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Layers of Atmospheres

Atmosphere

Atmosphere is a thick gaseous envelope surrounding the Earth from all sides and attached to earth through the force of gravitation.

There are various Layers of Atmosphere which are mention below:

Troposphere

  • It extends up to 16km from the Earth's surface.Thickness varies from 8km at the poles to 16km at the equator.
  • At every 165m,there is a drop of 1degree. This is refer to be a Normal Lapse Rate of Temperature.
  • Tropopause separate troposphere from stratosphere.
  • This layer of atmosphere accounts for practically the entire water vapour,all dust particles and most of the Carbon dioxide contained in the atmosphere.Due to this all weather phenomena such as condensation,precipitation and storms,etc occur in the troposphere only.
  • The top of the troposphere is called the tropopause. This is lowest at the poles, where it is about 7 - 10 km above the Earth's surface. It is highest (about 17 - 18 km) near the equator.
  • The lowest part of the troposphere is called the boundary layer. This is where the air motion is determined by the properties of the Earth's surface. Turbulence is generated as the wind blows over the Earth's surface, and by thermals rising from the land as it is heated by the sun. This turbulence redistributes heat and moisture within the boundary layer, as well as pollutants and other constituents of the atmosphere.

Stratosphere

  • The stratosphere extends up to about 50km, where stratosphere separates it from the mesosphere.
  • The phenomena in this layer is temperature inversion.
  • The temperature rises in this layer from about -60 degree at the tropopause to 0 degree at stratopause.
  • The part of the stratosphere,in which there is a concentration of ozone is ozonosphere.It absorbs ultraviolet radiation,which is harmful for us.
  • Stratosphere is a free from dust particles and also from atmospheric turbulences.Hence,this layer is considered ideal for flying of jet aircrafts.
  • Now humans have stopped making most of the harmful CFCs we expect the ozone hole will eventually recover over the 21st century, but this is a slow process.

Mesosphere

  • Mesosphere extends above the stratosphere up to a height of about 80km.
  • In this layer,the temperature decreases with height like in the troposphere and it falls from about 0°C at its base about -100°C at 80km height.
  • It is the coldest layer of atmosphere.
  • Mesopause marked the upper limit of the mesosphere.A transitional layer separates mesosphere from ionosphere.

Ionosphere

  • Ionosphere is located above the mesosphere and extends up to about 600km.
  • This layer is ionosphere because it contains electrically charged ions that reflect the radio waves back to the earth.
  • Absorption of solar radiation by ionised particles cause an increase in temperature with increasing height in the ionosphere.
  • Due to large concentration of ionised particles in this layer the ionosphere acts as a protective layer against meteorites .

Thermosphere

  • The zone between the 85km and 400km above the surface is refer to be thermosphere.In this layer,the temperature increases with increasing in altitude.
  • The upper limit of the thermosphere,the thermopause is generally at an altitude of about 600km.
  • The day temperature at 600km altitude exceed 1400 °C while at night temperature remain about 225°C.
  • The upper part of the thermosphere contains only the lighter gases like helium and hydrogen.

Exosphere and Magnetosphere

  • The outermost part of the atmosphere of the earth is exosphere.
  • This zone of the atmosphere extends up to a height of about 900km.
  • The upper limit of the atmosphere layer between the earth's atmosphere and the space.The outer part of the exosphere is refer as Magnetosphere.
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influence of atmospheric pressure

Altitude-Air pressure increases,when air descends due to the decrease in volume.When air arises its volume increases and the outward pressure of its molecule is spread over a larger area and its pressure decreases.

Temperature-The pressure of air rises, when its temperature falls.Low temperature at the poles cause the air to contract-high pressure develops;whereas the high temperature along the equator cause the air to expand-low pressure develops.

Greenhouse effect


A greenhouse gas is called that because it absorbs infrared radiation from the Sun in the form of heat, which is circulated in the atmosphere and eventually lost to space. Greenhouse gases also increase the rate at which the atmosphere can absorb short-wave radiation from the Sun, but this has a much weaker effect on global temperatures.


The CO2 released from the burning of fossil fuels is accumulating as an insulating blanket around the Earth, trapping more of the Sun’s heat in our atmosphere. Actions carried out by humans are called anthropogenic actions; the anthropogenic release of CO2 contributes to the current enhanced greenhouse effect.


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