兰州理工大学机构知识库

Reliably predicting the geomorphology and climate of planetary bodies requires knowledgeof the dynamic threshold wind shear velocity below which saltation transport ceases. Herewe measure this threshold in a wind tunnel for four well-sorted and two poorly sorted sandbeds by visual means and by a method that exploits a regime shift in the behavior of the sur-face roughness caused by momentum transfer from the wind to the saltating particles. Forour poorly sorted sands, we find that these measurement methods yield different thresholdvalues because, at the smaller visual threshold, relatively coarse particles do not participatein saltation. We further find that both methods yield threshold values that are much larger(60–250%) for our poorly sorted sands than for our well-sorted sands with similar medianparticle diameter. In particular, even a rescaling of the dynamic saltation threshold based onthe 90th percentile particle diameter rather than the median diameter cannot fully capturethis difference, suggesting that relatively very coarse particles have a considerable control onthe dynamic threshold. Similar findings were previously reported for water-driven sedimenttransport. Our findings have important implications for quantitative predictions of saltationtransport-related geophysical processes, such as dust aerosol emission.