The various layers in the atmosphere are distinguished, by what happens to the temperature in that particular layer. In this post we shall learn about the layers of the atmosphere which are classified according to their thermal charecterestics. In our previous lesson, we had understood about the Thermal Structure of Atmosphere.
TROPOSPHERE AND TROPOPAUSE
The lowest layer of the atmosphere is called as Troposphere. In the troposphere, temperature falls with height as a result of which temperature reduces with increasing height. The height of troposphere is between 16 to 18 kilometres at the Equator and 8 to 10 kilometres near the Poles. The average height of troposphere is considered as as 11 kilometres.
Tropopause which defines the upper limit of troposphere is the next layer of the atmosphere. Tropopause is an isothermal layer which means the temperature would remain constant with increase in height.
STRATOSPHERE AND STRATOPAUSE
The next layer is called a Stratosphere which extends from the end of tropopause to about 50 kilometres above the earth’s surface. In the stratosphere, temperature tends to increase with height.
The next layer is called as Stratopause which signifies the upper limit of stratosphere. In the Stratopause, the temperature stops increasing any further and is therefore called as an isothermal layer where the temperature remains constant.
MESOSPHERE AND MESOPAUSE
The next layer is called as Mesosphere which extends from the upper limit of Stratopause to about 80 kilometres above the earth’s surface. In the mesosphere, temperature again starts falling with height. By now, you would have guessed that the next layer. The next layer is called as Mesopause, which is an isothermal layer where the temperature remains constant.
THERMOSPHERE – EXOSPHERE
Above the Mesopause, we have the Thermosphere where temperature again starts increasing with height. And finally, we have Exosphere which extends above 700 kilometres from the Earth’s surface. In the Thermosphere, the air density is very low and atmosphere can be considered to be almost absent.
There is a layer called Ionosphere, which is found in the upper levels of Stratosphere. In the Ionosphere, you would find a lot of free ions or free electrons. This Ionospheric layer is responsible for many types of radio wave transmissions and would be discussed in great detail in Radio Navigation.
In this post we have understood about the various layers of the atmosphere. We shall understand about Troposphere and Tropopause in detail in our next lesson where most of our flying activity takes place.