Volume 9, Number 4 • July/August 2001 • Advanced Technologies

Air Pollution Monitored from Space

This flat global map shows concentrations of carbon monoxide (CO) at altitudes of 15,000 feet. Dark green colors in these images indicate the highest levels of CO (450 parts per billion). Medium green colors indicate the lowest levels of CO (50 ppb). Terra sees CO in the atmosphere from 2–3 miles above the surface, where it interacts with other gases and forms ozone. This pollutant can move upward to altitudes where it can be blown rapidly for great distances or it can move downward to the surface. CO is an air pollutant that also produces ozone, a greenhouse gas that is a human health hazard. Photo provided by Goddard Space Flight Center.

NASA’s Terra spacecraft has produced the most complete view ever assembled of the world’s air pollution churning through the atmosphere, crossing continents and oceans. For the first time, policymakers and scientists now have a way to identify the major sources of air pollution and can closely track where the pollution goes anywhere on Earth.

The new global air pollution monitor onboard Terra is the innovative Measurements of Pollution in the Troposphere, or MOPITT experiment, which was contributed to the Terra mission by the Canadian Space Agency. The instrument was developed by Canadian scientists at the University of Toronto and built by COM DEV International of Cambridge, Ontario. A team at the U.S. National Center for Atmospheric Research (NCAR) processed the data. MOPITT is making the first long-term global observations of the air pollutant, carbon monoxide, as Terra circles the Earth from pole to pole, 16 times every day. Carbon monoxide is a byproduct of the incomplete burning of fossil fuels by cars, industry, home heating and the burning of natural organic matter such as wood.

“With these new observations, you clearly see that air pollution is much more than a local problem. It’s a global issue,” said John Gille, MOPITT Principal Investigator at NCAR in Boulder, Colorado. “Much of the air pollution that humans generate comes from natural sources such as large fires that travel great distances and affect areas far from the source.”

The first MOPITT observations were released at the annual American Geophysical Union spring meeting in Boston, Massachusetts.

The most dramatic features, taken last year from March to December, are the immense clouds of carbon monoxide from grassland and forest fires in Africa and South America. The plumes slowly travel across the Southern Hemisphere as far as Australia during the dry season in that part of the world.

Gille was surprised to discover a strong source of carbon monoxide in Southeast Asia. The air pollution plume from this region moves over the Pacific Ocean and reaches North America, frequently at fairly high concentrations, according to Gille. While fires are the major contributor to these carbon monoxide plumes, he suspects, at times, industrial sources may also be a factor.

“The MOPITT observations represent a powerful new tool for identifying and quantifying pollution sources, and for observing the transport of pollution on international and global scales,” said atmospheric chemist Daniel J. Jacob at Harvard University in Cambridge, Massachusetts, who used MOPITT data this spring in a major field campaign to study air pollution from Asia. “Such information will help us improve our understanding of the linkages between air pollution and global environmental change, and it will likely play a pivotal role in the development of international environmental policy.”

MOPITT also captured the extensive air pollution generated by the forest fires in the western United States last summer. A major source of air pollution during the wintertime in the Northern Hemisphere is the burning of fossil fuels for home heating and transportation, which can be seen wafting across much of the hemisphere.

Although MOPITT cannot distinguish between individual industrial sources in the same city, it can map different sources that cover a few hundred square miles. This is accurate enough to differentiate air pollution from a major metropolitan area, for example, from a major fire in a national forest. About half of the global emissions of carbon monoxide are caused by human activities.

Carbon monoxide is not only a hazardous air pollutant, it is also a chemical compound that produces ozone, a greenhouse gas that is a human health hazard. MOPITT sees carbon monoxide in the atmosphere from two to three miles above the surface, where it interacts with other gases and forms ozone. This pollutant can move upward to altitudes where it can be blown rapidly for great distances, or it can move downward to the surface.

By tracking plumes of carbon monoxide, scientists are able to track the movements of other pollutants such as nitrogen oxides that are also produced by the same combustion processes but cannot be directly detected from space. Q

For more information, please contact David Steitz at NASA Headquarters, & 202/358-1730, ) dsteitz@hq.nasa.gov Please mention you read about it in Innovation.

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