I parsed that as "I'm pretty sure I saw them many times, so these particular clouds can't really be rare" + "it never occurred to me that some cloud types could be actually so rare to be news if you so see them".
Unless you live near the Arctic Circle these are quite rare to see. I thought I saw something similar from sunny Florida and it turned out to be regular cirrus clouds getting lit up by the sun.
Also, a 2D picture doesn't give you the depth information to see that these are really, really far away. Like I've seen meteor showers and have no doubt the altitude they are at. These cloud formations are about that height (50-100km)
I can't find anything in Google Books either. I'm assuming it should be "arrive as", but this is either a translation of something or a misattribution.
At best, these are rare in the context of SF norms. They are also more common than described, just that normally they go unobserved. We only really notice them at dawn when they get hit by sunlight early due to altitude.
The category is not an arbitrary one, primarily because they are higher than other weather phenomena, being in the mesosphere. In fact, there is a hypothesis that they did not occur (or perhaps only occasionally even by the standard of their current rarity, such as after large volcanic explosions) until the industrial revolution.
I've been often surprised at how many "cloud nerds" are in the US, that know so many of the Latin classification terms for different cloud formations. In Europe it seems to be a much more niched thing, and I've never heard anyone discuss clouds at this level.
Is it a subject for which importance is placed in school?
Wouldn't say importance, but I do recall a class where some of the different types of clouds and weather patterns were mentioned. Well, it was either class or a Discovery Channel program, back when they still did educational things.
These days it's probably curious youtubers mentioning these things. I probably underestimate how educational youtube and co are. Mind you, it's superficial knowledge at best, and with the rapid fire distractions going on, it'll be in the one ear and out the other.
I grew up in the United States. I have a vivid memory of learning the words for clouds (e.g., cumulus, stratus, cirrus, etc) at the age of six in the first grade. We didn't need to able to spell them, but we had to be able to identify them by matching pictures of the clouds with the words.
I experimented with visual ray cloud busting for a while.
Get concentrated up with meditation first. Then find a likely target (fluffy yet defined. Isolated...). Lay sharpened gaze upon the cloud. Starts to break up in a minute.
I caught such on camera about 10-12 years ago in southern Sweden. Though curious enough for me to go get my camera, at the time they didn't strike me as rare as I had seen them form before.
I have the same feeling that these are not very uncommon. My guess is, as I'm also from Sweden, is that the period of time the sun is in the right position for this is much longer at these latitudes.
I'm certain Iv'e seen clouds like these many times, at least 5 times if not more.
They're not especially rare at these latitudes (I live in southern Finland, ~61°N). You see them fairly frequently on summer nights, rocket launches or not. But what is interesting that nobody seems to have written anything about them until the 20th century, which could indicate that suitable condensation nuclei did not exist in the upper atmosphere before humans started emitting them.
I live in SF and didn't see the clouds that morning... but did see the rocket launch. Even though it's relatively tiny in the sky being over 200 miles away, still very cool. I was able to see the initial boost phase (surprisingly clearly), the stage separation, the second stage continuing on its way and some of the booster maneuvering for landing... just illuminated dots on the sky with some faintly visible exhaust plume.
The reported "clouds" probably didn't really become visible until later, well after I went back inside.
These clouds are only visible before sunset or after sunrise. They're very weak and make themselves visible when the surface is in the shadow, but they are not thanks to their impressive an highly unusual altitude (they're well well above all weather).
On the right latitudes 60+ these can be seen each year in the months around summer solstice during the short nights. Here's a timelapse over 2 hours if you want to see how some types of them move through the sky https://imgur.com/gallery/PlyifNr
Noctilucent clouds are the only natural-occuring ice on the planet that isn't hexagonal, instead having mostly cubic crystals, which are stable in the low temp/low pressure environment. Cubic ice is very similar to hexagonal, unlike some of the more exotic ices that exist in high pressure and/or high temp environments in places like Europa's mantle.
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[ 2.3 ms ] story [ 100 ms ] threadAlso, a 2D picture doesn't give you the depth information to see that these are really, really far away. Like I've seen meteor showers and have no doubt the altitude they are at. These cloud formations are about that height (50-100km)
https://www.google.com/search?q=%22they+will+first+arrive+us...
Is it a subject for which importance is placed in school?
These days it's probably curious youtubers mentioning these things. I probably underestimate how educational youtube and co are. Mind you, it's superficial knowledge at best, and with the rapid fire distractions going on, it'll be in the one ear and out the other.
Also, big federal agencies in USA (like NASA) have a sizable education/outreach budget. NOAA would be no exception, a quick search returns $34M.
Get concentrated up with meditation first. Then find a likely target (fluffy yet defined. Isolated...). Lay sharpened gaze upon the cloud. Starts to break up in a minute.
(my copy of The Cloudspotter's Guide, their first publication - written by one of the society's founders - is in the bookshelf next to me as I type)
I'm certain Iv'e seen clouds like these many times, at least 5 times if not more.
The article explicitly states the rarity is at the given latitude:
“Such clouds are very rare at this latitude and also in winter…”
Naturally they chose to over-emphasize the rarity aspect in the headline, otherwise no-one would bother clicking.
http://www.nightskyhunter.com/Noctilucent%20Clouds.html
It describes what they are, how they differ from normal clouds, and how to recognise them.
The reported "clouds" probably didn't really become visible until later, well after I went back inside.