Extended POLIPHON dust conversion factor dataset for lidar-derived cloud condensation nuclei and ice-nucleating particle concentration profiles

Abstract

Mineral dust is abundant in the atmosphere. To assess its climate impact, it is essential to obtain information on the three-dimensional distribution of cloud condensation nucleation (CCN) and ice-nucleating particle (INP) concentrations related to mineral dust. The POlarization LIdar PHOtometer Networking (POLIPHON) method uses aerosol-type-dependent conversion factors to transform lidar-derived aerosol optical parameters into CCN- and INP-relevant microphysical parameters. We present a global dataset of conversion factors at 532 nm obtained using Aerosol RObotic NETwork (AERONET) observations at 137 sites for INP and 123 sites for CCN calculations. Dust presence is identified using a column-integrated dust ratio threshold of 80 %, derived from the AERONET columnar particle linear depolarization ratio at 1020 nm. INP-relevant conversion factors (c250,d, cs,d, and cs,100,d) exhibit distinct regional patterns, generally lower near deserts and increasing downstream from dust sources. CCN-relevant conversion factors (c100,d and χd) display significant site-to-site variation. A comparison of dust-related particle concentration profiles derived using both POLIPHON and the independent Optical Modelling of the CALIPSO Aerosol Microphysics (OMCAM) retrieval shows that profiles generally agree within an order of magnitude. This result is consistent with the respective retrieval uncertainties and corroborates the usefulness of lidar observations for inferring dust-related CCN and INP concentration profiles.