Study On The Characteristics Of Aerosol Level And Vertical Distribution In Shaanxi

To discuss the horizontal and vertical distribution characteristics of aerosol in Shaanxi province from 2015 to 2017,the ground air quality,MODIS and CALIPSO satellite data were used in this study.The distribution characteristics of PM10 in Shaanxi based on the ground monitoring data was Guanzhong>northern Shannxi province>southern Shannxi prowince,winter>spring>autumn>summer.From 2015 to 2017,The annual average of PM10 is higher than 100?g.m-3,and the concentration of PM10 in the Guanzhong area and Yanan area were relatively large,while the southern of Shaanxi was lower.The monthly change of PM10 was like "U".The distribution characteristics of AOD based on MODIS was Guanzhong>southern Shaanxi province>northern Shaanxi province,spring>summer>autumn>winter.The standard deviation of AOD was highest in southern Shaanxi province and lowest in Guanzhong.DEM was negatively correlated with AOD value.In addition,local pollution and meteorological factors were also important for the distribution of AOD.Analysis of the vertical optical properties of aerosols in Shaanxi province by using CALIPSO data showed that low-altitude atmosphere is greatly affected by aerosols,the backscatter coefficient and its dispersion degree were the largest in 0-2km,which was dominated by the relatively regular fine particles,and was mainly affected by human pollution.The atmosphere in 2-6km was greatly affected by external sand dust,and its backscatter coefficient,depolarization ratio and color ratio were all larger than the range of 6?8km.Northem Shaanxi province occured sand and dust easily in the spring,which led to non-spherical and coarse particles aerosol.The atmosphere was stable in 6?8km,and the backscatter coefficient,depolarization ratio and color ratio had very small difference among time and regions.Based on the relative humidity,the haze episode of Xi'an from December17 to 21 was divided into dry haze,wet haze and haze,and the vertical distribution characteristics of aerosol at different stages were analyzed.The study shows that in addition to the dust transported from northwest region,dust aerosols with large depolarization ratio and color ratio play dominant role in earlier stage;more fine particle generating with the increasing relative humidity in the mid,the extinction coefficient had risen to 1.7km-1,and pollution aerosols played dominant role instead,then mixtures of pollution and dust were observed and coarse particle accumulate in close to the ground when relative humidity decreases.The high-altitude is controlled by blocking weather situation and the surface is controlled by uniform pressure,breeze,high humidity and double temperature inversion contributed to the increasing of pollutant together,and the change of temperature inversion intensity had a certain lag consistency with the growth and decline of pollutants.