Tropopause

Article By:

Murgatroyd, R. J. Meteorological Office, Bracknell, United Kingdom.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.712100

The boundary between the troposphere and the stratosphere in the atmosphere. The tropopause is broadly defined as the lowest level above which the lapse rate (decrease) of temperature with height becomes less than 6°F/mi (2°C/km). In low latitudes the tropical tropopause is at a height of 9–10.5 mi or 15–17 km (−135°F or 180 K) and the polar tropopause between tropics and poles is at about 6 mi or 10 km (−63°F or 220 K). There is a well-marked “tropopause gap” or break where the tropical and polar tropopause overlap at 30–40° latitude. The break is in the region of the subtropical jet stream and is of major importance for the transfer of air and tracers (humidity, ozone, radioactivity) between stratosphere and troposphere. Tropopause breaks also occur in the neighborhood of polar jet streams. The height of the tropopause varies seasonally and also daily with the weather systems, being higher and colder over anticyclones than over depressions. The detailed vertical temperature structure is often complex, showing multiple or laminated tropopauses and it is often difficult to decide on the precise height of the tropopause, particularly in winter at high latitudes. See also: Air temperature; Atmosphere; Radio-wave propagation; Stratosphere; Troposphere

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