Monday 21 January 2013

The Atmosphere


Atmosphere:

The atmosphere is a very thin layer of air and moisture around the Earth.
 

The atmosphere itself is not physically uniform but has significant variations in temperature and pressure with altitude, which define a number of atmospheric layers. These include:

1.     Troposphere:  (0 to 16 km) is closest to Earth’s surface. It contains 78% Nitrogen, 21% Oxygen, small amounts of gases like Argon, Carbon dioxide and most of the atmosphere’s moisture and plays a vital role in our weather system.

2. Stratosphere: (16 to 50 km) is dry and contains higher concentration of Ozone than any other layer.

3. Mesosphere (50 to 80km) has similar composition with the exception of moisture and ozone. Here, the density and temperature of these gases are very low

4. Thermosphere (80 to 640km) is made up of two layers, one is Ionosphere where high-energy electromagnetic waves from Sun are absorbed causing particles to become electrically charged ions. The other outer layer is Exosphere containing very few particles mainly Hydrogen.

The boundaries between these four layers are defined by abrupt changes in temperature, and are as follows:

1.      Tropopause,
 
2.     Stratopause
 
3.     Mesopause.

 In the troposphere and mesosphere, temperature generally falls with increasing altitude, whilst in the stratosphere and thermosphere, temperature rises with increasing altitude.

 
 

Ozone (O3), or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. The highest levels of ozone in the atmosphere are in the stratosphere, in a region also known as the ozone.
Ozone Depletion in the Stratosphere 

Ozone depletion takes place when more ozone is destroyed than produced leading to an overall destruction of stratospheric ozone. Ozone loss can occur naturally for a shorter period of time but chlorine and bromine released from man-made synthetic compounds are now considered and acknowledged  as the main cause of Ozone depletion.
 
 

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