The troposphere is the first earth’s atmosphere layer.
"It contains about 80% of the mass of the atmosphere. It has high concentrations of water and low concentrations of ozone. The weather is in the troposphere with temperature going as low as -55."
(Air transport, global warming and the environment, Editorial, Transportation Research Part D, Elsevier, 2009)
It is "the lower atmosphere, to a height of 8-15 km above Earth, where temperature generally decreases with altitude, clouds form, precipitation occurs, and convection currents are active".
(http://virtualskies.arc.nasa.gov/glossary/T.html)
=> In brief page