Environmental Chemistry

Stratosphere – Definition and Characteristics

Stratosphere – Definition and Characteristics

Our atmosphere supports life on Earth. The atmosphere consists of thin layers of gases. These gases form the 5 layers of the atmosphere from top to bottom. These layers are named in sequence as -1) Troposphere 2) Stratosphere 3)Mesosphere 4) Ionosphere & 5) Exosphere. The stratosphere is the second most layer of the atmosphere spreading up to the height of about 50 km from the surface of the earth and is ideal for flying aircraft.

stratosphere

Source: pixabay.com

Characteristics of Stratosphere

1. Height 

It extends up to a height of 10 to 50 km. From the earth’s surface. The average height is however 40 km. At the poles, the stratosphere starts at about 8 km. So it is nearest to the poles.

2. Temperature Inversion

The lower layers of the stratosphere are colder & as we move upwards, the upper layers become hotter. This is different from troposphere & other layers of the atmosphere, where the temperature falls with the increase in height. This fall in temperature in the stratosphere, as we move upwards is temperature inversion.

Therefore, there are two different layers or strata of temperatures in the stratosphere, colder and warmer. This is the reason why the stratosphere name is given.

3. Calm & stable layer

The stratosphere is a very calm & stable layer unlike the troposphere, which is a turbulent layer. This layer is calm and stable because of the absence of any vertical air currents. The reason for this is that the vertical air current flows from the warmer (lower ) layer to the colder (upper) layer.

In the troposphere, the vertical air always flows upwards due to the presence of convection currents. But in the stratosphere, there is temperature inversion so there is no or little flow of vertical air current upwards. This is the reason for the calmness of the stratosphere. In other words, the stratosphere is free from any weather disturbances.

4. Suitable for flying aircraft

The stratosphere is free from any weather disturbance like a thunderstorm, clouds, turbulence, etc. This is because of the absence of any conventional current flow, as explained above. Therefore, this layer is suitable for flying jet aircraft. The aircraft always flow up to a height of above 10 km.

5. The flow of jet streams

However, this layer is characterized by the flow of horizontal air currents called jet streams. These jet streams are fast-flowing streams of current flowing from west to east direction. Jet streams have a speed of about 340 km/hr. the air crafts which are flying from west to east get a boost in their velocity by a push from jet streams.

Thus, they are able to save on time & fuel costs. For example, a flight from London(Europe) to New York (America) takes lesser time than a flight from New York to London because of a jet stream.

6. Region of ozone formation

Stratosphere is the region where about 90 % of ozone is formed. Ozone (chemical formula: O3 ) is a gas that is formed by the action of the sun’s rays on oxygen present in the stratosphere.

Ozone is important as it absorbs harmful ultraviolet rays of the sun. Ultraviolet rays destroy human cells and are harmful to life on earth. Thus stratosphere supports life on the earth.

Thus, we can conclude that stratosphere the second most layer is very important for the survival of humans and also it is important for the jet aircrafts.

Questions on Stratosphere

Q. Why the use of chlorofluorocarbons is banned worldwide?

Ans: Chlorofluorocarbons were widely used in refrigerators, fire extinguishers, etc. A few years a hole had been found in the atmosphere, over Antarctica by the scientists. The reason for the hole was the destruction of ozone by chlorofluorocarbons. This allowed the harmful UV rays from the sun to reach the earth’s surface. So, in 1996 the use of chlorofluorocarbons was banned worldwide.

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