Feeds

Scientists seek noctilucent cloud enlightenment

More night-shining expected in 2009, but why?

  • alert
  • submit to reddit

Intelligent flash storage arrays

Scientists are suggesting 2009 may prove a bumper year for northern hemisphere noctilucent clouds - high-altitude pre-dawn and post-sunset features illuminated by the Sun from below the horizon.

According to New Scientist, skywatchers last week snapped the first examples of the clouds, although NASA's Aeronomy of Ice in the Mesosphere (AIM) spacecraft got the first indications back on 22 May.

Noctilucent clouds occur at around 80km up in the atmosphere. They were first spied hovering above polar regions in 1885, "suggesting they may have been caused by the eruption of Krakatoa two years before".

However, they have of late been creeping towards the equator, now appearing at latitudes as low as 40°.

Why this is happening is unclear. Some suggest "it could be due to an increase in greenhouse gases... because the gases actually cause Earth's upper atmosphere to cool, and the clouds need cold temperatures to form".

First satellite snaps of the noctilucent clouds. Image credit: NASABack in 2007, AIM principal investigator James Russell III of Hampton University suggested the increased frequency of Polar Mesospheric Clouds (PMCs, as they're known when viewed from space - see pic) might be due to "a connection with global changes in the lower atmosphere, and could be an early warning that our environment is being altered".

He said: "It is clear that PMCs are changing, a sign that a distant and rarified part of our atmosphere is being altered, and we do not understand how, why, or what it means."

New Scientist, though, notes that "their abundance also seems to rise and fall with the Sun's 11-year cycle of activity", elaborating: "The clouds thrive when the sun is quiet and spews less ultraviolet radiation, which can destroy water needed to form the clouds and can keep temperatures too high for ice particles to form."

The Sun has in recent years been relatively quiet, prompting AIM lead scientist Scott Bailey to predict around twice as may noctilucent clouds as when the Sun hits peak activity.

But no one's really sure what to expect. New Scientist adds that the clouds' activity "seems to peak roughly a year after solar activity hits its minimum, which researchers believe happened in December 2008".

Bailey, though, noted that "the exact time lag between solar minimum and peak cloud activity is uncertain, and researchers aren't entirely convinced a lag even exists". He concluded: "There's no explanation for it. Every model says the clouds should respond immediately to what the sun is doing."

Accordingly, those of you hoping to enjoy some noctilucent cloud action might get the best chance between mid-June and mid-August - or not, as the case may be. ®

Security for virtualized datacentres

More from The Register

next story
Boffins who stare at goats: I do believe they’re SHRINKING
Alpine chamois being squashed by global warming
Comet Siding Spring revealed as flying molehill
Hiding from this space pimple isn't going to do humanity's reputation any good
Experts brand LOHAN's squeaky-clean box
Phytosanitary treatment renders Vulture 2 crate fit for export
LONG ARM of the SAUR: Brachially gifted dino bone conundrum solved
Deinocheirus mirificus was a bit of a knuckle dragger
MARS NEEDS WOMEN, claims NASA pseudo 'naut: They eat less
'Some might find this idea offensive' boffin admits
No sail: NASA spikes Sunjammer
'Solar sail' demonstrator project binned
Carry On Cosmonaut: Willful Child is a poor taste Star Trek parody
Cringeworthy, crude and crass jokes abound in Steven Erikson’s sci-fi debut
prev story

Whitepapers

Choosing cloud Backup services
Demystify how you can address your data protection needs in your small- to medium-sized business and select the best online backup service to meet your needs.
Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
Storage capacity and performance optimization at Mizuno USA
Mizuno USA turn to Tegile storage technology to solve both their SAN and backup issues.