Observational Study On Aerosol Scattering Phase Function And Other Radiative Properties In Rao Yang In North Of China

Aerosol radiative properties are key factors in the process of aerosol radiative forcing calculation and the largest source of uncertainty.Especially,the scattering phase function and asymmetry factor are of special importance as they can reflect the illustration of the direction of radiative transfer.A set of aerosol radiative parameters including the scattering phase function were obtained at Rao Yang Meteorology Administration?an agricultural district?during 16 June and 18 August of 2014.As reported in the experiment,the mean and standard deviation of scattering coefficient at 450 nm,525nm,635 nm was 430.3±274.9Mm^-1,403.8±274.7Mm^-1and 321.5±227.5Mm^-1,respectively.The average value of absorption,single scattering albedo and Angstrom exponent was 31±19 Mm^-1,0.91 ±0.06 and 1.00±0.36.The pollution occurred in Rao Yang was affected by the speed and direction of wind.When pollution occurred,the station was usually under the control of wind comes from south.What's more,different aerosol optical properties presented with different directions of wind.What's more,one improved approach was proposed to calculate the asymmetry factor with the combination of scattering phase function and backscattering ratio.The result suggested that the improved HG aerosol particle phase function can fit the aerosol scattering phase function observed in Hebei Rao Yang(PM_2.5)well.What's more,the observed results of forward scattering phase function?15-20?and the backscattering ratio are all in good agreement with the numerical results.The average asymmetry factors at the wavelength of 635 nm,525nm and 450 nm wavelengths are 0.53,0.57 and 0.57 respectively.Two examples of two different pollution status?dirty period and clean one?were chosen,depending on the scattering coefficient.The asymmetry exponent was higher in the dirty periods than that in the clean ones,indicating the particle radius was larger when compared the dirty periods and clean ones.Depend on the phase function and backscattering ratio measured with polar nephelometer and refractive index estimated from the chemical components analysis of samples,we calculated the parameters of size distribution.Then compare the value of PM₁/PM_2.5 calculated from the weighted and fitted size distribution,indicating a good agreement.What's more,we calculated the asymmetry from the fitted size distribution and try to discuss the difference when using two different error function.One error function treats the observed phase function remained unchanged and another one take the observed phase function logarithm.The result found the value of asymmetry factor would be more stable when use the fitted size distribution to calculate it.