What kind of layers in the atmosphere?

• There are five distinct layer of the atmosphere:

Troposphere

Stratosphere

Mesosphere

Thermosphere

Exosphere

• Troposphere

This is the first layer of the atmosphere. It extends to a height of 18 km at the equator and 8 km at the poles.

In this layer temperature decreases with the height. This is due to the fact that the density of air decreases with height and so the heat absorbed is less. It contains more than 90% of gases in the atmosphere.

Since most of the water vapour form clouds in this layer, all weather changes occur in the troposphere (‘tropo’ means ‘change’).

The height at which the temperature stops decreasing is called tropopause. Here the temperature may be as low as -58 degree Celsius.

• Stratosphere

This is the second layer of the atmosphere. It extends from the tropopause to about 50 km.

Temperature increases due to the absorption of the ultraviolet radiation of the sun by ozone present in this layer. The temperature slowly increases to 4 degree Celsius.

This layer is free from clouds and associate weather phenomena. Hence it provides ideal flying conditions for large jet planes.

At about 50 km the temperature begins to fall again. This marks the end of the stratosphere. The end of the stratosphere is called the stratopause.

• Mesosphere

Above the stratosphere lies the mesosphere.

The mesosphere extends to a height of 80 km.

Here the temperature decreases again, falling as low as -90 degree Celsius.

The end of this layer is known as the mesopause.

• Thermosphere

The thermosphere lies above the mesosphere.

This layer extends to a height of about 640 km.

In this layer temperature rises dramatically reaching upto 1480 degree Celsius.

This increase in temperature is due to the fact that the gas molecules in this layer absorb the x-rays and ultraviolet radiation of the sun.

This results in the break up of the gas molecules into positively and negatively charged particles or ions. Thus, this layer is also known as the ionosphere.

The electricity charged gas molecules of the thermosphere reflect radio waves from the earth back into space. Thus this layer also helps in long distance communications.

The thermosphere also protects us from meteors and obsolete satellites, because its high temperature burns up nearly all the debris coming towards the earth.

• Exosphere

This layer lies above the thermosphere.

The exosphere extends beyond the thermosphere upto 960 km.

It gradually merges with interplanetary space.

The temperature in this layer range from about 300 degree Celsius to 1650 degree Celsius.

This layer contains only traces of gases like oxygen, nitrogen, argon and helium because the lack of gravity allows the gas molecules to escape easily into space.