title: Two-year measurements of surface ozone at Dangxiong, a remote highland site in the Tibetan Plateau.
abstract: Measurements of surface O3 and carbon monoxide (CO) were made from September 2009 to August 2011 at Dangxiong (30.48°N, 91.10°E, 4187 m a.s.l.), a remote highland site in a southern valley of the Nyainqêntanglha Mountains in the Tibetan Plateau, China. The monthly mean O3 mixing ratio ranged from 29.1 to 51.4 ppb, with an average of 38.5 ppb, and the maximum value was observed in May. The average diurnal cycle of O3 concentration showed a minimum in early morning and a maximum in the afternoon, with a broader "high platform" from the late morning to the late afternoon, and resembled that of surface wind speed. The concentration of surface O3 was highly significantly correlated with tropospheric column O3 over the regions surrounding Dangxiong and with that of surface O3 observed at a site north of the Nyainqêntanglha Mountains, suggesting a good regional representativeness of surface O3 at Dangxiong. In the afternoon when stronger winds blew, surface air showed distinct features of free-atmospheric air, with higher O3, lower CO, and lower relative humidity (RH). The negative O3-CO and O3-RH correlations in most months indicate a significant influence of air masses from the free troposphere. Trajectory analysis suggests that air masses originating from the south of the site make a negative net contribution to surface O3 and a positive contribution to CO and humidity, and those from the northwest sector contribute conversely to the respective quantities.
authors.affiliation: Centre for Atmosphere Watch & Services, Meteorological Observation Centre, China Meteorological Administration, Beijing 100081, China.
authors.forename: Weili
authors.initials: W
authors.lastname: Lin
authors.affiliation: Key Laboratory for Atmospheric Chemistry, Chinese Academy of Meteorological Sciences, Beijing 100081, China. Electronic address: xuxb@cams.cma.gov.cn.
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Xu
authors.affiliation: Key Laboratory for Atmospheric Chemistry, Chinese Academy of Meteorological Sciences, Beijing 100081, China.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Zheng
authors.affiliation: Dangxiong Meteorological Bureau, Lhasa 851500, China.
authors.forename: Jaxi
authors.initials: J
authors.lastname: Dawa
authors.affiliation: Lhasa Meteorological Bureau, Lhasa 850000, China.
authors.forename: Ciren
authors.initials: C
authors.lastname: Baima
authors.affiliation: Key Laboratory for Atmospheric Chemistry, Chinese Academy of Meteorological Sciences, Beijing 100081, China; Department of Atmospheric and Oceanic Sciences, McGill University, Montreal, Quebec, Canada.
authors.forename: Jin
authors.initials: J
authors.lastname: Ma
mesh_terms: D000393:Air Pollutants / Q000737:chemistry; D000531:Altitude; D002248:Carbon Monoxide; D002940:Circadian Rhythm; D010126:Ozone / Q000737:chemistry*; D012621:Seasons; D018609:Tibet; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D010126:Ozone; D002248:Carbon Monoxide
keywords: Impact of transport and vertical mixing; Surface ozone; Tibetan Plateau