Structure of the atmosphere

Structure of the Atmosphere

The vertical  structure consisting of several layers of the atmosphere, determined primarily by the phenomena that occur there,are separated from one another by change of the slope of the graph of temperature vs altitude.There are 4 basic layers of atmosphere.They are given below-

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere

The layers are discussed below-
Troposphere

The lowest layer of atmosphere in which living organism operate is called troposphere.It is the region of strong air movements and cloud formation characterized by sleady decrease in temperature.It is a mixture of several gasses which is remained fairly in abundance.However water vapor and dust occured in troposphere in extremely variable concentration.The average temperature of this layer is about 15 degree celcious,It is the suitable layer for living organisms.
Sratosphere
Stratosphere is the air mass extending from the upper most level of the troposphere to upper most level of stratosphere,about 50 km above surface of the earth.Ozone present there forms an ozone layer called ozonosphere.It is formed full from oxygen through a photochemical reaction where oxygen molecule splits to form atomic oxygen.




The atomic oxygen combines with molecular oxygen and ozone is formed.
Although the reaction are reversible in nature however percentage of ozone remain constant.


It forms an umbrella called ozone-umbrella that absorbs the UV radiation coming from the sun.Moreover,it serves as a blanket an reducing the cooling rate of the earth.Therefore am equilibrium between ozone and rest of the air is a significant factor of the environment.The line at the end of the stratosphere and start of the mesosphere is called stratopause where we see the subsonic aircraft.


Mesosphere

Above of the stratosphere the layer mesosphere is found.It is characterized by cold temperature and low atmospheric pressure.The temperature drops reaching a minimum of -95 degree centigrade 80-90 km above the earth surface.
Thermosphere

Above the mesosphere,is thermosphere extending up to 500 km above the earth surface.It is characterized by an increase in the temperature from the mesosphere  upper zone to the thermosphere where ionozation of molecules oxygen occur is called the ionosphere.
       
The another layer of the atmosphere is exosphere.In the atmosphere above the ionosphere is called exosphere of the outer space which lacks of atmosphere except that of hydrogen and helium and extends 32190 km from the surface of the earth.It has very high temperature due to solar radiations.