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THE ATMOSPHERE:
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.
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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.
STRUCTURE (LAYERS) OF ATMOSPHERE
The atmosphere is divided into 5 layers.
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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
TROPOSPHERE:
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.
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.
MESOSPHERE:
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.
IONOSPHERE:
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.
EXOSPHERE:
ü
This is the outermost layer of the atmosphere.
ü
The extent or the boundary of this layer is not clear.
Miscellaneous:
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 Sq.cm 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.
AURORA BOREALIS |
ü The Aurora of southern hemisphere is called
Aurora Australis.
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.
BAROMETER |
ü Aneroid Barometers are the modern barometers
that do not make use of any liquids.
ANEROID BAROMETER |
ü Barograph is an instrument that records the
atmospheric pressure continuously.
BAROGRAPH |
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.
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