Atlantic Transport of Anthropogenic Aerosol Optical Depth (AOD) in 2003

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. 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. 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 affected the local environment. Yu points out, however, that the matter of pollution transport is a global one. "Our study focused on East Asian pollution transport, but pollution also flows from Europe, North America, the broader Asian region and elsewhere, across bodies of water and land, to neighboring areas and beyond," he said. "So we should not simply blame East Asia for this amount of pollution flowing into North America." In fact, a recent model study conducted by Mian Chin, co-author of this study and an atmospheric scientist at NASA Goddard suggests that European pollution also makes significant contribution to the pollution inflow to North America. "Satellite instruments give us the ability to capture finer measurements, on a nearly daily basis across a broader geographic region and across a longer time frame so that the overall result is a better estimate than any other measurement method we've had in the past," said study co-author Lorraine Remer, a physical scientist and member of the MODIS science team at NASA Goddard. The MODIS instrument can distinguish between broad categories of particles in the air, and observes Earth's entire surface every one to two days, enabling it to monitor movement of the East Asian pollution aerosols as they rise into the lower troposphere, the area of the atmosphere where we live and breathe, and make their way across the Pacific and up into the middle and upper regions of the troposphere. Remer added that the research team also found that pollution movements fluctuate during the year, with the East Asian airstream carrying its largest "load" in spring and smallest in summer. The most extensive East Asian export of pollution across the Pacific took place in 2003, triggered by record-breaking wildfires across vast forests of East Asia and Russia. Notably, the pollution aerosols also travel across the ocean quickly, journeying into the atmosphere above North American in as little as one week. "We cannot determine at what level of elevation in the atmosphere the pollution ends up once it crosses over to North America, so we do not have a way in this study to assess what actual impact it has on air quality here," said Remer. "Nevertheless, we realize there is indeed impact. For example, particles like these have been linked to regional weather and climate effects. Since pollution transport is such a broad global issue, it is important moving forward to extend this kind of study to other regions, to see how much pollution is migrating from its source regions to others, when, and how fast," said Remer.