temperature inversion


temperature inversion
Meteorol.
inversion (def. 12).
[1940-45]

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In meteorology, an increase of air temperature with altitude.

Such an increase is a reversal of the normal temperature condition of the troposphere, where temperature usually decreases with altitude. Inversions play an important role in determining cloud forms, precipitation, and visibility. An inversion acts as a lid, preventing the upward movement of the air below it. Where a pronounced inversion is present at a low level, convective clouds cannot grow high enough to produce showers and, at the same time, visibility may be greatly reduced by trapped pollutants (see smog). Because the air near the base of the inversion is cool, fog is frequently present there.

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      a reversal of the normal behaviour of temperature in the troposphere (the region of the atmosphere nearest the Earth's surface), in which a layer of cool air at the surface is overlain by a layer of warmer air. (Under normal conditions air temperature usually decreases with height.)

      Inversions play an important role in determining cloud forms, precipitation, and visibility. An inversion acts as a cap on the upward movement of air from the layers below. As a result, convection produced by the heating of air from below is limited to levels below the inversion. Diffusion of dust, smoke, and other air pollutants is likewise limited. In regions where a pronounced low-level inversion is present, convective clouds cannot grow high enough to produce showers and, at the same time, visibility may be greatly reduced below the inversion, even in the absence of clouds, by the accumulation of dust and smoke particles. Because air near the base of an inversion tends to be cool, fog is frequently present there.

      Inversions also affect diurnal variations in air temperature. The principal heating of air during the day is produced by its contact with a land surface that has been heated by the Sun's radiation. Heat from the ground is communicated to the air by conduction (thermal conduction) and convection. Since an inversion will usually control the upper level to which heat is carried by convection, only a shallow layer of air will be heated if the inversion is low and large, and the rise in temperature will be great.

      There are four kinds of inversions: ground, turbulence, subsidence, and frontal.

      A ground inversion develops when air is cooled by contact with a colder surface until it becomes cooler than the overlying atmosphere; this occurs most often on clear nights, when the ground cools off rapidly by radiation. If the temperature of surface air drops below its dew point, fog may result. Topography greatly affects the magnitude of ground inversions. If the land is rolling or hilly, the cold air formed on the higher land surfaces tends to drain into the hollows, producing a larger and thicker inversion above low ground and little or none above higher elevations.

      A turbulence inversion often forms when quiescent air overlies turbulent air. Within the turbulent layer, vertical mixing carries heat downward and cools the upper part of the layer. The unmixed air above is not cooled and eventually is warmer than the air below; an inversion then exists.

      A subsidence inversion develops when a widespread layer of air descends. The layer is compressed and heated by the resulting increase in atmospheric pressure, and as a result the lapse rate of temperature is reduced. If the air mass sinks low enough, the air at higher altitudes becomes warmer than at lower altitudes, producing a temperature inversion. Subsidence inversions are common over the northern continents in winter and over the subtropical oceans; these regions generally have subsiding air because they are located under large high-pressure centres.

      A frontal inversion occurs when a cold air mass undercuts a warm air mass and lifts it aloft; the front between the two air masses then has warm air above and cold air below. This kind of inversion has considerable slope, whereas other inversions are nearly horizontal. In addition, humidity may be high, and clouds may be present immediately above it.

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Universalium. 2010.

Look at other dictionaries:

  • temperature inversion — temperatūros apgrąža statusas T sritis radioelektronika atitikmenys: angl. temperature inversion vok. Temperatururmkehr, f rus. инверсия температуры, f pranc. inversion de température, f …   Radioelektronikos terminų žodynas

  • temperature inversion — noun Date: 1921 inversion 6 …   New Collegiate Dictionary

  • temperature inversion —   a situation where temperature of air in the lower troposphere increases with height …   Geography glossary

  • temperature inversion — /ˈtɛmprətʃər ɪnˌvɜʒən/ (say tempruhchuh in.verzhuhn) noun an anomalous increase of temperature with height in the troposphere, which is often quite stable and acts as a lid on the air beneath it, trapping haze …   Australian English dictionary

  • temperature inversion — noun : an increase of temperature with height through a layer of air …   Useful english dictionary

  • inversion — [ ɛ̃vɛrsjɔ̃ ] n. f. • 1529; lat. inversio, de invertere « retourner » I ♦ A ♦ Sens spéciaux 1 ♦ Déplacement (d un mot ou d un groupe de mots) par rapport à l ordre normal ou habituel de la construction. Inversion du sujet dans l interrogation (ex …   Encyclopédie Universelle

  • Inversion — In*ver sion, n. [L. inversio: cf. F. inversion. See {Invert}.] [1913 Webster] 1. The act of inverting, or turning over or backward, or the state of being inverted. [1913 Webster] 2. A change by inverted order; a reversed position or arrangement… …   The Collaborative International Dictionary of English

  • Inversion (meteorology) — In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. It almost always refers to a temperature inversion, i.e., an increase in temperature with height, or to the layer within which such an… …   Wikipedia

  • inversion — /in verr zheuhn, sheuhn/, n. 1. an act or instance of inverting. 2. the state of being inverted. 3. anything that is inverted. 4. Rhet. reversal of the usual or natural order of words; anastrophe. 5. Gram. any change from a basic word order or… …   Universalium

  • inversion — In meteorology, a departure from the usual decrease or increase with altitude of the value of an atmospheric property. Also, the layer through which this departure occurs, called the inversion layer, or the lowest altitude at which the departure… …   Aviation dictionary


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