Observational Study On The Characteristics Of Ozone Over The Surface Of Semi-Arid Region

Ozone is a very important greenhouse gas in the atmosphere,and can absorb UV very strongly.The oxidative of ozone is very strong,so it can participate in the most chemical and photochemical reactions.People have focused more attention on the influence of ozone to climate and environment on the background of global warming. In this paper,the observation data of ozone about one year and some other kinds of correlative data in SACOL are used to analyze the variation characteristics of ozone for the first time.The factors that influence ozone concentration variation are also analyzed for the first time.The ozone concentration over surface in this area is estimated and simulated,in order to know the basal characteristic of ozone in semi-arid area in detail.The main research outcomes are as follows:Under the different backgrounds of weather,the diurnal variation characteristic of ozone concentration over surface is that:there is only one peak value in clear sky, cloudy and dusty days,while there are several peak values in the overcast,rainy and snowy days.The variation range of ozone concentration is the largest in clear sky days,and the average is also the largest,followed by cloudy,overcast,precipitation.The seasonal variation of ozone concentration is that the average ozone concentration in daytimes is the largest in summer,and then followed by autumn, spring and winter;the average concentration during nights is also the largest in summer,and then followed by spring,autumn and winter.The ozone concentration in SACOL can reach first class national environmental quality standard in the whole year.There are very strong corresponding relations between ozone concentration and surface temperature;the peak(valley)value of ozone concentration is about 1-2 hours earlier(later)than the peak(valley)value of temperature.The change trend of ozone and temperature is similar.Precipitation plays a very important role in wet removal of ozone.Ozone concentration can be reduced down when the cold front pass through this area. There is a negative correlationship between ozone and its precursor such as NO, NO₂ and CO,and its trend of daily variation contrary to them.The increasing of ozone concentration is advantageous to that NO and NO₂ convert to other forms of nitrogen oxide,and could cause decreasing of NO and NO₂ concentration.There is a significant correlationship between ozone concentration and NO₂/NO,and the ozone concentration is decreasing while NO₂/NO increasing.There is a similar annual variation trend between surface ozone concentration and ultraviolet radiation,and both of their values reach to the maximum from June to August of a year,and the minimum values appear between November and January.In daytime,the ground ultraviolet radiation in clear sky days is much higher than that in cloudy and overcast days,and the value in cloudy day is higher than that in overcast day.Corresponding to the ultraviolet radiation,the ozone concentration has the same variation trend.The appearance time of peak(valley)value of diurnal variation of ozone concentration is later than the appearance time of peak(valley)value of UV-AB.The main factors that influence ozone concentration are analyzed,such as solar radiation,chemical and photochemical reactions,aerosol and so on.According to the law of energy conversion and conservation of ultraviolet radiation,a theoretical model for the surface ozone concentration simulation is established.Using the data observed in SACOL from August to October in 2007,the parameters of this model are estimated by stepwise regression analysis.The multi-correlation coefficients R in both cases are above 0.9 no matter in clear sky or the actual sky days.Photochemistry,NO₂ concentration,ultraviolet radiation and aerosol concentration all have significant effects on ozone concentration.In overcast and rainy days,ultraviolet radiation has little contribute to ozone concentration,and the R is 0.881.In clear sky days, photochemistry is the most important impact factor on the ozone concentration,and then followed by NO₂ concentration,ultraviolet radiation and aerosol concentration; in actual sky days,the order is photochemistry,aerosol,ultraviolet radiation and NO₂, and in rainy days,the order is photochemistry,aerosol and NO₂.