As a President Emeritus of local Astronomy Association branch of Ursa ry, Mikkeli, I have observed noctilucent clouds (~55-95 km) very much in Finland.
There are many subtypes of noctilucent clouds but they basically form in a boundary where the space dust impacts with the earth's athomosphere in high speed impacts. These dust particles that burn in the air provide small nuclei for water vapour to condense on their surfaces and so accrue size to the size a fiftieth of the width of a strand of human hair. Sweden sent in 1970's rockets to this altitude to collect samples of these ice chrystals. They are very difficult to reach as they are way above balloon's reach and only rockets can go making their sampling very expensive and rare. There is nothing to link them with sulphur or dust with ground, it is combination of terrestrial water vapour and dust particles streaming from the sky into our athomosphere, basically interplanetary dust cloud nucleating atmospheric water vapour. I think noctilucent clouds are beautiful and lit the skies with sunlight even far into subarctic which cannot see the midnight sun directly. They do reflect sunlight away but is little, one cannot see them in the day time due to blue scattering occurring on the athmosphere below that masks them completely. In the darker night time skies they become visible. Therefore, noctilucent clouds impact on global warming is negligible, propbably less than effect of full moon. There are much brighter, rare, clouds lower down (~25-35 km) that occasionally form in stratosphere. These reflect more light, but due to their rarity impact also is very low. Kind regards, Albert > Date: Wed, 24 Jun 2009 12:30:24 +0100 > From: [email protected] > To: [email protected] > CC: [email protected] > Subject: [geo] Re: noctilucent clouds > > > > Hi John, > > Thanks for the picture. > > According to The Telegraph: > > Meteorologists refer to them as NLCs or "polar mesospheric clouds". This > is because they form right on the boundary of the mesosphere (between > the stratosphere and space). The mesosphere is dry and cold (about > -123°C), unlike the warm, moist troposphere below, where all the other > clouds form. These noctilucent clouds are composed of tiny ice crystals > – a fiftieth of the width of a strand of human hair. Noctilucent clouds > are on the increase – there are twice as many as there were 35 years ago > and they're moving south: a visible result of global warming. [End quote] > > I'd like to think that somebody is taking our concerns for global > warming and Arctic sea ice seriously, and quietly experimenting with > stratospheric sulphate aerosols. But the more likely explanation is ice, > as described above by The Telegraph. > > Cheers, > > John > > > John Gorman wrote: > > interesting bit in UK Telegraph about strange cloud phenomenon last week > > noctilucent clouds at about 50miles > > anyone know whether they are likely to be sulphuric acid aerosol? > > John Gorman > > > > > > > _________________________________________________________________ Get the best of MSN on your mobile http://clk.atdmt.com/UKM/go/147991039/direct/01/ --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
