The composition of atmosphere is made up of different gases which surrounds the earth. Two important gases nitrogen and oxygen together are found on the 99% part of the atmosphere. The other components includes carbon dioxide, argon, carbon monoxide, neon, helium and various other gases.
Gases
The composition of the atmosphere is very important when we want to know many properties of a given atmosphere at a given place . The composition of the earth atmosphere depends on its sources and sinks.
Carbon dioxide is meteorologically a very important peas as it is transparent to the incoming solar radiation but opaque to the outgoing terrestrial radiation.
Absorbs a part of terrestrial radiation and reflects back some part of it towards the earth’s surface. Largely responsible for the greenhouse 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
Water vapour is the most variable constituent of the atmosphere. Its concentration depends on several factors, but most importantly its partial pressure (or saturation vapour pressure) depends on the temperature.
As the atmosphere cools down, due to increasing altitude, there is a greater likelihood of water droplets forming in it which results in higher water vapour concentrations. At the tropopause, the latter reaches its maximum level where condensation occurs at its greatest rate.
In the warm and wet tropics, it may account for four per cent of the air by volume, while in the dry and cold areas of desert and Polar Regions, it may be less than one per cent of the air.
Water vapour also decreases from the equator towards the poles. It also absorbs parts of the insolation from the sun and preserves the earth’s radiated heat. It thus, acts like a blanket allowing the earth neither to become too cold nor too hot.
Dust Particles
There are two sources where atmosphere gets such small solid particles: the Earth’s surface and the outer space.
Atmosphere has numerous functions; it is involved in both water and energy transfer, stores carbon dioxide, keeps large amount of different gases etc.
These functions could not be fully accomplished if atmosphere did not contain particles like dust and ashes. Small solid particles make our atmosphere changeable and diverse and create an environment where life could exist on Earth.
Dust particles are generally concentrated in the lower layers of the atmosphere; yet, convectional air currents may transport them to great heights.
The higher concentration of dust particles is found in subtropical and temperate regions due to dry winds in comparison to equatorial and Polar Regions. Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.
