Dec 19, 2013
Insight: heavy pollution in China changes rainfall patterns
Air pollution, such as the particulates suspended in the atmosphere as aerosols, is a big problem in eastern China. Everyone knows that aerosols are not good for human health, and meteorologists have found that aerosols also influence the climate. In a new study, published in Environmental Research Letters (ERL), we have found that the emission of anthropogenic sulphur dioxide, which can be converted to sulphate aerosols, is unevenly distributed over eastern China. During the past two decades, the Beijing–Tianjin–Hebei area and Yangtze River delta appear to have been more polluted than the area between them, and it was interesting to find out whether the uneven distribution of sulphur dioxide emissions could have altered the climate in this region.
We conducted sensitive experiments using a regional climate model coupled with a chemical model to explore the influence of sulphate aerosols on the climate in eastern China. The model results showed that rainfall decreased in the Beijing–Tianjin–Hebei area and Yangtze River delta but increased in the Huang-Huai River region during 1999–2008, compared with 1989–1998. The change in the decadal rainfall pattern in the model is similar to that actually observed.
Further analysis showed that the decreased (increased) rainfall is caused by anomalous downward (upward) currents associated with the uneven distribution of sulphur dioxide emissions. Large amounts of emitted sulphur dioxide result in downward air motion over the Beijing–Tianjin–Hebei area and Yangtze River delta. Because there are strong downward currents to the south and north of the Huang-Huai River region, an upward current is formed in this area thanks to a compensation effect.
In the present work, we only considered the climatology of the atmospheric circulation and did not consider indirect effects. In the future, the annual variation of the atmospheric circulation needs to be considered, and we intend to explore the indirect effect of sulphate aerosols on decadal rainfall change.
About the author
Yang Zhou is a research associate in the School of Atmospheric Sciences, Nanjing University, Jiangsu, People’s Republic of China.