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Hi,
It is indeed the time….
Had a couple of displays so far. Last Saturday was mostly hidden by tropospheric cloud but could be seen in the breaks.
There was another display this morning (2015/6/11-12). Moderate brightness but quite extensive and some nicely detailed features.Picture was taken at 02.27am BST.
Here’s hoping we get better displays as the summer goes on.
Also, if you have a pair of binoculars to hand, have a look at the NLC with them. The detail that can be seen is extraordinary at times. It’s also a good way to help identify faint NLC from twilight illuminated cirrus. The cirrus will not show any of this detail but even faint NLC generally does.
Cheers,
Bill.Hi Hygge,
I’ve dabbled briefly as a student that’s all. Indeed the fun is in the minutiae!
I’ll need to decide on how I’m going to spell them though, my spalling is crep….;-)
And Hi to Michael,
Your pics are fantastic, I really like the middle one with the hint of a coloured arc, lovely!
Whatever the reason, I do find NLC absolutely fascinating. I find them simply intruiging. I can still remember the night in July 1986 when I first saw them. The sky was just glowing with them. It was a remarkable sight and that sensation of intrigue has never gone away.
cheers,
Bill.Hi,
I can’t say for sure but the NLC Laconosous might have me to blame…
A number of years ago I took images of a very unusual NLC display that had “holes” in it.Now, the description lacunosus is from the latin, full of hollows or sometimes net or honeycomb like. However net like structures appear in NLC all the time so to differentiate between these linear features and more circular holes. The holes as a separate entity if you see what I mean. I proposed a lacunosous term might be applicable viz type L, be used to describe this.
Lacanosus being the closest tropospheric cloud which can have distinct holes I used this as an example. See images attached
Tropospheric: Cirrocumulus Laconosous.
Ergo
NLC: Laconosous.
This has been picked up an re-circulated by lots of places. But in many years of observing NLC I’ve only ever seen it a handful of times. Seems the “genuine” Type L is quite rare. So enigmatic it most certainly is…. ;-)
Keep your eyes peeled, I’d love to see more images of this.
cheers,
Bill.Hi,
Yep, I remember seeing that a while back.
But as far as I can tell they are looking at slightly different things.Polar Mesospheric Clouds exist over, well, the polar regions. The satellite instruments are looking at purely UV data. This limits the size of particle that are observed.
So what they are seeing isn’t the same as the visual NLC that we as humans observe.
They are probably related (I once read the line somewhere that NLC’s were the ragged southern edge of the PMC sheet) but the AIM satellite does not see NLC it sees PMC.Looking at the graph it only goes back to the 80’s. That’s only a couple of solar cycles and look at the difference in the solar activity over that period. Solar activity has an effect on the amount of UV arriving at the Earth. That in turn has an effect of the photochemisty going on.
The other thing to note VERY carefully is the y axis. These are units with an exponent of 10 e -6. So, far left top line, starts at ~11 e-6 and ends far right at ~ 13 e-6. Since the exponent hasn’t changed this is an increase of 2 parts per million in albedo. (I’m not a geophyisicist but I do have reservations about using the word “large” in their subtext a 2ppm!) It’s even smaller at the lower latitude end….
I don’t know if you’ve open up the papers listed but if I remember correctly there are some graphs where the error bars are bigger than the span of measurements. They also have merged different data sets and I’d bet the radiometery isn’t better than 1% ( that equivalent to 1000 parts per million).It’s presenting stuff such as this using words like “large” to the public that breeds the mild climate hysteria. I could be cynical and say that’s the goal, it improves the grant application chances…
However, these guys are professional scientists, so maybe they’re right but I still urge caution before embuing NLC with overtones of man made doom just yet. Of course, it also why they’re worth watching! ;-)
cheers,
Bill.Hi,
Despite the thick cloud and even light drizzle, I had the same experience up here in Glasgow.
With what seemed like the whole department up on the roof balcony, right on maximum coverage the clouds thinned and we had a great view for a couple of minutes.
I was really surprised by the crowds that seemed to spontaneously gather in the park across the road. LOTS of people out, probably cursing the clouds, but the clouds ended up giving us a comfortable and dramatic view (for a short while at least ;-)After the eclipse ended the clouds disappeared and there was lovely blue sky, typical….!
cheers,
Bill.Hi,
Exactly.
In good years there are several displays from your latitude so keep your eyes peeled!
cheers,
Bill.Hi Marsha,
Whilst you’re on the lower edge of the envelope I’ve seen reports from the US so there’s a chance.
I didn’t make the point about the solar cycle very clearly. What I mean is that NLC do get more frequent when the solar cycle is at its low point, then they reduce a bit when the solar cycle peaks but there is a delay in this effect. Roughly speaking if the solar max was last year the NLC occurence would probably be at a minimum this year. I hope that makes a bit more sense.
