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

[摘要] Ice-nucleating particles (INPs) enable ice formation,profoundly affecting 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 tobe a very effective INP through immersion freezing in mixed-phase clouds.However, despite the fact that quartz has a significantly lower ice nucleation activity,it is more abundant than K-feldspar in atmospheric desert dust andtherefore may be a significant source of INPs. In this contribution, we testthis hypothesis by investigating the global and regional importance ofquartz as a contributor to INPs in the atmosphere relative to K-feldspar. Wehave extended a global 3-D chemistry transport model (TM4-ECPL) to predictINP concentrations from both K-feldspar and quartz mineral dust particleswith state-of-the-art parameterizations using the ice-active surface-site approach for immersion freezing. Our results show that, althoughK-feldspar remains the most important contributor to INP concentrationsglobally, affecting mid-level mixed-phase clouds, the contribution of quartzcan also be significant. Quartz dominates the lowest and the highestaltitudes of dust-derived INPs, affecting mainly low-level and high-levelmixed-phase clouds. The consideration of quartz INPs also improves thecomparison between simulations and observations at low temperatures. Oursimulated INP concentrations predict ∼  51 % of theobservations gathered from different campaigns within 1 order of magnitudeand ∼  69 % within 1.5 orders of magnitude, despitethe omission of other potentially important INP aerosol precursors likemarine bioaerosols. Our findings support the inclusion of quartz in additionto K-feldspar as an INP in climate models and highlight the need for furtherconstraining their abundance in arid soil surfaces along with theirabundance, size distribution, and mixing state in the emitted dustatmospheric particles.

[学科分类] 医学（综合）