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STRUCTURE OF ATMOSPHERE

by Sruthi.p New sruthi

Pages 2 and 3 of 21

SOCIAL SCIENCE
8TH
STRUCTURE OF ATMOSPHERE
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STRUCTURE OF ATMOSPHERE
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The composition of the atmosphere is somewhat uniform up to about 90 kilometers from the surface of the earth.This part of the atmosphere is called homosphere.Beyond this there is no uniformity in the gaseous composition.So the part of the atmosphere beyond 90 km from the earth is called asheterosphere.Based on the temperature at different levels,atmosphere can be divided into different layers.
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TROPOSPHERE
This layer extends up about 90 Km from the surface of the earth and lies close to the earth.The height of the troposohere is more in the equatorial regions because of strong convection here.Almost all the weather and climatic phenomena such as cloud formation,rain,snow,wind,thunder and lightening etc.take place in this layer.In the troposphere the temperature decreases at a uniform rate of one degree celcious for every 165 meters of altitude. this is called normal lapse rate.
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TROPOSPHERE
This layer extends up about 90 Km from the surface of the earth and lies close to the earth.The height of the troposohere is more in the equatorial regions because of strong convection here.Almost all the weather and climatic phenomena such as cloud formation,rain,snow,wind,thunder and lightening etc.take place in this layer.In the troposphere the temperature decreases at a uniform rate of one degree celcious for every 165 meters of altitude. this is called normal lapse rate.
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STRATOSPHERE
Extends up to a height about 50 kilometer from the earth and lies above the tropopause. the lower parts of the stratosphere there is no change in temperature with altitude. This zone is called isothermal zone. Beyond this there is increase in temperature with altitude. Ozone layer which forms part of this layer absorbs the harmful ultraviolet rays from the sun and prevents it from reaching the earth. Allows the free movement of jet aircrafts through clear atmospheric conditions and absents of air gutters. The zone of transition above the stratosphere is called stratopause.
MESOSPHERE
Extends from about 50 to 80 km altitude from the earth.Temperature decreases with altitude and the lowest temperature of the atmosphere is felt at the mesospause. The meteors on reaching the mesosphere gets burned out due to friction. The zone of transition above the mesosphere is called mesopause.
THERMOSPHERE
Extends from about 80km to 600km altitude.There is considerable increase in temperature with altitude.The lower part of the thermosphere is known as ionosphere. Ionosphere helps in the transmission of radio waves.
EXOSPHERE
The exosphere gradually fades away in to the realm of interplanetary space. Although some experts consider the thermosphere to be the uppermost layer of our atmosphere, others consider the exosphere to be the actual "final frontier" of earths gaseous envelope. Infact,the air in the exosphere is constantly-though very gradually-"leaking" out of earths atmosphere into outer space.There is no clear-cut upper boundary where the exosphere finally fades away into space.
SIGNIFICANCE OF ATMOSPHERIC LAYERS
The atmosphere is an important part of what makes Earth livable. It blocks some of the sun's dangerous rays from reaching Earth. It traps heat ,making earth a comfortable temparature. And the oxygen with in our atmosphere is essential for life.

Earth's atmosphere has five major and several secondary layers. From lowest to highest, the major layers are the troposphere, stratosphere, mesosphere, thermosphere and exosphere.
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