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Cloud-sniffing drones soar over Asia

Researchers track China’s plume of pollution. What effect did Olympic hiatus have?

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Why the focus on Asia? “It’s simple,” says Dan Murphy, a researcher with the National Oceanic and Atmospheric Administration’s Earth Systems Research Laboratory in Boulder, Colo. He was a lead researcher in this past spring’s ARCPAC project to gather data on the effect of aerosols on solar radiation and clouds in the Arctic. “Asia has a large population, its economies are developing so rapidly, and its emissions are large and changing rapidly.” Moreover, the historical record for air pollution there is not as extensive or consistent as similar measurements in the West.

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Indeed, one of Ramanathan’s goals is to help set up a baseline against which efforts to improve China’s air quality can be measured.

In May, the US Department of Energy in a separate effort set up a portable atmospheric-radiation monitoring station in Shouxian, 300 miles west of Shanghai. The experiment, in collaboration with Chinese researchers, aims to better understand the effect that soot and aerosols have in the region through their effect on clouds.

Satellite data show that clouds in southern China hold a lot of liquid water, but the clouds aren’t producing the amount of rain such moisture-laden clouds might be expected to drop, says Mark Miller, an atmospheric scientist at Rutgers University in New Brunswick, N.J., and one of the US scientists involved in the effort. “We’re trying to find out why clouds in southern China are operating under a different set of rules,” he says.

Vast plumes of aerosols, soot, and smoke, dubbed atmospheric brown clouds, can have far-reaching effects, geographically. While aerosols appear to have a net cooling effect, black soot particles warm things up. Work by scientists at Scripps suggests that soot’s warming effect may be contributing to an increasingly early snow melt and runoff in the Sierras and other western ranges.

In the Arctic, Asian pollution has been measured as far east as Greenland. And now, scientists are beginning to build a historical record of soot-fall there. Earlier this month, a team led by Joseph McConnell from the Desert Research Institute in Reno reported finding soot dating back to 1788 in ice cores from Greenland. Based on the trends they see, soot – largely from eastern North America – may have been responsible for early 20th century warming in the Arctic. And migrating soot and aerosols often carry chemical pollutants that accumulate where the particles land.

In the southern hemisphere, re­­searchers in Australia have shown through modeling studies how Asian haze over the tropical Indian Ocean appears to redirect monsoon-related winds, driving more rain to northwestern Australia than might otherwise be the case.

[Editor's note: The original version of this article misstated Joseph McConnell's affiliation. He works for the Desert Research Institute in Reno.]