Temporal And Spatial Variation Characteristics Of Black Carbon Concentration And Snow Grain Size In Northeast Of China From 2001 To 2016

The change of surface albedo and the radiative forcing effect of black carbon and snow grain size in snow is one of the hotspots of current academic circles.Knowing the concentration of black carbon in snow and snow grain size is the key to accurately evaluate its influence on snow-covered albedo and its radiative forcing effect.Based on the MOD09GA ground reflectivity data,the Asymptotic radiative transfer theory?ART model?is used to simulate the surface black carbon?BC?concentration and snow grain size of the surface layer in Northeast China from 2001 to 2016.The spatial and temporal distributions of BC concentration and snow grain size and their variation characteristics were analyzed.The results show:?1?The average annual BC concentration of Northeast China from 2001 to 2016fluctuated between 1089.927ng/g and 1257.300ng/g,with an average of 1197.468ng/g and an annual increase of 5.1329ng/g,showing no significant increase.The coefficient of variation is 0.034.There were also differences in BC concentrations during the winter months.The 16-year simulation results were the highest in BC in December,with an average of 1200 ng/g or more,followed by January and February,respectively,at 1248.619 ng/g and 983.635 ng/g.The concentration of BC in the three provincial capital cities did not increase significantly during the period from 2001 to2016,compared with Changchun(7.914ng·g^-1·a^-1)and Shenyang(7.795ng·g^-1·a^-1).Harbin BC has the fastest increase in BC concentration,which is 8.124 ng·g^-1·a^-1.?2?The BC concentration of the snow in Northeast China generally shows the spatial distribution characteristics of the higher in the north and the lower in the south,and the value range is between 310 ng/g and 1561 ng/g.The average BC concentration of snow in Liaoning Province,Jilin Province and Heilongjiang Province was 788.960 ng/g,962.440 ng/g and 1103.617 ng/g,respectively.There are two high-value areas in the BC concentration of the snow in Northeast China.They are industrial corridors composed of Daqing,Qiqihar and Heihe,and coal-forest industrial producing areas composed of Hegang,Jiamusi and Shuangyashan.Above 1200ng/g.Xiaoxing'anling and Changbai Mountain areas are relatively low-value areas of snow cover,with an average value below 900 ng/g.The high-value areas in December,January and February are also distributed in these two centers.In addition,the Daxinganling area is also a high-value area in December.?3?The BC concentration of snow in 81.805%of Northeast China increased from 2001 to 2016.The increase was mainly concentrated in the northern and central parts of Heilongjiang Province,most of Jilin Province and the western and eastern parts of Liaoning Province.The regions with the largest increase are distributed in the Greater Xing'an Mountains,Heihe,Yichun,Yanbian Korean Autonomous Prefecture,Southeastern Tonghua City,Fuxin City,Huludao City,etc.,with a growth rate of50⁹4.306ng·g^-1·a^-1.Significantly increased area accounted for 6.975%of the total area,mainly distributed in the northeastern part of the Greater Xing'an Mountains,the eastern part of Heihe City,the northern edge of Yichun City,and the southeast of Shuangyashan City.The BC concentration reduction area in Northeast China accounts for 18.195%of the total area,and is concentrated in the eastern and southwestern parts of Heilongjiang Province,the western part of Jilin Province,and the central and western parts of Liaoning Province.The region with the largest reduction is located in the east of Hegang City and the south of Qiqihar City.In the western part of Baicheng City,Chaoyang City,Jinzhou City and Dalian City,the reduction range is between-43.962^-6ng·g^-1·a^-1.?4?In the mountainous areas such as Xiaoxing'anling and Changbai Mountain,due to the high altitude,the impact of human activities is small,so it is a low-value zone with snow black carbon concentration.Shenyang,Changchun,Harbin,Daqing and other regions have large cities,concentrated industrial production and large population density.Therefore,it is a high-concentration zone for snow black carbon concentration.The expansion of cities in the northern Qiqihar,southern Heihe and northern Suihua areas,population density and energy use increased,resulting in a significant increase in snow black carbon concentration in the region.The overall winter wind speed in the northeast is low,the overall stratification of the atmosphere is relatively stable,and the pollutants are not easily diffused.Therefore,the concentration of black carbon in the northeast is higher.Especially in the central and northern parts of Heilongjiang Province,the atmospheric stratification is stable,and the topographical influence,the pollutants are not easy to spread,leading to the northern part of Qiqihar,the southern part of Heihe and the northern part of Suihua as the high value center of snow black carbon content in the northeast.?5?From 2001 to 2016,the average annual snow grain size distribution in Northeast China fluctuated between 430.830⁴52.384?m,the average value was440.823?m,and the annual growth was 0.259?m/a,showing no significant increase trend,and the coefficient of variation was 0.014.There are also differences in snow grain size during the winter months.The 16-year simulation results show that the snow grain size is the largest in December,with an average of 453.923?m,followed by January and February,which are 450.768?m and 417.777?m,respectively.The snow-capped snow particles in Heilongjiang Province,Jilin Province and Liaoning Province showed no significant increase,and the growth rates were 0.312?m/a,0.198?m/a and 0.201?m/a,respectively.?6?The snow grain size in Northeast China generally shows the spatial distribution characteristics of high in the north and low in the south,and the value range is between 380.248?m and 497.141?m.The average snow and snow grain sizes in Liaoning Province,Jilin Province and Heilongjiang Province were 418.201?m,429.193?mg and 440.437?m,respectively.The high snow grain size areas are distributed in areas such as Suihua,Qiqihar,Heihe and Hegang,Jiamusi,Shuangyashan,etc.The snow and snow particles are all above 448.550?m.Xiaoxing'anling,Changbai Mountain,eastern Liaoning Province and western hilly areas are relatively low-volume areas with a particle size below 416?m.?7?The snow grain size of the 49.978%region in Northeast China increased from 2001 to 2016.The increase was mainly concentrated in the northern and central parts of Heilongjiang Province,the central and eastern parts of Jilin Province,and most of Liaoning Province.The regions with the largest increase were distributed in the Greater Xing'an Mountains,Heihe,Yichun,Yanbian Korean Autonomous Prefecture,Baishan City,Huludao City,southern Anshan City,southeast of Yingkou City,and Dalian City.The growth rate was between 2.206?m/a and-9.223?m/a.Significantly increased area accounted for 4.494%of the total area,mainly distributed in the northeastern part of the Greater Xing'an Mountains,the eastern part of Heihe City,the central and northern Mudanjiang.The snow grain size reduction area in Northeast China accounts for 50.022%of the total area,and is concentrated in the northeastern and central and western regions.The areas with the largest reduction are distributed in Jixi City,Baicheng City,Songyuan City,Fuxin City,etc.,with a reduction of-1?m/a.-8.232?m/a.Significantly reduced areas are mainly distributed in the west of Harbin,in the south of Baicheng City,in the north of Jinzhou City,and in the central part of Fuxin City.