Discussion on NLCs

[Roman White]

I want to see everyone's opinion on this subject:
Do NLCs refer to 'Astronomy' section or to 'Weather' section (e.g. on this forum)?

I have a similar dilemma on my website: I don't know whether to put an NLC page to 'Astronomy' section or to 'Weather' section.

My opinion: NLCs have a 80 km elevation above an planet's surface, this means they exist in the upper parts of Earth's atmosphere (mesosphere). In this case they refer to weather, as well as Cirrus.
But in the other hand, NLC observations are nearly the same as astronomic observations. In this case they may refer to astronomy.

Someone can say that meteors also arrive in an Earth's atmosphere (even in the lower parts of it). But meteor bodies come from cosmos, and NLCs exist in the atmosphere constantly.

My vote: 'Weather'

[martinastro]

I have gone through this battle many times myself. They really fall into both categories so either would be fine. In my personal view, I place them in the Astronomy section.  A Pick between....

Astronomy

Atmospherics

I don't think they should be in a weather section because all our weather takes place in the troposphere and NLCs dominate the Mesosphere far above.

Paul will know what section to post NLC images. I'm sure the astronomy section will be fine. 

Great question Roman 

[Paul]

Excellent question Roman! I've always put them in astronomy but only because they are something that I observe using astronomical techniques at a time of the year that proper astronomy is difficult to do as it doesn't get properly dark.

With my admin hat on, I'm entirely happy to see reports of observations in either place.

P.

[brianb]

They really fall into both categories so either would be fine.

Hmmm, perhaps we should measure the height (triangulation? Running up there with a tape measure is hardly possible ) ... space (therefore astronomy) starts at 100 Km.

[martinastro]

Another way to look at it is that the meteoritic particles which cause NLCs in our atmosphere come from Space 

[brianb]

the meteoritic particles which cause NLCs in our atmosphere come from Space

If that's the true source of the necessary condensation nuclei - volcanic dust injection into the stratosphere is a possibility, and the conjectured link between NLC frequency & intensity and solid fuel rocket launches remains unproven either way.

Possibly there are several sources for condensation nuclei in the upper stratosphere / mesophere.

[Roman White]

and the conjectured link between NLC frequency & intensity and solid fuel rocket launches remains unproven either way.

Hmm, very interesting, I have never heard this before.

[martinastro]

The link between rocket launches and NLC formation is not a good one. Yes, NLC type clouds have been seen after launches but they are very different from real NLCs. There were no rockets around in 1849 when NLCs were first recorded by Thomas R. Robinson from Armagh Observatory. NLCs cannot be explained by rockets or plane contrails as some people suggest because they simply do not match the historical data.

The true cause of NLCs is still unknown as you say, the dust either comes from below or from above, perhaps both. Volcanic dust would have it's role to play by being ejected into the Troposphere, the jet stream may drive it into the stratosphere but I can't understand how this material would enter the Mesosphere unless gravity waves can do this, Ken kennedy from the BAA thinks they can. I think an extraterrestial source is the best explanation, at least, that's what I believe. There are tones of meteoritic material entering the Earth's atmosphere every day, greater in abundance than volcanic ash.

Most people reject the dust theory now but I think it holds weight. Here's a NASA article

http://science.nasa.gov/headlines/y2003/19feb_nlc.htm