Atmosphere & their Structure

Atmosphere & their Structure

Atmosphere:

•  It is a colourless, tasteless and odourless mixture of gases that
  surround the earth.
•  It extends up to a height of about 1600 km.
• However 99 per cent of total mass of the atmosphere is within
  40 km from the earth.

• Structure of atmosphere: Based on vertical temperature differences

I. Troposphere:

• It is the lower layer of atmosphere
•  Extending up to a height of 8 to 18 km from the earth surface. (RPSC, AA0-09).
• Temperature decreases with increase in altitude at the rate of 6 ‘V /km.
• It influences earth climate.
• It is dense part of atmosphere, contains 85 per cent of the atmosphere’s mass.
•  All weather phenomena like clouds, rain, mist, fog, dew etc. occur in troposphere. (JRF, Ph. D -09)

2. Stratosphere:

•  It lies beyond the height of 8 to 18 km extending up to 50 km.
•  Warmest layer, Uniform temperature with altitude.
• It is the actual seat of most of the photochemical reactions in air.
• Presence of Ozone layer, hence also called ozonosphere

3. Mesosphere:

•  It lies above the stratosphere; a height of 50 km extending up to 80 km from the earth surface.
•  Cold region.
• Strong decrease in temperature with increase in altitude.

4. Thermosphere:

•  It is the outermost layer called exosphere.
•  From earth surface extending a height of 80 km up to 1600 km.
•  The lower layer of thermosphere is called ionosphere.
•  Long distance radio communication is made possible through this ionized layer.
•  Temperature increase with altitude.

Composition of atmospheric air:  (Gases Volume  in %)

• Nitrogen -78.08%
• Oxygen -20.95%
• Argon – 0.93% (RPSC,AA 0-09)
• Carbon dioxide – 0.03%

 Composition of soil air :

•  Nitrogen percentage is more or less same as in atmosphere.
•  Oxygen levels decrease as compared to atmosphere.
•  CO2 levels will be nearly 8-10 times more (0.25%) as compare to atmosphere.