Ice nucleation activity of mineral dust from Morocco and Iceland in immersion freezing mode and its relationship with mineralogy and particle size

Abstract. Ice nucleation activity (INA) in the mixed-phase cloud regime has been extensively studied. Nevertheless, most research has focused on particles smaller than a few micrometers. Moreover, the INA dependence on mineralogical composition and size of the tested particles is often not well characterized, particularly for particles larger than ten micrometers in diameter. This gap is significant, as studies suggest that large mineral dust particles can travel long distances. Here, we used natural soil dust samples collected during field campaigns in Morocco and Iceland and characterized in terms of their mineralogical composition and size. The samples’ INA was tested in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber, the Ice Nucleation Spectrometer of the Karlsruhe Institute of Technology (INSEKT), the new AIDA mini (AIDAm), and the IR-DROFA freezing assay in more than 300 experiments. Moroccan samples exhibited INA comparable to that reported for K-feldspar in previous studies, with no dependence on particle size. In contrast, Icelandic samples showed lower INA than in other studies using samples of similar composition, along with a subtle size dependence, linking to pyroxene content as an important driver of INA. Our findings elucidate the role of larger dust particles in ice nucleation through immersion freezing, and their relationship with mineralogy and size for low- and high-latitude sources.