Editing Mesopause

{{Short description|The temperature minimum at the boundary between the mesosphere and the thermosphere}}
{{Distinguish|menopause}}
 
The '''mesopause''' is the point of minimum temperature at the boundary between the [[mesosphere]] and the [[thermosphere]] [[Atmosphere of Earth|atmospheric]] regions. Due to the lack of solar heating and very strong [[radiative cooling]] from [[carbon dioxide]], the mesosphere is the coldest region on Earth with temperatures as low as -100&nbsp;°C (-148&nbsp;°F or 173 [[Kelvin|K]]).<ref>International Union of Pure and Applied Chemistry. "mesosphere". Compendium of Chemical Terminology Internet edition</ref> The altitude of the mesopause for many years was assumed to be at around 85&nbsp;km (53&nbsp;mi), but observations to higher altitudes and modeling studies in the last 10 years have shown that in fact there are two mesopauses - one at about 85&nbsp;km and a stronger one at about 100&nbsp;km (62&nbsp;mi), with a layer of slightly warmer air between them.<ref>{{cite journal|author=Xu, Jiyao|author2=Liu, H.-L.|author3=Yuan, W.|author4=Smith, A.K.|author5=Roble, R. G.|author6=Mertens, C.J.|author7=Russell, J.M.|author8=Mlynczak, M.G.|title=Mesopause structure from Thermosphere, Ionosphere, Mesosphere, Energetics, and Dynamics (TIMED)/Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER)|journal=Journal of Geophysical Research|volume=112|issue=D9|doi=10.1029/2006jd007711|bibcode=2007JGRD..112.9102X|year=2007|s2cid=54715803|doi-access=free}}</ref>

Another feature is that the summer mesopause is cooler than the winter (sometimes referred to as the ''mesopause anomaly''). It is due to a summer-to-winter circulation giving rise to upwelling at the summer pole and downwelling at the winter pole. Air rising will expand and cool resulting in a cold summer mesopause and conversely downwelling air results in compression and associated increase in temperature at the winter mesopause. In the mesosphere the summer-to-winter circulation is due to [[gravity wave]] dissipation, which deposits momentum against the mean east–west flow, resulting in a small north–south circulation.<ref>The Physics of Atmospheres, John Theodore Houghton, section and references therein of ''The general circulation of the middle atmosphere''</ref>

In recent years the mesopause has also been the focus of studies on global [[climate change]] associated with increases in CO<sub>2</sub>. Unlike the [[troposphere]], where [[greenhouse gases]] result in the atmosphere heating up, increased CO<sub>2</sub> in the [[mesosphere]] acts to cool the atmosphere due to increased radiative emission. This results in a measurable effect - the mesopause should become cooler with increased CO<sub>2</sub>. Observations do show a decrease of temperature of the mesopause, though the magnitude of this decrease varies and is subject to further study.<ref>{{cite journal|last1=Beig|first1=G.|last2=Keckhut|first2=P.|last3=Lowe|first3=R.P.|display-authors=etal|title=Review of mesospheric temperature trends (2003)|journal=Rev. Geophys.|volume=41|issue=4|page=1015|doi=10.1029/2002rg000121|bibcode=2003RvGeo..41.1015B|year=2003|doi-access=free}}</ref> Modeling studies of this phenomenon have also been carried out.<ref>{{cite journal|last1=Roble|first1=R.G.|last2=Dickinson|first2=R.E.|year=1989|title=How will changes in carbon-dioxide and methane modify the mean structure of the mesosphere and thermosphere?|journal=Geophys. Res. Lett.|volume=16|issue=12|pages=1441–1444|doi=10.1029/gl016i012p01441|bibcode=1989GeoRL..16.1441R|url=https://zenodo.org/record/1231392}}</ref><ref>{{cite journal|last1=Akmaev|first1=R.A.|last2=Fomichev|first2=V.I.|last3=Zhu|first3=X.|year=2006|title=Impact of middle-atmospheric composition changes on greenhouse cooling in the upper atmosphere|journal=J. Atmos. Sol.-Terr. Phys.|volume=68|issue=17|pages=1879–1889|doi=10.1016/j.jastp.2006.03.008|bibcode = 2006JASTP..68.1879A }}</ref><ref>{{Cite journal |last=Cnossen |first=Ingrid |last2=Harris |first2=Matthew J. |last3=Arnold |first3=Neil F. |last4=Yiğit |first4=Erdal |date=2009 |title=Modelled effect of changes in the CO2 concentration on the middle and upper atmosphere: Sensitivity to gravity wave parameterization |journal=Journal of Atmospheric and Solar-Terrestrial Physics |series=Long-Term Changes and Solar Impacts in the Atmosphere-Ionosphere System |volume=71 |issue=13 |pages=1484–1496 |bibcode=2009JASTP..71.1484C |doi=10.1016/j.jastp.2008.09.014 |issn=1364-6826}}</ref>

==See also==

* [[Jet stream]]
* [[Maximum parcel level]]

==References==
{{Reflist}}

{{Earth's atmosphere}}
{{Authority control}}

[[Category:Atmospheric thermodynamics]]
[[Category:Atmospheric boundaries]]
[[Category:Atmosphere of Earth]]