Editing Cloud (section)

===Other types===
{{see also|List of cloud types}}
[[File:Clouds in the drakensberge 03.jpg|alt=Clouds on mountains|thumb|Clouds on mountains]]
Supplementary features and accessory clouds are not further subdivisions of cloud types below the species and variety level. Rather, they are either ''hydrometeors'' or special cloud types with their own Latin names that form in association with certain cloud genera, species, and varieties.<ref name="clouds - species and varieties" /><ref name="Aerographer2012" /> Supplementary features, whether in the form of clouds or precipitation, are directly attached to the main genus-cloud. Accessory clouds, by contrast, are generally detached from the main cloud.<ref name="features">{{Cite web |year=2017 |editor-last=World Meteorological Organization |title=Features, International Cloud Atlas |url=https://cloudatlas.wmo.int/principles-of-cloud-classification-supplementary-features.html |access-date=1 February 2018}}</ref>

====Precipitation-based supplementary features====
One group of supplementary features are not actual cloud formations, but precipitation that falls when water droplets or ice crystals that make up visible clouds have grown too heavy to remain aloft. ''Virga'' is a feature seen with clouds producing precipitation that evaporates before reaching the ground, these being of the genera cirrocumulus, altocumulus, altostratus, nimbostratus, stratocumulus, cumulus, and cumulonimbus.<ref name="features" />

When the precipitation reaches the ground without completely evaporating, it is designated as the feature ''praecipitatio''.<ref name="Dunlop77-78">{{harvnb|Dunlop|2003|pp=77–78}}</ref> This normally occurs with altostratus opacus, which can produce widespread but usually light precipitation, and with thicker clouds that show significant vertical development. Of the latter, ''upward-growing'' cumulus mediocris produces only isolated light showers, while ''downward growing'' nimbostratus is capable of heavier, more extensive precipitation. Towering vertical clouds have the greatest ability to produce intense precipitation events, but these tend to be localized unless organized along fast-moving cold fronts. Showers of moderate to heavy intensity can fall from cumulus congestus clouds. Cumulonimbus, the largest of all cloud genera, has the capacity to produce very heavy showers. Low stratus clouds usually produce only light precipitation, but this always occurs as the feature praecipitatio because this cloud genus lies too close to the ground to allow the formation of virga.<ref name="clouds - species and varieties" /><ref name="Aerographer2012" /><ref name="features" />

====Cloud-based supplementary features====
''Incus'' is the most type-specific supplementary feature, seen only with cumulonimbus of the species capillatus. A [[cumulonimbus incus]] cloud top is one that has spread out into a clear anvil shape as a result of rising air currents hitting the stability layer at the [[tropopause]] where the air no longer continues to get colder with increasing altitude.<ref name="cumulonimbus-incus">{{Cite web |date=5 August 2009 |title=Cumulonimbus Incus |url=http://epod.usra.edu/blog/2009/08/cumulonimbus-incus.html |access-date=23 October 2012 |publisher=Universities Space Research Association}}</ref>

The ''mamma'' feature forms on the bases of clouds as downward-facing bubble-like protuberances caused by localized downdrafts within the cloud. It is also sometimes called ''mammatus'', an earlier version of the term used before a standardization of Latin nomenclature brought about by the World Meteorological Organization during the 20th century. The best-known is [[cumulonimbus with mammatus]], but the mamma feature is also seen occasionally with cirrus, cirrocumulus, altocumulus, altostratus, and stratocumulus.<ref name="features" />

A ''tuba'' feature is a cloud column that may hang from the bottom of a cumulus or cumulonimbus. A newly formed or poorly organized column might be comparatively benign, but can quickly intensify into a funnel cloud or tornado.<ref name="features" /><ref name="Aerographer">{{Cite web |last=Aerographer/Meteorology |year=2012 |title=Roll cloud formation on cumulonimbus |url=http://meteorologytraining.tpub.com/14269/css/14269_27.htm |url-status=dead |archive-url=https://web.archive.org/web/20130518082044/http://meteorologytraining.tpub.com/14269/css/14269_27.htm |archive-date=18 May 2013 |access-date=5 July 2012}}</ref><ref name="Dunlop79">{{harvnb|Dunlop|2003|p=79}}</ref>

