NLC discussion

Update (2013/06/11): I noticed that one of the tweets was out of order. I've put it back in the correct chronology.

This post comes about due to noctilucent cloud (NLC) images from last night. It is a conversation I had on Twitter today. A few people re-tweeted (RT) my NLC images and, out of curiosity, I looked at a couple of profiles to see if they were people I might want to follow. @ClimateRealists caught my eye because their next tweet was directed at my local weatherman (Paul Hudson) and included an astronomical connection:


I hadn't heard of a link between meteorites and noctilucent clouds so I responded.



The meteorite and moon reference turns out to be this interesting story that I missed when I was away travelling. The asteroid mentioned may have been one of the few that have gone by in the past few months or so.


I wanted to quickly clear up that my mention of "human history" was certainly not meant to imply that humans are the cause for NLCs (I was unaware of evidence one way or the other on that so was staying agnostic):






I read the Science@NASA article and was interested to find out that they said that observations showed that "meteor smoke" was the nucleation point for the water vapour that freezes and causes NLCs. There isn't much water vapour at the altitude of NLCs (80 km) as the scale height of water vapour is about 2 km. The Science@NASA article says that an increase in methane in the atmosphere is providing the extra water vapour that enhances NLCs so that we see them more now.





























NLCs are not a local phenomenon like normal clouds. They are at very high altitudes - about 8 times higher than passenger planes - so can be seen over very wide areas. In fact, @mars_stu and @yodatheoak's images of the NLCs seemed to be exactly the same clouds I was looking at last night.


In Tweetdeck I saw that they were using two different operating systems to send tweets.














































This was true. My next door neighbours had turned up at the door saying they thought a squirrel was stuck and would I help. We couldn't see up the drain pipe (it wasn't straight) so we couldn't tell if it was still there or not. I suggested we use a hosepipe to put a little bit of water on the roof and check if the water emerged at the bottom. I didn't want to drown the squirrel, just test if it was still there. It turned out that it was and a slightly damp squirrel darted out of the drain pipe and scampered off.








The meteor connection is an interesting idea. I'm not convinced that meteors alone can be the cause of NLCs as I don't really buy @ClimateRealists's argument that people had just referred to them as "strange clouds" before 1885 so they were there, they were seen, but unreported. It is possible that this assertion is true but I'd like to see something describing NLC-like phenomena from earlier dates before I'll take it seriously. Perhaps a historian of astronomy would be helpful here.

If they weren't seen before 1885, there is something different between before and after the late 19th century. The Science@NASA story that @ClimateRealists pointed me to suggested it was due to increasing methane. @ClimateRealists seem to object to that idea although @ClimateRealists's website does state that there has been climate change so perhaps they don't object. Perhaps they were just against the idea of a man-made cause and kept missing me telling them that I wasn't saying anything about that. I was only challenging their assertion that NLCs have been this bright and regular for astronomical timescales.

I can't help but worry that it is all my fault when someone seems to be at crossed-purposes with me for so long in a discussion especially when I've worried about that from the beginning. I get frustrated because I ask if there has been a misunderstanding and am told there isn't despite it increasingly seeming to be the case. This seems to happen semi-regularly for me. My frustration is largely at myself for not knowing what I'm doing wrong. Is it my use of language? Do I initially come across as aggressive? Am I mis-reading what the other person is saying? Am I losing the ability to understand other people? What can I do to improve? Ideas welcome.

Anyway, it would be pretty awesome if @ClimateRealist's suggestion, that "fall out" from the Moon/meteor incident had escaped the Moon and had contributed to this season's NLCs, turned out to be correct.

Posted in astro blog by Stuart on Sunday 09th Jun 2013 (23:19 BST) | 1 Comment | Permalink

Comments: NLC discussion

An interesting discussion, but if meteors are influencing the NLC would they not show more after a meteor shower peak?

(Next peak 12th August of Perseid meteor shower, Monday, the 12th of August 2013)

or one of the big meteors that have hit over the years...in any case more investigation is needed.

I'll keep photographing them as and when they appear.

Thanks

Posted by @Yodatheoak on Sunday 21st Jul 2013 (11:31 UTC)

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