Field Observation Evidence for Kink Points in the Vertical Kinetic Energy Flux Profiles of Wind‐Blown Sand Over Gobi and Its Significance

• Published in: Geophysical research letters Vol. 48; no. 3
• Main Authors: Tan, Lihai, Qu, Jianjun, Wang, Tao, Zhang, Kai, An, Zhishan
• Format: Journal Article
• Language: English
• Published: 16.02.2021
• Subjects: flux profiles; Gobi; kinetic energy; wind erosion; wind‐blown sand
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL091224

Wind‐blown sand over Gobi can cause severe sand abrasion. The vertical flux profiles, especially that of the kinetic energy (KE), determine the erosion intensity. However, the vertical distribution of the KE flux of wind‐blown sand over Gobi remains poorly understood. Here, we report comprehensive field‐based measurements of the vertical flux profiles of wind‐blown sand over three typical Gobi surfaces during four transport events. The results show that unlike the exponential decrease in the particle count flux with height, the KE flux profile curve was non‐monotonic and could be well fitted by a Pearson VII function. The height where the maximum KE flux density occurred (kink points) ranged from 0.09 to 0.15 m above the ground. In addition, the non‐monotonic KE flux profiles primarily emerged during periods of strong transport and were mainly caused by large saltating sand particles due to their high KE as they rebounded from the grain‐bed collision. Plain Language Summary Wind‐blown sand over Gobi has strong kinetic energy (KE) and can thus cause severe sand hazards such as abrading construction, damaging electric lines, and impeding traffic. To control these hazards, we should understand how the KE of wind‐blown sand over Gobi is distributed with height above the ground. In this study, we measured the vertical structure of the KE of wind‐blown sand over three typical Gobi surfaces during four dust storms. We found that the KE flux did not decrease with height in a monotonic way as did the particle count flux; rather, a maximum value occurred at heights of 0.09–0.15 m above the ground, that is, the kink point. This finding can be indirectly verified by the fact that the maximum abrasion in ventifacts, which are widely distributed in Gobi areas, occurs above a finite height above the ground rather than at the surface. Furthermore, we found that the occurrence of the kink points was caused mainly by large sand particles because they saltated in a higher trajectory and gained more KE than fine particles in the saltation process. Future efforts to control wind‐blown sand hazards in Gobi areas should take these results into account. Key Points The vertical kinetic energy (KE) flux profile of wind‐blown sand over Gobi can be well fitted by a Pearson VII function The height where the maximum KE flux occurs ranges from 0.09 to 0.15 m above the ground The non‐monotonic KE flux profile curve is mainly caused by the collision between large saltating sand particles and Gobi beds