An ''[[Arcus cloud|arcus]]'' feature is a roll cloud with ragged edges attached to the lower front part of cumulus congestus or cumulonimbus that forms along the leading edge of a squall line or thunderstorm outflow.<ref name="Ludlum473">{{Cite book |last=Ludlum |first=David McWilliams |url=https://archive.org/details/audubonsocietyfi00ludl/page/473 |title=National Audubon Society Field Guide to Weather |publisher=Alfred A. Knopf |year=2000 |isbn=978-0-679-40851-2 |page=[https://archive.org/details/audubonsocietyfi00ludl/page/473 473] |oclc=56559729}}</ref> A large arcus formation can have the appearance of a dark menacing arch.<ref name="features" />

Several new supplementary features have been formally recognized by the [[World Meteorological Organization]] (WMO). The feature ''fluctus'' can form under conditions of strong atmospheric wind shear when a stratocumulus, altocumulus, or cirrus cloud breaks into regularly spaced crests. This variant is sometimes known informally as a [[Kelvin–Helmholtz cloud|Kelvin–Helmholtz (wave) cloud]]. This phenomenon has also been observed in cloud formations over other planets and even in the Sun's atmosphere.<ref>{{Cite web |last=Fox |first=Karen C. |date=30 December 2014 |title=NASA's Solar Dynamics Observatory Catches "Surfer" Waves on the Sun |url=http://www.nasa.gov/mission_pages/sunearth/news/sun-surfing.html |website=NASA-The Sun-Earth Connection: Heliophysics |publisher=NASA |access-date=20 November 2014 |archive-date=20 November 2021 |archive-url=https://web.archive.org/web/20211120110428/https://www.nasa.gov/mission_pages/sunearth/news/sun-surfing.html |url-status=dead }}</ref> Another highly disturbed but more chaotic wave-like cloud feature associated with stratocumulus or altocumulus cloud has been given the Latin name ''asperitas''. The supplementary feature ''cavum'' is a circular fall-streak hole that occasionally forms in a thin layer of supercooled altocumulus or cirrocumulus. Fall streaks consisting of virga or wisps of cirrus are usually seen beneath the hole as ice crystals fall out to a lower altitude. This type of hole is usually larger than typical lacunosus holes. A ''murus'' feature is a cumulonimbus wall cloud with a lowering, rotating cloud base that can lead to the development of tornadoes. A ''cauda'' feature is a tail cloud that extends horizontally away from the murus cloud and is the result of air feeding into the storm.<ref name=ICA2017/>

====Accessory clouds====
Supplementary cloud formations detached from the main cloud are known as [[accessory cloud]]s.<ref name="clouds - species and varieties" /><ref name="Aerographer2012" /><ref name="features" /> The heavier precipitating clouds, nimbostratus, towering cumulus (cumulus congestus), and cumulonimbus typically see the formation in precipitation of the ''pannus'' feature, low ragged clouds of the genera and species cumulus fractus or stratus fractus.<ref name="pannus" />

