The Earth’s atmosphere is divided into four layers or ‘spheres’. Each layer is characterized by a different gradient of the temperature as a function of altitude.
The troposphere (between 0 and about 15 kilometers) is the first layer above the Earth’s surface and contains approximately 85 to 90 % of the mass of the Earth’s atmosphere. It is characterized by decreasing temperature with increasing altitude.
The troposphere’s thermal profile is largely the result of the heating of the Earth’s surface by incoming solar radiation. Heat is then transferred up through the troposphere by a combination of convective and turbulent transfer. Weather occurs in the Earth’s troposphere.
In the stratosphere (between approximately 15 and 50 km) the temperature rises as a function of increasing height.
This warming is the result of the direct absorption of solar radiation by the ozone layer, thereby preventing a large part of harmful ultraviolet radiation from the sun to reach the Earth’s surface.
The mesosphere is the next layer of the atmosphere (from 50 to 90 km), characterized by temperatures that decrease the further up one goes to an average of -90°C.
A lot of meteors burn up in this layer while entering the Earth’s atmosphere.
Thereafter the thermosphere takes over where temperatures increases steadily with altitude. It is the layer of the atmosphere which is first exposed to the Sun’s radiation.
The thermosphere also includes the ionosphere, a region of the atmosphere that is filled with charged particles, where especially the auroras occur.
The upper limit of Earth’s atmosphere is the exosphere where the atmosphere merges into space.