The atmosphere is a large blanket of air that surrounds the earth. The gravitational attraction of Earth keeps it closer to the earth’s surface. The three primary constituents of the atmosphere are argon, oxygen, and nitrogen. This article will explain to you about the atmosphere in detail which will be helpful for the UPSC Civil services exam.

What is the Atmosphere?

• The atmosphere is a protective covering of gases that shields all life on Earth by keeping temperatures within a certain range and deflecting harmful solar rays.
• The atmosphere allows the sun's heat to be retained rather than leaking back into space.
• It protects life forms from the sun's damaging radiation.
• Atmosphere plays an important role in the water cycle on Earth.
• There is no boundary between the atmosphere and outer space.
• The atmosphere gradually becomes less dense until it "blends" with the outer atmosphere.

Composition of Atmosphere

• The atmosphere is made up of a variety of gases.
• The two primary gases in the atmosphere are nitrogen and oxygen, which together make up 99 per cent of the atmosphere.
• The remaining gases in the atmosphere include argon, carbon dioxide, neon, helium, hydrogen, and others.
• The ratio of gases fluctuates in the upper layers of the atmosphere to the point where oxygen is almost non-existent at altitudes of 120 km.
• Carbon dioxide and water vapour is present only up to 90 kilometres from the earth's surface.
• The greenhouse effect is mostly caused by carbon dioxide gas.
• Incoming solar radiation passes through it, but outgoing terrestrial radiation does not.
• It absorbs some terrestrial radiation and reflects some of it back to the surface of the planet.
• Dust particles can also be seen in the atmosphere.
• They come from a variety of places, including fine soil, smoke-soot, pollen, dust, and dissolved meteoric particles.
• Dust and salt particles serve as hygroscopic nuclei, allowing water vapour to condense and form clouds.

*To know more about this, click Atmospheric Composition

Layers of Atmosphere

The structure of the atmosphere is divided into five layers based on temperature. These layers are as follows:

The Atmospheric Layers

Troposphere

• The lowest layer of the Earth's atmosphere is referred to as this troposphere.
• The troposphere begins at the earth's surface and rises to a height of 8 kilometres (poles) to 18 kilometres (equator).
• The existence of hot convection currents, which push gases upward, is the main reason for the higher height at the equator.
• This layer experiences a wide range of weather fluctuations.
• Water vapour and mature particles make up this layer.
• Temperature drops by 1 degree Celsius for every 165 metres of height when you climb higher in the atmosphere. This is referred to as a normal lapse rate.
• The Tropopause, or transitional zone, is the boundary between the Troposphere and the Stratosphere.

Stratosphere

• It is the atmosphere's second layer, located above the troposphere.
• It rises to a height of 50 kilometres above the earth's surface.
• This layer is extremely dry due to the lack of water vapour.
• As it is above stormy weather and has continuous, strong, horizontal winds, this layer gives significant advantages for aviation.
• This is where the ozone layer is found.
• UV rays are absorbed by the ozone layer, which protects the earth from hazardous radiation.
• The Stratosphere and Mesosphere are separated by the Stratopause.

Mesosphere

• The Mesosphere is the layer of the atmosphere that is above the stratosphere.
• It is the coldest layer in the atmosphere.
• The mesosphere begins at 50 kilometres above the Earth's surface and extends to 80 kilometres.
• In this stratum, the temperature declines as you climb higher.
• It hits -100 degrees Celsius at 80 kilometres.
• In this layer, meteors are burned up.
• Mesopause is the uppermost limit that divides Mesosphere and Thermosphere.

Thermosphere

• This layer extends from 80 to 400 km above Mesopause.
• This layer reflects radio waves that are sent from the earth.
• As you go higher in this layer, the temperature starts to rise again.
• This layer is where the aurora and satellites appear.

Exosphere

• It is the atmosphere's outermost layer.
• The exosphere is the region where molecules and atoms escape into space.
• It stretches from the top of the thermosphere to a distance of 10,000 kilometres.

Insolation and Heat Budget

• The term insolation refers to the amount of solar radiation that is intercepted by the earth.
• The earth absorbs some of this solar energy (insolation), which is then transmitted back into space via terrestrial radiation.
• The method through which the Earth maintains a constant temperature through the intake and outflow of heat is known as the heat budget.

Insolation and Heat Budget

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Significance of the Atmosphere for Earth

• The atmosphere shields life on Earth from incoming ultraviolet (UV) radiation, keeps the globe warm through insolation, and prevents temperature extremes between day and night.
• Living things require a precise composition of the atmosphere in order to breathe and live else they would perish if it was too high or too low for them to cope.
• This is the reason why life can't sustain on other planets as they do not have atmospheric composition like earth.
• Greenhouse gases in the atmosphere help to control global temperatures by trapping heat.
• Earth's temperatures would be freezing at night and scorching during the day if it didn't have an atmosphere.
• The atmosphere consistently regulates the Earth's climate and temperature.
• The Sun's light is scattered by the atmosphere as it expands out.
• It protects us from the micrometeorite collisions of space.

Conclusion

Shooting stars or meteorites would reach Earth and cause havoc, but as soon as they reach the atmosphere, they would burn up. The atmosphere also helps to keep the Earth's temperature in check. On the Earth's surface, all unprotected plant and animal life would perish. We can't live in a vacuum for very long, which is what we'd have if the atmosphere vanished suddenly. In short, the atmosphere is responsible for much of what makes Earth unique.