Characteristics of dust emission over desert steppe

Abstract

Desert steppe is widely distributed in wind erosion regions, and is also an important potential dust emission source in the regions. Recognition of dust emission characteristics of desert steppe is the foundation for accurate simulation of dust emission in wind erosion regions; however, few related studies have been conducted in desert steppe areas. In this study, we selected four sites in a region of desert steppe to conducting dust emission observations, analyzing the characteristics of horizontal saltation flux and vertical dust flux, identifying the suitable models for desert steppe, and examining the relationship between saltation bombardment efficiency and wind friction speed (u*). The results revealed the following: the supply of saltation particles in most desert steppe is unlimited, the intensity of saltation is reasonably high, and the modified Owen-type model is suitable for predicting sediment transport above desert steppe. Dust emission intensity in desert steppe is lower than that in other land use types under similar wind speeds. Schemes based on saltation bombardment theory (i.e., the MB95, Shao93, and Kok12 schemes) were found suitable for predicting vertical dust flux above desert steppe, the Kok12 dust emission scheme performed slightly better than the other two schemes. Saltation bombardment is the main mechanism for dust emission when u*s exceeds a threshold u*s (u*ts), but aerodynamic entrainment also plays an important role in dust emission, especially when u*s < u*ts. The saltation bombardment efficiency of desert steppe is less than that of other land use types. The trend of change in saltation bombardment efficiency with wind speed varies at different sites. Soil properties affect the dependence of saltation bombardment efficiency on u*. Desert steppe is an important dust emission source in certain regions, and improved understanding of dust emission in desert steppe areas is required.