A group of accessory clouds comprise formations that are associated mainly with upward-growing cumuliform and cumulonimbiform clouds of free convection. ''Pileus'' is a cap cloud that can form over a cumulonimbus or large cumulus cloud,<ref name="GarretI">{{Cite journal |last1=Garrett |first1=T. J. |last2=Dean-Day |first2=J. |last3=Liu |first3=C. |last4=Barnett |first4=B. |last5=Mace |first5=G. |last6=Baumgardner |first6=D. |last7=Webster |first7=C. |last8=Bui |first8=T. |last9=Read |first9=W. |last10=Minnis |first10=P. |year=2006 |title=Convective formation of pileus cloud near the tropopause |journal=Atmospheric Chemistry and Physics |volume=6 |issue=5 |pages=1185–1200 |bibcode=2006ACP.....6.1185G |doi=10.5194/acp-6-1185-2006 |hdl-access=free |hdl=2060/20080015842 |s2cid=14440075 |doi-access=free }}</ref> whereas a ''velum'' feature is a thin horizontal sheet that sometimes forms like an apron around the middle or in front of the parent cloud.<ref name="features" /> An accessory cloud recently officially recognized by the World Meteorological Organization is the ''flumen'', also known more informally as the ''beaver's tail''. It is formed by the warm, humid [[inflow (meteorology)|inflow]] of a super-cell thunderstorm, and can be mistaken for a tornado. Although the flumen can indicate a tornado risk, it is similar in appearance to pannus or [[scud (cloud)|scud]] clouds and does not rotate.<ref name=ICA2017/>

==== Mother clouds ====
[[File:Port of Piraeus Panoramic View.JPG|thumb|Cumulus partly spreading into stratocumulus cumulogenitus over the port of [[Piraeus]] in Greece]]

Clouds initially form in clear air or become clouds when fog rises above surface level. The genus of a newly formed cloud is determined mainly by air mass characteristics such as stability and moisture content. If these characteristics change over time, the genus tends to change accordingly. When this happens, the original genus is called a ''mother cloud''. If the mother cloud retains much of its original form after the appearance of the new genus, it is termed a ''genitus'' cloud. One example of this is ''stratocumulus cumulogenitus'', a stratocumulus cloud formed by the partial spreading of a cumulus type when there is a loss of convective lift. If the mother cloud undergoes a complete change in genus, it is considered to be a ''mutatus'' cloud.<ref name="mother-clouds">{{Cite web |year=2017 |editor-last=World Meteorological Organization |title=Mother clouds, International Cloud Atlas |url=https://cloudatlas.wmo.int/principles-of-cloud-classification-mother-clouds.html |access-date=2 June 2017}}</ref>
[[File:Sunset and Clouds.jpg|thumb|Cumulonimbus mother cloud dissipating into stratocumulus cumulonimbogenitus at dusk]]

====Other genitus and mutatus clouds====

The genitus and mutatus categories have been expanded to include certain types that do not originate from pre-existing clouds. The term ''flammagenitus'' (Latin for 'fire-made') applies to cumulus congestus or cumulonimbus that are formed by large scale fires or volcanic eruptions, the latter having reached altitudes of {{cvt|57|km|mi}},<ref name="z578">{{cite web | title=Tonga volcano had highest plume ever recorded, new study confirms | website=University of Oxford | date=2022-01-15 | url=https://www.ox.ac.uk/news/2022-11-04-tonga-volcano-had-highest-plume-ever-recorded-new-study-confirms | access-date=2025-03-18}}</ref> and nuclear [[mushroom cloud]]s having an upward extend of up to {{cvt|67|km}}.<ref>{{cite magazine |last=Veselov |first=A.V. |title=Tsar-bomba |magazine=Atompress |year=2006 |volume=43 |issue=726 |page=7}}</ref> Smaller low-level "pyrocumulus" or "fumulus" clouds formed by contained industrial activity are now classified as cumulus ''homogenitus'' (Latin for 'man-made'). [[Contrail]]s formed from the exhaust of aircraft flying in the upper level of the troposphere can persist and spread into formations resembling cirrus which are designated cirrus ''homogenitus''.  If a cirrus homogenitus cloud changes fully to any of the high-level genera, they are termed cirrus, cirrostratus, or cirrocumulus ''homomutatus''. Stratus cataractagenitus (Latin for 'cataract-made') are generated by the spray from waterfalls. ''Silvagenitus'' (Latin for 'forest-made') is a stratus cloud that forms as water vapor is added to the air above a forest canopy.<ref name="mother-clouds" />