NASA satellite eyes atmosphere to improve pollution and climate forecasting

December 08, 2005

Thanks to the latest sophisticated, satellite-based instruments, local and regional air pollution and their sources can now be observed closely from space. Researchers using new, nearly up-to-the-hour data from NASA's Aura satellite are now tracking important pollutants such as ozone and nitrogen oxide. What's more, the satellite's first global observations of ice in clouds will provide climatologists, weather forecasters and public officials around the world the ability to make better predictions of future climate change.

Launched in 2004, Aura helps scientists understand how atmospheric composition affects and responds to Earth's changing climate. The satellite works to reveal the processes that connect local and global air quality, and also tracks the extent Earth's protective ozone layer is recovering. The satellite is one in an international fleet of Earth-observing satellites nicknamed the "A-Train" that monitor the planet's atmosphere.

"Aura is offering us a whole new way of looking at how pollution travels around the Earth, and precisely what the sources are," said Mark Schoeberl, project scientist for Aura at NASA's Goddard Space Flight Center, Greenbelt, Md. "The better we understand the origins of pollution, the more public health stands to benefit, across borders."

Aura boasts four instruments that provide researchers new glimpses of the Earth's lower atmosphere, or troposphere: the Ozone Monitoring Instrument (OMI); the Tropospheric Emission Spectrometer (TES); the Microwave Limb Sounder (MLS); and the High Resolution Dynamics Limb Sounder (HIRDLS).

"What's so new and striking is that we're now able to capture the first-ever global, daily, urban-scale measurements from space of air pollutant nitrogen dioxide. And now we can make this information available on a pilot basis mere hours after actual measurements are attained," said Pieternel Levelt of the Royal Netherlands Meteorological Institute, who is the OMI principal investigator. "When these measurements are eventually obtained on a global scale, the world will have better future air pollution forecasts."

Researchers such as Levelt expect that OMI will soon be providing daily, up-to-the-hour, observations of the path of pollution across the United States and Asia as it has begun to do of Europe.

Ozone in the troposphere is a major component of air pollution affecting public health and vegetation, and it's also a greenhouse gas. There are large uncertainties in our understanding of the chemical processes that determine ozone levels and the relative importance of human-induced and natural sources.

"Until the Aura launch, our ability to directly observe tropospheric ozone above the surface was very limited," said Daniel Jacob, professor of Atmospheric Chemistry and Environmental Engineering at Harvard University, Cambridge, Mass., and member of Aura's TES science team. "The simultaneous global mapping of tropospheric ozone and carbon monoxide from the TES provides a new and dramatic look at the global circulation of this pollution source and its relationship with carbon monoxide."

Researchers at the 2005 Fall Meeting of the American Geophysical Union in San Francisco, Dec. 5-9, 2005, are in talks about Aura, a sort of "atmospheric night watchman," and how its continued breakthrough clues to air pollution and changes in atmospheric composition are better informing their knowledge of the Earth's climate.

Recently, Aura's MLS instrument began offering the first observations of ice in clouds on a global basis. Ice forms in clouds high in the atmosphere where temperatures are below freezing. By quantifying how much cloud ice there is, scientists can determine the amount of solar energy reflected back to space as well as the amount of radiation trapped by the Earth's atmosphere. In the former, the ice clouds act to cool the planet. In the latter, the ice clouds act to warm the planet. The balance of these two processes is key to determining the nature and magnitude of climate change.

To properly model clouds, it is vital to have exact measurements of their physical characteristics. Some important factors to know include: whether they are made of ice or liquid; the concentration of ice or liquid; and the sizes and shapes of the cloud droplets or crystals.

According to Duane Waliser, a principle scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., "When combined with data from other satellites in NASA's 'A-Train' constellation of satellites, particularly the CloudSat mission to be launched in 2006, these new cloud measurements from Aura form groundbreaking satellite data for evaluating atmospheric models and reducing uncertainties in the way clouds are represented in them. This contributes to improved predictions of weather and climate."

NASA/Goddard Space Flight Center

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