Emissions may trigger cirrus clouds
NERC corporate
Planet Earth online
Grants
Studentships
Science impacts
Research papers
Contact us
SEARCH
HOME LATEST NEWS FEATURES & SPECIAL REPORTS LATEST NEWS
PODCASTS & VIDEO BLOGS & OPINION NEWS
Log in
Search term(s)
NERC SCIENCE LINKS RSS FEEDS TOOLS
Emissions may trigger cirrus
clouds
Emissions may trigger cirrus clouds
Sign up for email alerts
Deepest black smokers found in
Caribbean
13 April 2010, by Tamera Jones
Bookmark this page (explain)
Launch success for CryoSat-2
Emissions particles from forest fires and burning fossil fuels
could be speeding up cloud formation high in our atmosphere,
say scientists. This may affect whether these clouds either
warm or cool the Earth.
Herbicides are second best
solution
Isotopes track old extinction
EDITOR'S CHOICE
Meteoric fall of the dinosaurs
Sea turtles to hatch fewer males
Oil palms no good for ants
Promiscuity prevents extinction
Native plants could benefit
African farmers
Until now researchers
thought that the ice in
wispy cirrus clouds formed
when water droplets
containing dissolved salts
freeze.
But Dr Benjamin Murray
from the University of
Leeds, along with an
international team of
researchers, has shown
Cirrus clouds.
for the first time that this
may not be true for cirrus clouds in the tropics.
In most parts of the world cirrus clouds are found around eight
kilometres up in the atmosphere. But in the tropics they're as high as
17 kilometres, where temperatures can be as low as minus 90o C.
In a paper published in Nature
Geoscience, Murray and his
colleagues describe how ice in
these cirrus clouds doesn't form
when liquid droplets freeze.
Instead it forms on solid, glasslike water particles. These
glassy particles behave like solids, but have a liquid-like structure,
'much like a child's toy marble,' explains Murray.
'No-one realised these things
could exist in the atmosphere
until now.'
Dr Benjamin Murray,
University of Leeds
'No-one realised these things could exist in the atmosphere until now,'
he adds.
Crucially, these glassy particles only form when they have something
to cling onto, like organic matter. This organic material can come from
forest fires or burning fossil fuels.
Scientists realised something strange was going on when they
measured the water content of cirrus clouds high in the atmosphere.
They expected to find only ice with very little water vapour. Instead,
they found that the air in the clouds contained much more water
vapour than they expected.
'The fact that there are ice crystals in these clouds means we didn't
expect them to be supersaturated,' says Murray.
In an earlier experiment in the lab, Murray had discovered that under
the conditions in which icy cirrus clouds form, water droplets turn into
glassy particles when organic compounds are around.
This led him to wonder how these glassy particles affect the formation
of real clouds. Luckily, an 84-m2 cloud simulation chamber in
Germany allowed him to investigate.
He and his team introduced either glassy particles or liquid droplets
into the cloud simulation chamber, lowered the temperature to minus
80o C and watched for when ice crystals started forming.
They found that ice crystals formed later in the liquid droplet
experiment compared with the glassy particle experiment. And in the
glassy particle experiment, ice formed only on the particles. It also
turned out that the glassy particles changed the cloud properties,
leading to unexpectedly high humidity.
http://planetearth.nerc.ac.uk/news/story.aspx?id=705[13.04.2010 22:00:52]
Email this page to a friend
RELATED LINKS
News
Scientists rank climate cooling
schemes, 28 Jan 2009
UK scientists probe clouds' links
to climate, 22 Oct 2008
Geoengineering under fire,
5 Oct 2008
Features & special reports
Whitening the clouds,
14 Dec 2009
Cloud forests, 7 Jul 2008
Cloud birth, 7 Apr 2008
Podcasts & video
Ice clouds and viper venom,
16 Nov 2009
Blogs & opinion
VOCALS - understanding clouds
and climate, 16 Nov 2008
External links
Benjamin Murray - University of
Leeds
Paper abstract
Emissions may trigger cirrus clouds
They then used a computer model to find out what this meant for real
clouds. They found that ice particles began to form sooner when they
introduced glassy particles.
'We're now keen to find out how glassy particles trigger ice formation,
how widespread they are in the atmosphere and exactly how human
activities affect their formation,' says Murray.
Benjamin J. Murray, Theodore W. Wilson, Steven Dobbie, Zhiqiang
Cui, Sardar M. R. K. Al-Jumur, Ottmar Möhler, Martin Schnaiter,
Robert Wagner, Stefan Benz, Monika Niemand, Harald Saathoff, Volker
Ebert, Steven Wagner & Bernd Kärcher, Heterogeneous nucleation of
ice particles on glassy aerosols under cirrus conditions, Nature
Geoscience 3, 233 - 237 (2010), published online: 21 March 2010 |
doi:10.1038/ngeo817
Interesting? Spread the word using the 'tools' menu on the right.
Home
Back to top
Your comments
Post a comment
There are no comments at this time. Be the first to comment on this
news story.
ABOUT THIS SITE
FOLLOW US ON TWITTER
BECOME A FAN ON FACEBOOK
© Copyright Natural Environment Research Council 2008
http://planetearth.nerc.ac.uk/news/story.aspx?id=705[13.04.2010 22:00:52]
SEARCH
Search term(s)