  Polarimetric observations of the twilight sky are effective for the
investigations of scattering properties of the atmosphere at different
altitudes. Modern computer technique allows to reduce the influence of multiple
scattering on the twilight sky background which is necessary for the aerosol
investigations. In this paper the results of polarimetric observations of the
twilight sky are discussed and compared with the numerical analysis by MCC++
model for different models of atmospheric aerosol. As it was found, the model
of urban troposheric and background stratospheric aerosol shows the best
agreement with observed polarimetric properties of the twilight sky.
