The Troposphere is the lowermost portion of Earth's atmosphere.
It is the densest layer of the atmosphere and contains approximately 75 percent of the mass of the atmosphere and almost all the water vapor and aerosol.
The troposphere extends from the Earth's surface up to the tropopause where the stratosphere begins.
The depth of the troposphere is greatest in the tropics (about 16km) and smallest at the poles (about 8km).
The lower part, where friction on the Earth's surface influences with air flow, is the planetary boundary layer or peploshere which is 2 km deep on average, dependent on the landform, and which is separated from the rest of the tropospere by the capping inversion layer.