Editing Capping inversion

{{Short description|Elevated inversion layer that caps the part of the atmosphere closest to the ground}}
{{no footnotes|date=March 2013}}
[[File:Kreuzberg (Rhoen).JPG|thumb|right|A capping inversion limits the vertical development of clouds. In this image taken near [[Kreuzberg (Rhön)]], the inversion is below the top of the mountain tops.]]
[[File:Atmospheric boundary layer.svg|thumb|Diagram showing the daily changes to the capping inversion on top of Earth's [[planetary boundary layer]].]]
A '''capping inversion''' is an elevated [[Inversion (meteorology)|inversion layer]] that caps a convective [[planetary boundary layer]].

The boundary layer is the part of the atmosphere which is closest to the ground.  Normally, the sun heats the ground, which in turn heats the air just above it.  [[Thermal]]s form when this warm air rises into the cold air (warm air is less [[density|dense]] than cold air), a process called [[convection]]. A convective layer such as this has the potential for cloud formation, since [[condensation]] occurs as the warm air rises and cools. An inversion occurs when the normal temperature (warm air below, cold air above) profile is reversed, creating a [[atmospheric stability|stable configuration]] of dense, cold air sitting below lighter, warm air. An elevated inversion layer is thus a region of warm air above a region of cold air, but higher in the atmosphere (generally not touching the surface).

A capping inversion occurs when there is a boundary layer with a normal temperature profile (warm air rising into cooler air) and the layer above that is an inversion layer (cooler air below warm air). Inversions can develop under [[high pressure area]]s. Downward motion within these systems can cause warming aloft, producing a capping inversion.<ref name="MetOffice">{{cite web |title=What is a temperature inversion? |url=https://weather.metoffice.gov.uk/learn-about/weather/types-of-weather/temperature/temperature-inversion |publisher=Met Office |access-date=25 April 2025}}</ref>

Cloud formation from the lower layer is "capped" by the inversion layer. [[Air stagnation]] may result from a capping inversion from diffusing from a region, increasing the concentration of pollutants and exacerbating poor [[air quality]].<ref name="Bailey et al. 2011">{{cite journal |last1=Bailey |first1=Adriana |last2=Chase |first2=Thomas N. |last3=Cassano |first3=John J. |last4=Noone |first4=David |title=Changing Temperature Inversion Characteristics in the U.S. Southwest and Relationships to Large-Scale Atmospheric Circulation |journal=Journal of Applied Meteorology and Climatology |date=June 2011 |volume=50 |issue=6 |pages=1307–1323 |doi=10.1175/2011JAMC2584.1|doi-access=free }} {{free access}}</ref> If the capping inversion layer or "cap" is too strong it will prevent thunderstorms from developing. A strong cap can result in [[fog]]gy conditions.

However, if the air at the surface is [[convective instability|unstable]] enough, strong updrafts can be forced through the capping inversion.  This selective process of only allowing the strongest updrafts to form [[thunderstorm]]s often results in outbreaks of [[severe weather]]. The role of capping inversions in bolstering the intensity of severe weather was realized in conceptual models that were developed by atmospheric science researchers in the late 1960s and had been recognized as a characteristic of tornado-producing airmasses as early as 1954.<ref>{{cite journal |last1=Carlson |first1=Toby N. |last2=Farrell |first2=Robert J. |title=The Lid Strength as an Aid in Predicting Severe Local Storms |journal=National Weather Digest |date=1983 |volume=8 |issue=2 |pages=27–39 |url=http://nwafiles.nwas.org/digest/papers/1983/Vol08No2/1983v008no02-Carlson-Farrell.pdf |access-date=22 May 2022 |publisher=National Weather Association}}</ref><ref>{{cite journal |last1=Banacos |first1=Peter C. |last2=Ekster |first2=Michael L. |title=The Association of the Elevated Mixed Layer with Significant Severe Weather Events in the Northeastern United States* |journal=Weather and Forecasting |date=1 August 2010 |volume=25 |issue=4 |pages=1082–1102 |doi=10.1175/2010WAF2222363.1 |publisher=American Meteorological Society|bibcode=2010WtFor..25.1082B |doi-access=free }} {{free access}}</ref> In some severe weather events, this capping inversion can emerge when a warm and dry [[Mixed layer#Atmospheric mixed layer|mixed layer]] originating over a high [[plateau]] moves over a cooler and moister airmass, forming an "elevated mixed layer" (EML).<ref name="Carlson et al. 1983">{{cite journal |last1=Carlson |first1=T. N. |last2=Benjamin |first2=S. G. |last3=Forbes |first3=G. S. |last4=Li |first4=Y-F. |title=Elevated Mixed Layers in the Regional Severe Storm Environment: Conceptual Model and Case Studies |journal=Monthly Weather Review |date=July 1983 |volume=111 |issue=7 |pages=1453–1474 |doi=10.1175/1520-0493(1983)111<1453:EMLITR>2.0.CO;2|doi-access=free }} {{free access}}</ref> ENLs can be identified in [[Atmospheric sounding|radiosonde soundings]] by their steep temperature [[lapse rate]]s and an increase in [[relative humidity]] from the bottom to the top of the layer.<ref>{{cite journal |last1=Banacos |first1=Peter C. |last2=Ekster |first2=Michael L. |title=The Association of the Elevated Mixed Layer with Significant Severe Weather Events in the Northeastern United States |journal=Weather and Forecasting |date=1 August 2010 |volume=25 |issue=4 |pages=1082–1102 |doi=10.1175/2010WAF2222363.1|doi-access=free}}</ref> They can be found worldwide downwind of high terrain, such as over [[South Asia]], eastern Australia, east of the [[Rocky Mountains]] in the central U.S. and northern [[Mexico]], and east of the foothills of the [[Andes]].<ref name="Carlson et al. 1983" /><ref name="Ribeiro and Bosart 2018">{{cite journal |last1=Ribeiro |first1=Bruno Z. |last2=Bosart |first2=Lance F. |title=Elevated Mixed Layers and Associated Severe Thunderstorm Environments in South and North America |journal=Monthly Weather Review |date=January 2018 |volume=146 |issue=1 |pages=3–28 |doi=10.1175/MWR-D-17-0121.1|doi-access=free }} {{free access}}</ref> The [[Spanish plume]] weather pattern over western and central Europe, commonly associated with strong thunderstorm events, is also associated with an EML.<ref>{{cite journal |last1=Schultz |first1=David M. |last2=Young |first2=Martin V. |last3=Kirshbaum |first3=Daniel J. |title=The “Spanish Plume” Elevated Mixed Layer: Review of its Use and Misuse within the Scientific Literature |journal=Monthly Weather Review |date=25 February 2025 |doi=10.1175/MWR-D-24-0139.1|doi-access=free}}</ref>

==See also==
*[[Convective available potential energy]]
*[[Convective inhibition]]

==References==
{{Reflist}}

== External links ==
*[https://web.archive.org/web/20070817100924/http://amsglossary.allenpress.com/glossary/search?id=capping-inversion1 Capping Inversion] - AMS Glossary of Meteorology
*[https://web.archive.org/web/20070409061401/http://education.arm.gov/nsdl/Library/glossary.shtml#Capping_inversion#Capping_inversion Capping Inversion] - National Science Digital Library

{{Meteorological variables}}

[[Category:Boundary layer meteorology]]
[[Category:Atmospheric thermodynamics]]

[[fr:Couche d'inversion#Inhibition de la convection]]