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DY: Fachverband Dynamik und Statistische Physik

DY 21: Granular Matter

DY 21.8: Vortrag

Mittwoch, 19. März 2025, 11:15–11:30, H43

Aerodynamic origin of aeolian mineral dust emission — Sandesh Kamath^1,2, Yaping Shao², and •Eric Parteli¹ — ¹Fakultät für Physik, Universität Duisburg-Essen — ²Institut für Geophysik und Meteorologie, Universität zu Köln

Atmospheric dust aerosol particles exert a substantial impact on climate, radiation balance, and various other components of the Earth's system. However, state-of-the-art climate models rely on empiric parameterization schemes for the vertical dust flux at emission. While such schemes are derived from wind-tunnel simulations on flat granular beds, environmental soils are often characterized by a spatial distribution of non-erodible elements and crusts. Indeed, the vertical flux predicted by the various schemes often differs from observations by orders of magnitude. Here we develop a numerical tool for the particle-based simulation of wind-blown transport of granular particles in the atmospheric boundary layer. Our model accurately reproduces the observed minimal threshold wind shear velocity for direct fluid entrainment over the entire broad range of particle diameters from dust to gravel particles. However, we show that a topographic effect in polydisperse beds and soils with large non-erodible elements lowers the minimal threshold for dust entrainment substantially. This finding challenges our understanding that dust is mainly ejected at sand grain-bed collisions, rather than being directly entrained by wind. Our simulations show that dust can be emitted as single grains, as dust agglomerates, or coated on the surface of sand grains, depending on dust grain size.