Draw a suitable diagram for the structure of the atmosphere and label it and describe it.

The atmosphere consists of almost concentric layers of air. These layers are of varying temperature and density. Density is highest near the earth’s surface and goes on decreasing upwards.

The atmosphere can be divided into five layers of air.
They are described below:

1. Troposphere: It is the lowest layer of the atmosphere. It extends roughly up to a height of 9-10 km near the poles and about 18 km at the equator. The temperature decreases with the height in this layer. The normal lapse rate of temperature is 1°C for 165 metres. It is a vast physical laboratory of the air in which nature is always showing some experiment, on a grand scale. Formation of clouds and various forms of precipitation; heating and cooling and development of pressure system; blowing of winds and the acts of respiration by all types of life, are all taking place in this layer of the atmosphere. It is an unstable layer of the atmosphere. The vertical currents moving throughout the year make it unstable. All weather changes occur in this layer which are useful for the life on earth.

Tropopause: The upper layer of troposphere is called tropopause. It is a thin layer and its height changes according to latitudes. In fact, this is a transitional zone which connects the lower troposphere with the upper stratosphere.

2. Stratosphere: It extends up to the height of 50 km. The temperature remains constant up to the height of 20 km, in this layer. Afterwards, it increases upto the height of 50 km because of the presence of ozone. The ozone absorbs the most harmful ultra-violet rays of the sun. Clouds are almost absent in this layer. There is Very little of dust particles and water-vapour in this. The air movements are horizontal. It provides ideal flying condition for jet aeroplanes because, it is free from clouds and other weather disturbances.

3. Mesosphere: The mesosphere lies above the stratosphere, which extends up to a height of 80 km. In this layer, once again, temperature starts decreasing and reaches upto to -100°C at the height of 80 km.

4. Ionosphere: It is located between 80 and 400 km. It is an electrically charged layer. Radio waves transmitted from the earth are reflected back to the earth by this layer. Temperature again starts to increase with height because of sun’s radiation.

5. Exosphere: It is the uppermost layer of the atmosphere extending beyond the ionosphere. This layer is extremely (rarefied) and gradually merges with the outer space.

In fact, we know very little about the atmosphere extending beyond 64 km above the sea-level.