Explaining the phenomenon of five-colored clouds in the sky of Ho Chi Minh City, is there a "bad omen" coming?

The phenomenon of five-colored clouds appearing in the sky in Saigon recently made many people excited to take photos and share them on social networks. The phenomenon of iridescent clouds can be easily observed with the n.aked eye.

On the afternoon of May 12, five-colored clouds appeared in the sky of Ho Chi Minh City. Many people found it strange and competed to take photos to s.how off on social networks. The brilliant color of this cloud quickly attracted people's attention. In many locations, you can easily see colorful clouds. This phenomenon lasts for a few minutes then disappears.

Many people did not hesitate to record these impressive moments on their phones and share them on social networks. On social networking sites, many people expressed their excitement and surprise at the unique beauty of iridescent clouds.

Besides, many Facebook Fanpages and famous artists such as Hong Van, Ho Ngoc Ha,... also shared about seeing iridescent clouds this afternoon. Everyone felt amazed by the beautiful, sparkling natural scene. However, this is not the first time the cloud phenomenon has appeared in Vietnam or Ho Chi Minh City.

In June 2020, this five-colored cloud appeared in the sky in Hanoi and some other provinces. The cloud also lasted a few minutes in the afternoon then disappeared. Or even longer, five-colored clouds in Hanoi in 2010, Saigon in 2011, Quy Nhon in 2012...

Mr. Nguyen Anh Tuan, Chairman of the Ho Chi Minh City Astronomy Club, said that iridescent clouds are not a rare phenomenon. However, the iridescent clouds appearing in the sky of Ho Chi Minh City this afternoon have beautiful colors and are much larger in size than previous appearances. Therefore, people in Ho Chi Minh City can easily observe this cloud.

"With decades of experience observing astronomical phenomena, I evaluate this afternoon's iridescent clouds as the most beautiful and widest among the iridescent clouds that have ever appeared in Ho Chi Minh City" - Mr. Tuan said. .

It is known that the colors in the clouds when this phenomenon occurs are not the same as the rainbow phenomenon (7 colors) according to the solar spectrum, but the colors in the iridescent clouds are sometimes pale, sometimes very colorful.

According to the beliefs of people in Taiwan (China), China, Singapore,... the appearance of five-colored clouds is considered a sign of luck and auspiciousness. As for countries like Scotland, Canada,... iridescent clouds appear, signaling that very harsh weather is approaching.

Many people speculate that the appearance of iridescent clouds is a sign of bad weather or a strange "omen" about to happen. This information spread online, causing many people to be confused. Some rumored information is widely spread on social networks such as: "SO2 storm", "ozone layer hole", "extremely heavy rain coming soon"...

Regarding this issue, Mr. Le Dinh Quyet - Head of the Forecasting Department of the Southern Regional Hydrometeorological Station: "We can only observe the rainbow phenomenon when we turn our backs on the sun, that is, usually appears in the morning or evening, the viewing angle is 42 degrees; or occurs when it has just stopped raining.

As for the phenomenon of iridescent clouds, we can observe more widely, in any location. This is just an optical phenomenon in meteorology, does not indicate any signs of upcoming weather developments."

What is the phenomenon of iridescent clouds?

Cloud iridescence, often called "cloud iridescence", is the appearance of colors in a cloud similar to what we see on oil films in a puddle of water, lying in the general vicinity of the Sun or Moon. It is a phenomenon most commonly seen in altocumulus, cirrocumulus, lenticular clouds and spiral clouds. Iridescence is also seen in rarer stratospheric clouds (or "nacreous clouds").

Colors are usually pastel, but can be very vibrant. When occurring close to the Sun, the effect can be difficult to detect as it is submerged in the Sun's glare. This can be overcome by blocking sunlight with one's hand or observing it under a tree or building. Other aids are dark glasses, or observing the sky reflected in a convex mirror or in a lake.

This effect is similar to iridescence. Iridescent clouds are diffraction phenomena caused by small water droplets or small ice crystals that scatter light individually. Larger ice crystals do not produce iridescence, but can cause halos, another optical phenomenon.

If parts of the cloud contain small water droplets or ice crystals of similar size, their cumulative effect is seen as color. The cloud must be optically thin, so that most rays encounter only a single droplet. Therefore, iridescence is mainly seen at cloud edges or in semi-transparent clouds, while newly formed clouds produce the most brilliant and colorful iridescence. When the particles in a thin cloud are very similar in size over a wide range, the iridescence takes the form of a corona, a bright circular disk around the Sun or Moon surrounded by one or more color ring.

According to scientists, the appearance of iridescent clouds often comes with h.ot, dry weather. As h.ot air rises, it meets cold winds and condenses into clouds.

Sunlight will then refract through the ice crystals in the clouds, however, due to low humidity, the water droplets in the clouds cannot combine into large enough raindrops and fall to the ground.