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Daily University Science News
A unique
new service that harnesses satellite data to powerful high-speed
computing could soon lead to much-improved weather forecasts
and help make basking in the sun a lot safer.
The
"fast ozone profile" service developed by the
Royal Netherlands Meteorological Institute (KNMI) within
the ESA Data User Program is a world first, and it can deliver
a three-dimensional map of ozone in the atmosphere worldwide
within a few hours.
Ozone
helps to shield the Earth's surface -- and sunbathers --
from the harmful ultraviolet light rays of the sun. If an
ozone hole opens above Europe in the summer, for example,
then the risk of sunburn and in the longer term, skin cancer,
increases dramatically for sun-worshippers at the beach
or on the piste.
The speed of the new service makes it possible to broadcast
warnings far more quickly, and to make more accurate forecasts
of potential danger.
What
matters to sunbathers is the total amount of ozone above
their heads. But the new service is more sophisticated still.
Rather than simply calculating the amount of ozone in a
tower of air reaching from ground to space, the new service
can plot a profile of the density of ozone at various altitudes.
"The
main reason for making this service available is to enable
the creation of improved weather forecasts," says Ronald
van der A, a senior project scientist at KNMI. "Ozone
moves with the wind in the high atmosphere -- we call it
a stratospheric tracer. Because we can generate these three-dimensional
profiles quickly, we can create moving maps from a series
of snapshots, and so start to model the behavior of the
stratosphere much more accurately."
"Three
years ago, most people thought that this could not be feasible,"
remembers ESA's Claus Zehner, who extended the ERS ground
segment to provide GOME measurements very fast to KNMI for
the development of this new service to users.
(GOME
is the Global Ozone Monitoring Experiment aboard the European
Remote-Sensing satellite, ERS-2, launched in 1995 and continuing
to make an important contribution to environmental monitoring
and our understanding of the physical and chemical processes
underlying Earth systems, on the global and local scale
alike.)
"The
big challenge is the computation," Ronald van der A
explains. "To calculate total ozone, you're using only
part of the spectrum of light scattered back by the Earth's
atmosphere. But to generate the profile, you look at a much
wider spectrum, each segment of which corresponds to a 'backscattering
layer' at a particular altitude in the atmosphere.
"Again,
in itself this is not such a big task -- the real breakthrough
is to be able to extract this profile information from the
data in near real-time. We can publish the profiles within
three hours of the data being gathered."
With
the Fast Delivery service, data are acquired and processed
up to total ozone columns/global maps within three hours
after acquisition, and are then used in a model to forecast
the ozone and an algorithm is applied to give the UV index,
allowing accurate forecasting within 24 hours.
Although
it still takes three days to cover the global surface, the
near-real-time processing allows a complete global picture
to become available in the same timeframe, which is a major
advance over any previous efforts.
"Equally,"
adds Ronald van der A, "because we can see events developing
quickly, if we spot a hole appearing, we can alert local
scientists who can then monitor the event hour by hour using
equipment carried aboard specially-launched balloons, called
sondes."
The
service is now live, providing GOME ozone profiles to scientists
around Europe, including the service to offer UV index forecasting.
"And
we will certainly continue the service when Envisat is launched,"
emphasizes van der A. "The SCIAMACHY instrument aboard
Envisat may well allow us to improve the quality still further."
(SCIAMACHY,
the SCanning Imaging Absorption Spectrometer for Atmospheric
CartograpHY, is one of the ten instruments aboard ESA's
new environmental satellite, Envisat, ready for launch this
summer.)
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