troposphere

The lowest of the concentric layers of the atmosphere, occurring between the Earth's surface and the tropopause. It is the zone where atmospheric turbulence is at its greatest and where the bulk of the Earth's weather is generated. It contains almost all the water vapour and aerosols and three-quarters of the total gaseous mass of the atmosphere. Throughout the troposphere temperature decreases with height at a mean rate of 6.5°C/km and the whole zone is capped by either an inversion of temperature or an isothermal layer at the tropopause. (Source: WHIT)