Structure of Atmosphere (NCERT Notes for Geography)

Our atmosphere is composed of many components. But the structure of the atmosphere is a combination of various layers.

Structure of Atmosphere (UPSC Notes):- Download PDF Here

The structure of the atmosphere is represented in a pictorial form below:

There are five layers in the structure of the atmosphere depending upon temperature. These layers are:

• Troposphere
• Stratosphere
• Mesosphere
• Thermosphere
• Exosphere

This is an important topic in the Geography syllabus for UPSC 2022 Exam.

Troposphere

• It is considered as the lowest layer of Earth’s atmosphere.
• The troposphere starts at the surface of the earth and goes up to a height of 8 kms (poles) to 18 kms (equator). The main reason of higher height at the equator is due to presence of hot convection currents that push the gases upward.
• All kinds of weather changes occurs within this layer.
• This layer has water vapor and mature particles.
• Temperature decreases with increasing height of atmosphere at the rate of 1 degree Celsius for every 165 m of height. This is called Normal lapse rate.
• Tropopause, the transitional zone, separates Troposphere and Stratosphere.

Stratosphere

• It is the second layer of the atmosphere found above the troposphere.
• It extends up to a height of 50 km from the earth’s surface.
• This layer is very dry as it contains little water vapour.
• This layer provides some advantages for flight because it is above stormy weather and has steady, strong, horizontal winds.
• The ozone layer is found in this layer.
• The ozone layer absorbs UV rays and safeguards earth from harmful radiation.
• Stratopause separates Stratosphere and Mesosphere.

Mesosphere

• The Mesosphere is found above the stratosphere.
• It is the coldest of the atmospheric layers.
• The mesosphere starts at 50 km above the surface of Earth and goes up to 80 km.
• The temperature drops with altitude in this layer.
• By 80 km it reaches -100 degrees Celsius.
• Meteors burn up in this layer.
• The upper limit is called Mesopause which separates Mesosphere and Thermosphere.

Thermosphere

• This layer is found above Mesopause from 80 to 400 km.
• Radio waves that are transmitted from the earth are reflected by this layer.
• The temperature starts increasing again with increasing height in this layer.
• Aurora and satellites occur in this layer.

Ionosphere

• The lower Thermosphere is called the Ionosphere.
• The ionosphere consists of electrically charged particles known as ions.
• This layer is defined as the layer of the atmosphere of Earth that is ionized by cosmic and solar radiation.
• It is positioned between 80 and 400 km above the Mesopause.

Exosphere

• It is the outermost layer of the atmosphere.
• The zone where molecules and atoms escape into space is mentioned as the exosphere.
• It extends from the top of the thermosphere up to 10,000 km.

Structure of Atmosphere (UPSC Notes):- Download PDF Here

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