Troposphere

From the Greek word tropos, meaning turning, troposphere is the zone of moisture-laden storms between the surface and the stratosphere above. Because ice crystals must form before precipitation can begin, the troposphere rises to 10–12 mi (16–19 km) over the equator but grades downward to 5–6 mi (8–9 km) over the poles. It is marked by a sharp drop in temperature vertically, averaging 3.5 degrees per 1,000 ft (305 m) because of exponentially decreasing density of air molecules. Actual "lapse" rates vary enormously, ranging from inversions, where temperatures rise and trap pollutants, to steep lapse rates with warm surface air topped by very cold polar air; the latter produces dangerous storms.

troposphere The layer of the atmosphere between the Earth's surface and the tropopause, within which the air temperature on average decreases with height at a rate of about 6.5°C/km, though variations that sometimes occur include inversions (temperature increase with height within some limited layer). Most of the atmospheric turbulence and weather features occur in this layer, which contains almost all the atmospheric water vapour and most of the aerosols in suspension in the atmosphere (although there is also an important aerosol layer at about 22 km). See also ATMOSPHERIC STRUCTURE.

troposphere The layer of the atmosphere between the Earth's surface and the tropopause, within which the air temperature on average decreases with height at a rate of about 6.5°C/km, though variations that sometimes occur include inversions (temperature increase with height within some limited layer). Most of the atmospheric turbulence and weather features occur in this layer, which contains almost all the atmospheric water vapour and most of the aerosols in suspension in the atmosphere (although there is also an important aerosol layer at about 22 km).

trop·o·sphere / ˈträpəˌsfi(ə)r; ˈtrō-/ • n. the lowest region of the atmosphere, extending from the earth's surface to a height of about 6–10 km (the lower boundary of the stratosphere).DERIVATIVES: trop·o·spher·ic / ˌträpəˈsfi(ə)rik; -ˈsferik; ˌtrō-/ adj.

troposphere The lowest level of the earth's atmosphere, extending from the earth's surface to a height of about 10 km (its thickness varies from 7 km at the poles to 28 km at the equator). Within the troposphere temperature falls with increasing height, although temperature inversions can occur.