Editing Cloud (section)

===Varieties===
Genus and species types are further subdivided into ''varieties'' whose names can appear after the species name to provide a fuller description of a cloud. Some cloud varieties are not restricted to a specific altitude level or form, and can therefore be common to more than one genus or species.<ref name="varieties">{{Cite web |year=2017 |editor-last=World Meteorological Organization |title=Varieties, International Cloud Atlas |url=https://cloudatlas.wmo.int/principles-of-cloud-classification-varieties.html |access-date=1 February 2018}}</ref>

====Opacity-based====
[[File:Sleepy Twilight.jpg|thumb|left|A layer of stratocumulus stratiformis perlucidus hiding the setting sun with a background layer of stratocumulus cumulogenitus resembling distant mountains]]
All cloud varieties fall into one of two main groups. One group identifies the opacities of particular low and mid-level cloud structures and comprises the varieties ''translucidus'' (thin translucent), ''perlucidus'' (thick opaque with translucent or very small clear breaks), and ''opacus'' (thick opaque). These varieties are always identifiable for cloud genera and species with variable opacity. All three are associated with the stratiformis species of altocumulus and stratocumulus. However, only two varieties are seen with altostratus and stratus nebulosus whose uniform structures prevent the formation of a perlucidus variety. Opacity-based varieties are not applied to high clouds because they are always translucent, or in the case of cirrus spissatus, always opaque.<ref name="varieties" /><ref name="Aerographer2012">{{Cite web |last=Aerographer/Meteorology |year=2012 |title=Cloud Variety |url=http://meteorologytraining.tpub.com/14269/css/14269_20.htm |url-status=dead |archive-url=https://web.archive.org/web/20121221005913/http://meteorologytraining.tpub.com/14269/css/14269_20.htm |archive-date=21 December 2012 |access-date=2 July 2012 |website=meteorologytraining.tpub.com}}</ref>

====Pattern-based====
[[File:Sculpting La Silla’s Skies.jpg|thumb|left|Cirrus fibratus radiatus over ESO's [[La Silla Observatory]]<ref>{{Cite web |title=Sculpting La Silla's Skies |url=http://www.eso.org/public/images/potw1433a/ |access-date=23 August 2014 |website=www.eso.org |publisher=ESO}}</ref>]]

A second group describes the occasional arrangements of cloud structures into particular patterns that are discernible by a surface-based observer (cloud fields usually being visible only from a significant altitude above the formations). These varieties are not always present with the genera and species with which they are otherwise associated, but only appear when atmospheric conditions favor their formation. ''Intortus'' and ''vertebratus'' varieties occur on occasion with cirrus fibratus. They are respectively filaments twisted into irregular shapes, and those that are arranged in fishbone patterns, usually by uneven wind currents that favor the formation of these varieties. The variety ''radiatus'' is associated with cloud rows of a particular type that appear to converge at the horizon. It is sometimes seen with the fibratus and uncinus species of cirrus, the stratiformis species of altocumulus and stratocumulus, the mediocris and sometimes humilis species of cumulus,<ref name="Cumulus Humilis-Skynews">{{Cite web |last=Cumulus-skynews |year=2013 |title=Clouds: Their curious natures |url=http://cumulus-skynews.tumblr.com/post/49212742113/5a-cumulus-humilis-radiatus-the-latin-term |access-date=26 August 2014}}</ref>{{Unreliable source?|date=February 2022|reason=is there a better source than tumblr? If reliable maybe add a hidden comment to say why}}<ref name="Pretor-Pinney20">{{Cite book |last=Pretor-Pinney |first=Gavin |url=https://books.google.com/books?id=ix4qy7FihDcC |title=The Cloudspotter's Guide: The Science, History, and Culture of Clouds |date=2007 |publisher=Penguin Group |isbn=978-1-101-20331-6 |page=20 |author-link=Gavin Pretor-Pinney}}</ref> and with the genus altostratus.<ref name="radiatus">{{Cite web |year=2017 |editor-last=World Meteorological Organization |title=Variety Radiatus, International Cloud Atlas |url=https://cloudatlas.wmo.int/clouds-varieties-radiatus.html |access-date=5 April 2018}}</ref>
[[File:Morning Sky 7.jpg|thumbnail|upright|Altocumulus stratiformis duplicatus at sunrise in the California Mojave Desert, US (higher layer orange to white; lower layer gray)]]

Another variety, ''duplicatus'' (closely spaced layers of the same type, one above the other), is sometimes found with cirrus of both the fibratus and uncinus species, and with altocumulus and stratocumulus of the species stratiformis and lenticularis. The variety ''undulatus'' (having a wavy undulating base) can occur with any clouds of the species stratiformis or lenticularis, and with altostratus. It is only rarely observed with stratus nebulosus. The variety ''lacunosus'' is caused by localized downdrafts that create circular holes in the form of a honeycomb or net. It is occasionally seen with cirrocumulus and altocumulus of the species stratiformis, castellanus, and floccus, and with stratocumulus of the species stratiformis and castellanus.<ref name="varieties" /><ref name="Aerographer2012" />

====Combinations====
It is possible for some species to show combined varieties at one time, especially if one variety is opacity-based and the other is pattern-based. An example of this would be a layer of altocumulus stratiformis arranged in seemingly converging rows separated by small breaks. The full technical name of a cloud in this configuration would be ''altocumulus stratiformis radiatus perlucidus'', which would identify respectively its genus, species, and two combined varieties.<ref name="clouds - species and varieties" /><ref name="varieties" /><ref name="Aerographer2012" />