<P> The troposphere is the lowest layer of Earth 's atmosphere , and is also where nearly all weather conditions take place . It contains approximately 75 % of the atmosphere 's mass and 99 % of the total mass of water vapor and aerosols . The average depths of the troposphere are 20 km ( 12 mi ) in the tropics , 17 km ( 11 mi ) in the mid latitudes , and 7 km ( 4.3 mi ) in the polar regions in winter . The lowest part of the troposphere , where friction with the Earth 's surface influences air flow , is the planetary boundary layer . This layer is typically a few hundred meters to 2 km ( 1.2 mi ) deep depending on the landform and time of day . Atop the troposphere is the tropopause , which is the border between the troposphere and stratosphere . The tropopause is an inversion layer , where the air temperature ceases to decrease with height and remains constant through its thickness . </P>
since we live at the surface of the earth what layer of the atmosphere would this be
troposphere