what is atmosphere? write in brief with data about its structure.
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Earth is enveloped by a deep blanket of gases extending several thousands of kilometres above its surface. This gaseous cover of the earth is known as the atmosphere.
Compared to the earth’s radius, the atmosphere appears to be only a very thin layer of gases. However, because of the force of gravity, it is inseparable from the earth.
Oxygen
Oxygen, although constituting only 21% of total volume of atmosphere, is the most important component among gases. All living organisms inhale oxygen. Besides, oxygen can combine with other elements to form important compounds, such as, oxides. Also, combustion is not possible without oxygen.
Nitrogen
Nitrogen accounts for 78% of total atmospheric volume. It is a relatively inert gas, and is an important constituent of all organic compounds. The main function of nitrogen is to control combustion by diluting oxygen. It also indirectly helps in oxidation of different kinds.
Carbon dioxide
The third important gas is Carbon Dioxide in dry air and is a product of combustion. Green plants, through photosynthesis, absorb carbon dioxide from the atmosphere and use it to manufacture food and keep other bio-physical processes going.
Being an efficient absorber of heat, carbon dioxide is considered to be of great climatic significance. Carbon dioxide is considered to be a very important factor in the heat energy budget.
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Explanation:
. This gaseous cover of the earth is known as the atmosphere.
Compared to the earth’s radius, the atmosphere appears to be only a very thin layer of gases. However, because of the force of gravity, it is inseparable from the earth.
Composition of atmosphere
The atmosphere is a mixture of many gases. In addition, it contains huge numbers of solid and liquid particles, collectively called ‘aerosols’.
Some of the gases may be regarded as permanent atmospheric components which remain in fixed proportion to the total gas volume.
Other constituents vary in quantity from place to place and from time to time. If the suspended particles, water vapour and other variable gases were excluded from the atmosphere, then the dry air is very stable all over the earth up to an altitude of about 80 kilometres.
Oxygen
Oxygen, although constituting only 21% of total volume of atmosphere, is the most important component among gases. All living organisms inhale oxygen. Besides, oxygen can combine with other elements to form important compounds, such as, oxides. Also, combustion is not possible without oxygen.
Nitrogen
Nitrogen accounts for 78% of total atmospheric volume. It is a relatively inert gas, and is an important constituent of all organic compounds. The main function of nitrogen is to control combustion by diluting oxygen. It also indirectly helps in oxidation of different kinds.
Carbon dioxide
The third important gas is Carbon Dioxide in dry air and is a product of combustion. Green plants, through photosynthesis, absorb carbon dioxide from the atmosphere and use it to manufacture food and keep other bio-physical processes going.
With increased burning of fossil fuels – oil, coal and natural gas – the carbon dioxide percentage in the atmosphere has been increasing at an alarming rate.
Water Vapour
Water Vapour is one of the most variable gaseous substances present in atmosphere – constituting between 2% and 4% of the total volume (in cold dry and humid tropical climates respectively).
Water vapour is the source of precipitation and clouds. On condensation, it releases latent heat of condensation —the ultimate driving force behind all storms.
Soild Particles
The Solid Particles present in the atmosphere consist of sand particles (from weathered rocks and also derived from volcanic ash), pollen grains, small organisms, soot, ocean salts; the upper layers of the atmosphere may even have fragments of meteors which got burnt up in the atmosphere. These solid particles perform the function of absorbing, reflecting and scattering the radiation.
Structure of atmosphere
The atmosphere can be studied as a layered entity – each layer having its own peculiar characteristics. These layers are systematically discussed below.
Troposphere
The fall in temperature is called ‘lapse rate’. (more about this in future posts)
The troposphere is marked by temperature inversion, turbulence and eddies.
It is also meteorologically the most significant zone in the entire atmosphere (Almost all the weather phenomena like rainfall, fog and hailstorm etc. are confined to this layer).
Stratosphere
It lies beyond troposphere, up to an altitude of 50 km from the earth’s surface.
The temperature in this layer remains constant for some distance but then rises to reach a level of 0°C at 50 km altitude.
This rise is due to the presence of ozone (harmful ultraviolet radiation is absorbed by ozone).
Mesosphere
This is an intermediate layer beyond the ozone layer and continues upto an altitude of 80 km from the earth’s surface.
The temperature gradually falls to -100°C at 80 km altitude.
Meteorites burn up in this layer on entering from the space.
Thermosphere
In thermosphere temperature rises very rapidly with increasing height.
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.
Person would not feel warm because of the thermosphere’s extremely low pressure.
Aurora’s are observed in lower parts of this layer.
Exosphere
This is the uppermost layer of the atmosphere extending beyond the ionosphere above a height of about 400 km.
The air is extremely rarefied and the temperature gradually increases through the layer.
Light gases like helium and hydrogen float into the space from here.