Rare Rainbow Scarf Cloud Stuns Residents in China: How Did It Form?

Residents in the city of Haikou, Hainan Province in China were treated to a spectacular cloud show on August 21, 2022, when a rare rainbow 'scarf' cloud appeared in the form of a cap or hood above the upper part of a cumuliform cloud.

According to Mashable, residents were dumbfounded by its strange appearance which left some onlookers with a sense of the surreal and supernatural feeling that it seems like an apocalyptic sign.

Rainbow-Colored Pileus Clouds

The video of the rainbow-colored clouds was shared several times on Twitter and it shows a mesmerizing view of a pileus cloud with different colors above the city of Haikou. It was shot on Sunday and since then has gone viral on social media. Its colors give a lovely appearance to the sky that is rarely seen.

The type of the cloud in the video is known as the scarf or pileus cloud and according to the World Meteorological Organisation (WMO), these clouds are an accessory to a small horizontal cloud in a form of a cap or hood either above or attached to the upper part of a cumuliform cloud.

Pileus clouds also have some superstitions regarding it, mostly about bad weather coming. China has recently been experiencing a sweltering heatwave and authorities have been trying to generate rain through cloud seeding technology to alleviate the drought conditions in many regions of the country, such as the Yangtze River basin.

Cloud seeding is a technology that triggers rain involving the use of aircraft into the clouds and releasing silver iodide that induces rainfall. Scientists believe that geoengineering might be used in the future to prevent the worsening impacts of climate change on the planets.

How Do Pileus Clouds Form?

Pileus clouds were formed through the updraft of a thunderstorm, which creates a smooth cloud above a growing cumulus or cumulonimbus cloud, according to Mashable.

In terms of its rainbow-colored appearance, the news outlet explains that light is diffracted and produces the vivid colors of a rainbow when sun rays hit the millions of tiny crystals or water droplets within the cloud. That is why it created the rainbow effect shown in the viral video.

However, these mesmerizing rainbow-colored pileus clouds are often short-lived as the main cloud underneath eventually rises up because of convection and then absorbs the rainbow cloud above.

Pileus clouds have long been noted as an indicator of severe weather and can also be found in mountains, ash clouds, and pyrocumulus clouds from erupting volcanoes, and in some mushroom clouds after a nuclear explosion.

But it should be noted that not all pileus clouds yield beautiful rainbow effects such as the one filmed in the city of Haikou. That means it is a rare sighting and residents there are lucky to have seen such an amazing spectacle of the rainbow-colored pileus clouds.

Experts also said that these types of clouds should not be confused with the lenticular clouds that stand alone, unlike pileus clouds. Mint reported that Lenticular clouds resemble lentils and are easily distinguished because of their flying saucer shape and smooth edges.

Check out more news and information on Rainbow in Science Times.