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December 14, 2006
NASA TROPICAL
OZONE STUDIES YIELD SURPRISES
Two new NASA-funded studies of
ozone in the tropics using NASA satellite data not previously available
are
giving scientists a fuller understanding of the processes driving ozone
chemistry and its impacts on pollution and climate change.
Ozone pollution caused by burning
of fossil fuels is a major health concern in Earth's Northern
Hemisphere mid
latitudes, including the United States.
But for the more than two-thirds of
Earth's population that lives in the tropics - the area bounded by the
Tropic
of Cancer on the north and Tropic of Capricorn on the south - ozone
levels in
Earth's lower atmosphere, called the troposphere, are also driven by
other mechanisms,
namely biomass burning (the burning of forests, grass lands, etc.).
In the first study, NASA and
university researchers investigated the extent of biomass burning in
the
southern tropics and quantified its effects on ozone formation. Biomass
burning
is the driving form of pollution in these tropical areas. It adversely
affects
air quality and influences climate by producing carbon monoxide and
nitrogen
oxides, two pollutants that lead to the formation of ozone.
Until recently, scientists have had difficulty measuring how much
biomass
burning is occurring in this region, since much of it takes place in
the
world's developing countries. In addition, the complex interactions
between
chemistry, weather and natural sources of ozone make it difficult to
understand
how biomass burning and ozone formation are linked.
With the launch of new atmospheric monitoring satellites such as NASA's
Aura in
the past few years, scientists now have new ways to track different
chemicals
present in Earth's atmosphere. These data are giving researchers a more
complete picture of the causes and effects of atmospheric pollution.
The scientists combined atmospheric models with actual measurements of
ozone,
carbon monoxide and nitrogen dioxide in Earth's lower atmosphere,
collected
from NASA and European Space Agency satellites during November 2004.
This combination technique led to
a surprising result: the amount of biomass burning in sub-equatorial Africa and the
Indonesia/Australia region was
underestimated, by a factor of between two and three.
The new combination technique also enabled the researchers to link the
observed
biomass burning to ozone that was later formed over and downwind of
these
regions.
"Combining these new satellite data with atmospheric models will
dramatically
improve our understanding of the complex processes relating pollution
sources
to ozone throughout Earth's troposphere," said lead author Dr. Dylan
Jones
of the University of Toronto, Ontario, Canada.
"Biomass burning and ozone formation in this region are particularly
sensitive to climate patterns such as El Nino," added co-author Dr.
Kevin
Bowman of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
"Using this approach, we will be able to monitor how changes in these
patterns impact air quality and climate throughout the tropics."
In the second study, to be published soon in Geophysical Research
Letters, NASA
and university researchers investigated intraseasonal (30- to 90-day)
variations of tropical total ozone -- the amount of ozone present in a
column
of Earth's atmosphere -- and whether they are connected to a climate
pattern
known as the Madden-Julian Oscillation.
The Madden-Julian Oscillation is a cyclical pattern of slow,
eastward-moving
waves of clouds, rainfall and large-scale atmospheric circulation
anomalies
that can strongly influence long-term weather patterns around the
world. It's a
30-to-90-day cycle, and it spans nearly half of Earth's equator,
primarily over
the Indian Ocean
and western Pacific.
Using NASA satellite data, the researchers found the total amount of
ozone in
the tropics varies significantly in association with the Madden-Julian
Oscillation, with the strongest connection observed in the subtropics.
These
relatively short-term variations were found to be comparable to more
well-known, longer time scale variations, such as El Nino or the solar
cycle.
The subtropical high and low pressure systems generated by the
Madden-Julian
Oscillation in the upper troposphere were found to trigger upward and
downward
shifts of the tropopause (the top edge of the troposphere), which leads
to
variations in subtropical total ozone. In the high pressure systems
that trail
the oscillation's region of heavy rainfall, upward air motion draws up
ozone-poor tropospheric air, decreasing the amount of subtropical total
ozone.
In the low pressure systems that lead the oscillation's region of heavy
rainfall, downward air motion pushes down ozone-rich air from the
stratosphere,
increasing the amount of subtropical total ozone.
"This study demonstrates the potential for new global ozone
measurements
such as the Atmospheric Infrared Sounder to improve our understanding
of ozone
chemistry and its effects on climate change," said lead author Dr. Yuk
Yung of the California Institute of Technology, Pasadena, Calif.
"Further
detailed data analyses of ozone from ozone measuring balloons,
satellite
instruments and models are needed to better understand the processes at
work."
Study co-author Dr. Baijun Tian of JPL says this finding is significant
because
scientists already know that the beginning of Madden-Julian Oscillation
cycles
is potentially predictable two to four weeks in advance. "This implies
that variations in total atmospheric ozone may also be predictable with
similar
lead times over much of the tropics," he said.
For the biomass burning study, Aura's Tropospheric Emission
Spectrometer
instrument contributed ozone and carbon monoxide measurements. Nitrogen
dioxide
readings were collected from the Scanning Imaging Absorption
Spectrometer for
Atmospheric Chartography instrument on the European Space Agency's
Envisat
spacecraft. Additional carbon monoxide readings were gathered by the
Canadian
Space Agency's Measurements of Pollution in the Troposphere instrument
on
NASA's Terra spacecraft.
For the Madden-Julian Oscillation study, data were obtained from NASA's
Atmospheric Infrared Sounder on its Aqua spacecraft and its Total Ozone
Mapping
Spectrometer on the National Oceanic and Atmospheric Administration's
Nimbus-7
spacecraft.
For
more information and images, visit:
http://www.nasa.gov/vision/earth/lookingatearth/ozone-20061214.html
For more
information
about Aura and
the
Tropospheric Emission Spectrometer,
visit:
http://www.nasa.gov/mission_pages/aura/main/index.html
For
more information
about Aqua and
the
Atmospheric Infrared Sounder,
visit:
http://www.nasa.gov/mission_pages/aqua/index.html
For
more information
about Terra and
Measurements of Pollution in the Troposphere, visit:
http://www.nasa.gov/mission_pages/terra/index.html
For
more
information about the Total Ozone Mapping Spectrometer, visit:
http://jwocky.gsfc.nasa.gov/n7toms/n7sat.html
##
Contact:
Alan Buis
NASA Jet Propulsion Laboratory
818-354-0474
alan.d.buis@jpl.nasa.gov
This text is
derived from:
http://www.nasa.gov/vision/earth/lookingatearth/ozone-20061214.html
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