Flow patterns influencing the seasonal behavior of surface ozone and carbon monoxide at a coastal site near Hong Kong |
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| Institution: | 1. Environmental Engineering Unit, Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong;2. Department of Atmospheric Science, Nanjing University, Nanjing 210093, People''s Republic of China;3. Climate Monitoring and Diagnostics Laboratory, NOAA/ERL Boulder, CO 80303, USA;1. Department of Earth and Environmental Sciences Columbia University, 61 Route 9W, Palisades, NY 10964, USA;2. Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY, USA;3. Nelson Institute Center for Sustainability and the Global Environment (SAGE), University of Wisconsin-Madison, Madison, WI, USA;4. NOAA Geophysical Fluid Dynamics Laboratory and Atmospheric and Oceanic Sciences, Princeton University, 201 Forrestal Road, Princeton, NJ, USA;5. School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge, MA, USA;6. Department of Atmospheric and Oceanic Sciences & Laboratory for Climate and Ocean-Atmosphere Studies, School of Physics, Peking University, China;7. UCAR/NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ, USA;8. U.S. EPA, National Center for Environmental Assessment, Research Triangle Park, NC, USA;1. Department of Environmental Science, Tezpur University, Tezpur 784028, India;2. Department of Environmental Studies, Visva Bharati, Bengal, India;3. Department of Public Health Sciences, University of Rochester, Rochester, NY, United States;1. Department of Occupational health and Environmental Health, School of Public Health, Capital Medical University, Beijing, China;2. National Center for Chronic and Noncommunicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, 27 Nanwei Road, Xicheng District, Beijing 100050, China;3. Department of Occupational and Environmental Health Sciences, Peking University School of Public Health, 38 Xueyuan Road, Haidian District, Beijing 100191, China;4. Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, USA;1. Institute of Urban Meteorology, China Meteorological Administration, Beijing, 100089, China;2. Beijing Shangdianzi Regional Atmosphere Watch Station, Beijing, China;3. College of Life & Environmental Science, Minzu University of China, Beijing, 100081, China;4. John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA;5. School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing, 210044, China;6. Tianjin Environmental Meteorology Center, Tianjin, 300074, China |
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| Abstract: | Surface O3 and CO were measured at Cape D’Aguilar, Hong Kong during the period of January 1994 to December1996 in order to understand the temporal variations of surface O3 and CO in East Asia–West Pacific region. The isentropic backward trajectories were used to isolate different air masses reaching the site and to analyze the long-range transport and photochemical buildup of O3 on a regional scale. The results show that the diurnal variation of surface O3 was significant in all seasons with daily O3 production being about 20 ppbv in fall and 10 ppbv in winter, indicating more active photochemical processes in the subtropical region. The distinct seasonal cycles of O3 and CO were found with a summer minimum (16 ppbv)–fall maximum (41 ppbv) for O3 and a summer minimum (116 ppbv)–winter maximum (489 ppbv) for CO. The isentropic backward trajectory cluster analyses suggest that the air masses (associated with regional characteristics) to the site can be categorized into five groups, which are governed by the movement of synoptic weather systems under the influence of the Asian monsoon. For marine-originated air masses (M-SW, M-SE and M-E, standing for marine-southwest, marine-southeast and marine-east, respectively) which always appear in summer and spring, the surface O3 and CO have relatively lower mixing ratios (18, 16 and 30 ppbv for O3, 127, 134 and 213 ppbv for CO), while the continental air masses (C-E and C-N, standing for continent-east and continent-north, respectively) usually arrive at the site in winter and fall seasons with higher O3 (43 and 48 ppbv) and CO (286 and 329 ppbv). The 43 ppbv O3 and 286 ppbv CO are representative of the regionally polluted continental outflow air mass due to the anthropogenic activity in East Asia, while 17 ppbv O3 and 131 ppbv CO can be considered as the signature of the approximately clean marine background of South China Sea. The very high CO values (461–508 ppbv) during winter indicate that the long-range transport of air pollutants from China continent is important at the monitoring site. The fall maximum (35–46 ppbv) of surface O3 was believed to be caused by the effects of the weak slowly moving high-pressure systems which underlie favorable photochemical production conditions and the long-range transport of aged air masses with higher O3 and its precursors. |
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