THE USE OF RAMAN LIDAR FOR THE CHARACTERIZATION OF PARTICLE HYGROSCOPICITY: ASSESSMENT OF CASE STUDIES COLLECTED DURING COPS

Model studies have demonstrated that relative humidity has a critical influence on aerosol climate forcing. The relationship between aerosol backscattering and relative humidity has been investigated in numerous studies. Hygroscopic properties of aerosols influence particle size distribution and refractive index and hence their radiative effects. Aerosol particles tend to grow at large relative humidity values as a result of their hygroscopicity. Raman lidars with aerosol, water vapour and temperature measurement capability are potentially attractive tools for studying aerosol hygroscopicity as in fact they can provide continuous altitude-resolved measurements of particle optical, size and microphysical properties, as well as relative humidity, without perturbing the aerosols or their environment. The present analysis is focused on selected case studies characterized by the presence of different aerosol types with different hygroscopic behaviour