Understanding how aerosol particles interact with atmospheric water is critical to understanding their impact on climate and precipitations. Ice Nuclei Particles (INP) trigger the formation of atmospheric ice crystals at temperatures ranging from -5 °C up to -30 °C. They are challenging to characterize because of their scarceness in the atmosphere and their variability, especially at temperatures warmer than -20 °C. At these temperatures, the aerosol particles of biological origin can contribute significantly to INP number concentration. This study incorporates a series of offline, long-term, size-segregated measurements of INPs, collected at the Puy de Dôme station (PUY, 1465 m a.s.l.). PUY is an ideal place to study INPs concentrations as it is advected by a variety of air masses, with about 20% of them originating in the free troposphere. We measured concentrations of INPs between -5 and -18 °C, with concentrations of 0.001 INP/Lair at the warmest temperatures, and between 0.01 and 0.1 INP/Lair at the coldest temperatures. We observe that the majority of INP measured at temperatures warmer than -15 °C are heat labile, in line with other studies. We observe a higher contribution of heat labile INPs during the winter and lower ratios in spring. The INP variability was statistically compared with collocated aerosol characterization at the site. INPs were mainly linked to local and marine tracers. We propose a new parameterization using the total number of aerosols. This parameterization is optimized for warmer temperature INPs. The parameterization showed good performance when tested on independent data sets

This manuscript compares aerosol size distributions and microphysical property measurements from the Raman lidar BASIL and from aircraft sensors during HyMeX-SOP1. The attention was focused on a measurement session on 02 October 2012, with BASIL measurements revealing the presence of a lower aerosol layer extending up to 3.3 km and an elevated layer with extending from 3.6 km to 4.6 km. Aerosol size distributions and microphysical characteristics were determined from three-wavelength particle backscattering and extinction profile measurements through a retrieval approach based on Tikhonov regularization. A good agreement is found between BASIL retrievals and the microphysical sensors’ measurements for all considered aerosol dimensional and microphysical characteristics. Specifically, BASIL and in-situ volume concentration values are 1-3.5 mm3cm-3 in the lower layer and 2-4 mm3cm-3 in the upper layer. Furthermore, effective radius values from BASIL and the in-situ sensors’ measurements are in the range 0.2-0.6 mm both in the lower and upper layer. Particle size distributions were determined at 2.2, 2.8, 4 and 4.3 km, with again a good agreement between the Raman lidar and the microphysical sensors throughout the considered height interval. These results, in combination with Lagrangian back-trajectory analyses and chemical composition measurements, indicate that aerosols below 3 km were possibly originated by forest fires in North America or by anthropogenic activities in North-Eastern Europe, while aerosols above 3 km were originated over the North Atlantic and presumably include both a marine and an organic component. This interpretation is compatible with the lidar retrieved profiles of particle complex refractive index.