05/12/2011

Pollution from China Suppresses Rain over East China Sea

Summary

Rapid economic growth over the last 30 years in China has led to a significant increase in aerosol loading, which is mainly due to the increased emissions of its precursors such as SO₂ and NO_x. In this study, partially supported by DOE, the authors show that these changes significantly affect wintertime clouds and precipitation over the East China Sea downwind of major emission sources. Satellite observations show a 50% increase of cloud droplet number concentration from the 1980s to 2005. In the same time period, precipitation frequency reported by voluntary ship observers was reduced from more than 30% to less than 20% of the time. A back trajectory analysis showed the pollution in the investigation area to originate from the Shanghai-Nanjing and Jinan industrial areas. A model sensitivity study was performed, isolating the effects of changes in emissions of the aerosol precursors SO₂ and NO_x on clouds and precipitation using a state-of-the-art regional model including chemistry and aerosol indirect effects. The model was able to simulate similar changes in cloud droplet number concentration over the East China Sea when the current industrial emissions in China were reduced to the 1980 levels. Modeled changes in precipitation were somewhat smaller than the observed changes but still significant. The study reveals a significant impact of local pollution on precipitation.

References

Bennartz, R., J. Fan, J. Rausch, L. R. Leung, and A. K. Heidinger. 2011. “Pollution from China Increases Cloud Droplet Number, Suppresses Rain over the East China Sea,” Geophysical Research Letters 38, L09704. DOI: 10.1029/2011GL047235.