List of cloud types

The list of cloud types groups all genera as high, middle, multi-level, and low. These groupings are determined by the altitude level or levels in the troposphere at which each of the various cloud types are normally found. Small cumulus are commonly grouped with the low clouds because they do not show significant vertical extent. Of the multi-level genus-types, those with the greatest convective activity are often grouped separately as towering vertical. The genus types all have Latin names.
The genera are also grouped into five physical forms. These are, in approximate ascending order of instability or convective activity: stratiform sheets; cirriform wisps and patches; stratocumuliform patches, rolls, and ripples; cumuliform heaps, and cumulonimbiform towers that often have complex structures. Most genera are divided into species with Latin names, some of which are common to more than one genus. Most genera and species can be subdivided into varieties, also with Latin names, some of which are common to more than one genus or species. The essentials of the modern nomenclature system for tropospheric clouds were proposed by Luke Howard, a British manufacturing chemist and an amateur meteorologist with broad interests in science, in an 1802 presentation to the Askesian Society. Very low stratiform clouds that touch the Earth's surface are given the common names fog and mist, which are not included with the Latin nomenclature of clouds that form aloft in the troposphere.
Above the troposphere, stratospheric and mesospheric clouds have their own classifications with common names for the major types and alpha-numeric nomenclature for the subtypes. They are characterized by altitude as very high level and extreme level. Three of the five physical forms in the troposphere are also seen at these higher levels, stratiform, cirriform, and stratocumuliform, although the tops of very large cumulonimbiform clouds can penetrate the lower stratosphere.

Cloud identification and classification: Order of listed types

In section two of this page, height ranges are sorted in approximate descending order of altitude expressed in general terms. On the cross-classification table, forms and genus types are shown from left to right in approximate ascending order of instability.
In sections three to five, terrestrial clouds are listed in descending order of the altitude range of each atmospheric layer in which clouds can form:

mesospheric layer;
stratospheric layer;
tropospheric layer.
* Within the troposphere, the cloud levels are listed in descending order of altitude range.
** Non-vertical genus types are sorted into approximate descending order of altitude of the cloud bases.
** Vertical or multi-level genera and genus sub-types can be based in the low or middle levels and are therefore placed between the non-vertical low and mid-level genus types and sub-types. These thick clouds are listed in approximate descending order of altitude of the cloud tops.
*** The species associated with each genus type are listed in approximate ascending order of instability where applicable.
*** The constituent varieties and associated supplementary features and mother clouds for each genus or species are arranged in approximate order of frequency of occurrence.

In section six, the cloud types in the general lists and the mother clouds in the applicable classification table are sorted in alphabetical order except where noted. The species table shows these types sorted from left to right in approximate ascending order of the convective instability of each species. The table for supplementary features has them arranged in approximate descending order of frequency of occurrence.
In section seven, extraterrestrial clouds can be found in the atmospheres of other planets in the Solar System and beyond. The planets with clouds are listed in order of their distance from the Sun, and the clouds on each planet are in approximate descending order of altitude.

Cloud cross-classification throughout the homosphere

The table that follows is very broad in scope much like the cloud genera template near the bottom of the article and upon which this table is partly based. There are some variations in styles of nomenclature between the classification scheme used for the troposphere and the higher levels of the homosphere. However, the schemes presented here share a cross-classification of physical forms and altitude levels to derive the 10 tropospheric genera, the fog and mist that forms at surface level, and several additional major types above the troposphere. The cumulus genus includes four species that indicate vertical size which can affect the altitude levels.

	Stratiform non-convective	Cirriform mostly non-convective	Stratocumuliform limited-convective	Cumuliform free-convective	Cumulonimbiform strong-convective
Extreme-level	Noctilucent veils	Noctilucent billows or whirls	Noctilucent bands
Very high-level	Nitric acid & water polar stratospheric	Cirriform nacreous PSC	Lenticular nacreous PSC
High-level	Cirrostratus	Cirrus	Cirrocumulus
Mid-level	Altostratus		Altocumulus
Towering vertical				Cumulus congestus	Cumulonimbus
Multi-level or moderate vertical	Nimbostratus			Cumulus mediocris
Low-level	Stratus		Stratocumulus	Cumulus humilis or fractus
Surface-level	Fog or mist

Mesospheric cloud identification and classification

s that form in the mesosphere come in a variety of forms such as veils, bands, and billows, but are not given Latin names based on these characteristics. These clouds are the highest in the atmosphere and are given the Latin-derived name noctilucent which refers to their illumination during deep twilight rather than their physical forms. They are sub-classified alpha-numerically and with common terms according to specific details of their physical structures.

Extreme-level stratiform, stratocumuliform, and cirriform

s are thin clouds that come in a variety of forms based from about and occasionally seen in deep twilight after sunset and before sunrise.
;Type 1 : Veils, very tenuous stratiform; resembles cirrostratus or poorly defined cirrus.
;Type 2 : Long stratocumuliform bands, often in parallel groups or interwoven at small angles. More widely spaced than cirrocumulus bands.
;Type 3: Billows. Clearly spaced, fibrous cirriform, roughly parallel short streaks.
;Type 4 : Whirls. Partial cirriform rings with dark centers.

Stratospheric cloud identification and classification

s form at very high altitudes in polar regions of the stratosphere. Those that show mother-of-pearl colors are given the name nacreous.

Very high-level stratiform

;Nitric acid and water polar stratospheric : Sometimes known as type 1, a thin sheet-like cloud resembling cirrostratus or haze. Contains supercooled nitric acid and water droplets; sometimes also contains supercooled sulfuric acid in ternary solution.

Very high-level cirriform and stratocumuliform

;Nacreous polar stratospheric cloud : Sometimes known as type 2, a thin usually cirriform or lenticular looking cloud based from about and seen most often between sunset and sunrise. Consists of ice crystals only.

Troposphere cloud identification and classification

Tropospheric clouds are divided into physical forms defined by structure, and levels defined by altitude range. These divisions are cross-classified to produce ten basic genus-types. They have Latin names as authorized by the World Meteorological Organization that indicate physical structure, altitude or étage, and process of formation.

High-level cirriform, stratocumuliform, and stratiform

High clouds form in the highest and coldest region of the troposphere from about 5 to 12 km in temperate latitudes. At this altitude water almost always freezes so high clouds are generally composed of ice crystals or supercooled water droplets.

Genus cirrus

Abbreviation: Ci
Cirriform clouds tend to be wispy and are mostly transparent or translucent. Isolated cirrus do not bring rain; however, large amounts of cirrus can indicate an approaching storm system eventually followed by fair weather.
There are several variations of clouds of the cirrus genus based on species and varieties:

Species

; Cirrus fibratus: High clouds having the traditional "mare's tail" appearance. These clouds are long, fibrous, and curved, with no tufts or curls at the ends.
; Cirrus uncinus: Filaments with up-turned hooks or curls.
; Cirrus spissatus: Dense and opaque or mostly opaque patches.
; Cirrus castellanus: A series of dense lumps, or "towers", connected by a thinner base.
; Cirrus floccus: Elements which take on a rounded appearance on the top, with the lower part appearing ragged.

Varieties

; Opacity-based: None; always translucent except species spissatus which is inherently opaque.
; Fibratus pattern-based:
; Pattern-based variety radiatus: Large horizontal bands that appear to converge at the horizon; normally associated with fibratus and uncinus species.
; Pattern-based variety duplicatus: Sheets at different layers of the upper troposphere, which may be connected at one or more points; normally associated with fibratus and uncinus species.
; Spissatus, castellanus, or floccus: Varieties are not commonly associated.