Polarization studies of atmospheric objects in the low troposphere by lidar

In the present work some results of polarization measurements in the planetary boundary layer are reported. The observations described were performed by a ground-based lidar over the region of the Sofia city (where various industrial enterprises exist along with a heavy transport and aerial communications). The data obtained when sounding in different meteorological situations (`clear' atmosphere, rain, fog, snowfall) are considered. Certain differences are established in the depolarization properties of `clear' atmosphere in dependence of the meteorological condition. The developments of fog and snowfall are traced; the effects of the underlying surface are sought when sounding in fog; various types of situations during a snowfall are pointed as well. An attempt is made to follow the development of the processes which proceed during an interaction between air masses with different properties (e.g. a front advection); as a result the formation of the cloud system over the region is traced. Definite differences between the microphysical properties of the aerosol near the clouds (Fmb, Ns) base and top are established as well.