Analyses Of The Aerosol Optical Properties And Direct Radiative Forcing Over A Group Of Urban And Industrial Region In Northeast China

Aerosol optical properties such as Aerosol Optical Depth (AOD), Angstromexponent (AE), Single Scattering Albedo (SSA), volume size distribution,refractive index real part and imaginary part are retrieved by using CE318dataover four urban and industrial areas in Northeast China, Shenyang, Anshan,Benxiand Fushun. Seasonal variations and influence factors of these parametersare analyzed. The relationship between AOD and AE are discussed at each site.The possible influence factors for these parameters are concluded. The maximumAOD appeared in spring and summer more than other seasons while the minimumAOD appeared in autumn. AE is lower in spring while higher in autumn andwinter.Aerosol direct radiative forcing (ADRF) and direct radiative forcingefficiency under clear sky condition at Top of Atmosphere (TOA) and surface arecalculated over the four sites. The seasonal variations and distribution of ADRFand the efficiency of ADRFare discussed at each site, respectively. Thedistribution of ADRF at TOA and surface against AOD are also discussed for foursites, respectively. Aerosol direct radiative forcing at surface and Top ofAtmosphere in Benxi are-222.90±76.61W/m2,-24.80±15.87W/m2，respectively.The annual averaged value is higher than the other three areas which indicate thatthe pollution of Benxi is most seriously, the cooling effect of aerosols to thesurface and Top of Atmosphere is stronger.The seasonal variations of Absorption AOD (AAOD) and AbsorptionAngstrom exponent (AAE) in Shenyang, Anshan and Fushun have been analyzedfor the first time. The results show that the AAOD is higher in winter and summerwhile lower in spring. The value of AAE in Shenyang is less than unity, while have higher values in Anshan (1.19) and Fushun (1.33). The results indicated thatthe AAE information can help to distinguish different type of aerosols in the threesites.The effects of Visibility imposed on Aerosol Optical Depth (AOD), Angstromexponent (AE), Single Scattering Albedo (SSA), volume size distribution,refractive index has been discussed over the four sites. Especially, we analyzed thecharacteristics and variations of aerosol optical parameters and direct radiationforcing properties under the lower visibility.The AOD and AE are decreased withthe increasing of visibility over the four sites. When the visibility is lower, theaerosol scattering properties in Anshan is significantly strongger than the otherthree regions, the value of Single Scattering Albedo is greater than0.90. Theaerosol absorption properties in Benxi is intensity with the value of SingleScattering Albedo smaller than0.85. Aerosol direct radiative forcing (ADRF)under clear sky condition at surface is increased with the decreasing visibility overthe four sites. The results indicate that the cooling effect of pollution atmosphereaerosols to the surface is obviously.The major conclusion including the follow points:1. The annual averaged aerosol optical depth at500nm in Shenyang is about0.69±0.38. Angstrom exponent is about0.88±0.26. The Single Scattering Albedo(SSAT/SSAF/SSAC) are about0.84±0.06，0.86±0.06，0.77±0.06, respectively. Therefractive index is1.47±0.028. The annual averaged aerosols direct radiativeforcing at surface under clear sky conditions is about-136.52±80.50W/m2. Theannual averaged ADRF at TOA is about-3.81±21.73W/m2. The efficiencies ofADRF at surface and TOA are about-267.77±86.38W/m2,-7.83±38.89W/m2,respectively. The annual averaged absorption aerosol optical depth at440nm,670nm，870nm，1020nm in Shenyang are about0.15±0.11，0.11±0.09，0.10±0.08,0.09±0.08，respectively. The absorption Angstrom exponent is about0.86±0.24.The annual averaged visibility is about13.88±7.39km.The SSAT is about0.82±0.06at440nm when visibility is lower than10km. The aerosol optical depthis about0.89±0.45. Angstrom exponent is about0.98±0.31. The refractive index is1.46±0.030.2. The annual averaged aerosol optical depth at500nm in Anshan is about0.65±0.33. Angstrom exponent is about0.79±0.26. The Single Scattering Albedo (SSAT/SSAF/SSAC) are about0.87±0.06，0.89±0.06，0.81±0.06, respectively. Therefractive index is1.49±0.018. The annual averaged aerosols directradiativeforcing at surface under clear sky conditions is