A Few Thoughts On The 2010 NLC Season

[markt]

This message is from Ken Kennedy via Martin McKenna, the European NLC coordinator...

''I feel it will be a very interesting year especially with the Sun returning to activity. Long term reports (Gadsden) of NLC activity certainly show a correlation between solar activity and NLC with maximum NLC sightings about a year or two following solar minimum. Higher levels of solar radiation may well not allow the temperature at the mesopause to drop to the critical temperature for ice nucleation and also the higher UV emissions may dissociate water more quickly so there may be two reasons for the inverse relationship between NLC and solar activity.

As it stands, 2009 was a year of very high frequency of NLC and I don't see much chance of a further increase. I would expect NLC activity to remain possibly as high as last year but it will be interesting to see if frequency decreases over the next year or two. The other area I have explored is a bit more subjective and that is brightness. However, taking a random selection of 198 observations which I received last year (your ones were included), 32 of these gave a brightness estimates of 4 or 5 out of 5. Within this selection, observers saw NLC on 40 nights. Of these 40 nights, 13 were scored as having a brightness of 4 or 5. These figures are considerably higher than in previous years and seem to back up my gut feeling that brightness has also been increasing, especially in 2009. This may be because there is an increase in water vapour at mesopause altitudes perhaps because of dissociated methane which has been increasing since 2007. It may also reflect the slower dissociation of water vapour with low solar activity''...Ken Kennedy.

I thought you may be interested in this! Lets hope Kens thoughts are right!

[mesospheric]

I'm bound to comment on the 'science' claims!

Firstly, it is true to say that Mr. McKenna left this group in response to there being no evidence to corroborate his very early sighting of NLC - which were not evident in the photographs he submitted. I and everyone else who has occasionally been the only spotter of a NLC formation, often in poor weather, has the 'unconfirmed' tag added to the report, and we of course have absolutely no issue with it, as it is good practice. I'm sorry if that is received as controversial, but it is entirely true, and should caution how we receive these 'dramatic' start of season posts, which seem to be an annual occurrence. So I hope Mr. McKenna now takes a more open view of why observational reports need to be confirmed by other sightings, or unequivocal photographic evidence.

Secondly, Mr. Kennedy says himself that the brightness estimates are 'subjective', and doesn't offer a means by which he is attempting to compare brightness between displays, even though this could be done readily using standardised photography or sky brightness devices, as two examples. Choosing random observations is poor practice, because the occurrence of NLC is affected by many complex, periodic atmospheric factors - and not only the sun's activity - that influence NLC extent and brightness (and even whether they are present or not).

Ultimately, NLC and mesospheric processes are much better understood than Mr. Kennedy's posting suggests, particularly the response of NLC to the solar cycle; we already know for certain that NLC will deteriorate in frequency, geographical extent and possibly brightness (however this is defined and measured) as solar output increases. There are many papers and general media reports, if he cares to search for them.

[PeteG]

wouldn't the term 'Solo Sighting' be a more friendly way of tagging?

Pete

[markt]

While I am excited that this forum is starting to come alive again as we all eagerly anticipate the start of the season I am very disappointed that issues of the past are being raked up again.

When I posted this I merely quoted Martin McKenna out of courtesy as he alerted me to Kens thoughts on the season. This has nothing to do with Martin. Let me make my stance on this perfectly clear: We WILL NOT tolerate this forum to be used a medium for public mudslinging against individuals. We do not pass judgement on other 'ex-members' of this forum and Martin McKenna is no exception.

May 15, 2010 5:56:49 GMT mesospheric said:

I'm bound to comment on the 'science' claims!

Firstly, it is true to say that Mr. McKenna left this group in response to there being no evidence to corroborate his very early sighting of NLC - which were not evident in the photographs he submitted. I and everyone else who has occasionally been the only spotter of a NLC formation, often in poor weather, has the 'unconfirmed' tag added to the report, and we of course have absolutely no issue with it, as it is good practice. I'm sorry if that is received as controversial, but it is entirely true, and should caution how we receive these 'dramatic' start of season posts, which seem to be an annual occurrence. So I hope Mr. McKenna now takes a more open view of why observational reports need to be confirmed by other sightings, or unequivocal photographic evidence.

Secondly, Mr. Kennedy says himself that the brightness estimates are 'subjective', and doesn't offer a means by which he is attempting to compare brightness between displays, even though this could be done readily using standardised photography or sky brightness devices, as two examples. Choosing random observations is poor practice, because the occurrence of NLC is affected by many complex, periodic atmospheric factors - and not only the sun's activity - that influence NLC extent and brightness (and even whether they are present or not).

Ultimately, NLC and mesospheric processes are much better understood than Mr. Kennedy's posting suggests, particularly the response of NLC to the solar cycle; we already know for certain that NLC will deteriorate in frequency, geographical extent and possibly brightness (however this is defined and measured) as solar output increases. There are many papers and general media reports, if he cares to search for them.

Regards Kens 'thoughts': The brighteness of NLC being subjective, I wonder if he is referring to the 1-5 scale of brightness? I know it doesn't say but a scale like that certainly becomes subjective once numerous people start using it - one persons 2 may be another persons 3... Sky brighteness devices are becomming more common these days so maybe as the yearly seasons progress we will see more observations using this. Standardised photography has been used for measuring light pollution levels (I think!), so could be used for NLC measurements. Maybe this is something we should look into on here to improve the accuracy of results?

There are alot of factors and mechanisms that contribute to NLC and one of the reasons I like this forum is that it brings people together to discuss all this!

Now, question is, when might we expect this season to actually get started?