Field observations of sand flux and dust emission above a gobi desert surface

摘要

Purpose Gobi deserts are a major source of natural and anthropogenic aerosols in China. However, the characteristics of the sand flow and dust emission processes are still an open question. This study intends to accurately describe the characteristics of the sand flow and dust emission and to determine the relationship between the sand transport rate and the vertical dust flux above a gobi surface. Materials and methods In this study, a field observation was conducted over a gobi (gravel) desert surface (Yangguan Gobi Desert, Gansu Province, China). We investigated the wind velocity, sand flux, and concentration of particles smaller than 10 mu m (PM10) by using cup anemometers, a sonic anemometer, sand traps, and DustTrak. Results and discussion We found that (1) piecewise regression described the vertical sand flux profiles; the upper part of the profile (above 17 cm) should be described by a power function and the lower part should be described by a Gaussian function. (2) An empirical model based on the modified Owen equation could predict the sand transport rate accurately. (3) The vertical dust flux was described well by F-v proportional to u(*)(3) and the dust emission above the gobi surface should follow A rho u(*t) (u(*)(2) - u(*t)(2)), where A is an empirical regression coefficient. (4) The efficiency of saltation bombardment (F-v/Q) was linearly related to the ratio u(*t)/u(*). Conclusions The results of this study show that the characteristics of the sand flow and dust emission above a gobi surface were highly different from those of bare sandy surface. In future research, it will be necessary to account for the effect of surface characteristics, and particularly the characteristics of the gravel, to improve the predictive ability of our model.