Haunting streams of air pollution from forest fires and other sources can be seen churning through Earth's atmosphere, crossing continents and oceans, courtesy of new data collected by NASA's Terra spacecraft.
These newly released images give policymakers and scientists a way to identify the major sources of air pollution and closely track where it goes, anywhere on the planet.
Terra's global air pollution monitor, called the Measurements of Pollution in the Troposphere, or MOPITT experiment, came from the Canadian Space Agency. The data was processed by a team at the U.S. National Center for Atmospheric Research (NCAR). MOPITT is making the first long-term global observations of the air pollutant carbon monoxide as Terra circles Earth from pole to pole, 16 times every day.
"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. "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 MOPITT observations were released Wednesday at the annual American Geophysical Union meeting in Boston.
Asian plume frequently reaches North America
The most dramatic features, taken from March to December 2000, are 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.
Gille was surprised to discover a strong source of carbon monoxide in Southeast Asia, where an air pollution plume moves over the Pacific Ocean and reaches North America frequently at fairly high concentrations, Gille said.
While fires are the major contributor to these carbon monoxide plumes, industrial sources may also be a factor, he said.
The Terra data "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," said Harvard University atmospheric chemist Daniel J. Jacob. He used MOPITT data this spring in a field campaign to study air pollution from Asia.
Sorting out pollution sources
MOPITT also captured the extensive air pollution generated by forest fires in the western United States last summer. A major source of air pollution during winter 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 (square kilometers). This is accurate enough to differentiate air pollution generated by a major metropolitan area, for example, from that of a major fire in a national forest. About half of the global emissions of carbon monoxide are caused by human activity.
Carbon monoxide is not only a hazardous air pollutant itself. 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 2 to 3 miles (3 to 5 kilometers) 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.
Carbon monoxide is a byproduct of the incomplete burning of fossil fuels by cars, industry and home heating, as well as by burning natural organic matter such as wood. 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.
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