Atmosphere of Earth

Composition of the atmosphere

Atmosphere is an envelope of gases. The height of the atmosphere is estimated between 16-29 thousand km from the sea level. The air is mechanical a mixture of several gases. The atmosphere is composed of gases vapour and particles.The enveloping mixture of gases contain huge no. of solid and liquid particles collectively called Aerosols.

Gases

Nitrogen (78%),  oxygen( 21% )  major gases of atmosphere. The remaining 1% is represented by argon (0.93%) carbon dioxide (0.03%) Neon (0.0018%), helium (0.0005%)

Ozone (0.00006%)  hydrogen, Krypton and methane etc.Also see in the table

 

Water Vapour

The water vapour contained in the atmosphere range between 0 and 5% by volume. The atmospheric vapour is received through the evaporation of moisture and the water from the water bodies like Seas and ocean, vegetation and soil covers it's depend on Temptation and decrease from the equator poleward in response to decrease in temperature toward the poles. The moisture content in the atmosphere contain sale of forms of condensation and precipitation e. g. 

Clouds, Fogs, dew, rainfall, Frost, hailstorm,Ice, snowfalls etc.

Structure of Atmosphere

The height of the atmosphere is up to 800 km. About 50% of the atmosphere lies below the altitude of 5.6 km and 97% of the atmosphere is confined to the height of only 29 km . On the basis of characteristic of temperature and the air pressure There are several layers from the Earth surface upward.

Troposphere

Lowest layer of atmosphere is known as troposphere. It is most important layer because almost all of the weather phenomena occur  in this layer. Temperature decrease with increasing height at the rate of 6.5 % per 1000 m. This rate of decrease of temperature is called Normal lapse rate. The average height of the atmosphere is about 15 km over the equator and 6Km over the poles. The upper limit of the troposphere is called tropopause which is about 1.5 km. The word troposphere  means "zone or region of mixing" whereas the word tropopause means "where the mixing stop".

 Stratosphere

The layer just above the atmosphere is called stratosphere. 

The average height over the middle latitude has been 25-30 km. On an average the upper limit of the stratosphere is taken to be 50 km. The upper limit of stratosphere is known as stratopause.

The lower part of this layer is very important for life forms in the biospheric ecosystem because there is concentration of ozone between the height of 15 to 30 km. The lower portion of the stratosphere having maximum concentration of the Ozone is called the ozonosphere between height of 15 km to 35 km from the sea level.

Ozone(O3)define as a three atom isotope of oxygen it's a blue irritating gas with pungent odour. It's act as a protective cover for the biological communities from the ultraviolet rays of solar radiation. It may be result of oxygen with individual oxygen molecules result in the creation of ozone    O2 + o → O3. There is gradual depletion of the ozone gas in the atmosphere due to increase in gases e. g. chlorofluorocarbon, carbon dioxide and nitrogen oxide. When chlorofluorocarbon reacts with water and thus depletes Ozone weather breaks Ozone into O2 and o. This would cause global warming, acid rain melting of Continental glaciers and rise in sea level, skin cancer to white-skinned people, poisonous smoke, decrease in photosynthesis, ecological disaster and ecosystem instability.

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Mesosphere

Mesosphere extends between 50 km and 80 km and the temperature again  decrease with increasing height. In fact rise of the temperature with increasing height in the stratosphere stopped at stratopause. The upper most limit of the mesosphere (80 km) temperature become  -80 degree centigrade is called mesopause.

Thermosphere

The part of the atmosphere beyond mesopause is known as thermosphere. The temperature increase rapidly with increasing height. The temperature cannot be measured by ordinary thermometer because the gases become very light due to the extreme low density.

Thermosphere is divided into two layer ionosphere and exosphere

 Ionosphere 

It extends from 80 km To 640 km. The number of ionic layer with increasing heights in this sphere e.g.

•  D layer
•  E layer
•  F layer
•  G layer

The layer between the height of 60 km 99 kilometre reflect the signals of low frequency radio waves but absorb the signal of medium and high frequency wave. This layer disappear with the sunset because it is observed with solar radiation.

E Layer also known as kennelly -Heaviside layer,, height between 99 km 130 km. This layer reflects the medium and high frequency radio waves back to the earth. This layer is produced due to interaction of the Solar ultraviolet Photon with nitrogen and nitrogen molecule and also disappear with the sunset.

Sporadic E layer is associated with high velocity means this layer reflective very high frequency radio wave.

E2 layer is generally found at height of 150 km and produced due to reaction of the ultraviolet solar photons with oxygen molecules and also disappear during Nights.

F layer  consists of two sub-layer

F1 and  F2 layers( 150 km 380 km)  are Appleton layer.. These layer reflect medium and high frequency radio wave back to the earth.

G layer 400 km and above most probable persist day and night but is not detectable.

Exosphere

It's a uppermost layer of the atmosphere .In fact we know very little about the atmosphere extends beyond 640 km height from the sea level. the density become extremely low the temperature become 5568 degree Celsius at this outer limit but this temperature is different from the air temperature of the Earth surface as it is never felt.

plz Visit Atmosphere of Earth part 2
https://nikitanirmalgeoinformation.blogspot.com/2018/10/atmosphere-of-earth-part-2.html