Aeolian sand transport over a dry playa surface: Sand flux density profiles, saltation layer height, and flux scaling laws and implications for dust emission dynamics

Abstract

Dry playa surfaces under saltation bombardment release abundant atmospheric dust particles. Understanding aeolian sand transport over dry playa surfaces is vital for gaining insight into the process of dust emission from these surfaces. Here, we report characteristics of aeolian sand transport over a dry playa surface based on systematic field measurements of three transport events, and the sand flux density profiles, saltation layer height, and flux scaling laws were examined. The results show that sand flux density decreases exponentially with increasing height over the dry playa surface, and 90 % of the sand flux is concentrated within 0.3 m above the surface. The average saltation layer height (zq) for the dry playa surface, with an average value of 0.13 m, is 2.6 times larger than that of the sand surface and only half of that over the gobi surface with similar median grain size. Sand transport rate (Q) over the dry playa surface is proportional to a quadratic equation of the shear velocity (u*) over the threshold shear velocity (u*t), u*2-u*t2, and this flux scaling law is supported by the negligible variation of zq with u*. This study indicates that sand transport rate model for the dry playa surface is consistent with the splash-dominated model of aeolian saltation over sand surfaces. Our results are significant for studies of dust emission from dry playa surfaces under saltation bombardment.