Composition of the Atmosphere
Composition 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.
- 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.
- 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.
- 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.
- 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
- 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.
- 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?
➢ 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