Chemical composition of Atmosphere Upsc

The Composition of Atmosphere are Gases, Water, Vapour and Dust Particles and the below table shows details of different gases in the air particularly in the lower atmosphere. Next, we’ll look into its chemical composition.

Chemical composition of atmosphere

In the atmosphere of the earth, the air is a mixture of gases that contains 78% Nitrogen, 21% oxygen, and 1% other gases which include Carbon dioxide, Argon, Neon, Helium, etc and also water vapour.

ConstituentVolume Percentage
Carbon di Oxide0.036
Gases and its volume in the Atmosphere

Composition of gases in Atmosphere

The proportion of gases gets changed in higher layers of the Atmosphere, in a way that the oxygen gets almost negligible in quantity at the height of 120km.

Carbon Di Oxide

Carbon dioxide and water vapor are found only up to the height of 90km from the earth’s surface. Carbon dioxide is a very important gas in the Earth’s Atmosphere, as it is transparent to the incoming solar radiation and it is opaque to the outgoing solar radiation.

This nature of Carbon dioxide absorbs some part of terrestrial radiation and reflects it back to the earth’s surface and it is the main factor for the Green House Effect.

The volume of Carbon dioxide keep raising for the past few decades due to human activities and other gases’ volume remains constant. This increase in the volume of Carbon dioxide in the atmosphere increases the temperature of the air.


Ozone is one of the important constituents in the atmosphere and it is found between 10 to 50 km above the earth’s surface. This gas acts as a filter and absorbs the ultraviolet ray from the sun rays and prevents it from entering the earth’s surface.

Composition of Atmosphere

Water Vapour

The water vapour is also a variable gas in the atmosphere, that decreases with altitude and it accounts for up to 4% by volume in warm and wet tropics.

But its volume is less than 1% in the cold and dry desert and also in the polar regions. It is to be noted that the Volume of the Water Vapour decreases from the Equator to towards the poles.

Another property of Water Vapour is, it acts similar to Carbon dioxide, by absorbing the parts of the insolation from the sum and preserves the earth’s radiated heat.

Just like a blanket, it neither allows the earth to become too hot or too cold. It also contributes to the stability and instability in the air.

Dust Particles

The atmosphere has enough capacity to keep the small solid particles and it originates from various sources.

Some of these small solid particles include sea salts, fine soil, smoke soot, ash, dust, pollen, and dust from meteors. These small solid particles called Dust particles are normally concentrated in the lower layers of the atmosphere.

And sometimes, convectional air currents transport the dust particles to greater heights.

The concentration of dust particles is high in the subtropical and temperate regions and it is because dry winds are higher in these regions compared to the equatorial and polar regions.

The dust and salt particles act as hygroscopic nuclei, using which the water vapor condenses to produces clouds.

* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.