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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