THE OBSERVATIONAL STUDY OF SURFACE OZONE AT LHASA SUBURB IN SUMMER 1998

As a part of investigation study on the "Summer Ozone Valley over the Tibet an Plateau", which was found by Zhou Xiujiin 1995, continuous measurement of surfaceozone was made at Suburb of Lhasa (29.65°N, 91.16°E, 3650 m a. s. l.) from June to September of 1998. The U V photometry method was used in the mea-surement with the instrument manufactured by Thermal Environment al Co., USA. The daily mean concentration of surface ozone varied in the range of 10-60 nL/L, higher in early summer and lower in late summer. The highest monthly mean ozone concent ration is the value of 41 nL/L in June, and the lower mont hly means of 20 nL/L in A ugust and in September. T he concent rat ion of surface ozone show ed a clear diurnal variation with a pronounced max im um from 10 to 18 o'clock, and a minimum f rom 4 to 6 o'clock at local time. The difference bet ween the daytime maximum and the dawn minimum was ranging from several nL/L t o 40 nL/L, and significantly controlled by the weather conditions such as solar radiation and raining events. Both of the daily mean ozone concent rat ion and t he maximum ozone concent rat ion showed a posit ive correlation, with afact or greater than 0.5, with the amount of daily solar irradiation. Wind also gave inf luences on the ozone concentration variation. The ozone concent ration was higher at windy condition than at relatively stable condition, especially during the night time. The above facts indicat ed obv iously t he characterist ics of local phot ochemical ozone production in surface ozone variation. The unique phenomena were noted, when checked the ozone data with the local religious events schedule, that the opened biomass burning of grinded flavor vegetation in the activities through out the city promoted higher ozone concent ration by emitting more precursors locally for short period of days.