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We present a two-year measurement results of surface ozone at Dangxiong (30.48oN,91.10oE,4187m),a remote highland site in a southern valley of Nyainqêntanglha Mountains,Tibetan Plateau,China.The monthly mean ozone mixing ratios range 29.1-59.4 ppbv with a mean value plus or minus standard deviation of 38.5±7.5 ppbv.If only are the data for12:00-17:00 local time considered,the monthly mean ozone mixing ratios are 37.5-63.5 ppbv with a mean value plus or minus standard deviation of 49.8±7.8 ppbv.The maximum ozone value is found to occur in May,in accordance with the spring ozone maximum phenomenon in the Northern Hemisphere.The average diurnal cycle of O3 concentration shows the minima in the early morning and the maxima in the afternoon.The O3 mixing ratio maintained an high and flat level for hours from the late morning to the afternoon,which is very consistent with the variation of surface wind velocity.Ozone increases with an increase of wind speed at relatively low wind speed and it keeps much smooth when the wind speed increases above a level (about 2.5 m/s in cold months and 3.0 m/s in warm months).The significant correlation of surface ozone with the column ozone from satellite data,along with the very similar day-to-day and week-to-week temporal fluctuations of surface ozone with those measured at another site in the northern side of Nyainqêntanglha Mountains,suggests a good regional representativeness of surface ozone observed at Dangxiong.The characteristics of air in the afternoon are strong wind,higher ozone,lower CO and lower relative humidity (RH),being the distinct features of the free atmosphere.The significant negative correlations of O3-CO and O3-RH in most months indicate a significant influence of air masses from the upper troposphere and lower stratosphere.5-day backward trajectory analysis shows that air masses coming from the south of the site have a negative contribution to surface ozone,humidity and a positive contribution to CO,and air masses from the northwest of the site across the whole plateau have a positive contribution to surface ozone and negative contribution to CO and humidity.Air masses from the west of the site have generally undergone relative long-range transport,originating from the Middle East and then making a positive contribution to surface ozone and CO at Dangxiong.