Everything which surrounds us may
collectively be termed as the
It is from the environment that we
get food to eat, water to drink, air to
breathe and all necessities of day to
day life. Environment around us
constitutes a life support system.
the basic components of the
1. Atmosphere or the air
2. Hydrosphere or the water
3. Lithosphere or the rocks and soil
4. The living component of the
environment or the biosphere
Atmosphere or the air
When you get chilly, you might wrap up in a
nice warm blanket. The earth has a blanket
too, called the atmosphere. We call it air for
short. The blanket of air that surrounds the
earth keeps us comfortable. We wouldn't be
able to live on Earth without an atmosphere.
A big layer of air called the atmosphere surrounds
The air within this layer moves from place to
place when it warms up or cools down.
This moving air is known as wind.
All of these winds are part of a global air
circulation system that acts to balance
temperature and pressure around the world.
In addition, winds move moisture and heat
around the world and also produce much of our
Earth isn't the only planet with an
atmosphere. Some planets have an
atmosphere made up of toxic
chemicals. Some big planets, like Jupiter,
are all atmosphere. Earth, however, is
the only planet that we know of, so far,
that has an atmosphere that makes life
• Air is the name given to the atmosphere used
in breathing and photosynthesis.
• While air content and atmospheric pressure
vary at different layers, air suitable for the
survival of terrestrial plants and terrestrial
animals is currently only known to be found in
Earth's atmosphere is made up of many
different chemicals, most of them in very
The main chemicals in air are oxygen at 21%,
nitrogen at 78%, and argon at less than 1%.
Some other chemicals that are there in very
small amounts are important too.
There is carbon dioxide, water vapour, ozone,
and man-made gasses including
• The atmosphere of Earth is a layer of gases
surrounding the planet , that is retained by
• The atmosphere protects life on Earth by
absorbing ultraviolet solar radiation, warming
the surface through heat retention
(greenhouse effect), and reducing
temperature extremes between day and night.
• The first layer is called the troposphere.
• People, plants, animals, and insects live in the
• It is the layer where all weather occurs.
• The troposphere begins at ground level and
extends 12km (7.5 miles) up into the sky
where it meets with the second layer called
• The stratosphere begins at the 12km (7.5 mile)
point and reaches 50km into the sky.
• An important layer of atmosphere containing
ozone is located inside the stratosphere.
• Ozone (O3) is a special form of oxygen, and the
ozone layer is very important to all life on earth.
• Ozone blocks large amounts of solar ultraviolet
radiation from entering the troposphere.
• Too much solar radiation can harm living things,
• The third layer is called the mesosphere.
• The mesosphere begins 50km above the
• Temperatures are warmest at the lowest level
of the mesosphere and coldest at its highest
• The fourth layer is called the thermosphere.
• The thermosphere begins 80km above the earth.
• Temperatures in the thermosphere go up when
moving farther away from ground level due to the
• The increase in temperature stops at this height,
beyond which lies the exosphere.
• The exosphere is the highest layer of the
• The exosphere extends to 40,000 miles above
the earth's surface.
• The thermosphere and the exosphere
together make up the upper atmosphere.
• The troposphere, stratosphere, mesosphere,
and thermosphere act together as a giant
• They keep the temperature on the earth's
surface from dipping to extreme icy cold that
would freeze everything solid, or from soaring
to blazing heat that would burn up all life.
• In the study of air pollution control the layers
of the air that are most important are the
troposphere and the stratosphere.
Within the five principal layers
determined by temperature are
several layers determined by other
• The ozone layer is contained within the
• In this layer ozone concentrations are about 2 to
8 parts per million, which is much higher than in
the lower atmosphere but still very small
compared to the main components of the
• It is mainly located in the lower portion of the
stratosphere from about 15–35 km, though the
thickness varies seasonally and geographically.
• About 90% of the ozone in our atmosphere is
contained in the stratosphere.
• A magnetosphere is that area of space,
around a planet, that is controlled by the
planet's magnetic field.
• It prevents most of the particles from the Sun,
carried in the solar wind, from hitting the
• The Sun and other planets have
magnetospheres, but the Earth has the
strongest one of all the rocky planets.
• The Earth's magnetosphere is a highly
dynamic structure that responds dramatically
to solar variations.
• The ionosphere, the part of the atmosphere
that is ionized by solar radiation,
• stretches from 50 to 1,000 km
• and typically overlaps both the exosphere and
• It forms the inner edge of the magnetosphere.
• It has practical importance because it
influences, for example, radio propagation on
planetary boundary layer
• The planetary boundary layer is the part of
the troposphere that is nearest the Earth's
surface and is directly affected by it, mainly
through turbulent diffusion.
• During the day the planetary boundary layer
usually is well-mixed, while at night it
becomes stably stratified with weak or
• The depth of the planetary boundary layer
ranges from as little as about 100 m on clear,
calm nights to 3000 m or more during the
afternoon in dry regions.
• When light passes through our atmosphere,
photons interact with it through scattering.
• If the light does not interact with the
atmosphere, it is called direct radiation and is
what you see if you were to look directly at the
• Indirect radiation is light that has been
scattered in the atmosphere.
• Different molecules absorb different wavelengths
• For example, O2 and O3 absorb almost all
wavelengths shorter than 300 nanometres'.
• Water (H2O) absorbs many wavelengths above
• When a molecule absorbs a photon, it increases
the energy of the molecule.
• We can think of this as heating the atmosphere,
but the atmosphere also cools by emitting
• Emission is the opposite of absorption, it is
when an object emits radiation.
• Objects tend to emit amounts and
wavelengths of radiation depending on their
"black body" emission curves, therefore hotter
objects tend to emit more radiation, with
• Colder objects emit less radiation, with longer
• The greenhouse effect is directly related to this
absorption and emission (or "blanket") effect.
• Some chemicals in the atmosphere absorb and
emit infrared radiation, but do not interact with
sunlight in the visible spectrum.
• Common examples of these chemicals are CO2
• If there are too much of these greenhouse gases,
sunlight heats the Earth's surface, but the gases
block the infrared radiation from exiting back to
• This imbalance causes the Earth to warm, and
thus climate change.
• Atmospheric circulation is the large-scale
movement of air through the troposphere,
and the means by which heat is distributed
around the Earth.
• The large-scale structure of the atmospheric
circulation varies from year to year, but the
basic structure remains fairly constant