Retrieval of aerosol optical and physical properties from ground-based spectral, multi-angular, and polarized sun-photometer measurements

An inversion algorithm to retrieve a complete set of aerosol optical and physical properties has been developed. The algorithm is based on sun-photometer measurements with emphasis on polarimetric observations. At present, these polarized sun-photometer observations are mainly provided by PHOTONS network included in AERONET worldwide network. With ground-based measurement of direct sun irradiance, as well as total and polarized sky radiance, most of key characteristics of atmospheric aerosols are retrieved, including spectral single-scattering albedo from UV to NIR wavelength, elements of scattering matrix F11 and − F12 (i.e. phase function and polarized phase function), complex refractive index, and size distribution. These parameters are fundamentally valuable in atmospheric physical and chemical studies. The theoretical accuracy is assessed based on three distinct bimodal log-normal aerosol models. The sensitivity studies to measurement uncertainties and to observing geometrical conditions are implemented to estimate the retrieval accuracy. Examples of typical retrievals when applying to real measurements are illustrated and compared with AERONET operational inversions. The particle shape-independent advantage of the retrieved single-scattering albedo, phase function, and polarized phase function is validated by considering a non-spherical aerosol model, which consisted of spheroid particles.