A method for estimating atmospheric aerosol properties using direct-sun photometric data

In this paper, a method for evaluating some parameters of the atmospheric aerosol, based on direct-sun photometric data, is presented. The procedure relies on fitting theoretical aerosol optical depth and Ångström coefficient spectra to their experimental counterparts resulting either directly from measurements or from numerical differentiation of measured data. Theoretical expressions depend on dimensional and analytic parameters of aerosols. The variations of model parameters allow for a rather accurate tailoring of the theoretical spectra and thus for a reasonable good fitting of these curves to the experimental ones. To verify the accuracy, the procedure is applied to measurements performed in three land areas with different background aerosol properties, and the results are compared to similar data found in the database of the Aerosol Robotic Network, which are obtained through an independent method. The relatively low average difference between these sets of data (falling below 20% for some parameters like the relative fraction of sub-micrometer aerosol particles) permits a validation of the proposed method.

► We describe a method to obtain some aerosol parameters from direct-sun photometry.
► We compare and fit Mie AOD computations to spectral AOD measurements.
► The aerosol volumetric content and the fraction of fine aerosols are obtained.
► The results for three different land areas compare well with similar AERONET products.