The atmosphere is divided into many concentric layers. The layers present at different heights from the surface are divided into mainly the following five layers.
The basis of this division of layers is considered to be the vertical distribution of temperature in the atmosphere:
1. Troposphere: This is the lowest layer of the atmosphere, in which 75 per cent of the total weight of the atmosphere is centered. The average height of this layer is 13 kms. Its height is 18 km. on the equator and 8 and 10 km on the poles.
This is the most important layer of the atmosphere because all weather phenomena occur in this layer. The decline in temperature with the increase in height is the biggest feature of this layer. In this, through a height of 1 km, the temperature decreases to 6.4 Celsius, which is called ‘normal lapse rate’ of temperature.
Almost all the processes related to seasons and weather that affect human beings are carried out in this layer. In this layer, dust particles and water vapor are present in large amount, causing formation of clouds, rainfall, and other climatic and weather related events. This layer is a subject of extensive study for the scientists.
The upper layer of the troposphere is called the Tropopause. Its thickness is only 1.5 km. Above this layer there is atmospheric stability. It is also called ‘the roof of seasonal changes’. This layer stops the fall of the temperature of the atmosphere.
2. Stratosphere: Its average height is considered to be 50 kilometers from the surface. Its thickness is less on the equator and more on the poles. Many scientists have considered ozone layer as part of the stratosphere due to which the height of this layer is considered to be 50 to 55 km. This layer is called stratosphere because the temperature remains constant here. Ozone layer is present in this layer, which absorbs ultraviolet rays coming from the Sun.
3. Mesosphere: It is extended up to 80 km. above the stratosphere. In this layer, the temperature starts falling along with altitude and the minimum temperature remains at -80°C. Further, the temperature increases.
4. Ionosphere: This layer starts from the upper boundary of the mesosphere. This layer extends up to 80-400 km. Electrical and magnetic phenomena occur in this layer. Radio waves return by reflecting from this layer. This sphere is divided into D, E and F layers. In this layer, the aurora borealis and the aurora australis occur. This sphere is the lowest part of the atmosphere.
5. Exosphere: This is the topmost part of the atmosphere which spreads above 400 km. There is no upper boundary layer of this layer. It is also called Magnetosphere, In this layer of the atmosphere, the gases become very sparse. In this layer, heat becomes excessive. Due to this, more information about this layer has not been obtained yet.
All these layers of the atmosphere are represented through the further diagram:
