
  • Ionosphere helps in radio communication or Telecommunication.

5. Exosphere:

  • It is the uppermost layer of Earth’s atmosphere which extends beyond Ionosphere and coincides with space.
  • Here also, the temperature is very high but it is different from earth’s temperature as the atmosphere is highly rarefied and gas molecules are very sparsely located from each other.
  • Geostationary satellites or Communication Satellites are located in Exosphere.
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