Peculiarities of condensation transformation of the atmospheric aerosol parameters at phase transition

The dependence of the size and optical parameters of atmospheric aerosol on relative humidity usually is a smooth curve described by a single-parameter formula of a Kasten-Hanel type. But sometimes, more often in spring, the dramatic increase of the scattering coefficient in a narrow range of relative humidity is observed (as a rule, at 60-70%). It is caused by phase transition (deliquescence) of the aerosol matter. To study this process, we have carried out detailed measurements of the angular scattering characteristics, including polarization, in the visible wavelength range with humidity step of 1%. Then these data were inverted to the particle size spectrum and refractive index at each value of relative humidity. Comparative analysis of the peculiarities of transformation of the aerosol microstructure in the case of phase transition and without it is presented.