Clouds in the sky can take on strange appearances: here are 10 incredible formations.
Clouds are formed from fine particles of water, either liquid (raindrops) or solid (ice or snow). They are suspended in the atmosphere, but are not all at the same height.
There are three main families of clouds: cirrus clouds are very thin, rather like curls of hair. Cumulus clouds form in clusters and can be several kilometers thick. Finally, stratus clouds are found at very low altitudes and form fog when close to the ground.
But there’s more to this classification than that: each family has its own variants with more or less bizarre appearances. In this article, we’ve brought together 10 types of clouds that make the sky spectacular, like those UFOs floating over Cape Town.
1. Lenticular clouds
Lenticular clouds usually form at altitude, due to the wind at the top of mountains. They are therefore usually found on mountains. They are sometimes mistaken for UFOs, since they can be flat and rounded, like spaceships or airplane wings.
Photo credit: Wikimedia – U.S. Fish and Wildlife Service
Lenticular clouds on Mount Hotaka / Photo credit: Wikimedia – Alpsdake
2. The cloud funnel (or snorkel)
The cloud funnel is formed by the condensation of water vapour in a rotating column of air. Its inverted cone shape is very impressive and can be formidable. In fact, when a cloud funnel touches the ground, it’s called a tornado (or a marine tornado when it touches water).
Photo credit: Flickr – sourtoe
Photo credit: Flickr – Frédérique Voisin-Demery
3. The cumulonimbus
The cumulonimbus is a cloud that everyone has seen. They are often associated with violent weather phenomena such as heavy showers, lightning or hail. They are anvil-shaped and very bulky. So, if you don’t like rain, it’s these towering clouds you’ve got to blame!
Photo credit: Wikimedia – Михал Орела
Photo credit: Flickr – Nicholas A. Tonelli
4. Pearly clouds
Pearly clouds are very rare, forming most often in winter, especially near the poles, as can be seen in the photos. Because of their altitude, they receive sunlight, particularly at dawn or dusk.
Pearly clouds in the Arctic / Photo credit: Pixabay – tpsdave
Pearly clouds in Antarctica / Photo credit: Pixabay – PublicDomainPictures
5. The fog
Fog is a meteorological phenomenon made up of droplets or fine ice crystals. Its composition is identical to that of a cloud, the only difference being that it is very low and touches the ground. With fog, visibility is difficult (less than 1 km), and we speak of mist when it is greater than this distance.
Photo credit: Pixabay – cafepampas
Fog in Dubai / Photo credit: Pixabay – laddhaashish20030
6. Arcus
Arcus clouds are very low and scroll-shaped. They sometimes appear during thunderstorms and are therefore associated with cumulonimbus clouds. They are located just before the line of precipitation (rain, snow or hail).
Arcus over the beach in Uruguay / Photo credit: Wikimedia – Daniela Mirner Eberl
In Queensland, Australia / Photo credit: Wikimedia – Mick Petroff
7. The mamma (or mammatus)
Mammatus are circular layers that form at the base of certain clouds due to a drier-than-usual zone of air. Their colors vary according to the sun: they can be like the sky, cottony white like the clouds, or yellow or orange with the rays.
Photo credit: Wikimedia – Craig Lindsay
Photo credit: Wikimedia – Matt Saal
8. The punch-hole
The punch-hole cloud takes the form of a large hole appearing in the middle of clouds. It is produced when the temperature of the water in the clouds falls below zero degrees, but has not yet frozen.
Photo credit: Wikimedia – H. Raab
9. The Kelvin-Helmholtz
The Kelvin-Helmholtz instability is a wave-like motion that forms as a result of temperature differences. As thermal fluids do not move at the same speed, clouds take on the shape of spectacular waves. Watching them, it’s as if the sky is transformed into a vast ocean.
Photo credit: Wikimedia – Astronautilus
10. Asperatus
The asperatus is a new type of cloud: it was only included in the World Meteorological Organization’s International Cloud Atlas in 2009. They haven’t been studied much, but they look like grandiose mammas.
Photo credit: Wikimedia – Agathman
Photo credit: Wikimedia – Ave Maria Mõistlik
Main photo credit: Nicholas A. Tonelli