| The relationship of ambient aerosol and visibility deterioration over Pearl River Delta(PRD)
have attached more and more attentions in recent years. The extinction coefficient of ambient
aerosol can be calculated with the Mie theory(N. Ma, 2014), which is based on a set of
measured dry aerosol number size distribution, ambient relative humidity, aerosol
hygroscopic growth factor, and the assumption of no activation. Using the parameters that can
be easily measured would make the extinction coefficient of ambient aerosol calculation more
widely available. PM2.5 (total mass concentration of dry aerosols with the aerodynamic
diameter smaller than 2.5μm) measurements are widely applied in PRD, the aerosol
concentrations could be estimated based on PM2.5 measurements and used to calculate the
extinction. However, with different size distributions, aerosol with the same mass
concentration may have different extinction coefficients. Ignoring the variations of the shapes
of aerosol size distributions may introduce an uncertainty in the calculation of aerosol
extinction coefficient. In order to quantify this uncertainty, the historical data of
aerosol size distribution need to be analyzed. In this paper, continuous measurements
of particle number size distributions and PM2.5 were simultaneously performed
at Guangzhou urban site from Nov. 2014 to Jan. 2015. The temporal and diurnal
statistical results of dry seasons would be used in the calculation of aerosol extinction
coefficient, and the extinction coefficients corresponding to a certain aerosol volume
concentration and relative humidity are given in the form of probability distribution. |