Anyway, keep a lookout low to the northern horizon through the summer nights June to July. I hope they oblige for you.
Cheers,
Bill.Hi Hygge,
Thanks, Whilst they’ve not been quite so prominent over the past couple years I would still use the word “common”. The very best displays last summer in the northern hemisphere (that I recorded) happened in the wee hours, 1am-3am local. That quite reasonably deters some people as there is never any guarantee!The occurence of NLC also show a clear anti phase relationship to solar activity (with some time lag). So, even with a weak solar max, the numbers are down a little at the moment. If you look through the archives on NLCNET you’ll see that NLC are recorded on most nights from somewhere across Europe through June and July, so they are there. It’s just they are often missed at any given location due to tropo cloud cover.
Here in the UK, particularly the NW mainland, even in summer the weather can put paid to seeing any.
What tends to catch peoples’ attention is when there is a really big “evening sector” display. Thats when they are seen before midnight. These last an hour or so before the sun dips down and they lose the illumination for a while. That’s whats been missing over the past few years.
Where are you (approximately)? If you’ve never seen them then persevere, it’ll be worth it. They can be more beautiful than any tropospheric cloud if you hit it lucky.I remember one night in 2006 when there was a cracker. I have never seen anything like it before or since. Strange long tendrils curling over the sky, really weird. Sadly no pictures as I had packed up at the observing site and at 3.30am was just too tired to un-pack the kit.
cheers,
Bill.Hi,
The past few postings got me thinking….A decade ago I put together a rather basic page on NLC’s after we had had a couple of years of tremendous displays. The NLCNET and forum were coming into reality at this time and there was a lot of interest.
It’s a bit basic, HTML 1.whatever in those days, no fancy graphics!
I’ve added a few more recent videos now but it might give people who are unfamiliar with the phenomena some background. It was a deliberate attempt to moderate some of the more extreme claims made about the “increasing” NLC activity.
Cheers,
Bill.Hi,
An excellent idea indeed…!I took this shot of La Palma when en route to Tenerife last year. The maximum altitude of La Palma is ~2400 metres, so this gives an idea of height scale.
Below are the rafts of stratocumulus that form at the temperature inversion and above is a solid lump of altocumulus.
cheers,
Bill.Hi Michael,
You are welcome. Monochrome imaging is quite an art. I don’t know if you’re of an age to remember when film was the medium used but IR film and appropriate filters could produce some amazing results.
Unless one is extremely brave and removes the IR blocking filter at lot of really good imaging effects are actually lost in standard DSLR imaging. The silicon in the detectors can be used out to over 1000nm, actually longer than most IR film but of course modifying the camera “ruins” it for everything else. (Mind you that depends on ones perspective!)Anyway NLC’s are very close to my heart. I’ve been observing them as an amateur since I first saw them in 1986 then as a “pro” whilst a postgrad in the mid 90’s. (I don’t know what the official CAS protocol is, but I hope nobody objects to a plug for another forum. I’m one of the admin team on the NLC observers forum at http://nlcnet.proboards.com/
This is usually very active from May through to August and is the forum for the NLCNET site mentioned by hygge)One of the intruiging possibilities about the NLC formation process is that meteoric ions are responsible. They are at the correct height and can be blown on very high speed winds.
So, if you think the last speed was fast have a look at this time lapse video I made from a series of stills.The images were taken from the observatory at Izana on Tenerife. The meteor flashes in the first frame and the decomposed remains are seen to drift from top right towards the centre left. Using some geometry I determined the wind speed to be 139m/s. Thats 499kph/310mph. This is up there with the fastest winds ever recorded!
However with the low atmospheric density and extremely low pressure it wouldn’t even rustle your hair; provided you lived long enough to think about it…. ;-)cheers,
Bill.Hi Michael,
Really excellent stuff! I do some research on NLC and a couple of years back cobbled together a piece of kit based on a monochrome low light level cctv camera.
I was interested in trying to determine the scattering properties of the MLC particles.
(they are tiny, a few hundred nanometers in diameter)
Most NLC images show the gorgeous sweeping bluey white shapes and forms.
It gets much more interesting and “3rd reality” as you put it when you image in monochrome.
The video was taken looking a lot higher than most NLC shots (almost but not quite overhead). The NLC were almost invisible to the unaided eye. It reveals the NLC in a whole new way. 82km up, shifting at 65m/s (~147mph) and a lot more ragged than people normally imagine!cheers,
Bill.Hi,
This is the only time I’ve seen nacreous clouds. Not much iridesence but very bright.
Taken at 16.23UT on 22/12/01. At my latitude ~55 deg 39 min north, sunset was at 15.51UT (basically the winter solstice). Sun was 4 degrees below the horizon at this time.Image is a scanned photograph, can’t find the negatives!
The display caused quite a still amongst local cloud spotters at the time!
Cheers,
Bill.
