Characteristics of the Aeolian Sediments Transported Above a Gobi Surface

Abstract

Gobi’s (gravel deserts) are one of the largest dust sources in northern China. Previous studies indicated that sand transport processes above the surface differed between Gobi and sand surfaces. However, the sand transport rate and related dust emission processes above Gobi (gravel) surfaces are still poorly understood. In this field study, we quantified this transport to provide important support for parameterizing Aeolian sediment transport models and clarifying the relationship between dust emission and transport. Threshold wind velocity can reach 0.38 ± 0.04 (mean ± SD) m s⁻¹ above Gobi surfaces. Compared to the most commonly used sand-transport models, we found that the Lettau and Lettau sediment transport model can be used to calculate horizontal sediment transport above a Gobi surface. The relationship between the vertical sediment transport (F_s) and shear velocity could be expressed using a power function. Although the horizontal sand transport and vertical flux (Q and F_s, respectively) above Gobi surfaces can be expressed similarly to previous results (i.e., using similar equation forms), the equation coefficients were much larger for the Gobi surface than for a shifting sand surface; that is, sediment transport was higher above the Gobi surface. This difference resulted from the larger sand transport rate and saltation height above the Gobi surface, and the larger transport and higher saltation height were related to the larger sand transport height and higher content of coarse sand transported above the Gobi surface.