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--Gopal.vishist 08:36, 1 July 2010 (UTC) climatology
Earth's atmosphere: -
- atmosphere is a gaseous envelope surrounding the earth extending thousands of kilometers above the earth's surface. Much of the life on earth exists at the bottom of the atmosphere where it meets the lithosphere and the hydrosphere. in fact, atmosphere directly or indirectly influences the vegetation pattern, soil type, an dtopography of this earth. Of the total mass of the atmosphere , 99% is within the height of 32 kms from the earth's surface. The atmosphere is held on to the earth because of the earth's gravitational force and is energized by the sun.
composition of the atmosphere
- mixture of several gasses.
- contains huge amount of solid and liquid particles -"aerosols"
- pure dry air consists mainly of nitrogen, oxygen, argon, co2, hydrogen, helium and ozone.
- composition of atmosphere upto an altitude of 99kms is uniform in terms of three major gasses -nitrogen, oxygen and argon. this layer is called HOMOSPHERE.
- above 90 kms the proportion of gasses changes with progressive increase in the proportion of lighter gasses. this layer is called HETEROSPHERE.
- NITROGEN AND OXYGEN COMPRISES 99%OF THE TOTAL VOLUME OF THE ATMOSPHERE.
- water vapours and dust particles are the important variables of weather and climate. they are the source of all forms of condensation and the principal absorbers of heat recieved from the sun and radiated from the earth.
- Water vapours comprises 3-4% of the total volume of the air. However the amount of water vapour present in the atmosphere decreases from equater towards the pole.
- ozone gas absorbs most of the ultravoilet rays radiated from the sun and thus prevents the earth from becoming too hot.
structure of the atmosphere : -[edit | edit source]
- On the basis of chemical composition the atmosphere is divided into two broad layers- Homosphere and Heterosphere.
- extends upto the height of 90 kms.
- uniform in the chemical composition.
- three thermal layers - troposphere, stratosphere and mesosphere.
- the proportion of gasses does not remains constant in this layer.
- thermosphere is the only layer in this sphere.
- extends upto 80-400kms.
exosphere: is the uppermost layer of the atmosphere extending beyond the ionosphere .
- extends beyond a height of 400 kms above the earth's surface.