Climatology: Composition of the Atmosphere

Composition of the Atmosphere

• The atmosphere is a mixture of many gases. In addition, it contains huge numbers of solid and liquid particles, collectively called ‘aerosols’.
• Some of the gases may be regarded as permanent atmospheric components which remain in fixed proportion to the total gas volume.
• Permanent gases in the atmosphere are

Different Constituents of the Atmosphere

1. Nitrogen
   • Nitrogen accounts for 78% of total atmospheric volume. 
   • It is a relatively inert gas and is an important constituent of all organic compounds. 
   • The main function of nitrogen is to control combustion by diluting oxygen. 
   • It also indirectly helps in the oxidation of different kinds.
2. Oxygen
   • Oxygen is a life-giving gas which accounts for 21% of the atmosphere.
   • Combustion is not possible without oxygen.
3. Carbon Dioxide
   • Carbon Dioxide which constitutes only about 0.3% of the dry air and is a product of combustion.
   • Green plants, through photosynthesis, absorb carbon dioxide from the atmosphere and use it to manufacture food and keep other bio-physical processes going.
   • Being an efficient absorber of heat, carbon dioxide is considered to be of great climatic significance.
   • Carbon dioxide is considered to be a very important factor in the heat energy budget.
   • More carbon dioxide in the atmosphere means more heat absorption. This could significantly raise the temperature at lower levels of the atmosphere thus inducing drastic climatic changes.
4. Ozone (03)
   • It is actually a type of oxygen molecule consisting of three, instead of two, atoms.
   • It forms less than 0.00005% by volume of the atmosphere and is unevenly distributed.
   • It is between 20 km and 25 km altitude that the greatest concentrations of ozone are found.
   • It is formed at higher altitudes and transported downwards.
   • Ozone plays a crucial role in blocking the harmful ultraviolet radiation from the sun.
   • Other gases found in almost negligible quantities in the atmosphere are neon, helium, hydrogen, xenon, krypton, methane etc.
5. Water Vapour
   • Gaseous form of water present in the atmosphere is called water vapour.
   • Its maximum amount in the atmosphere could be upto 4 percent.
   • The atmospheric vapour is received through the evaporation of moisture and water from the water bodies ,vegetation, and soil cover.
   • 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 decreases from low latitudes to high latitudes.
   • In the same way, its amount decreases with increasing altitude.
6. Dust Particles
   • Dust particles are generally found in the lower layers of the atmosphere.
   • These are composed of sand, smoke and oceanic salt.
   • These particles act as hygroscopic nuclei for condensation which result in precipitation.
   • These particulates help in the absorbing, reflecting, and scattering of the solar radiation which adds the varied charming colour of red and orange at sunrise and sunset.