National Geographic News
An iridescent cloud in Delhi, India.

This picture of an irridescent cloud was submitted by a National Geographic reader. The photo was taken in Noida, India.

Photograph by Harish Venkatesh

Lara Sorokanich

National Geographic

Published July 18, 2013

A halo of multicolored mist floats over an ominous storm. At first glance it looks like an angelic mural or even extraterrestrial activity. But this breathtaking photo is neither manipulated nor paranormal. It's an iridescent cloud, a phenomenon occurring right in our own atmosphere.

This photo was submitted to National Geographic by V. Harish, a university student and amateur photographer from Noida, India. It was captured in mid-July, shortly after a summer rainstorm, an ideal condition for rainbow clouds.

"I decided to take some shots of the after-shower scenery," said Harish. "As I was working on a shot of a dewdrop, my friend spotted an exuberant colored patch peeking above a cloud."

Iridescent clouds, known as "fire rainbows" or "rainbow clouds," occur when sunlight diffracts off water droplets in the atmosphere. And the recipe for these heavenly sights is actually pretty simple.

Like common cloud-to-ground rainbows, iridescent clouds usually accompany thunderstorms. According to atmospheric phenomena expert Les Cowley, they often appear in the late afternoon, on very hot and humid days. This stems from the fact that most rainbow clouds form on top of cumulus clouds—the fluffy cotton-ball-shaped clouds we often see in children's drawings.

"What happens is that the cumulus cloud, boiling upwards, pushes the air layers above it higher and higher," Cowley explained. "As the air gets pushed upwards, it expands and cools. And sometimes moisture in that air suddenly condenses into tiny droplets to form a cap cloud."

This "cap"—which scientists call a "pileus"—is the source of the brilliant spectacle.

"The droplets in the cap cloud scatter sunlight to form the gorgeous colors," Cowley said.

Though the ingredients for rainbow clouds seem simple, they're not spotted often, and are even less frequently photographed.

"For a moment we thought it was a portal opening for an alien species to come to Earth," said Harish, who had never seen a rainbow cloud before. "But the beauty of it really moved me, so I just took as many shots of it as I could."

A good call, according to Cowley, who says the rainbow clouds aren't a common occurrence.

"Not all pileus caps show iridescence," he said. "I usually get images of them from Florida, Southeast Asia, equatorial Africa."

"I felt very lucky to have seen this in India. It's a very rare sight," Harish said. "Me and the guy who accompanied still joke that it's an alien invasion, and share a laugh about it!"

Follow Lara Sorokanich on Twitter.

34 comments
Yashpal Krishna
Yashpal Krishna

I have seen it just yesterday. It was really beautiful.  In fact, it's the most amazing thing I have ever seen in the sky.


I do agree that it must be a really rare phenomenon, if not elsewhere, at least here in Visakhapatnam, India, for I am an avid skygazer and I neither saw nor heard about it before.


Unfortunately, I had neither a phone nor a camera. It would have really created a buzz in my friends' group had I uploaded a snapshot.


Anyway, thank you for the explanation and the photograph!

lotusgreen ~
lotusgreen ~

Hi Folks -- I don't know why my experience seems to vary so much from the article and the experience of those commenting here -- perhaps the weather here in San Francisco, but no -- I have a friend who lives in Montana's high desert whose experience matches mine: we see iridescence in clouds all the time!


I thing inadvertently mystifying it might deprive many folks from seeing them on their own. Practically every time there are thin clouds over the sun, you'll see these "rainbows." Some things will help: if you can find a way to block the sun and only see the clouds around it, that helps; if you have polarized sunglasses (most are), that helps; and also seeing it reflected in water, like a backyard pond helps. Sometimes, though, you'll see it with no helps at all.


Related are halos and sun-dogs and halos, less common in my experience than the iridescence but not impossible to experience -- which are also a a refraction phenomenon. See more here: http://www.atoptics.co.uk/

Flickr has a group devoted to the subject (though lately they seem to be heavy on halos): http://www.flickr.com/groups/sundogs_halos_sunpilars_atmosphericoptics/ and I have a set which, admittedly, includes some images which have been enhanced, and not altered:http://www.flickr.com/photos/lotusgreen/sets/72057594138939086/



DIANA DEES
DIANA DEES

Clouds like these can also be caused by the aerosol spraying of over 10 million tons annually of aluminum, plus barium, strontium, heavy metals, smart dust, sencil technology, and nanomaterials.  Check out Gobal Geo engineering  and Solar Radiation Management Programs.  Nasa has programs of,"Consistent Contrails," with,"Particles," to reflect solar radiation.  Aeronet.gov is another site.  Owning the Weather by 2025 is a US government paper describing weather modification tactics and goals.  National Geographic has always been a credible source of information and I would love to see more information on this very important topic!

Tom Day
Tom Day

I saw one of a couple of weeks ago. It's the first time as far I can remember that I've seen one. 1000 Islands, Ontario, Canada.

C ODonnell
C ODonnell

Saw one at the Woodstock concert, sort of.

Zuhair Ali
Zuhair Ali

Hi!~
i believe i have a picture of a rainbow cloud. I've wondered what it was until i read this article of yours

dadster dadster
dadster dadster

Harish , excellent work .

Its very rare in NOIDA . I have been living in Noida for 25 years and have had no luck to see one like this , though i am an avid sky-watcher in all weather conditions. There is always something great about the skies in day and night at all times   and some new scenery .and lighting too !
Congratulations ! Well Done. Keep it up ! 

Masrat Khan
Masrat Khan

Harish, this is great! You make the Shiv Nadar University very proud. Keep the clicking spirits up!

Debra Medlock
Debra Medlock

Not so rare! See them a lot here in the mountains! have photos of them on my camera right now.  Just look up, people, and see what's up there!

Andrew Booth
Andrew Booth

"For a moment we thought it was a portal opening for an alien species to come to Earth". Seriously?

Christian Duerig
Christian Duerig

Please notice, that those "rainbows" are of order 3 and higher. Prof. Walter Lewin explains you more in details about them via You Tube in his lecture "Love For Physics". It was in 2011 when the first photographs were taken from a rainbow of order 3. When you know where to look for them, you will discover them. You will learn to detect even the Green Flash. Have a lot of fun with Walter Lewin. (He has now retired from MIT) 

Arjun Singh Chouhan
Arjun Singh Chouhan

I've been lucky to see this phenomenon too and was even luckier to snap it too : )

Arjun Singh Chouhan
Arjun Singh Chouhan

I've been lucky to see this phenomenon too and was even luckier to snap it too : )

Carol Music
Carol Music

Thanks to NatGeo for sharing this photo and the explanation of these rare and most beautiful nature events. I love all things rainbow and now I have a new one to add to my list! To those below who shared their photos, my thanks as well!

Matt Marlin
Matt Marlin

Weather phenomena qualify as yet another unusual affinity of mine.  The "iridescent cloud" has to be one of the rarest and most breathtaking displays of mother nature.


Andrew Booth
Andrew Booth

@Debra Medlock I quite agree Debra. I've seen them too. Many people do see such weather phenomena - they just don't notice them or take any interest.

Christian Duerig
Christian Duerig

@Carolina E. 

Please, learn from Prof. Walter Lewin via You more about rainbows. I am sure, you will enjoy it. Have a bit patient until you know the phenomenon rainbow with all the details. The Rayleigh Scattering explains all. Crigs

Lara S.
Lara S.

@Andrew Booth @Debra Medlock How lucky that you get to see such beauty so frequently! I know that where I'm from it almost never happens—too cold most of the year!

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