This is the lowest layer of the atmosphere.

The height of this layer is about 18 kms on the equator and 8 kms on the poles.

The main reason of higher height at the equator is due to presence of hot convection currents that push the gases upward.

This is the most important layer of the atmosphere because all kinds of weather changes take place only in this layer.

Due to these changes development of living world take place on the earth. The air never remains static in this layer.

Therefore this layer is called changing sphere or troposphere.

The environmental temperature decreases with increasing height of atmosphere.

It decreases at the rate of 10C at the height of 165 metre. This is called Normal lapse rate.

The upper limit of the troposphere is called tropopause. This is a transitional zone.

In tropopause characteristics of both the troposphere and stratosphere are found.