Editing Stratosphere (section)

== Ozone layer ==
{{Further|Ozone layer}}
[[File:Layersofozone 1.jpeg 1240x510 q85 subsampling-2.jpg|thumb|The ozone layer in the stratosphere blocks harmful UV radiation from reaching the surface of the Earth. A gamma-ray burst would deplete the ozone layer, allowing UV radiation through.]]
The mechanism describing the formation of the ozone layer was described by British mathematician and [[geophysicist]] [[Sydney Chapman (mathematician)|Sydney Chapman]] in 1930, and is known as the Chapman cycle or [[ozone–oxygen cycle]].<ref>{{Cite book |last= Jacob |first=Daniel J. |url=http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap10.html |title=Introduction to Atmospheric Chemistry |date=1999 |publisher=Princeton University Press |isbn=9781400841547 |chapter=CHAPTER 10. STRATOSPHERIC OZONE |access-date=2020-10-20 |archive-url=https://web.archive.org/web/20190930034719/http://acmg.seas.harvard.edu/people/faculty/djj/book/bookchap10.html |archive-date=2019-09-30 |url-status=dead |via=acmg.seas.harvard.edu}}</ref> Molecular oxygen absorbs high energy sunlight in the [[UV-C]] region, at wavelengths shorter than about 240&nbsp;nm. Radicals produced from the homolytically split oxygen molecules combine with molecular oxygen to form ozone. Ozone in turn is [[photodissociation| photolyzed]] much more rapidly than molecular oxygen as it has a stronger absorption that occurs at longer wavelengths, where the solar emission is more intense. [[Ozone]] (O<sub>3</sub>) photolysis produces O and O<sub>2</sub>. The oxygen atom product combines with atmospheric molecular oxygen to reform O<sub>3</sub>, releasing heat. The rapid photolysis and reformation of ozone heat the stratosphere, resulting in a temperature inversion. This increase of temperature with altitude is characteristic of the stratosphere; its resistance to vertical mixing means that it is stratified. Within the stratosphere temperatures increase with altitude ''(see [[temperature inversion]])''; the top of the stratosphere has a temperature of about 270 [[Kelvin|K]] (−3[[°C]] or 26.6[[°F]]).<ref>{{Cite book |last=Seinfeld |first=J. H. |title=Atmospheric chemistry and physics: from air pollution to climate change |last2=Pandis |first2=S. N. |date=2006 |publisher=Wiley |isbn=978-0-471-72018-8 |edition=2nd |location=Hoboken, NJ}}</ref>{{pn|date=June 2024}}

This vertical [[Atmospheric stratification|stratification]], with warmer layers above and cooler layers below, makes the stratosphere dynamically stable: there is no regular [[convection]] and associated [[turbulence]] in this part of the atmosphere. However, exceptionally energetic convection processes, such as volcanic [[eruption column]]s and [[overshooting top]]s in severe [[Supercell|supercell thunderstorms]], may carry convection into the stratosphere on a very local and temporary basis. Overall, the attenuation of solar UV at wavelengths that damage DNA by the ozone layer allows life to exist on the planet's surface outside of the ocean. All air entering the stratosphere must pass through the [[tropopause]], the temperature minimum that divides the troposphere and stratosphere. The rising air is literally freeze-dried; the stratosphere is a very dry place. The top of the stratosphere is called the [[stratopause]], above which the temperature decreases with height.

=== Formation and destruction ===
{{Further|Ozone–oxygen cycle}}
Sydney Chapman gave a correct description of the source of stratospheric ozone and its ability to generate heat within the stratosphere;{{Citation needed|date=October 2021}} he also wrote that ozone may be destroyed by reacting with atomic oxygen, making two molecules of molecular oxygen. We now know that there are additional ozone loss mechanisms and that these mechanisms are catalytic, meaning that a small amount of the catalyst can destroy a great number of ozone molecules. The first is due to the reaction of [[hydroxyl radical]]s (•OH) with ozone. •OH is formed by the reaction of electrically excited oxygen atoms produced by ozone photolysis, with water vapor. While the stratosphere is dry, additional water vapour is produced in situ by the photochemical oxidation of [[methane]] (CH<sub>4</sub>). The HO<sub>2</sub> radical produced by the reaction of OH with O<sub>3</sub> is recycled to OH by reaction with oxygen atoms or ozone. In addition, solar proton events can significantly affect ozone levels via [[radiolysis]] with the subsequent formation of OH. [[Nitrous oxide]] (N<sub>2</sub>O) is produced by biological activity at the surface and is oxidized to NO in the stratosphere; the so-called NO<sub>x</sub> radical cycles also deplete stratospheric ozone. Finally, [[chlorofluorocarbon]] molecules are photolyzed in the stratosphere releasing chlorine atoms that react with ozone giving ClO and O<sub>2</sub>. The chlorine atoms are recycled when ClO reacts with O in the upper stratosphere, or when ClO reacts with itself in the chemistry of the Antarctic ozone hole.

Paul J. Crutzen, Mario J. Molina and F. Sherwood Rowland were awarded the Nobel Prize in Chemistry in 1995 for their work describing the formation and decomposition of stratospheric ozone.<ref>{{Cite web|title=The Nobel Prize in Chemistry 1995|url=https://www.nobelprize.org/prizes/chemistry/1995/summary/|access-date=2020-07-21|website=NobelPrize.org|language=en-US}}</ref>