Thunderstorms over Tibet provide a major pathway for water vapor and chemicals to travel from the lower atmosphere, which is directly influenced by human activities, into the stratosphere, where the protective ozone layer resides.
Dr. Rong Fu, associate professor in Georgia Tech's School of Earth and Atmospheric Sciences, who led this study, said that although there are more thunderstorms over India, the storms over Tibet have nearly three times more influence over the lower stratosphere.
"This study shows that thunderstorms over Tibet are mainly responsible for the large amount
of water vapor entering the stratosphere," said Fu. "The rainfall may not be as frequent over Tibet as over the Indian monsoon area, but because Tibet is at a much higher elevation than India, the storms over Tibet are strong and penetrate very high, and send water vapor right into the stratosphere."
The study was the result of collaboration between researchers from the Georgia Institute of Technology, Atlanta; NASA's Jet Propulsion Laboratory, Pasadena, California; and the University of Edinburgh, Scotland. They used data from three NASA satellites and collected more than 1000 measurements of high concentrations of water vapor in the stratosphere over the Tibetan Plateau and the Asian monsoon region.
They found that this Tibetan pathway to the upper atmosphere is also responsible for transporting carbon monoxide, besides the chemicals that destroy the ozone layer. "There's almost no carbon monoxide production in Tibet, so it's widely believed that carbon monoxide is transported to the tropopause over Southeast Asia and the Indian subcontinent," Fu said. The tropopause is a layer in the atmosphere that divides the lower atmosphere from the stratosphere, and is located at an altitude of about 18 kilometers over the tropics and Tibet.
Fu added that "when long-lived pollutants are transported out of the lower atmosphere, they can move rapidly. Pollutants from Asia, for example, can wind up on the other side of the world."
Image Credit: Rong Fu, Cinda Gillilan, Jonathan H. Jiang and Brian Knosp
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