Structure of Atmosphere for UPSC
The atmosphere is divided into strata with varied densities and temperatures. Density is greatest at the earth’s surface and decreases with increasing altitude.The structure of atmosphere is important tropic for comparative exams and Civil service exams. Depending on the temperature, the atmosphere’s structure is separated into five distinct strata. The troposphere, stratosphere, mesosphere, thermosphere, and exosphere are the five main layers of the atmosphere.
1. Troposphere
- The troposphere is the atmosphere’s lowest layer.
- It has an average height of 13 km and its elevation ranges from 8 km nearby poles to 18 km towards the equator. The equator has the thickest layer of troposphere because heat is carried to ample heights by powerful convectional currents.
- This layer is made up of dust particles and water vapour. This layer is responsible for all climatic and weather fluctuationssuch as fog, rainfall and hailstorms.
- Height of troposphere changes (decreases) from the equator towards the poles and from one season of a year to another season (height increases during summer and decreases during winter) because heat is transported to greater heights by strong convection currents at the equator.
- The temperature in this zone drops by 1° C with every 165m of height.
- This is the foundational sphere of all biological activity.
- Tropopause: The tropopause is the zone that separates the troposphere from the stratosphere. The tropopause air temperature is around minus 800C over the equator and approximately minus 450C over the poles. Because the temperature here is relatively constant, so, it is known as the tropopause.
2. Stratosphere
- The stratosphere is located above the troposphere. It reaches a height of 50 kilometres.
- This layer is almost completely devoid of clouds and related meteorological phenomena, providing the best circumstances for flying aeroplanes.
- Ozonosphere: The presence of an ozone gas layer in the stratosphere is one of its key characteristics.This layer filters ultraviolet radiation and protects life on Earth from dangerous forms of energy.
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| Structure of Atmosphere |
3. Mesosphere
- The mesosphere is located above the stratosphere, which reaches a height of 80 kilometres.
- Temperature decreases with increasing altitude in this zone as well like as in the Troposphere, reaching minus 100° C at a height of 80 kilometres.
- Meteorites that enter from space burn up in this zone.
- Characterized by very low air pressure.
- The Mesopause is the top limit of the mesosphere.
4. Thermosphere
- Temperature rises fast with increasing height in the thermosphere.
- Air pressure becomes extremely low due to very low atmospheric density.
- This layer includes the Ionosphere which lies above the Mesopause. It stretches between 80 and 400 kilometres. This layer facilitates radio transmission. This layer, in reality, reflects back to the ground radio waves received from the earth.
5. Exosphere
- The exosphere is the uppermost layer of the atmosphere.
- The air in this stratum is extremely thin.
- From here, light gases such as helium and hydrogen drift into space.
- In the exosphere, many weather satellites orbit the Earth.
- Low-Earth orbit is located in the lower exosphere, whereas mediumEarth orbit is located higher in the atmosphere.Satellite photos of the Earth show the upper exosphere threshold. The hazy blue glow that encircles the Earth is known as the “Geocorona.”
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