atmospheric layer

Each of the layers into which the atmosphere is divided for study purposes. Their number varies, depending on the criterion used. The most common division is into five layers (from bottom to top: troposphere, stratosphere, mesosphere, thermosphere, and exosphere), based on the vertical distribution of temperature. The number of layers is reduced to two if what is taken into account are physico-chemical properties (ozonosphere and ionosphere) or composition (heterosphere and homosphere).