NASA Study Tracks Global Sources, Transport of Air Pollution
A NASA and university study of ozone and carbon monoxide pollution in Earth's
atmosphere is providing unique insights into the sources of these pollutants
and how they are transported around the world.
For the first time, NASA and university researchers used simultaneous observations
of carbon monoxide and ozone from space to differentiate between ozone produced
from human activity and ozone produced from natural sources. Ozone is an important
pollutant and a major component of smog. At high quantities it is harmful to humans,
plants and entire ecosystems.
Image right: Artist concept of Aura spacecraft. Image credit: NASA + Browse version of image
The team, led by Dr. Daniel Jacob and Lin Zhang of Harvard University, Cambridge,
Mass., used global satellite observations to study regional sources of pollution
such as eastern China, the northeastern United States and South America. The team
also studied how ozone produced from those sources was transported across the globe.
The observations of carbon monoxide and ozone were obtained from the Tropospheric
Emission Spectrometer instrument onboard NASA's Aura satellite. The instrument, built
and managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., uses new methods to
measure ozone and carbon monoxide in the troposphere -- the part of Earth's atmosphere
between the surface and up to approximately 10 kilometers (6.2 miles) altitude.
"Global measurements of ozone and carbon monoxide are critical to understanding how
air pollution impacts atmospheric chemistry, especially in the troposphere," said Zhang.
"We're gaining a new understanding of how these chemicals flow out from continents and
are transported around the globe. Plus, our study provides a critical test of the
atmospheric models used to understand and predict how pollution is transported on
While ozone in the upper atmosphere helps to protect Earth from the sun's radiation,
ozone near the surface is a harmful pollutant. Surface ozone can be produced from
the chemical byproducts of human activities such as automobile emissions. Once produced,
ozone can be transported not only on a regional scale - such as from California to Nevada,
but on an intercontinental scale - such as from Asia to North America. This transported
(imported) ozone can lead to an overall enhancement in pollution at the surface.
Attributing elevated ozone levels to human activity is complicated by natural sources
of ozone precursors, such as lightning.
Carbon monoxide, however, is emitted into the atmosphere almost exclusively by incomplete
combustion and can generate ozone. It has a relatively long lifetime in the atmosphere
and hence is often used for identifying human-induced pollution.
"In the past, scientists relied exclusively on ground-based and aircraft instrument
readings," said Dr. Helen Worden, a member of the Tropospheric Emission Spectrometer
instrument science team at JPL. "These observations were sparse and did not provide
the global perspective that this new instrument does. It is providing the first
long-term, 3-D satellite observations of global tropospheric ozone and carbon
monoxide measured together."
Tropospheric Emission Spectrometer observations taken of the Northern Hemisphere
showed that ozone pollution can drift from Asian sources to western North America,
and from eastern North America to Europe. The team used these data to test the Goddard
Earth Observing System-Chem atmospheric chemistry computer model, which is one of the
primary tools used by scientists to study global-scale pollution. The consistency between
the instrument observations and model results indicates that the model can reliably
predict the impact of pollution produced in one country on another country.
Launched July 15, 2004, Aura is the third and final major Earth Observing System satellite.
Aura carries four instruments: the Ozone Monitoring Instrument, built by the Netherlands
and Finland in collaboration with NASA; the High Resolution Dynamics Limb Sounder, built
by the United Kingdom and the United States; and the Microwave Limb Sounder and
Tropospheric Emission Spectrometer, both built by JPL. Aura is managed by NASA's
Goddard Space Flight Center, Greenbelt, Md.
Results of the study are published in the Sept. 21 issue of Geophysical Research Letters.
For more information on Aura, visit: http://aura.gsfc.nasa.gov/
. For more on the
Tropospheric Emission Spectrometer, see: http://tes.jpl.nasa.gov/
JPL is managed for NASA by the California Institute of Technology.
Media contacts: Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif.
Erica Hupp/Dwayne Brown 202-358-1237/1726
NASA Headquarters, Washington