We know:

ü  That the Oxygen is the life breath of human beings.

ü  That the plants take Carbon dioxide and live.

ü  That there is an ozone layer in the atmosphere that protects us from the Ultra-Violet rays coming from the Sun.

ü  Where these gases are present?

ü  These are present in surroundings of the earth and it is called atmosphere.

The Components of Atmosphere

ü  Nitrogen – 78.0 %

ü  Oxygen - 21.0 %

ü  Argon – 0.93%

ü  Carbon dioxide – 0.03%.

ü  Neon – 0.0018 %

ü  Water vapour, dust particles, Helium, Ozone, Krypton, Xenon etc also present in the atmosphere.

ü  The Nitrogen and Oxygen are considered to be the permanent constituents of the atmosphere.

ü  Remaining gases are the variable constituents.

ü  The heavier gases are concentrated in the lower parts of the atmosphere.

ü  The lighter gases are concentrated in the upper layers of the atmosphere.

ü  The Nitrogen gas is important for vegetative growth.

ü  The Nitrogen gas is also helpful for combustion.

ü  The Carbon dioxide gas absorbs the heat from the Sun and the earth.

ü  CO2 is a major nutrient for plants.

ü  High concentration of CO2 in the atmosphere leads to the Greenhouse effect.


The atmosphere is divided into 5 layers.

  • Troposphere

  • Stratosphere

  • Mesosphere

  • Ionosphere 

  • Exosphere

The 5 layers are divided into 2 groups.

ü  Homo sphere: (The composition of gases is almost similar)

ü  Troposphere

ü  Stratosphere

ü  Mesosphere

ü  Hetero sphere: (The composition of gases is not similar)

ü  Ionosphere

ü  Exosphere


ü  This is the lowermost layer in the atmosphere.

ü  We live in this layer.

ü  The height of troposphere at the equator is 16 km.

ü  The height of troposphere at the poles is 8 km.

ü  This layer accounts for water vapor and dust particles.

ü  This layer also accounts for most of the CO2.

ü  The temperature decreases with the increase of height

ü  The Tropo pause separates the Troposphere with the Stratosphere.


ü  This is the second layer in the atmosphere.

ü  The Ozone layer is present in this layer. (Please remember).

ü  Ozone layer is present 25 to 30 km above the surface of the earth.

ü  This zone is called ozonosphere.

ü  The temperature is very high as this layer absorbs the UV rays.

ü  Air pockets are absent in this layer.

ü  There is an absence of water vapour in this layer.

ü  The layer is calm and clear.

ü  This layer provides the better visibility to the pilots.

ü  This layer is suitable for the high speed jet flights.

ü  The temperature increases with the increase of height

ü  This layer is present up to 50 km.

ü  The Chlorofluro-carbons are responsible for the depletion of the Ozone layer.

ü  This is called Ozone hole.


ü  This is the 3rd layer.

ü  This is a transitional layer.

ü  This layer is present up to 80 km.

ü  This layer is considered to be the coldest layer.

ü  The temperature decreases with the increase of height. 


ü  This is the 4th layer in the atmosphere.

ü  This is an electrically conducting layer.

ü  They reflect the radio waves back to the earth.

ü  The Ionosphere helps in radio communication.

ü  This layer acts as a protective layer against meteorites. (Meteorites are burnt in this layer).

ü  The height is up to 400 km.


ü  This is the outermost layer of the atmosphere.

ü  The extent or the boundary of this layer is not clear.


ü  The earth receives heat from the sun and is called insolation.

ü  The surface of the earth receives the heat at the rate of 1.94 calories per per minute.

ü  The vast amount of energy coming to and leaving the earth is called radiation.

ü  The Sun radiation is in the form of short waves.

ü  Radiation from the earth is called terrestrial radiation.

ü  The terrestrial radiation is in the form of long waves.

ü  What is the average temperature of the earth?

ü  This remains constant because of the incoming and outgoing radiation. This is called heat budget.

ü  The heat budget is not uniform throughout the earth.

ü  Up to 400 latitude the amount of solar radiation is received is high than it is lost to space.

ü  Above the 400 latitude the amount of radiation received is less than it is lost.

ü  Aurora is a luminous phenomenon observed in the atmosphere in the high altitude regions.

ü  The Aurora is produced by the entry of the charged particles from the sun into the earth’s magnetic field and occurs at a height of 100 km.

ü  The Aurora are visible in high latitudes of both northern and southern hemispheres.

ü  The Aurora of northern hemisphere is called Aurora Borealis.


ü  The Aurora of southern hemisphere is called 
Aurora Australis.


ü  Weather primary elements are Temperature, Humidity and Wind.

ü  Weather changes from time to time.

ü  The climate is the average of daily changing weather conditions over a long period of time.

ü  The proportion of incident solar radiation reflected from the surface of the earth is called albedo.

ü  The earth receives only 1/2000 millionth part of the total energy emitted by the sun.

ü  Most of the energy emitted by the sun is not received by the earth because of absorption, scattering and reflection.

ü  Depending on the temperature distribution the globe can be divided into three temperature zones.

1.      Torrid Zone or Tropical zone: The temperature remains high. This is 23 ½ 0 N and 23 ½ 0 S.

2.      Temperate Zone: The temperature remains moderate.

3.      Frigid Zone (Polar regions): The temperature remains low.

ü  Isotherms: The lines joining places with same temperature.

ü  Atmospheric pressure is the column of air extending vertically over a given area on the earth’s surface.

ü  Atmospheric pressure is measured by Barometer.


ü  Aneroid Barometers are the modern barometers that do not make use of any liquids.


ü  Barograph is an instrument that records the atmospheric pressure continuously.


ü  Wind: The air moving in a definite direction.

ü  Air always moves from the area of high pressure to the low pressure area.

ü  Easterly winds: Blows from East to west.

ü  Westerly winds: Blows from West to East.

ü  Doldrums or Variable winds: 50 N and S.

ü  Trade Winds: 50 to 300 N and S. They blow 
from North to South in the Northern hemisphere and South to North in the southern hemisphere.

ü  Horse latitudes: Between 300 and 400 N and S.

ü  Westerly winds: Between 350 and 600 N and S.

ü  Westerly’s in the southern hemisphere also called Roaring forties, Furious fifties and Screaming sixties.