Vol. 16, issue 05-06, article # 15

Abstract:

Results of spectropolarimetric measurements of optical and microphysical characteristics of near-ground aerosol are given. Daily measurements were carried out during February 1999 and February-May 2000 at the Zvenigorod Scientific Station, Institute of Atmospheric Physics, Russian Academy of Sciences. The spectropolarimeter recorded polarization components of light scattered by the near-ground aerosol at three scattering angles: 45, 90, and 135° in the wavelength range of 0.4-0.76 mkm with spectral resolution of 10 nm. The instrument was equipped with a low-temperature heater for heating the incoming air. The instrument made it possible to estimate the aerosol condensation activity (the Hanel parameter) from measured characteristics of wet and dry aerosol. The distribution of the Hanel parameter is found to be close to Gaussian with a variance of 0.3 and mean of 0.4-0.5. The correlation between the Hanel parameter and the scattering coefficient is low; however, a spread in values of the Hanel parameter increases markedly with a decrease of the scattering coefficient. The inverse problem was solved for the main body of data obtained for both wet and dry aerosol, i.e., the volume distribution of particles and the complex refractive index of the particulate matter were obtained, which made it possible to estimate the condensation growth factor of particles. Based on the principal-component statistical analysis of the growth factor, a regression relation between the growth factor magnitude and relative air humidity was obtained, which is a microphysical justification of the Hanel formula.