The Troposphere is the lowest level of Earth’s atmosphere where we live in. Literally, troposphere means, ‘change’ or ‘turning ball’. The gases in this level turn and mix due to the difference in air temperature and density. Troposphere extends up to 8 to 10 km at the Equator. It acts as a warm blanket to moderate the extremes of the outer space. It contains almost 99% of the water vapor in the atmosphere, which forms clouds and rain.
With the increase of distance from the surface, the temperature decreases everywhere with height at the rate of 6 per km, owing to the decrease air pressure. As a bulk of air moves upwards, it expands because of the lower pressure and when air expands, it cools. So, air higher up is cooler than air lower down. However, actual change of temperature with height varies from day to day, depending on the weather.
The uppermost part of the Troposphere is called the ‘Tropopause’, while the lowest part is called the ‘Boundary layer’. In boundary layer the air motion is determined by the properties of the Earth's surface. As the surface is heated by the Sun, a current of warm air rises up and as the wind blows over the Earth’s surface, turbulence is generated. Turbulence in its turn redistributes heat and moisture, as well as pollutants and other constituents of the atmosphere within the boundary layer.