Layers of the atmosphere: layers are-
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Troposphere literally means the region of mixing. It has been derived from the Greek word `Tropos` meaning mixing or turbulence
Definition- Lowermost layer of the atmosphere many types of atmospheric disturbances occurs and many atmospheric elements are presents so turbulence is seen and life exists.
Extended- The layer extended up to 14 km in height from the sea level. It varies from latitude to latitude, in the equatorial region, it spreads up to 16 km, in the Poler region it spreads up to 8km and in mid-latitude, it spreads up to 9 km. Height also varies in different seasons, in January at 45° north and south average height will be 12.5 km and in July 15 Km.
Temperature: In the troposphere temperature decreases according to the increase in height i.e 6.4° C/km or Normal lapse Rate as a result temperature in the upper troposphere remains -57°C to -60°C.
Elements: Nitrogen, Oxygen, Carbon dioxide, Water Vapour, aerosols.
Characteristics: i) Clouds, Thunderstorms, Cyclones, and anticyclones form in this atmosphere.
ii) Lower part of the troposphere is divided into three categories- a) Frictional layers- Extended up to 1km from the surface (b) Surface boundary layer-Extended up to meters from the surface (c) Laminar layer - Extended up to millimetres from the surface.
iii) Jet Streem sometimes goes beyond the troposphere which increases the height of the troposphere.
iv) Atmospheric disturbances increase in the upper troposphere because of the mixing of air and wind speed.
v) It contains about 75% of atmospheric elements (Gaseous mass, moisture, dust particles etc.)
Tropopause:- The word 'Tropopause` has taken from the Greek word it means `where mixing stops` The intermediate layer presents in between two prominent layers troposphere and stratosphere. This layer behaves like a wall between layers and restricts the mixing of air and temperature as well.
Extention- From the sea level 17 km in the equatorial region, 9-10 km in the polar region, Wide- 1.5 km.
Temperature:- -60°C temperature found in the upper part of the tropopause.
➤Stratosphere:
Definition- Second major atmospheric layer which lies above stratopause is called Stratosphere.
Extention- This layer extends upwards from the tropopause about 50 km.
Temperature- The lower stratosphere is isothermal in nature, which means the temperature is not increased or decreases with the increase of altitude. But beyond 20-22 km temperature increase with the increase of height because of the absorption of the suns' ultraviolet radiation by ozone, where the temperature may exceed 0° and air density is much less, so even limited absorption produces a much temperature. Sometimes in the polar region at the height of 25km in winter temperature suddenly increase goes up to -40°C from -80°C, ti is called the 'explosion of worming'.
Characteristics- i) Density of the air in the stratosphere is much less, clear and dry.
ii) Circulation changes and high wind speed are observed in this layer.
iii) `Cirrus` cloud formed due to circulation changes in this sphere. This cloud is also known as the 'Mother of Pearl Cloud'.
iv) Jet air flight proper this layer to fly because of less atmospheric disturbance and good visibility because of less dense air.
v) Very valuable layer because of ozone gas which presents in between 25 to 35 km. This ozone layer can protect us from harmful ultraviolet rays coming to us by the solar radiation formed sheld of life. Ozone can be found up to 80 km.
Statopause- upper part of the stratosphere is known as stratopause.
➤Mesosphere- Third major atmospheric layer is the mesosphere.
Extended- This layer presents above 50 km from the earth's surface to 80 km.
Temperature- Temperature decreases in this sphere and goes down up to-80°C at the uppermost part.
Characteristics- i) 'Noctilucent clouds are observed in this layer, particularly in the summertime. This cloud formation is due to meteoric dust particles, which act like ice crystal nuclei and moisture water vapours that come from the upward movement of air due to the convection process because of vertical decrease of temperature (or moisture can be produced by the oxidation of methane).
ii) In this layer the air pressure is very low.
Mesopause- upper part of the Mesosphere is known as Mesopause.
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➤Ionosphere- According to Peterson, Ionosphere lies beyond the ozonosphere at the height of about 60km above the earth's surface, however, if we consider Mesosphere, then the height will be about 80-90km above the earth's surface.
Extention- 90km to 640 km (approx)
Temperature- Lower Ionosphere considered as Thermosphere. Oxygen gas interacts with Sun's Ultraviolet rays so heat goes up to 700°C at a height above 200km. At the start of the Thermosphere, the temperature is around 100°C. However, it can be changed according to latitude and seasons. Another reason to increase temperature is the very low density of air. However, this kind of high temperature is not possible to feel by the biological body (like a human).
Characteristics- i) Layers- This layer can be subdivided by the following layers- a) D-layer(60-90km)-It can reflect low frequency but above the medium and low frequency and disappear after sunset. b) E- layer (90-100 km) - It is known as the 'Kennelly -Heaviside' layer. It reflects the medium and high-frequency radio waves. It is produced by ultraviolet photons from the sun interacting with nitrogen and nitrogen molecules. ii) Sporadic E layer- This layer produces aurora light. High-velocity wind flows here. It affects high-frequency radio waves. iii) E₂ layer (150 km)- It is found above the E layer. It is produced by ultraviolet photons interacting with oxygen. c) F-layer (150-380 km)- It is known as The 'Appleton' layer. This layer is subdivided into two layers F₁ and F₂ layers. It can reflect high and medium velocity radio waves. F₁ layer is very important for communication. F₂ layer is prominent at noontime in the winter season. d) G layer (above 400km)- This layer is found above the F layer. This layer occurs because of the interaction of UV photons with nitrogen atoms and free electrons are produce the G layer. e) H layer- This layer found after G.
ii) Aurora - Aurora in the poles sky occurs because of this layer. An Aurora is a beautiful display of colourful lights on both poles and is very prominent at night. This light occurs when charged particles from the sun interact with atoms and molecules (gases) in the upper atmosphere. Some particles get defected around the earth, where other charged particles interact with the magnetic field lines, follow the earth's magnetic field then create currents of charged particles within the magnetic field to travail both poles. Charged particles are display different colours (oxygen charged particles produce green and red lights and nitrogen-charged particles produce shows blue and purple) in the sky. When it is shown in the north pole, it is called aurora borealis and in the south pole aurora australis.
➤Exosphere-
Definition- This layer is generally considered the outermost layer where atoms and molecules are can escape into space.
Extention- 500km to 750 km (approx)
Temperature- Temperature goes up to 5568°C because thin air can absorb more heat.
Characteristics- i) Composition- Atoms of oxygen, hydrogen and helium are present in gaseous form. Neutral helium and hydrogen atoms have very low atomic weight so they can easily escape and air pressure is almost none so the chances of molecular collision are also very less.
ii) Helium is produced by the action of cosmic radiation on nitrogen and the source of Hydrogen comes from the breakdown of water vapour and methane.
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➤Magnetosphere- Above Exosphere Magnetosphere lies and this sphere almost merges to space. This layer is a magnetic layer (bubble) of the earth that can protect us from harmful solar wind and storms.
Extention- 750km to Space.
Occurrence- This magnetic field is generated by the convective motion of charge, molten iron in the earth's outer core which is a present internal part of the earth or far blew the interior earth.
Characteristics- i) Doughnut shaped magnetic field full of charged particles, present in the earth's Magnetosphere was discovered by James A Van Allen, the American physicist in 1958, according to his name belt known Van Allen Belt.
ii) Van Allen belt is most intense over the equator and absent on the poles (South and North).
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