On World Metrological Day, March 23, the International Cloud Atlas declared the discovery of new cloud specie and 11 new cloud types, enriching the learning of cloud enthusiasts.

Good news for all cloud enthusiasts, as twelve new clouds have been recognised by the reputed international cloud atlas which is being newly published after long gap of 30 years by the World Meteorological Organization (WMO).

One New Cloud Specie and 11 new types of clouds in this Cloud Atlas-

These newest additions to the cloud atlas( International handbooks for cloud identification) include, 11 new types of cloud which are all subdivisions of basic cloud genera that already exists. However, one new species of cloud that has been added in this cloud atlas is the volutus or roll cloud. Other new types of cloud include in this cloud atlas are  – Asperitas, Cavum, Cauda, Fluctus, Flumen and Murus, Cataractagenitus, Flammagenitus, Homogenitus, Silvagenitus and Homomutatus.

Voltus Cloud – is the only new cloud species that is added in this cloud atlas and is a relatively rare, low-level, horizontal, tube-shaped cloud and is associated with thunderstorm but are completely detached from the base of cumulonimbus cloud. Volutus is a Latin term for rolled, which matches its appearance.

volutus cloud

Asperitas- which means rough-like in Latin, as these clouds looks like the tossing of the waves at sea when viewed from below.

asperitas cloud

Cavum-which is a hole-punch cloud within a thin and extensive layer of cloud.


Cauda– is a horizontal, tail-shaped cloud at low levels extending from the main precipitation region of a supercell cumulonimbus to the murus cloud. It is typically attached to the wall cloud, and the bases of both are typically at the same height.


Flactus– which is a relatively short-lived wave formation, usually on the top surface of the cloud, in the form of curls or breaking waves (Kelvin-Helmholtz waves).

Flumen- is basically bands of low clouds associated with a supercell severe convective storm (Cumulonimbus), arranged parallel to the low-level winds and moving into or towards the supercell.


Murus – is a localized, persistent, and often abrupt lowering of cloud from the base of a cumulonimbus from which spouts sometimes form.


Cataractagenitus is a special cloud type that may develop locally in the vicinity of large waterfalls as a consequence of water broken up into spray by the falls. The downdraft caused by the falling water is compensated for by the locally ascending motion of air.


Flammagenitus is a cloud develop as a consequence of convection initiated by heat from forest fires, wildfires or volcanic eruption activity.

Flammagenitus cloud

Homogenitus– which is a cloud developed as a consequence of human activity. Examples are aircraft condensation trails (contrails), or clouds resulting from industrial processes, such as cumuliform clouds generated by rising thermals above power station cooling towers

Homogenitus Cloud

Silvagenitus– is a cloud that is developed locally over forests as a result of increased humidity due to evaporation and evapotranspiration from the tree canopy.

silvagenitus cloud

Homomutatus– Last to be included in the list  of cloud atlas is the spectacular Homomutatus cloud that may be observed, over a period of time and under the influence of strong upper winds, to grow and spread out over a larger portion of sky, and undergo internal transformation such that the cloud eventually takes on the appearance of more natural cirri-form clouds.


The International Cloud Atlas is a global reference book that has been published since the late 19th century that aims to identify types of cloud. The new edition has now embraced the digital age and for the first time public can access this atlas on the web portal.


This new addition in the cloud atlas  is a great gift that any cloud enthusiast as he can now better classify observations based on these new  inclusions.


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