Disparities in aeolian sand transport across low and high wind speeds in the atmospheric surface layer

Synchronously measured high-frequency wind speeds and saltation mass flux data were used to investigate the wind-blown sand transport dynamics across low and high wind speeds in the atmospheric surface layer. Our study reveals that the probability density functions (PDFs) of non-zero values of saltation mass flux follow an exponential distribution at relatively low wind speeds (u_τ < 0.35 m s⁻¹). However, these PDFs shift to a lognormal distribution at relatively high wind speeds (u_τ > 0.45 m s⁻¹). Additionally, the response of saltation mass flux to turbulent motions varies with wind speed. For example, sweep turbulent events contribute 55% to the total saltation mass flux at low wind speeds, whereas they contribute 45% at high wind speeds. Furthermore, Bagnold's formula, Kawamura's formula, and the formula developed by Martin and Kok are effective at high wind speeds. However, due to the intermittency of aeolian sand transport at low wind speeds, these formulas are invalid. We employed the condition-averaged saltation sand transport rate (Q_c) to investigate the scaling laws of saltation sand transport rates. Compared to the time-averaged saltation sand transport rate used in previous studies, Q_c values align more closely with the formula developed by Martin and Kok.