  Polarization measurements of the twilight background with Wide-Angle
Polarization Camera (WAPC) are used to detect the depolarization effect caused
by stratospheric aerosol near the altitude of 20 km. Based on a number of
observations in central Russia in spring and summer 2016, we found the
parameters of lognormal size distribution of aerosol particles. This confirmed
the previously published results of the colorimetric method as applied to the
same twilights. The mean particle radius (about 0.1 micrometers) and size
distribution are also in agreement with the recent data of in situ and
space-based remote sensing of stratospheric aerosol. Methods considered here
provide two independent techniques of the stratospheric aerosol study based on
the twilight sky analysis.
