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A '''capping inversion''' is an elevated inversion layer that caps a convective [[boundary layer]], keeping the convective elements from rising higher into the atmosphere.
{{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.
==External Links==

* [http://www.nsdl.arm.gov/Library/glossary.shtml#Capping_inversion National Science Digital Library - Capping Inversion]
An inversion occurs when the normal temperature (warm air below, cold air above) profile is reversed, creating a 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). 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> EMLs 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>

==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]]


{{Meteorology-stub}}

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

Latest revision as of 06:25, 8 November 2023

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.
Diagram showing the daily changes to the capping inversion on top of Earth's planetary boundary layer.

A capping inversion is an elevated 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. Thermals form when this warm air rises into the cold air (warm air is less 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 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). 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.[1] If the capping inversion layer or "cap" is too strong it will prevent thunderstorms from developing. A strong cap can result in foggy conditions.

However, if the air at the surface is unstable enough, strong updrafts can be forced through the capping inversion. This selective process of only allowing the strongest updrafts to form thunderstorms 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.[2][3] In some severe weather events, this capping inversion can emerge when a warm and dry mixed layer originating over a high plateau moves over a cooler and moister airmass, forming an "elevated mixed layer" (EML).[4] EMLs 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.[4][5]

See also

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References

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  1. ^ Bailey, Adriana; Chase, Thomas N.; Cassano, John J.; Noone, David (June 2011). "Changing Temperature Inversion Characteristics in the U.S. Southwest and Relationships to Large-Scale Atmospheric Circulation". Journal of Applied Meteorology and Climatology. 50 (6): 1307–1323. doi:10.1175/2011JAMC2584.1. Free access icon
  2. ^ Carlson, Toby N.; Farrell, Robert J. (1983). "The Lid Strength as an Aid in Predicting Severe Local Storms" (PDF). National Weather Digest. 8 (2). National Weather Association: 27–39. Retrieved 22 May 2022.
  3. ^ Banacos, Peter C.; Ekster, Michael L. (1 August 2010). "The Association of the Elevated Mixed Layer with Significant Severe Weather Events in the Northeastern United States*". Weather and Forecasting. 25 (4). American Meteorological Society: 1082–1102. Bibcode:2010WtFor..25.1082B. doi:10.1175/2010WAF2222363.1. Free access icon
  4. ^ a b Carlson, T. N.; Benjamin, S. G.; Forbes, G. S.; Li, Y-F. (July 1983). "Elevated Mixed Layers in the Regional Severe Storm Environment: Conceptual Model and Case Studies". Monthly Weather Review. 111 (7): 1453–1474. doi:10.1175/1520-0493(1983)111<1453:EMLITR>2.0.CO;2. Free access icon
  5. ^ Ribeiro, Bruno Z.; Bosart, Lance F. (January 2018). "Elevated Mixed Layers and Associated Severe Thunderstorm Environments in South and North America". Monthly Weather Review. 146 (1): 3–28. doi:10.1175/MWR-D-17-0121.1. Free access icon
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