The Recovery of Parameters of the Multimode Atmospheric Aerosol Component Based on Polarization Measurements of the Sky over Kyiv

Abstract According to the data of spectral polarimetric measurements of the sky at the zenith above the observation site GAO, Holosiiv, Kyiv, the vectors of probable values of the parameters of the three main aerosol modes were restored. The quantitative ratio of these modes in the aerosol component of the atmosphere was determined. By comparing those results with the characteristics of atmospheric aerosols determined in the previous work of the authors, changes in the number and magnitudes of the parameters of the main aerosol modes were revealed between the two observation dates and the possible reasons for this were considered. The parameters of the two main coarse modes were determined. For the first coarse mode the geometric mean radius of particles r0 = 20.4 µm, the real part of the refractive index nr = 1.44, the dispersion σ2 = 0.15. A second aerosol coarse mode in the form of water mist was detected. The recovered parameters of this mode are: r0 = 18.4 µm, nr = 1.38, σ2 = 0.49. The parameters of the third main finely dispersed aerosol mode remained unchanged: r0 = 0.11 µm, nr = 1.45, σ2 = 0.11. But a significant decrease in the share of this fine mode in the total value of the degree of linear polarization of the atmospheric aerosol component was detected. A sign of a slight presence of the fourth aerosol mode in the atmosphere was noted. Additions have been made to the description of the Method for recovering the characteristics of the multimode aerosol component of the atmosphere based on spectral polarimetric measurements of a cloudless blue sky, which was developed by the authors. The formulas for analyzing measurement data and determining the characteristics of the aerosol component of the atmosphere with three or more main modes are represented. A procedure for performing the analysis in sequential stages with corresponding model calculations and evaluations of their results is proposed. Recommendations are provided for organizing and performing polarization measurements of the sky in order to obtain data acceptable for correct reconstruction of the parameters of the main modes of atmospheric aerosols. Problems of using other methods for determining the characteristics of the aerosol component in the atmosphere, when using them for arbitrarily selected observation positions, with significant changes in the saturation of air with aerosols and the presence of complex multimode aerosol compositions, are noted.