NSF PR 01-31 - April 19, 2001
Media contacts:
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Cheryl Dybas, NSF
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(703) 292-8070
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cdybas@nsf.gov
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Harvey Leifert, AGU
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(202) 777-7507
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hleifert@agu.org
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Anatta, NCAR
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(303) 497-8604
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anatta@ucar.edu
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Program contact:
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Jay Fein, NSF
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(703) 292-8527
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jfein@nsf.gov
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This material is available primarily
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Researchers Achieve Best Global Picture Ever of
Climate-Modifying Aerosol Particles
In a polluted city, it is hard to miss the murky skies
created by the tiny particles called aerosols (mostly
sulfate, carbon, dust, salt, and nitrate). But, scientists
have been hard-pressed to track the global behavior
of aerosols, which influence climate, along with visibility
and human health.
Satellites and research aircraft provide important
detail, but these data are incomplete, and the aerosol
pathways are difficult to discern. Now, scientists
Philip Rasch, William Collins, Brian Eaton and colleagues
at the National Center for Atmospheric Research (NCAR)
in Boulder, Colorado, have found a novel way to bring
aerosol data into computer-model projections. The
new technique is described in two papers appearing
in the April 16 issue of the Journal of Geophysical
Research, published by the American Geophysical
Union.
"Aerosols influence our climate in a variety of ways,
both globally and regionally, so it's imperative that
scientists represent aerosols as accurately as possible
in climate models," says Jay Fein, director of the
National Science Foundation (NSF)'s climate dynamics
program, which funded the research along with NASA.
"This work by Collins and Rasch represents a major
step forward in achieving this goal."
"Regional and global exchange of aerosols is a key
area of upcoming climate research," says Collins.
"This technique is providing perhaps the best current
estimate of aerosols available in the world."
The aerosol modeling technique has already produced
surprising results from the 1999 Indian Ocean Experiment
(INDOEX). Model results suggest that aerosols remain
in India's dry winter atmosphere several days longer
than previously thought. Since aerosols are thought
to have an overall cooling effect, this finding could
have global climate implications, if it proves valid
in other dry regions.
These results are a consequence of the detail afforded
by the new technique. Most models of global chemistry
simulate the behavior of aerosols in general terms
instead of tracking their actual motions within day-to-day
weather. Collins and Rasch devised a method of incorporating
aerosol data into an atmospheric transport and chemistry
model created at NCAR, the Scripps Institution of
Oceanography and the Max-Planck Institute of Meteorology
in Hamburg, Germany.
As the model's predicted weather moves forward in time,
satellite data are used to adjust aerosol behavior
as needed. This allows aerosol motion to be predicted
up to 48 hours in advance. During INDOEX, the NCAR
team combined daily simulations into a threemonth-long
picture of aerosol transport across the region. The
model is now being used to guide this spring's Aerosol
Characterization Experiments--Asia, an international
effort based in Japan.
Rasch and Collins have already expanded the technique
to incorporate aerosol readings from lidar (radar-like
laser) into the model, in addition to the satellite
and aircraft data. Lidar can observe the aerosol prevalence
at various heights, looking either upward from the
ground or downward from space. Two aerosol-observing
lidars will be deployed on NASA satellites, one later
this year.
"In the middle and upper atmosphere, aerosols can
travel long distances before washing or falling out,
so vertical detail provided by the technique is especially
important for understanding aerosol transport around
the globe and its lifetime in the atmosphere," explains
Rasch.
The National Science Foundation is NCAR's primary sponsor.
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