An inversion algorithm for retrieval of aerosol optical and physical properties from ground-based solar and sky radiance

Abstract

An inversion algorithm has been developed for retrieving a set of parameters of aerosol scattering and microphysical properties from POM02 sky-radiometer measurements. POM01/02 is the main observation instrument of Skynet. It’s designed to measure solar and sky irradiance with waveband ranging from visible to infrared, as well as the measurement of polarization sky radiance at 870nm wavelength. Teruyuki Nakajima developed a software package to analyze its observation data named SKYRAD.pack. SKYRAD.pack code can retrieve the columnar aerosol features, such as optical depth, single-scattering albedo, phase function and size distribution, provided the input parameters, such as complex refractive index and ground albedo, are correctly given. In our algorithm, most of aerosol key characteristics, including single-scattering albedo, phase function, polarized phase function at 870nm, complex refractive index, and size distribution, are retrieved from direct and scattered solar irradiance as well as polarized sky radiance at 870nm, by using a polarized radiative transfer code RT3. This method requires only measurement of the aerosol’s optical thickness and an estimate of the ground’s reflectance and does not need any specific assumption about properties of the aerosol. The preliminary results are reported in the paper. Aerosol property; Polarization; Retrieval algorithm.