Role of K-feldspar and quartz in global ice nucleation by mineral dust in mixed-phase clouds

. Ice formation is enabled by Ice Nucleating Particles (INP) at higher temperatures than homogeneous formation and can profoundly affect the microphysical and radiative properties, lifetimes, and precipitation rates of clouds. Mineral dust emitted from arid regions, particularly potassium-containing feldspar (K-feldspar), has been shown to be the most efficient 25 INP through immersion freezing in mixed-phase clouds. However, despite quartz having a significantly lower ice nuclei activity, it is more abundant than K-feldspar in atmospheric desert dust, and therefore may be a significant source of INP. In this contribution, we test this hypothesis by investigating the global and regional importance of quartz as a contributor to INP in the atmosphere relative to K-feldspar. We have extended a global 3-D chemistry transport model (TM4-ECPL) to predict INP concentrations from both K-feldspar and quartz mineral dust particles with state-of-the-art parameterizations using the ice 30 nucleation active surface site approach for immersion freezing. Our results show that K-feldspar remains the most important contributor to INP concentrations globally, but also the contribution of quartz can be significant, for example reaching up to 60% over Eurasia at 700hPa and up to 4 across the middle and high latitudes of the Southern Hemisphere. Importantly, our calculations show that quartz may affect different cloud level regimes (low-level clouds) than K-feldspar (mid-level clouds). Additionally, the consideration of quartz INP improves the comparison between simulations and observations at low 35 temperatures. Our simulated INP concentrations predict ~51% of the observations gathered from different campaigns within Here we present, to our knowledge, the first global modelling studying the role of airborne mineral dust as a precursor of INP, accounting for both its quartz and feldspar contents. We simulate the three-dimensional global distribution of INP concentrations, evaluate the model results against observations, and investigate a) the importance of quartz relative to feldspar in INP formation and b) potentially missing INP sources other than dust minerals. To achieve this, we use a well-documented global 3-D chemistry-transport model to simulate the global temporally and spatially varying immersion-mode distributions of INP from feldspar and quartz minerals. airborne dust than K-feldspar, partly compensating for their lower ice nucleating activity with respect to K-feldspar. We find that [INP] quartz dominates at lower altitudes over locations with abundant emissions but low INP concentrations. There are regions of the global atmosphere, in particular over mid-and high- latitudes of Eurasia, where quartz contributes over 40% (at a temperature of -20 o C,800hPa) and over 60% (at ambient model temperature, 700hPa) to the total 420 INP concentration derived from dust aerosols represented by quartz and K-feldspar. The quartz contribution becomes increasingly important with decreasing temperature, giving high INP concentrations at temperatures below −35°C and high altitudes. Consideration of quartz-derived INP is improving the comparison with observations for high INP concentrations at low temperatures and relatively low INP concentrations at temperatures around -20 o C. These results highlight the important role of quartz in increasing INP concentrations, mainly over the mid-to-high latitudes of both hemispheres.