Our earth is surrounded by a huge blanket of air called atmosphere. All living beings on this earth depend on it for their survival. It provides us the air we breathe and protects us from the harmful effects of the sun’s rays. Without this blanket of protection, we would be baked alive by the heat of the sun during day and get frozen during night. So it is this mass of air that has made the temperature on the earth liveable. so you always wish to know that what is atmosphere , let me tell you about it in detail.
What is atmosphere / वायुमंडल क्या है
the word atmosphere is taken from the Greek work [Atmos] which means vapour or gases and sphaira which means ball or globe. gaseous cover by which our planet earth is enveloped is known as the atmosphere.
it is like a deep blanket of gases extanding several thousands of kilometers.
it is inseparable from earth due to the gravitational force.
99 percent of the total mass of atmosphere is confined to 32 km from earth surface.
question : do you know how many layers are there in atmosphere ?
answer : there are 5 layers in the atmosphere.
layers of atmosphere / वायुमंडल की परतें
The atmosphere can be studies as a layered entity (based on the temperature)
4. thermosphere ( has ionosphere)
Structure of Atmosphere / वायुमंडल की संरचना
1. Troposphere :-
It is the First and the lowest layer of earth atmosphere. Troposphere start at Earth’s surface and goes up height of 7- 20 kms. In India it is around 16 kms. Trooper means change since all weather changes occur in this layer and air remains static, it is called Troposphere.
This layer has water vapour and dust particles. Altogether phenomena like rainfall, fog and hailstorm etc. Are confined to this layer. All cyclones, storms and precipitation occur here, as water vapour and solid particles lie within this.
In this layer temperature decrease with height. Temperature decreases at the rate of 1 degree Celsius for every 165 m of height and average around 6.5 degree Celsius dropped in every 1 km. The fall in temperature is called lapse rate.
The reason is that the Troposphere’s gases absorb very little of the incoming solar radiation. Instead the ground absorb this radiation and then heats tropospheric near by conduction and convection.
Thickness of Troposphere:-
maximum at equator – 20 km
Minimum at polar regions – 7 km
Main reasons :-
1. High insolation at equator.
2. Air is less dense at equator.
3. Gravitational pull on atmosphere is more at poles than equator (Earth is obtate spheroid / obtate ellipsoid)
4. Centrifugal force maximum at equator.
2. Stratosphere :-
It is the second layer of atmosphere above troposphere. It extend beyond Troposphere up to 50 km of height. This is very dry as it contain little water vapour.
This layer provides some advantage for flight because it is above Stormy weather and has a steady strong horizontal winds. Temperature increasing due to the absorption of ultraviolet radiation of sun by ozone present in this layer. This increase in temperature with height means warmer air is located above cooler air. Stratosphere separates stratosphere and mesosphere.
The ozone layer :-
Stratosphere contains a layer of ozone between 15 to 35 km from earth surface. This layer is called ozonosphere. The ozone layer absorbs ultraviolet rays from the sun and safeguards earth from the harmful radiation. It absorbs 97 – 99 % of UV radiation from the sun. Thus this layer has relatively higher temperature.
90% of ozone molecules are in the stratosphere (good ozone) and 10% are in the Troposphere ( bad ozone).
3. Mesosphere :-
It is founded above the stratosphere. It is starts at 50 km above the surface of Earth and goes up to 85 km. The temperature drops with altitude in this layer. Bi a ti kilometre it reaches -100 degree Celsius. It is the coldest of the atmospheric layers.
meteors burn up in this layer of dense layer due to creation of friction and lot of heat. The upper limit is called Mesopause which separates mesosphere and thermosphere.
4. Thermosphere :-
This layer is found above Mesopause.
Starts at 80 km above the surface of Earth and goes up to 400 km.
This layer is completely cloudless and free of water vapor.
“Thermo” means heat, and the temperature in this layer can reach around 2000 degrees Celsius.
The increase in temperature is due to absorption of high energy X-rays and UV radiations of the Sun, which causes the few particles present to heat up considerably.
It also results in Photoionization (the breakup of the gas molecules into ions), and thus contains lonosphere.
The International Space Station orbits in this layer. In this layer many Low Earth Orbit satellites are present. The Aurora also occurs here.
In the ionosphere, the ions of the solar wind collide with atoms of oxygen and nitrogen from the Earth’s atmosphere. The energy released during these collisions causes a colorful glowing halo around the poles-an aurora. Most auroras happen in Thermosphere.
The upper limit is called Thermopause which separates Thermosphere and Exosphere.
It is an abundant layer of electrons and ionized atoms and molecules that stretches from about 48 km above the surface to the edge of space at about 965 km. overlapping into the Mesosphere and Thermosphere.
Ionosphere is a result of Photoionization (the breakup of the gas molecules into ions).
Ionosphere is important because it reflects and modifies radio waves used for communication and d navigation.
5. Exosphere :-
It is the outermost layer of atmosphere.
It extends from the top of the thermosphere up to 10,000 km. Though in some places it is said that its upper limit is quite uncertain. The Exosphere contains many of the satellite orbiting Earth. It gradually merges interplanetary space.
Importance of Atmosphere / वायुमंडल का महत्व
Atmosphere acts as a protective blanket or shield for earth.
Without it temperature at the equator would rise to 180 degree Celsius during day and drop as well as -220 degree Celsius at night.
It burns up meteors that would bombard the earth’s surface from space
It absorbs most of the cosmic rays & protects living things from their effects. It is fortunate for life on earth that atmosphere filters out tissue damaging UV radiations.
Atmosphere has been essential in maintaining heat balance on earth.The atmosphere absorbs the heat radiations emitted by the sun. It also absorbs the radiations reemitted from the earth in the form of IR radiations, therefore it serves as the important heat stabilizing function and prevents the tremendous temperature extremes.
It is able to nurture life on earth.
It has been a vital carrier of water from oceans to land as a part of hydrological cycle.
Without atmosphere there would be no sound, no flight, no lightening, no clouds, no rains. Therefore the surface of earth would be barren and sterile as the moon.
Composition of Atmosphere :-
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