Les Cowley

Image of the Day…” Upside-down Rainbow…”

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Brief, beautiful circumzenithal arc

Circumzenithal arcs are sometimes referred to as “upside-down rainbows” or “a smile in the sky.”

View larger. | Photo by Amanda Cross.

Amanda Cross in Lancashire, UK, submitted these photos to EarthSky. They show the beautiful sky phenomenon known as a circumzenithal arc. Amanda wrote:

Sun halo spotted on the school run, dashed home for camera then the circumzenithal arc appeared above, smiling. Worth dashing home for! Smiling in the sky, upside down rainbow 🙂

Only lasted 10 minutes then it was gone, brief but beautiful.

Photo by Amanda Cross.

Les Cowley of the great website Atmospheric Optics says of these graceful and colorful arcs:

The circumzenithal arc, CZA, is the most beautiful of all the halos. The first sighting is always a surprise, an ethereal rainbow fled from its watery origins and wrapped improbably about the zenith …

Look straight up near to the zenith [overhead point in your sky] when the sun if fairly low and especially if sundogs are visible. The center of the bow always sunwards and red is on the outside.

Les says that the most ideal time to see a circumzenithal arc is when the sun is at a height of 22 degrees in the sky. Look here to see Les Cowley’s illustration of the various kinds of halo phenomena, related to circumzenithal arcs.

Bottom line: Photo from September, 2015 – Lancashire, UK – of a circumzenithal arc. They’re sometimes called upside-down rainbows, or “a smile in the sky.”

Source…..www.earthskynews.org

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Image of the Day….Whale Rainbows…!!!

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Whale rainbows

I didn’t know whales could produce their own rainbows, but … they can.

Iridescence above a whale in Monterey Bay. Photo by William Drumm via Oceana

Here’s a collection of photos, and a video, of rainbows made by whales. Atmospheric Optics guru Les Cowley told me:

These are rainbows made by drops from the whale’s blowholes rather than the more usual raindrops.

These are true rainbows, not iridescence like the iridescence you sometimes see in clouds. Les told me:

Iridescence can be anywhere but it is most common close to the sun. The colors are disordered and pastel.

Rainbows (at least the everyday ones!) are opposite the sun. Their colors are always in the order red, orange, yellow, green, blue, indigo, violet.

Les Cowley has another whale rainbow photo in his Optics Picture of the Day series.

Also, be sure to check out the video below, which rsean9000 posted on YouTube in 2011, after a whale-watching cruise in Nova Scotia.

Whales’ blowholes, of course – which are their noses – are on the top of their heads. A whale breathes through its blowhole, but, contrary to any whale cartoons you might have seen, whales don’t actually blow water through their blowholes. Instead, they blow out a combination of air (they breathe out carbon dioxide, just as we human mammals do) and mucus. A whale’s out-breath is warm from the whale’s warm body, just as your out-breath is warm. In the colder and lower-pressure air above, water vapor that’s present condenses out above the whale as droplets.

View larger. | Iridescence in the mist of a blue whale - one of our world's most endangered species - off the coast of southern California in 2014. Image via Craig Hayslip/Oregon State University.It’s this spray of fine droplets, known as the blow, that creates the rainbow.

Iridescence in the mist of a blue whale – one of our world’s most endangered species – off the coast of southern California in 2014. Image via Craig Hayslip/Oregon State University.

Source…..www.earthsky.org

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This Date in Science….Feb 11 2010……When a Spacecraft Destroyed a Sundog…

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February 11, 2010. On this date – the coolest space launch ever for us sky fans! I ran into this image and video yesterday via a post on Google+. I was interested when I saw a quote from the person who runs the world’s absolute best website for sky optics, Les Cowley of the website Atmospheric Optics. It turns out this story has been around a few years, but I liked it and thought you might, too. It began with the launch five years ago of NASA’s Solar Dynamics Observatory (SDO), one of several observatories that keep an eye on our sun. It seems that when SDO lifted off from Cape Canaveral on February 11, 2010, on its mission to observe the sun, it first destroyed a sundog in Earth’s atmosphere – in the process bringing to light the new form of ice halo – and teaching those who love and study sky optics new things about how shock waves interact with clouds.

The video above shows SDO’s 2010 launch via an Atlas V rocket. Watch it now, and turn up the volume to hear people cheer when the spacecraft’s passage through the atmosphere destroyed the sundog – which is a bright spot in the sky, formed by refraction of sunlight through plate-shaped ice crystals, which drift down from the sky like leaves fluttering from trees. If you have to, watch it twice to see the luminous column of white light that appears next to the Atlas V.

Les Cowley explained in this 2011 post at Science@NASA:

When the rocket penetrated the cirrus, shock waves rippled through the cloud and destroyed the alignment of the ice crystals. This extinguished the sundog.

The sundog’s destruction was understood. The events that followed were not. Cowley said:

A luminous column of white light appeared next to the Atlas V and followed the rocket up into the sky. We’d never seen anything like it.

Cowley and colleague Robert Greenler at first couldn’t explain this column of light. Then they realized that the plate-shaped ice crystals were organized by the shock wave from the Atlas V. Cowley explained:

The crystals are tilted between 8 and 12 degrees. Then they gyrate so that the main crystal axis describes a conical motion. Toy tops and gyroscopes do it. The earth does it once every 26000 years. The motion is ordered and precise.

Love it!

View larger. | Optics experts in the U.K. have discovered a new form of ice halo. Image Credit: NASA/Goddard/Anne Koslosky View larger. | When the Solar Dynamic Observatory (bright streak in lower right quadrant of photo) lifted off from Cape Canaveral on February 11, 2010, its launch enabled optics experts to discover a new form of ice halo. Image via NASA/Goddard/Anne Koslosky

Bottom line: When NASA’s Solar Dynamics Observatory (SD0) lifted off from Cape Canaveral on February 11, 2010, on its mission to observe the sun, it first destroyed a sundog in Earth’s atmosphere – in the process bringing to light the new form of ice halo – and teaching those who love and study sky optics new things about how shock waves interact with clouds.

Via Science@NASA website

SOURCE:::: http://www.earthskynews.org

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