about-102.14±52.59W/m2. Theannual averaged ADRF at TOA is about-25.37±20.99W/m2. The efficiencies ofADRF at surface and TOA are about-208.45±66.11W/m2,-48.91±32.76W/m2,respectively. The annual averaged absorption aerosol optical depth at440nm,670nm,870nm,1020nm in Anshan are about0.10±0.07,0.05±0.04,0.05±0.04,0.04±0.04, respectively. The absorption Angstrom exponent is about1.19±0.39.The annual averaged visibility is about13.56±6.20km.The SSAT is about0.88±0.05at440nm when visibility is lower than10km. The aerosol optical depthis about0.88±0.35. Angstrom exponent is about0.93±0.31. The refractive index is1.46±0.016.3. The aerosol optical depth in Benxi is largest in the four sites.Angstrom exponentis smaller than the other three sites which indicate that the size of aerosol particlesin Benxi is much larger. The annual averaged aerosol optical depth at500nm inBenxi is about0.82±0.34. Angstrom exponent is about0.52±0.22. The SingleScattering Albedo (SSAT/SSAF/SSAC) are about0.81±0.03，0.82±0.03，0.81±0.09, respectively. The refractive index is1.46±0.041. The annual averagedaerosols direct radiative forcing at surface under clear sky conditions is about-222.90±76.61W/m2. The annual averaged ADRF at TOA is about-24.80±15.87W/m2. The efficiencies of ADRF at surface and TOA are about-337.65±102.43W/m2,-40.59±22.84W/m2, respectively. The annual averagedvisibility is about12.83±5.68km.The SSAT is about0.80±0.08at440nm whenvisibility is lower than10km. The aerosol optical depth is about1.21±0.48.Angstrom exponent is about0.74±0.26. The refractive index is1.47±0.046.4. The aerosol optical depth in Fushun is the minimum in the four sites. Theannual averaged aerosol optical depth at500nm in Fushun is about0.45±0.27.Angstrom exponent is about0.84±0.29. The Single Scattering Albedo(SSAT/SSAF/SSAC)are about0.85±0.06，0.88±0.05，0.77±0.06，respectively. Therefractive index is1.49±0.025. The annual averaged aerosols directradiativeforcing at surface under clear sky conditions is about-85.94±37.49W/m2. Theannual averaged ADRF at TOA is about-13.28±16.19W/m2. The efficiencies ofADRF at surface and TOA are about-232.86±61.19W/m2,-27.81±28.91W/m2,respectively. The annual averaged absorption aerosol optical depth at440nm， 670nm，870nm，1020nm in Fushun are about0.08±0.04，0.04±0.02，0.03±0.02，0.03±0.02，respectively. The absorption Angstrom exponent is about1.33±0.36.The annual averaged visibility is about11.52±5.84km.The SSAT is about0.84±0.05at440nm when visibility is lower than10km. The aerosol optical depthis about0.54±0.30. Angstrom exponent is about1.04±0.26. The refractive index is1.48±0.026.5. Both coarse and fine particles have larger scattering properties in Anshan whilein Benxi, both coarse and fine particles have larger absorption properties. Thecoarse particles have strongger absorption ability in Shenyang and Fushun. Thereare not obvious effects of AOD on the aerosol absorption ability in Shenyang, butin Anshan, Benxi and Fushun, there is higher absorption ability under low AODand higher scattering ability under high AOD.6.Fine particles play a main role in summer particle distribution. In spring, thecoarse particles are dominant. There is a mixture effect of both fine and coarseparticles in autumn and winter which presented a typical city characteristic. WhenAOD is higher, the aerosol fine particle volume has been increased significantly.The results show that fine particles may be the important factors influencing theregional aerosol optical depth.7. The aerosols directradiative forcing (ADRF) at surface under clear skyconditions is higher in summer and lower in autumn and winter. Aerosol directradiative forcing at the top of atmosphere over the four sites is higher in spring andlower in winter. The positive direct radiative forcing at the top of atmosphereoccurred in winter at Shenyang and Fushun. The result may be due to the highsurface albedo because of the snow cover in the northeast China.8.The annual averaged values of Absorption Angstrom Exponent (AAE) inShenyang，Anshan，Fushun are about0.86±0.24，1.19±0.39，1.33±0.36respectively. The values of AAE show that aerosols in Shenyang may be resultfrom black carbon coated with either absorbing or nonabsorbing material. Aerosolparticles in Anshan may contain a large amount of black carbon. In Fushun area,the dominant aerosol prticles may be related to the biomass burning.