pileus
A pileus is a small, cap- or hood-shaped accessory cloud that forms above the top of a rapidly growing cumulus cloud or thundercloud. Its unusual appearance has also prompted UFO speculation.
Pileus is an accessory cloud form listed in the World Meteorological Organization (WMO) cloud atlas. According to the WMO definition, it is a cloud of small horizontal extent, in the form of a cap or hood, situated above the top of a cumuliform cloud or attached to its upper part. It occurs mainly together with cumulus and cumulonimbus clouds. Several pileus clouds can often be seen one above another.
How does it form?
According to the definition of the American Meteorological Society (AMS), a pileus forms when a moist layer of air is lifted locally by the cloud growing beneath it. As the cumulus cloud below continues to grow, it often breaks through the cap.
Connection to the UFO topic
In August 2022, a tower-like cloud formation shimmering in rainbow colors was photographed over Pu'er in China's Yunnan Province. NASA's astronomy image site (Astronomy Picture of the Day) identified it as an iridescent pileus cloud: the uniformly sized water droplets in the cloud split sunlight into colors. Among the comments under the image, alongside an explosion, chemicals and a government hologram, many also suspected a UFO or extraterrestrials.
Sources
- Pileus (WMO International Cloud Atlas)
- Pileus (AMS Glossary of Meteorology)
- Strange halo over town in China ignites conspiracy theories. Experts have explanation (2022. szeptember 7.)