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The aerosol optical depth over the eastern slope of the Tibetan Plateau (ESTP) is extremely large--and even more so than some important industrialized regions and deserts, which is the result of a combination of human activities and natural conditions, according to Prof. Yuzhi LIU at Lanzhou University.

Prof. Liu and her team--a group of researchers from the Key Laboratory for Semi-Arid Climate Change of the Ministry of Education, College of Atmospheric Sciences at Lanzhou University--have had their findings published in Advances in Atmospheric Sciences. A combination of satellite observations and reanalysis datasets was used to analyze the spatiotemporal distribution, classification and source of pollutants over the ESTP. The accumulation mechanism of aerosols over the region is also discussed.

"Known as 'the roof of the world', the TP [Tibetan Plateau] is a sensitive indicator and regulator of climate change, playing a significant role in driving the climate change of the Northern Hemisphere and even the globe through thermal and mechanical forcing. The addition of abundant aerosols in the air over the TP poses new climatic and environmental risks," said Dr Rui Jia, the lead author of the study.

"Aerosols over the ESTP are substantial, and even more so than those over the most densely populated and industrialized regions and deserts. These aerosols are high in load and complex in type, which can be further lifted to high altitude and mixed with clouds," she explains. "Studying the aerosol transport processes and physical mechanisms of aerosol accumulation on a large scale over the ESTP is important."

"Local emissions related to human activity contribute directly to the accumulation of sulfate and carbonaceous aerosols over the Sichuan Basin," Dr Jia explains. "In addition, in spring, abundant carbonaceous aerosols emitted from forest, grassland and savanna fires in Southeast Asia can be transported to the ESTP by the prevailing southwesterly wind."

"Additionally, the high aerosol loading over the ESTP is also directly related to the meteorological background. The terrain-driven circulation can trap aerosols in the Sichuan Basin and these aerosols can climb along the ESTP due to the perennial updraft" states Dr Jia. "Of course, more precipitation is beneficial for the wet deposition of the aerosols," she adds.

The corresponding author, Professor Liu, summarizes the causes of aerosol pollution over the ESTP as local emissions, transport from outside the region, and the accumulation of pollutants under specific geographical conditions.

"The inward transport, smaller vertical temperature gradient and terrain-driven circulation contribute greatly to the accumulation of aerosols over the ESTP, which poses greater challenges to environmental governance than that from local emissions." Says Prof. Liu.

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