Troposphere

Troposphere, lowermost zone of the earth's atmosphere, extending from the earth's surface up to 5–6 mi (8–9 km) over the poles and 8–10 mi (12.8–16 km) over the equator. In this zone normal lapse rates prevail, i.e., temperatures decrease with altitude. The top of the troposphere is called the tropopause.

See also: Atmosphere.