Write a short note on the following layers of atmoshere.
(a) Troposphere
(b) Stratosphere

Explanation

(a) Troposphere
(i) The layer of atmophere which begin at the earth's surface and exteds up to 20 km hight above the surface is called troposphere.
(ii) It holds the maximum percentage of the total mass of the atmosphere.
(iii) The density of the air the temperature gradually decrease with height. As we move to the upper layers the temperture drops from about `17^(@)C" to "-51^(@)C`. The fall in temperature with increse in height at the rate of `6^(@)"C/km"` is called lapse rate.
(iv) Most of the weather phenomena occur in this layer due to repai variation in temperature.
(v) The height and thickness of this layer cvaries from the equator to the poles.
(b) Stratosphere
(i) The layer of atmosphere above the troposphere which extends up to 50 km above the earth's surgace is called stratophere.
(ii) It holds 19% of the atmopheric gases.
(iii) Temperature does not alter much up to a height of about 25 km from the earth's surface. Above this, temperature increases with hight due to the absorption of highly energetic UV rediations. Here thetemperature rises from `60^(@)C" to "-15^(@)C`. This increase of temperature with height is called Incersion layer. The region that extends from 25 km to 40 km above the earth's surface is called ozonosphere or ozone layer. This absorbs harmful UV radiations and thus protects life on the earth.
(iv) Aerophanes fly in this layer.