What are the divisions in earths atmosphere primarily based upon

Temperatures gradient

Explanation:

There are distinct temperature gradient differences in the layers of atmosphere usually due to the main air molecule composition of the layers, the density of the molecules. The Troposphere the lowest layers is the densest and temperature decreases with increase in altitude. The stratosphere, on the other hand, has an increase in temperature with increase in altitude. Temperatures decrease with altitude in the mesosphere while the parameter increases with altitude in the thermosphere.