Everything which surrounds us may collectively be termed as the

Environment.

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 environment are:1. Atmosphere or the air 2. Hydrosphere or the water3. Lithosphere or the rocks and soil4. 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.

WindA big layer of air called the atmosphere surrounds

the Earth. 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 weather

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

possible.

• 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 troposphere.

Earth's atmosphere is made up of many different chemicals, most of them in very small amounts.

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 chlorofluorocarbons (CFC's).

http://en.wikipedia.org/wiki/File:Atmosphere_gas_proportions.svg

• The atmosphere of Earth is a layer of gases surrounding the planet , that is retained by Earth's gravity.

• 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.

Troposphere

• The first layer is called the troposphere. • People, plants, animals, and insects live in the

troposphere. • 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.

Stratosphere. • 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, including people.

Mesosphere.

• The third layer is called the mesosphere.• The mesosphere begins 50km above the

earth's surface. • Temperatures are warmest at the lowest level

of the mesosphere and coldest at its highest level.

Thermosphere

• 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 sun's energy.

• The increase in temperature stops at this height, beyond which lies the exosphere.

http://en.wikipedia.org/wiki/File:Earth's_atmosphere.svg

Exosphere

• The exosphere is the highest layer of the atmosphere.

• 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 safety blanket.

• 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.

Other layersWithin the five principal layers determined by temperature

are several layers determined by other properties

ozone• The ozone layer is contained within the

stratosphere. • 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 atmosphere.

• 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.

magnetosphere• 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 Earth.

• 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.

Ionosphere• 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

the thermosphere. • It forms the inner edge of the magnetosphere. • It has practical importance because it

influences, for example, radio propagation on the Earth.

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 intermittent mixing.

• 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.

Physical properties

Scattering• 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 Sun.

• Indirect radiation is light that has been scattered in the atmosphere.

Absorption

• Different molecules absorb different wavelengths of radiation.

• For example, O2 and O3 absorb almost all wavelengths shorter than 300 nanometres'.

• Water (H2O) absorbs many wavelengths above 700 nm.

• 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 radiation.

Emission• 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 shorter wavelengths.

• Colder objects emit less radiation, with longer wavelengths.

• 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 and H2O.

• 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 space.

• This imbalance causes the Earth to warm, and thus climate change.

Circulation• 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