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Simultaneous observations of spectral aerosol optical thickness and angular sky brightness in the almucantar during clear sky conditions in certain air masses allow to estimate the main climate-relevant aerosol parameters: columnar values of the aerosol size distribution, real part of refractive index, phase function and asymmetry parameter. For this purpose a retrieval algorithm, the Coupled Inversion Radiation Transfer program (CIRATRA) has been developed. Such parameters could be obtained for aged polar air (xP) and aged subtropical air (xS) at the site Melpitz (50 km east of Leipzig). The closure between calculated radiation flux density and the measured one allows also the estimation of the columnar absorption parameters (imaginary part of refractive index and single scattering albedo). For this purpose the accuracy of the fluxes must be within 3 % and the result depends on assumptions about the water vapour content in the atmosphere. The columnar size distribution of xP/xS air masses in the radius range of 0.06 to 4 µm at the site Melpitz could be characterized by bimodal or even trimodal distributions with mode radii r01 = 0.077 ± 0.011 µm, r02 = 0.41 ± 0.10 µm and r03 = 1.25 ± 0.40 µm. The columnar complex refractive index for both air masses is obtained as m = (1.52 ± 0.04) - i (0.022 ± 0.003).