Structure of atmosphere: The atmosphere is a thin layer of gases which surrounded the earth that is held in place by the gravity.
It protect us from ectromagnetic radiation gives by earth. The density of atmosphere decreases outward because the gravitational attraction of the planet, which pulls the gases and aerosol (microscopic suspended particle of dust, H2O, smokes, chemicals) inwards.
Atmosphere of earth has been able to contain water in each of its three phases (solid, liquid, gas) that has been essential for the development of life.
The atmosphere of earth is the mixture of Nitrogen (78.08%), oxygen (20.95%), argan (0.93%) with carbon dioxide (0.04%) water (H2O), inert gases such as Helium, Neon, krypton and other constituent such as nitrogen oxides, compounds of sulphur and compounds of ozone are found in lesser amount.
Structure of Atmosphere
The Structure of Atmosphere can be divided into layers, these layers are :-
1. Troposphere (0 to 12 KM)
2. Stratosphere (12 to 50 KM)
3. Mesosphere (50 to 80 KM)
4. Thermosphere (80 to 700 KM)
5. Exosphere (700 to 10,000 KM)
Troposphere is the lowest part of atmosphere, the part in which we live in. Troposphere contains weather, clouds, rain and snow etc.
The troposphere contain about 75% of all air in the atmosphere and almost water vapour cloud and rain.
Troposphere extends to an average height of about 12 km from the earth surface of a sphere is bounded above by the tropopause , boundary marked in most places by a temperature inversion.
It is compressed by the orerlying layers so that most of its weight in the troposphere lies in its lower region.
There exist a thin buffer zone between the troposphere and next layer known as tropopause.
The troposphere is also called boundary layer.
In the structure of atmosphere, the second layer of atmosphere is called stratosphere. The stratosphere extend from the top of the troposphere to about 50 km above the ground.
Ozone Layer is founded within the atmosphere that contains relatively high concentration of the gas. In the stratosphere, the temperature rises with increase in altitude.
The rise of temperature is caused by the absorption of ultraviolet radiation (UV), radiation from the sun.
Stratosphere varies in thickness and the air flow is majorly horizontal. It is thinner above the equator and deep above the poles.
In this layer temperature drops with increase altitude. It is the coldest place on the earth and have average temperature about – 85°C.
The air in the mesosphere is far too thin to breadth because air pressure at the bottom of the layer is below 1% of the pressure at sea level, and the pressure continuously dropping as go higher.
It is also called upper troposphere due to the absence of ultraviolet. In the mesosphere noctitucent cloud or the ice cloud formed by the deposition of the very small amount of water vapour on nickle containing dust. Nickle cloud is silver-white and light blue in colour.
The fourt layer for the ‘structure of atmosphere‘ is thermosphere. It extends from the mesopause (separate from mesosphere) at an altitude of about 80 km to and altitude range of about 700 km.
The height of thermosphere varies due to the change in solar activity. In this layer the temperature increases with height.
The temperature of thermosphere layer can close the session as high as 1500°C. The air is so rarefied in this layer that and molecule of Oxygen or nitrogen travel of about 1 km between collisions with other molecules.
This layer has not cloud and free from water vapour, nonhydrometrological phenomena such as Aurora Australis and Aurora Borealis seen in the thermosphere occasionally.
Thermosphere contains electrically charged particle known as ion and hence it is called inosphere. Radio waves transmitted is reflected back to the earth by this layer and because of this radio broadcasting has become possible.
This is the top layer as well as last structure of atmosphere. The exosphere is the most distant region from the earth’s surface an upward travelling molecules can escape to space in the exosphere.
This layer is the transitional zone between earth’s atmosphere and interplanetary space. Gases are very sparse in this layer due to the lack of gravitational forces therefore the density of air is very less.
Hydrogen is present in the exosphere with some Helium, Carbon Dioxide and Atomic Oxygen near it’s base.
Exosphere may be considered as the part of interplanetary or outer space because it is hard to define the boundary between the exosphere and the outer space.