Atmospheric solid particles are mostly non-spherical and play significant roles in climate, weather, ecosystems, and human health. However, our understanding of these particles is largely based on the theories for extremely small particles and experiments conducted in liquid mediums, where the particle-to-fluid density ratio differs vastly from atmospheric conditions. Here we combined a novel experimental setup and particle-resolved simulations to investigate the behaviour of sub-millimetre ellipsoids of varying shapes in still air. Our results revealed complex decaying oscillation patterns involving numerous twists and turns in these particles, even with particle Reynolds numers far below the onset of wake-induced instabilities, starkly contrasting their dynamics in liquid mediums. We also found that the key settling characteristics exhibit non-linear and non-trivial dependencies on shape. Our findings suggest that the dynamics observed in this study may have significant implications for the behaviour of naturally occurring atmospheric particles such as snowflakes and volcanic ash.

non-spherical atmospheric particles,settling,experiment,numerical simulation