Measuring and modeling black carbon (BC) contamination in the SE Tibetan Plateau |
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Authors: | Junji Cao Xuexi Tie Baiqing Xu Zhuzi Zhao Chongshu Zhu Guohui Li Suixin Liu |
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Institution: | (1) SKLLQG, Institute of Earth Environment, Chinese Academy of Science, Xi’an, China;(2) National Center for Atmospheric Research, Boulder, CO, USA;(3) Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau, Chinese Academy of Science, Beijing, China;(4) The Graduate School of Chinese Academy of Science, Xi’an, China;(5) Molina Center for Energy and the Environment, La Jolla, CA, USA; |
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Abstract: | Black carbon (BC) concentrations were measured in the southeast (SE) Tibetan Plateau along the valley of the Yarlung Tsangpo
River during winter (between November, 2008 and January, 2009). The measured mean concentration (0.75 μg m−3) is significantly higher than the concentrations (0.004–0.34 μg m−3) measured in background and remote regions of the globe, indicating that Tibetan glaciers are contaminated by BC particles
in the Plateau. Because BC particles play important roles for the climate in the Tibetan Plateau, the sources and causes of
the BC contamination need to be understood and investigated. In this study, a mesocale dynamical model (WRF) with BC particle
modules is applied for analyzing the measurement. The analysis suggests that the major sources for the contamination in the
SE Plateau were mainly from the BC emissions in eastern Indian and Bangladesh. Because of the west prevailing winds, the heavy
emissions in China had no significant effects on the SE Plateau in winter. Usually, the high altitude of the Himalayas acts
a physical wall, inhibiting the transport of BC particles across the mountains to the plateau. This study, however, finds
that the Yarlung Tsangpo River valley causes a 'leaking wall', whereby under certain meteorological conditions, BC particles
are being transported up onto the glacier. This too causes variability of BC concentrations (ranging from 0.3 to 1.5 μg m−3) in a time scale of a few days. The analysis of the variability suggests that the “leaking wall” effect cannot occur when
the prevailing winds were northwest winds, during which the BC transport along the valley of the Yarlung Tsangpo River was
obstructed. As a result, large variability of BC concentration was observed due to the change of prevailing wind directions. |
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