33 Science -- Atmosphere and Climate Change

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Layers of Atmosphere

The Earth's atmosphere is made up of five imaginary layers which are categorized on the basis of various factors such as density, temperature, variation and altitude. Here are the main facts that you need to know about these atmospheric layers:

1. Troposphere

i] It is the lowermost layer and closest layer to the Earth's surface.

ii] It extends up to 16 km from the earth's surface. It's width/altitude is about 8 km to 10 km in poles and about 1 km in the equatorial region.

iii] About 95% of atmosphere lies in this region.

iv] In this region the temperature decreases with the increase in 1 km altitude at the rate of about 6.5 degree celsius.

v] It is also known as the variable layer/changeable layer since it's temperature varies in accordance with altitude.

vi] This layer is associated with weather factors like cloud, rain, frost, hailstorm, fog, storm, tornado, thunder struck, lightening, etc. These factors directly affect weather on earth. Therefore, scientists study this layer to forecast weather.

vii] It contains different gases like Nitrogen, oxygen, carbon dioxide, water vapour, dust particles and other particulates.

viii] The uppermost/ boundary layer of troposphere is called Tropopause.

2. Stratosphere

i] It is the layer of atmosphere just above the troposphere extended to the altitude from 16 km to 50 km above the earth.

ii] The main components of this layer are ozone, nitrogen, oxygen and nascent oxygen.

iii] This layer is also called ozonosphere since it contains ozone layer at it's upper surface(mainly at the altitude of 20 km to 30 km of this layer).

iv] It absorbs 99% of the Ultraviolet radiation coming from sun towards the earth's surface.

v] The temperature increases with the increase in altitude in stratosphere because of increase in magnitude of ozone upward.

vi] As the stratosphere is clear and cloudless, jet planes often fly in this layer.

vii] Temperature varies in this layer from -56 to -2 degree celsius.

viii] The uppermost layer or boundary of stratosphere is stratopause.

3. Mesosphere

i] It lies just above stratosphere  and extends from 50 km-80 km from Earth's surface.

ii] Gases like nitrogen, oxygen and ozone, etc. are found in this layer.

iii] It is the coldest layer of atmosphere and the temperature of this layer gradually decreases with altitude as it has very less ozone to absorb the sun's rays which is only at its lower surface.

iv] The streaks(trails) of hot gases left by meteors are seen in this layer known as the meteor shower.

v] Very strong wind blows in mesosphere which blows eastward during during winter and westward in summer.

vi] It's uppermost layer is called mesopause and has temperature -109 degree celsius.

4. Thermosphere

i] It is the layer of atmosphere above mesosphere and extended from 80 km to 720 km from the Earth's surface.

ii] It has a very thin layer of air and wind is very low.

iii] Since the gaseous particles are ionized due to extreme heat and the ions are present in the thermosphere, this layer is also known as the ionosphere.

iv] It contains gases like hydrogen and helium in the uppermost region whereas the lower region contains gases like nitrogen and oxygen (even at it's nascent form).

v] Due to more and direct effect of solar radiation(UV-radiation), the thermosphere have the high temperature and the temperature increases with the increase in altitude ranging about -110 to 1500 degree celsius.

vi] The ionized gaseous particles like nitrogen and hydrogen reflect the high frequency(HF) and short wave(SW) radio signals back to Earth and help in distance communication. Thus, this layer is considered to be very important for distance communication.

vii] sometimes, these ions also glow in different colors of light display known as "Aurora".

viii] The uppermost layer of this layer is called thermopause.

5. Exosphere

i] It is the topmost layer of atmosphere which is extended above 720 km above the earth's surface.

ii] Since it is the border between the atmosphere and space, it is also called the fringe region.

iii] It has very thinly distributed atoms of hydrogen and helium in the upper region and oxygen, nitrogen, carbon dioxide in the lower regions.

iv] This layer is very hot as the temperature varies between 1200-6000 degree celsius.

v] The density of air in this layer is extremely low that molecules moving at high speed rarely collide with each other. 

vi] The gravity in this layer is also so weak that the molecules or atoms of air  blow with very high speed or escape out in space.

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