One of the most remarkable weather phenomenon of recent times has been the appearance of Noctilucent clouds during June and July.
The 2019 season appears to be exceptional as a record amount of moisture has entered the upper atmosphere and allowed water vapor to condense onto particles of meteor dust at 80 kms or so above the earths surface.
These two photos were taken from Cork on the south coast of Ireland on Monday night the 17th of June 2019.
Both photos were taken well after sunset and it shows the Noctilucent clouds being illuminated by sunlight coming over the North Pole.
Radio wise, there is some question as to whether these clouds at 80 kms have any impact on signals? In recent times, there have been some extraordinary openings from Europe to Japan on 50 MHz. Is there a connection?
3 comments:
Great photos. Well, I think there is a strong possebility these clouds have impact. Though it all depends on how they are aligned in relation to ES "clouds" and of course the direction to Japan. I've found that when I spotted NLCs so far this year next morning there was propagation to Asia on 6m although not always from my QTH. Sometimes from Finland <-> Japan or from southern Europe <-> Japan. There was a Japanese station that investigated this kind of fenomenon and wrote a report about it. 73, Bas
Hi Bas, I remember reading something a few weeks back that these clouds are rotating around the North Pole.
I wonder if there might be a pattern to the openings to Japan on 6m? Do they repeat after a certain number of days? It might be worth checking.
73's de John, EI7GL
Hi John,
In relation to your question about periodicity, there are a number of what are known as planetary waves circulating that modulate temperature at NLC/PMSE height. These vary from a day or so to several days, but perhaps the most dominant is the 5-day wave.
There is also a thermal tide on a more-or-less daily basis, explaining why NLC tend to be seen more often after, rather than before, UT midnight.
PMSE/NLC and the like are all related in their underlying mechanisms. NLC can be present but no visible. PMSE can be present, but outside the usually very narrow beamwidth of a MST radar that detects them.
PMSE also tend to appear for a while in winter, which reminds us of the 50MHz mini-peaks then on the radio, too.
So, whilst we can't quite yet say which one of the various phenomena is allowing 6m openings in the dead of night to JA, it's pretty clear that the presence of conductive, metallic meteoric debris, surrounded by charged ice, is going to cause something along the lines of unusual propagation at VHF.
Have a look at: https://mw1cfnradio.blogspot.com/2019/06/pmse-nlc-and-other-things-rarefied.html
And maybe my book: https://www.amazon.co.uk/Space-Clouds-Noctilucent-Science-Behind-ebook/dp/B00K83BHT2/ref=sr_1_1?keywords=space+clouds&qid=1561282572&s=gateway&sr=8-1
Post a Comment