Field Evidence of Sand Impact‐Controlled Dust Emission From a High‐Elevation Source Region on the Northeastern Tibetan Plateau

Abstract

The impact of saltating sand grains on the ground surface is a fundamental mechanism driving both sand transport and dust emission in aeolian research. In low‐air‐density and high‐elevation regions, the dynamic conditions of dust emission are different with low‐elevation regions, which leads to various aeolian sand transport processes and further affects the cycle of sand and dust around the world. Due to the scarcity of field measurements, this process remains poorly understood in high‐elevation regions (>3,000 m). This study investigates the number and kinetic energy (KE) of transported sand grains, sand transport rate ( Q ), and PM ₁₀ concentration under natural field conditions to elucidate the role of sand impact in dust emission and transport processes. Field data were also used to evaluate existing shear velocity‐based sand transport and dust emission models. Results show that PM ₁₀ concentration over sandy surfaces in the source region can reach up to 10 ⁵  µg m ⁻³ , substantially higher than previously reported values. The ratio of the number of saltating sand grains at different heights serves as an effective indicator of dust emission intensity: Both Q and PM ₁₀ concentration decrease as this ratio increases. During transport events, Q increases linearly with the number of sand grains near the surface, and PM ₁₀ concentration exhibits increases linearly with Q . Both Q and PM ₁₀ increase as power functions of shear velocity. We demonstrate that the quadratic scaling between KE and sand transport number ( N ) is a direct consequence of low air density saltation dynamics, which enhances dust emission efficiency. The empirical relationships between N , KE, Q , and PM ₁₀ are quantified. Among these, the near quadratic scaling KE   N ^1.66 is consistent with a low‐density saltation physics, while other power‐law exponents (e.g.,  Q    u ∗ ³ ) are site‐specific and highlight the need for process‐based models that explicitly account for grain size and surface type. Current models systematically underestimate sand transport rates. These findings emphasize the importance of studies in high‐elevation regions and the differences of dust emission process between low and high elevation conditions and provide new insights for improving dust emission models and underscore the importance of conducting more comprehensive field studies across diverse arid landscapes to advance predictive capabilities.