Definition

Lower part of the terrestrial ATMOSPHERE, extending from the surface up to a HEIGHT varying from about 9 km at the POLES to about 17 km at the EQUATOR, in which temperature de­creases fairly regularly with HEIGHT. From an analogy with the ATMOSPHERE, the term is sometimes applied in OCEANOG­RAPHY to the upper ocean layer of relatively high temperature that is found in middle and lower LATITUDES and within which strong CURRENTS are present. See STRATOSPHERE.