NCERT Summary: Air Notes | EduRev

Geography for UPSC CSE

UPSC : NCERT Summary: Air Notes | EduRev

The document NCERT Summary: Air Notes | EduRev is a part of the UPSC Course Geography for UPSC CSE.
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Composition of the Atmosphere

NCERT Summary: Air Notes | EduRevComposition of Atmosphere

  • Carbon dioxide released in the atmosphere creates a greenhouse effect by trapping the heat radiated from the earth. It is therefore called a greenhouse gas.
  • Nitrogen and oxygen are two gases that make up the bulk of the atmosphere. Carbon dioxide, helium, ozone, argon, and hydrogen are found in lesser quantities.
  • Nitrogen is the most plentiful gas in the air. Oxygen is the second most plentiful gas in the air. Green plants produce oxygen during photosynthesis.
  • Carbon dioxide is another important gas. Green plants use carbon dioxide to make their food and release oxygen. Humans or animals release carbon dioxide.

Structure of the Atmosphere

  • Our atmosphere is divided into five layers starting from the earth’s surface.
  • These are Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.

Troposphere

  • This layer is the most important layer of the atmosphere.
  • Its average height is 13 km.
  • The air we breathe exists here.
  • Almost all the weather phenomena like rainfall, fog, and hailstorm occur in this layer.

Stratosphere

  • Above the troposphere lies the stratosphere.
  • It extends up to a height of 50 km.
  • This layer is almost free from clouds and associated weather phenomenon, making conditions most ideal for flying aeroplanes.
  • One important feature of the stratosphere is that it contains a layer of ozone gas, which protects us from the harmful effect of the sun's rays.

Mesosphere

  • This is the third layer of the atmosphere.
  • It lies above the stratosphere.
  • It extends up to a height of 80 km.
  • Meteorites burn up in this layer on entering from space.

Thermosphere

  • In the thermosphere, the temperature rises very rapidly with increasing height.
  • The ionosphere is a part of this layer.
  • It extends between 80-400 km.
  • This layer helps in radio transmission.
  • In fact, radio waves transmitted from the earth are reflected back to the earth by this layer.
    Try yourself:The layer of the atmosphere which contains dust particles and water vapour is called 
    View Solution

Exosphere

  • The uppermost layer of the atmosphere is known as the exosphere.
  • This layer has very thin air.
  • Light gases like helium and hydrogen float into space from here.

Weather and Climate

  • The average weather condition of a place for a longer period of time represents the climate of a place.
  • The degree of hotness and coldness of the air is known as temperature.
  • An important factor that influences the distribution of temperature is insolation.
  • Insolation is the incoming solar energy intercepted by the earth.
  • The amount of insolation decreases from the equator towards the poles.
    NCERT Summary: Air Notes | EduRev
  • Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface.
  • The air pressure is highest at sea level and decreases with height.
  • Horizontally the distribution of air pressure is influenced by the temperature of the air at a given place. In areas where the temperature is high the air gets heated and rises.
  • This creates a low-pressure area. Low pressure is associated with cloudy skies and wet weather.
  • High pressure is associated with clear and sunny skies.
  • The movement of air from the high-pressure areas to low-pressure areas is called wind.
    Try yourself:Which of the following does not affect the distribution of insolation? 
    View Solution

Winds can be broadly divided into three types.

  • Permanent winds - The trade winds, westerlies, and easterlies are the permanent winds. These blow constantly throughout the year in a particular direction.
  • Seasonal winds - These winds change their direction in different seasons. For example monsoons in India.
  • Local winds - These blow only during a particular period of the day or year in a small area. For example, land and sea breeze. Do you recall the hot and dry local wind of northern planes of India? It is called a loo.
  • On the basis of mechanism, there are three types of rainfall: convectional rainfall, Orographic rainfall, and the cyclonic rainfall
    NCERT Summary: Air Notes | EduRev

NCERT Summary: Air Notes | EduRev

NCERT Summary: Air Notes | EduRev

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NCERT Summary: Air Notes | EduRev

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