| To explore the mechanisms responsible for formation and variation of O3 at the surface in clean area and the effect of some relative gas on it,the variation characteristics of the surface O3 and CO concentration over Mt.Waliguan have been analyzed based on near eight years of continuous observations of surface O3 at Waliguan atmospheric baseline observatory from August 1994 to June 2002, combined with the CO data in the same period,compared to the analysis of surface O3 and CO data of other three near high elevation globe background stations of northern hemisphere.The correlation of the surface concentration of O3 and CO in the four stations has slao been studied.The variation characteristics of total ozone over Waliguan from 1998 to 2002 have been analyzed,and the correlation of the surface concentration of O3 and total ozone has also been studied.Based on the analyses mentioned above,the following major conclusions can be drawn from this study:1.Similar as the other three high elevation stations,the value of surface O3 is about 47.7×10-9at Waliguan,and it has the tendency of increasing slowly year by year.The surface concentration of O3 at Waliguan had exhibited obvious seasonal variation,with the maximum O3 appearing in summer,the minimum O3 appearing in fall-winter,while the highest values of the other three stations appeared in spring. The daily difference range of Waliguan surface concentration of O3 was relatively small,with the daily minimum appearing at noon and the maximum at night and early morning,similar with Izana and Mauna Loa station.Photochemistry reactivity is not the major factor of the increse of O3 concentration.The dynamic transport contributes more to O3 variation than the photochemistry reactivity.2.The concentration of CO is 131.87×10-9at Waliguan,different from the other three stations,and it has the tendency of increasing slowly year by year.The concentration of CO at Manna Loa and Jungfraujoch stations has the obvious downtrends,and the down tendency of Izana is not obvious.The CO average seasonal cycle has non-symmetrical characteristic at Waliguan,with the maximum in March,minimum in November.The maximum of CO at Mauna Loa,Jungfraujoch and Izafia stations appears in spring,but the low value of CO in summer.3.The surface concentrations of O3 correlated to some extent with the concentration of CO at Waliguan,but the correlation was not marked,similar as the Izafia station.The correlation coefficient at Mauna Loa is high,but the surface ozone and CO are almost incorrelate at Jungfraujoch station.Although the four alpine stations are all located in clean areas,the mechanism of ozone production and change is not the same.4.The total ozone that appears downtrend has obvious annual and seasonal variation at Waliguan.The total ozone is low in summer,which keeps to autumn,and the value of ozone is high in winter and spring.The frequency of low total ozone is higher in summer-autumn than in winter-spring.The surface concentrations of O3 negatively correlated to some extent with the total ozone at Waliguan,but the correlation was not marked.
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