The Quantitative Contribution Of Aerosols To Actinic Radiation Flux And Atmospheric Oxidation

Actinic flux refers to the integral of the effective photochemical radiation flux in all directions in a volume,which can cause photolysis of atmospheric components.Ozone photochemistry is the driving force of atmospheric photochemistry.Previous few studies focused on the influence of photochemistry on the photochemistry driving the photochemistry reaction.Aerosol and clouds were the key factor causing radiation flux attenuation.Revealing the effect of aerosol on photosynthetic radiation flux can improve the radiation parameterization scheme.It is important to quantitatively the influence of Aerosol Changes on atmospheric oxidation capacity and air quality.Based on the simultaneous observation of actinic flux and sub-band solar irradiance in Xianghe and Beijing,the evolution characteristics of photolysis rate were analyzed and the reconstruction scheme of NO₂ photolysis rate suitable for North China was constructed.The quantitative contribution of aerosol to photochemical radiation flux and photolysis rate was evaluated by mathematical statistics and TUV radiation transfer model.The main conclusions are as follows:?1?The photolysis rate has obvious sinusoidal diurnal variation characteristics.In the diurnal variation,the observed photolysis rate of the two stations was single peak,which was high in the middle of the day and low in the morning and evening.The average value of j?O¹D?in Xianghe was smaller than that in Beijing.At noon,j?O¹D?in Beijing was about 1.33 times higher than that in Xianghe.Compared to Xianghe station,the diurnal variation of the photolysis frequencies rate in Beijing was wider,the morning increases and the decrease in the afternoon was slower.In terms of seasonal variation,the seasonal variation trend of Xianghe j?O¹D?was consistent with that of j?NO₂?,j?NO₂?in Beijing was larger in spring and autumn,;j?O¹D?in winter and summer was the largest in summer,followed by spring,and the smallest in winter.?2?The larger the zenith angle of the sun,the smaller the maximum value of j?NO₂?was.In the specified Ks interval,the change of j?NO₂?with the cosine of solar zenith angle can be expressed in the form of power function.The scatter plot of j?NO₂?varied with the change of Ks satisfies the cubic function relation.The test results shown that the accuracy of the model based on clear sky index and solar zenith angle cosine was enough high.The MABE of instantaneous and temporal values were 10.5%and 8.7%,respectively,and the RMSE values were 0.00053 and 0.00040,respectively.It can be used to estimate the instantaneous and small size of Xianghe j?NO₂?.Applying the formula to Beijing,the MABE value and RMSE value of the instantaneous calculated value were 26.2%and 0.0013,respectively.It was shown that the fitting model for estimating the photolysis frequencies of Xianghe can be used to estimate the instantaneous and hourly j?NO₂?in North China.?3?Based on the long-term radiation observation of 45 CERN field stations and the reconstruction method of j?NO₂?in Xianghe,and the j?NO₂?at the national scale were obtained.The results shown that the average relative error of j?NO₂?estimation scheme based on solar altitude angle was less than 10%in clear sky?K_S>0.75?.The estimation of j?NO₂?based on global radiation was better than that of the former in the case of small clearness index.The j?NO₂?was lower in the northeast and higher in the south and southwest of China.Under the non-clear sky?K_S<0.75?,the southwest basin and Jing-jin-ji region?represented by Beijing Forest Station?were low value areas and South China,North China and North China Plain were high value areas.?4?The slope of the photolysis rate constant decreased with the increase of AOD.The lower the SZA,the closer the relationship between j?NO₂?and AOD was to linearity.Conversely,the higher the SZA the relationship between j?NO₂?and AOD was tend to be nonlinear.In summer,aerosol reduced j?O¹D?by 56%and j?NO₂?by82%,and in winter,aerosol reduced j?O¹D?and j?NO₂?by 218%and 184%,respectively.The energy in the whole spectral region of the polluted day has been obvious attenuated,especially in the ultraviolet spectral region,and further affected j?NO₂?.In summer,the average values of O_X and j?NO₂?in Xianghe River increased with the increase of K_S,while the average value of AOD decreases with the increase of K_S.The diurnal variation of O_X was unimodal,the wave valley was about in the morning,the peak was about in the afternoon,and the amplitude of decline was slower at night.The correlation coefficients between j?NO₂?and O_X and PM2.5 were 0.58 and0.14,respectively,which all had passed the significant test of 0.001.The absorption and scattering of solar radiation by clouds and aerosols significantly attenuated the photochemical radiation in Xianghe in summer.