The Wind-Blown Sand Experiment in the Empty Quarter Desert: Roughness Length and Saltation Characteristics

The Empty Quarter Desert, one of Earth's major dust sources, frequently experiences dust storms due to wind erosion. Despite its significance as a primary dust source on a global scale, in-situ observations from this region had not been reported until very recently. In summer 2022, the WInd-blown Sand Experiment (WISE) Phase-1 was initiated in the Empty Quarter Desert of the United Arab Emirates, and continued until 7 February 2023. Utilizing a diverse array of instruments, we measured winds, temperature, humidity, radiation fluxes, saltation, and the physical and optical properties of dust aerosols, atmospheric electric fields, and soil characteristics. A total of 38 distinct sand-saltation events were recorded from September 2022 to February 2023, with activity peaking between 13:00 and 14:00 local time. Key findings include the identification of dominant wind patterns, and the measurement of the average aerodynamic roughness length (z₀) at 0.8 ± 0.6 mm, and the thermal roughness length (z_h) at 0.3 ± 0.5 mm—the first estimation of z_h for this area. In-situ observations revealed that dust particle concentrations near the surface increased 1.7-fold on days with saltation compared to days without it. Moreover, we determined a wind-speed threshold for initiating saltation at 7.70 m s⁻¹. This comprehensive data set significantly advances our understanding of atmospheric-soil interactions and sand movement dynamics, providing invaluable insights for ongoing research into desert environments and the global dust cycle.