ATMOSPHERE COMPOSITION AND STRUCTURE

Earth is a unique planet because the life is found only on this planet. The air has a special place among the conditions necessary for life. The air is a mixture of several gases. The air encompasses the earth from all sides. The air surrounding the Earth is called the atmosphere. The atmosphere is an integral part of our Earth. It is connected with the earth due to the gravitational force of the earth. It helps in stopping the ultra violet rays harmful for the life and maintain the suitable temperature necessary for life.

Importance of the Atmosphere:

 (i) Oxygen is very important for the living beings.

 (ii) Carbon dioxide is very useful for the plants. 

(iii) Dust particles present in the atmosphere create suitable conditions for the precipitation. 

(iv) The amount of water vapour in the atmosphere goes on changing and directly affects the plants and living beings.

 (v) Ozone protects all kinds of life on the earth from the harmful ultra violet rays of the sun. 

COMPOSITION OF THE ATMOSPHERE 

The atmosphere is composed of gases, water vapour and dust particles.  The proportion of gases changes in the higher layers of the atmosphere in such a way that oxygen will be almost in negligible quantity at the height of 120 km. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the earth. 

Gases:

Carbon dioxide is meteorologically a very important gas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation. It absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. It is largely responsible for the green house effect. The volume of other gases is constant but the volume of carbon dioxide has been rising in the past few decades mainly because of the burning of fossil fuels. This has also increased the temperature of the air. 

Ozone is another important component of the atmosphere found between 10 and 50 km above the earth’s surface and acts as a filter and absorbs the ultra-violet rays radiating from the sun and prevents them from reaching the surface of the earth.

Water vapour:

Gaseous form of water persent in the atmosphere is called water vapour. Water vapour present in the atmosphere has made life possible on the earth Water vapour is the source of all kinds of precipitation. Its maximum amount in the atmosphere could be upto 4 percent. Maximum amount of water vapour is found in hot-wet regions and its least amount is found in the dry regions. Generally, the amount of water vapour goes on decreasing from low latitudes to high latitudes.Water vapour reaches in the atmosphere through evaporation and transpiration. Evaporation takes place in the oceans, seas, rivers, ponds and lakes while transpiration takes lace from the plants, trees and living beings.

Dust Particles: 

Dust particles are generally found in the lower layers of the atmosphere. These particles are found in the form of sand, smoke and oceanic salt. Sand particle have important place in the atmosphere. These dust particles help in the condensation of water vapour. During condensation water vapour gets condensed in the form of droplets around these dust particles. Due to this process the clouds are formed and precipitation is made possible. 

SAYANTANI SINGH