NASA satellite measures pollution from east Asia to North America

In a new NASA study, researchers taking advantage of improvements in satellite sensor capabilities offer the first measurement-based estimate of the amount of pollution from East Asian forest fires, urban exhaust, and industrial production that makes its way to western North America.

China, the world’s most populated country, has experienced rapid industrial growth, massive human migrations to urban areas, and considerable expansion in automobile use over the last two decades. As a result, the country has doubled its emissions of man-made pollutants to become the world’s largest emitter of tiny particles called pollution aerosols that are transported across the Pacific Ocean by rapid airstreams emanating from East Asia.

Hongbin Yu, an associate research scientist of the University of Maryland Baltimore County working at NASA’s Goddard Space Flight Center in Greenbelt, Md., grew up in China and taught there as a university professor, where he witnessed first-hand and studied how pollution from nearby power plants in China affected the local environment. Early this decade, scientists began using emerging high-accuracy satellite data to answer key questions about the role tiny particles play in the atmosphere, and eventually expanded their research to include continent-to-continent pollution transport. So Yu teamed with other researchers to take advantage of the innovations in satellite technology and has now made the first-ever satellite-based estimate of pollution aerosols transported from East Asia to North America.

The new measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on NASA’s Terra satellite substantiate the results of previous model-based studies, and are the most extensive to date. The new study will be published this spring in the American Geophysical Union’s Journal of Geophysical Research-Atmospheres.

“We used the latest satellite capabilities to distinguish industrial pollution and smoke from dust transported to the western regions of North America from East Asia. Looking at four years of data from 2002 to 2005 we estimated the amount of pollution arriving in North America to be equivalent to about 15 percent of local emissions of the U.S. and Canada,” Yu said. “This is a significant percentage at a time when the U.S. is trying to decrease pollution emissions to boost overall air quality. This means that any reduction in our emissions may be offset by the pollution aerosols coming from East Asia and other regions.”

Yu and his colleagues measured the trans-Pacific flow of pollution in teragrams, a unit of measurement of the mass of pollution aerosol (1 teragram is about 2.2 billion pounds). Satellite data confirmed 18 teragrams -- almost 40 billion pounds -- of pollution aerosol was exported to the northwestern Pacific Ocean and 4.5 teragrams – nearly 10 billion pounds -- reached North America annually from East Asia over the study period.