Clouds radiation feedback processes in Polar Regions have been identified as key uncertainties in the prediction of global climate in GCMs. To better understand clouds-radiation interactions in these regions, knowledge of arctic clouds properties has to be improved. In particular, mixed phased clouds, which frequently occur in Arctic, present a large variety of physical characteristics and involve very complex microphysical and dynamical processes between liquid and ice phases, currently not yet well understood, and poorly documented. In order to improve the knowledge of arctic clouds properties, the Laboratoire de Météorologie Physique (LaMP) is involved from several years in several airborne measurement campaigns dedicated to the study of arctic clouds (ASTAR 2004, ASTAR 2007, POLARCAT 2008, SORPIC 2010), providing optical and microphysical in situ measurements from a unique combination of airborne probes (CPI, Polar néphélomètre, PMS FFS-100, 2D-S, Nevzorov...). Furthermore, the airborne radar/lidar system RALI from LATMOS will provide in addition active remote sensing measurements. This study will present a statistical analysis of arctic mixed phase clouds optical and microphysical properties based on these in situ measurements, representing more than 40 flights. The first main objective of this study is to investigate the ice particles and clouds droplets growth processes into the clouds, and their interaction with radiation. The second main objective is to provide accurate profiles of relevant clouds parameters to contribute to the improvement of clouds representation in global and mesoscale models and to improve airborne and spatial remote sensing retrievals algorithms (CALIPSO, CloudSat, EarthCare...). These relevant parameters are for example the thermodynamic phase, geometrical characteristics (height, thickness), and optical and microphysical properties (asymmetry parameters, optical depth, liquid/water fraction, ice crystals morphology, size and concentration, IWC...).