PNNL

In surprising results of a study published in Nature Communications, Pacific Northwest National Laboratory researchers, working with scientists from the Scripps Institution of Oceanography, Nanjing University of Information Science & Technology, and the Chinese Academy of Meteorological Sciences, found that desert dust actually promotes winds over China to whisk away human-caused pollution. When the dust is absent, the air doesn't move, allowing pollution to build up and linger in the atmosphere.

"Less dust in the atmosphere causes more solar radiation to reach the surface," PNNL atmospheric researcher Dr. Yang Yang told the British Broadcasting Corporation. "It weakens the temperature difference between the land and the sea, and impacts the circulation of the winds to cause a stagnation over eastern China, and that causes an accumulation of air pollution."

Especially during the winter, their research showed that reduced dust levels led to a 13 percent increase in human-caused pollution over eastern China.

Why It Matters: Dust from East Asia and local pollution from burning fossil fuels are two atmospheric-driven blights that plague communities and people in China. The surprising finding of this research is that the two very often can't coexist. Under the right conditions, the dust soaks up radiated solar energy, like mini-solar collectors in the atmosphere. The additional heat provokes winds that then drive out human-caused air pollution, much of it emitted from vehicles, energy production, and industry.

Methods: The dust in the region comes from the Gobi Desert in northern China and southern Mongolia, as well as the highlands of northwest China. The researchers found that the Gobi had a much larger influence than other deserts. The simulations showed that dust's ability to capture and hold heat acts as a benefit under certain conditions. The PNNL research team and collaborators used two 150-year pre-industrial simulations in the Community Earth System Model (CESM) and a present-day simulation of the GES-Chem model to quantify the impact of dust-wind interactions on pollution over eastern China.

They found that the dust-wind interactions accounted for about 13 percent of the increase in aerosol concentrations over eastern China.

What's Next? Pollution is not only caused by local emissions, but also foreign sources through long-range transport. Researchers plan to examine the influence of local and foreign sources on the decadal variation of human-caused air pollution and its relationship with the weakening of local winds.

For more information, read PNNL news release "More natural dust in the air improves air quality in eastern China."

Acknowledgments

Sponsors: The PNNL researchers were supported by the U.S. Department of Energy Office of Science (SC) Biological and Environmental Research (BER) as part of the Regional and Global Climate Modeling program. The National Science Foundation supported this work as part of the DOE SC BER Decadal and Regional Climate Prediction using Earth System Models (EaSM) program.

Reference: Yang Y, L Russell, S Lou, H Liao, J Guo, Y Liu, B Singh, and S Ghan. 2017. "Dust-Wind Interactions Can Intensify Aerosol Pollution Over Eastern China." Nature Communications 8: 15333. DOI: 10.1038/ncomms15333