Effects Of Aerosol Optical Properties Based Vertical Observation On Radiation During Heavy Pollution Episodes In Beijing

Base on the continuous observation of aerosol optica l properties from CE-318sun-photometer a nd PM mass concentration in Be ijing,the monthly varia tion a mong aerosol optica l de pth（AOD）,?ngstr?m wave length expone nt（AE）,single scattering a lbedo（SSA）and partic le spectrum distribution from January to December 2018 were ana lyze d.Combine d with Raman-Mie Lidar vertica l detection,the vertica l varia tion of aerosols extinc tion c oeffic ie nt（ECs）in different pollution e pisodes were ana lyze d in de ta il.Using the observationa l data,the shortwave radia tive heating rates（HR）during the pollution process were calculate d by a shortwave radiative transfer model.The results show that spring whic h has the highest partic ulate concentration in the atmosphere is affected by mixing of coarse and fine partic les,other seasons are dominated by fine-mode partic les.In spring,AE（0.80）is the lowest in the whole year and AOD_440nm is above 0.80.In summer a nd autumn,the c once ntration of partic ulate matter is equiva le nt,but the hygroscopic growth in summer leads to the ma ximum va lue of AOD a nd SSA,SSA_440nmreach 0.95,a nd autumn pollution process is ma inly c oncentra ted in Nove mber.The aerosol concentration in the atmosphere is low in January,February and December,with AOD_440nmbe low 0.40.In the three pollution episodes,the de gree of e xtinc tion from strong to weak is followe d by spring ha ze,spring dust,a nd winter ha ze.During ha ze eruption,aerosol scattering gra dua lly increases,the largest va lue of SSA_440nm is above 0.94,aerosols ma inly exist within 1.5 km a nd upper to 3.0 km,the maximum ave rage of the ECs within 3.0 km is0.43 km^-1 and 0.70 km^-1.During dust pollution,the str ong absorption of dust aerosol partic les caused SSA_440nmto decrease to 0.88,and aerosol ma inly e xisted within 5.0 km atmosphere.In the middle and late sta ge of dust e pisode,the vertica l turbule nce is gradua lly enhanced,whic h lift the he ight of ma in e xtinction zone from the ground to 2.2-4.5 km.The aerosol la yer can heat the atmosphere evide ntly,the magnitude of ra diative heating rates by aerosol depe nds on distribution of the aerosol in the vertica l direction,a nd the heating rate under the concent rated heating zone decreases rapidly.In c lean condition,ECs is less than 0.1 km^-1 which cause the HR of aerosol la yer within 10.0 K·day^-1.During winter ha ze process,the a verage HR of ma in heating la yer(>5.0 K·da y^-1)where is locate d in 1.5-3.0 km is about 13.89 K·da y^-1corresponding to the avera ge ECs 0.43 km^-1,while the HR under the ma in heating layer is only 0.99 K/day.In spring ha ze pollution,the average HR of ma in heating layer(>10.0K·day^-1)where is located in 0.8-2.0 km is a bout 22.42 K·day^-1 corresponding to the average ECs 0.70 km^-1,and the average HR within 1km is 4.70 K·day^-1 lower tha n the pre vious day.The ma gnitude of HR during dust process is equiva lent to the spring haze process,the maximum HR ca n reach 42.0 K·day^-1.In spring dust pollution,the a verage HR of ma in heating la yer(>10.0 K·da y^-1)where is locate d in 2.2-5.0 km is a bout 24.73 K·day^-1,while the HR within 1.5km is less tha n 0.50 K·da y^-1.HR depe nde ncy is affecte d by SSA,the cha nge of HR with SSA is more sens itive in pollution c ondition.With the a verage ECs is 0.43 km^-1,the decrease of SSA_440nm from 0.94 to 0.87 cause the HR of the middle and upper layer to increase by 3.74 K·day^-1,and the lower atmospheric HR is decreased by 0.81 K·day^-1.