Editing Cloud (section)

{{Short description|Visible mass of particles suspended in the atmosphere}}
{{Redirect-distinguish|Nephology|Nephrology}}
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{{Use dmy dates|date=August 2024}}
{{Use American English|date=June 2023}}
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[[File:ISS-40 Thunderheads near Borneo.jpg|alt=|thumb|upright=1.5|Cloudscape over [[Borneo]], taken by the [[International Space Station]]]]
{{Weather}}
In [[meteorology]], a '''cloud''' is an [[aerosol]] consisting of a visible mass of miniature [[liquid]] [[droplets]], [[ice crystals|frozen crystals]], or other [[particulates|particles]], suspended in the [[atmosphere]] of a [[planet]]ary body or similar space.<ref>{{Cite web |title=Weather Terms |url=http://www.erh.noaa.gov/box/glossary.htm |access-date=21 June 2013 |publisher=[[National Weather Service]]}}</ref> [[Water]] or various other chemicals may compose the droplets and crystals. On [[Earth]], clouds are formed as a result of saturation of the [[air]] when it is cooled to its [[dew point]], or when it gains sufficient [[moisture]] (usually in the form of [[water vapor]]) from an adjacent source to raise the dew point to the ambient [[temperature]].

Clouds are seen in the Earth's [[homosphere]], which includes the [[troposphere]], [[stratosphere]], and [[mesosphere]].
'''Nephology''' is the science of clouds, which is undertaken in the [[cloud physics]] branch of [[meteorology]]. The World Meteorological Organization uses two methods of naming clouds in their respective layers of the homosphere, [[Latin]] and [[common name]].

[[Genus]] types in the troposphere, the atmospheric layer closest to Earth's surface, have [[Latin]] names because of the universal adoption of [[Luke Howard]]'s [[nomenclature]] that was formally proposed in 1802. It became the basis of a modern international system that divides clouds into five physical ''forms'' which can be further divided or classified into [[altitude]] ''levels'' to derive ten basic ''genera''. The five main forms are [[stratus cloud|stratiform]] sheets or veils, [[cumuliform]] heaps, [[stratocumulus cloud|stratocumuliform]] bands, rolls, or ripples, [[cumulonimbus cloud|cumulonimbiform]] towers often with fibrous tops, and [[cirrus cloud|cirriform]] wisps or patches. ''Low-level'' clouds do not have any altitude-related prefixes. However ''mid-level'' stratiform and stratocumuliform types are given the prefix ''alto-'' while ''high-level'' variants of these same two forms carry the prefix ''cirro-''. In the case of stratocumuliform clouds, the prefix ''strato-'' is applied to the low-level genus type but is dropped from the mid- and high-level variants to avoid double-prefixing with alto- and cirro-. Genus types with sufficient vertical extent to occupy more than one level do not carry any altitude-related prefixes. They are classified formally as low- or mid-level depending on the altitude at which each initially forms, and are also more informally characterized as ''multi-level'' or ''vertical''. Most of the ten genera derived by this method of [[classification]] can be subdivided into ''species'' and further subdivided into ''varieties''. Very low stratiform clouds that extend down to the Earth's surface are given the common names ''fog'' and ''mist'' but have no Latin names.

In the stratosphere and mesosphere, clouds also have common names for their main types. They may have the appearance of veils or sheets, wisps, or bands or ripples, but not heaps or towers as in the troposphere. They are seen infrequently, mostly in the polar regions of Earth. Clouds have been observed in the atmospheres of other [[planet]]s and [[moons]] in the [[Solar System]] and beyond. However, due to their different temperature characteristics, they are often composed of other substances such as [[methane]], [[ammonia]], and [[sulfuric acid]], as well as water.

Tropospheric clouds can have a direct effect on [[climate change]] on Earth. They may reflect incoming rays from the Sun which can contribute to a cooling effect where and when these clouds occur, or trap longer wave radiation that reflects up from the Earth's surface which can cause a warming effect. The altitude, form, and thickness of the clouds are the main factors that affect the local heating or cooling of the Earth and the atmosphere. Clouds that form above the troposphere are too scarce and too thin to have any influence on climate change. Clouds are the main uncertainty in [[climate sensitivity]].<ref>{{Cite web |last1=Ceppi |first1=Paulo |last2=Williams |first2=Ric |title=Why clouds are the missing piece in the climate change puzzle |url=http://theconversation.com/why-clouds-are-the-missing-piece-in-the-climate-change-puzzle-140812 |access-date=21 January 2021 |website=The Conversation |date=11 September 2020 |language=en}}</ref>

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