APOD: Nacreous Clouds over Lapland (2023 Feb 09)

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Expand view Topic review: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by Chris Peterson » Fri Feb 10, 2023 1:14 am

SeedsofEarfth wrote: ↑Fri Feb 10, 2023 1:07 am This seems to me to be more of a meteorological discussion than an astronomical one.
As we discover more and more planets, and start observing details of their atmospheres, the two have significant overlap.

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by SeedsofEarfth » Fri Feb 10, 2023 1:07 am

This seems to me to be more of a meteorological discussion than an astronomical one.

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by johnnydeep » Thu Feb 09, 2023 7:49 pm

Ann wrote: ↑Thu Feb 09, 2023 6:58 pm
nrt wrote: ↑Thu Feb 09, 2023 6:19 pm What is the importance of mountains in the creation of these clouds? I have read multiple times they help in the process, but considering the height of the clouds (15 - 25km) and compared to the usual mountains in these areas are just 1 - 2km tall (if even that) I just don't get how they would matter.
I don't think mountains have anything to do with the formation of nacreous or noctilucent clouds. Lenticular clouds are another matter. They do form in the presence of mountains.
Opensnow wrote:

A lenticular cloud is a good "forecast indicator" as tall mountains accentuate incoming high-level moisture well ahead of an approaching front. This interception of high-level moisture forms lenticular clouds, and as a result, they are a good warning sign of an approaching weather front and sometimes a big snowstorm.
Ann
That pic of lenticular clouds is impressive! I wonder if it is normal for them to be stacked ziggurat-fashion like that, in mimicry of the mountain they form above...

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by orin stepanek » Thu Feb 09, 2023 7:43 pm

I don't much care how they are formed; but they do add to the beauty of the sky surrounding mother Earth! 8-)

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by Ann » Thu Feb 09, 2023 6:58 pm

nrt wrote: ↑Thu Feb 09, 2023 6:19 pm What is the importance of mountains in the creation of these clouds? I have read multiple times they help in the process, but considering the height of the clouds (15 - 25km) and compared to the usual mountains in these areas are just 1 - 2km tall (if even that) I just don't get how they would matter.
I don't think mountains have anything to do with the formation of nacreous or noctilucent clouds. Lenticular clouds are another matter. They do form in the presence of mountains.
Opensnow wrote:

A lenticular cloud is a good "forecast indicator" as tall mountains accentuate incoming high-level moisture well ahead of an approaching front. This interception of high-level moisture forms lenticular clouds, and as a result, they are a good warning sign of an approaching weather front and sometimes a big snowstorm.
Ann

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by nrt » Thu Feb 09, 2023 6:19 pm

What is the importance of mountains in the creation of these clouds? I have read multiple times they help in the process, but considering the height of the clouds (15 - 25km) and compared to the usual mountains in these areas are just 1 - 2km tall (if even that) I just don't get how they would matter.

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by Fred the Cat » Thu Feb 09, 2023 5:42 pm

Having Finnish grandparents who migrated to Astoria, Oregon, today's APOD gave me chills. :brr: It got a little chillier investigating the sights and sounds of Lapland.

Water laping around while you watch the northern lights shows a intestinal fortitude now lost in my own genome. :old: I do retain one tradition. :wink:

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by Chris Peterson » Thu Feb 09, 2023 5:40 pm

Ann wrote: ↑Thu Feb 09, 2023 5:26 pm
No one has answered yet, so I'd better say something.

This is a beautiful image, and Swedish television has recently shown us similar clouds over northern Sweden. Today's APOD is from Finland, east of Sweden.

The nacreous clouds "are related to" the noctilucent clouds that we see in the summer at latitudes comparable to southern Sweden. The similarity is that both the nacreous and the noctilucent clouds form in the stratosphere at very cold temperatures, and they shine in the sky before down or after sunset (noctilucent clouds can shine all night).

But the noctilucent clouds are blu-ish, whereas nacreous clouds are multicolored. Don't ask me why!
Nacreous clouds produce their visual effect through diffraction, which tends to create colors. Noctilucent clouds shine by reflection and a bit of scattering, which is why they are white or blue.

Re: APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by Ann » Thu Feb 09, 2023 5:26 pm


No one has answered yet, so I'd better say something.

This is a beautiful image, and Swedish television has recently shown us similar clouds over northern Sweden. Today's APOD is from Finland, east of Sweden.

The nacreous clouds "are related to" the noctilucent clouds that we see in the summer at latitudes comparable to southern Sweden. The similarity is that both the nacreous and the noctilucent clouds form in the stratosphere at very cold temperatures, and they shine in the sky before down or after sunset (noctilucent clouds can shine all night).

But the noctilucent clouds are blu-ish, whereas nacreous clouds are multicolored. Don't ask me why!

Noctilucent clouds by Dammfri School July 5 2020.jpg
Noctilucent clouds over my hometown of Malmö, July 5, 2020.

Ann

APOD: Nacreous Clouds over Lapland (2023 Feb 09)

by APOD Robot » Thu Feb 09, 2023 5:06 am

Image Nacreous Clouds over Lapland

Explanation: Vivid and lustrous, wafting iridescent waves of color wash across this skyscape from Kilpisjärvi, Finland. Known as nacreous clouds or mother-of-pearl clouds, they are rare. But their unforgettable appearance was captured looking south at 69 degrees north latitude at sunset on January 24. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers, the clouds can diffract sunlight even after sunset and just before the dawn.

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