APOD: Iridescent Clouds over Sweden (2020 Jan 15)

[APOD Robot]

Iridescent Clouds over Sweden

Explanation: Why would these clouds multi-colored? A relatively rare phenomenon in clouds known as iridescence can bring up unusual colors vividly or even a whole spectrum of colors simultaneously. These polar stratospheric clouds, also known as nacreous and mother-of-pearl clouds, are formed of small water droplets of nearly uniform size. When the Sun is in the right position and, typically, hidden from direct view, these thin clouds can be seen significantly diffracting sunlight in a nearly coherent manner, with different colors being deflected by different amounts. Therefore, different colors will come to the observer from slightly different directions. Many clouds start with uniform regions that could show iridescence but quickly become too thick, too mixed, or too angularly far from the Sun to exhibit striking colors. The featured image and an accompanying video were taken late last year over Ostersund, Sweden.

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[Ann]

More nacreous clouds from Sweden! Why didn't I get to see them?

Ann

[Lovecraft]

The Colour Out of Space!!!

[orin stepanek]

Pretty!

IridescentClouds_Strand_960.jpg (26.82 KiB) Viewed 5322 times

[Psnarf]

Does the term 'clouds clouds' refer to the atmospheric clouds and the reflection of the clouds?

[neufer]

More nacreous clouds from Sweden! Why didn't I get to see them?

• 1) You're at the wrong end of Sweden.
  2) You don't spend enough time outdoors at twilight.

[Ann]

More nacreous clouds from Sweden! Why didn't I get to see them?

• 1) You're at the wrong end of Sweden.
  2) You don't spend enough time outdoors at twilight.

You're half right, at least!

Ann

[Chris Peterson]

More nacreous clouds from Sweden! Why didn't I get to see them?

• 1) You're at the wrong end of Sweden.
  2) You don't spend enough time outdoors at twilight.

You're half right, at least!

Heck, in Sweden during the winter, even in the south, a lot of people go to work in the dark and come home in the dark. On the other hand, in the summer, you've got a lot of hours of twilight to enjoy. Not likely to see nacreous clouds in the summer, though. But you can look forward to noctilucent clouds then. And while you may have more gray days than you'd like, some of the best solar halos to be seen are in your part of the world on sunny days.

[neufer]

More nacreous clouds from Sweden! Why didn't I get to see them?

• 1) You're at the wrong end of Sweden.
  2) You don't spend enough time outdoors at twilight.

You're half right, at least!

At NOAA I applied the Fast Fourier Transforms I had used extensively in the Army to spectrally time analyze wind turbulence in order to generate Voigt profile IR & microwave absorption lines to calculate atmospheric transmittances.

I also invented my own Half Fast Fourier Transforms which produce Fourier Transforms when applied twice.

Unfortunately, for some reason, I could not get anyone to published my Half Fast Fourier Transform algorithm.

[schumach@texas.net]

Iridescence if present can also be observed by placing the Sun behind a distant object; that is, putting yourself in the shadow of that object such that you can see the sky near the Sun without being overwhelmed by brightness near the Sun. A tall building, electric transmission pylon, distant spire of rock et cetera all serve.

[Ann]

• 1) You're at the wrong end of Sweden.
  2) You don't spend enough time outdoors at twilight.

You're half right, at least!

Heck, in Sweden during the winter, even in the south, a lot of people go to work in the dark and come home in the dark. On the other hand, in the summer, you've got a lot of hours of twilight to enjoy. Not likely to see nacreous clouds in the summer, though. But you can look forward to noctilucent clouds then. And while you may have more gray days than you'd like, some of the best solar halos to be seen are in your part of the world on sunny days.

True, Chris. I'm not really complaining, just putting on a little show.

Ann

[Ann]

• 1) You're at the wrong end of Sweden.
  2) You don't spend enough time outdoors at twilight.

You're half right, at least!

At NOAA I applied the Fast Fourier Transforms I had used extensively in the Army to spectrally time analyze wind turbulence in order to generate Voigt profile IR & microwave absorption lines to calculate atmospheric transmittances.

I also invented my own Half Fast Fourier Transforms which produce Fourier Transforms when applied twice.

Unfortunately, for some reason, I could not get anyone to published my Half Fast Fourier Transform algorithm.

Oh wow, Art. I clicked that first link, and... yes, there are people there who are math geniuses who can think of phenomena in extremely abstract ways and have it make sense to them. I remember reading an interview with a little boy genius, who was asked to explain how he could understand maths the way he did. "I see the equations as a tree," he explained. "Branches grow out of the trunk or are cut off when I do my calculations."

M-hmm. I get that completely. ¯\_(ツ)_/¯ Anyway, Art, thanks for being a genius. It's refreshing to be in the company of people who see patterns in the framework of the world that are utterly obscure to me.

There are a few other really brilliant men here at Starship Asterisk*, unless I'm much mistaken. Thanks for being brilliant in the threads of Starship Asterisk*!

Ann

[Chris Peterson]

• 1) You're at the wrong end of Sweden.
  2) You don't spend enough time outdoors at twilight.

You're half right, at least!

At NOAA I applied the Fast Fourier Transforms I had used extensively in the Army to spectrally time analyze wind turbulence in order to generate Voigt profile IR & microwave absorption lines to calculate atmospheric transmittances.

I also invented my own Half Fast Fourier Transforms which produce Fourier Transforms when applied twice.

Unfortunately, for some reason, I could not get anyone to published my Half Fast Fourier Transform algorithm. :cry:

Reminds me of one of the first serious projects I was involved in out of college, designing a FFT processor for a PC. It was a full-sized ISA card, packed with chips, including its heart, a hardware multiplier chip. It was a pretty big project.

Today, when I'm doing demonstrations in front of a middle school class, I run real-time FFT analyses (with graphical output) on audio data on my cellphone, faster than that dedicated board was able to do.

[neufer]

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Nacreous clouds + sunshine = ozone hole =>

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