This data set is composed of in-situ measurement of arctic cloud microphysical properties (particle size distribution and volumic cloud particle diffusion properties) observed during the MOSAIC-ACA campaign, which occurred between August 30th and September 13th 2020. These measurements were made using the 2D stereoscopic (2D-S, SPEC Inc.) and Polar Nephelometer (Gayet et al., 1997) probes from the airborne measurement platform of the Laboratoire de Météorologie Physique (CNRS/UCA, Aubière, France). There is one file per flight. All files are in NetCDF format, with a complete description of the parameters inside. A detailed list of the parameters present in the data set is added in a separate document.