troposphere

https://doi.org/10.1351/goldbook.T06522
The lowest layer of the atmosphere, ranging from the ground to the base of the stratosphere (tropopause) at 10-15 km of altitude depending on the latitude and meteorological conditions. About 70% of the mass of the atmosphere is in the troposphere. This is where most of the weather features occur and where the chemistry of the reactive anthropogenic species released into the atmosphere takes place.
Source:
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2218 (https://doi.org/10.1351/pac199062112167)