Aeolian Dynamics During the Barchan–Parabolic Dune Transition: Field Observations and Modeling Results From the Mu Us Dune Field, Northern China

Transitions from mobile barchan dunes to stabilized parabolic dunes are widespread in semi-arid regions; however, the physical mechanisms driving this transformation remain unclear. Here, we combine high-resolution field measurements and numerical modeling to investigate airflow, sand transport, and grain-size dynamics on a barchan–parabolic transitional dune in the Mu Us dune field in northern China. Field observations reveal pronounced spatial heterogeneity in wind flow and sediment transport across the dune profile. Vegetation in interdune and dune-toe areas attenuates near-surface airflow and suppresses sand transport, reducing sediment supply to the stoss face. In contrast, the stoss face experiences accelerated but sediment-poor airflow, resulting in enhanced erosional efficiency and stoss-face elongation. Maximum shear velocity and sand transport occur on the mid–upper stoss face, whereas transport efficiency declines sharply near the crest, consistent with an upwind velocity shift associated with slope flattening and flow expansion. This reduction in sediment transport limits sediment continuity across the dune and promotes local surface stability. Grain-size analyses further revealed overall surface coarsening, reinforcing the resistance to wind erosion. Numerical simulations reproduce similar spatial patterns of aeolian dynamics on the stoss face but overestimate transport near the crest, highlighting the importance of resolving nonlinear crest-scale flow dynamics and grain-size dependent transport processes. Together, these results demonstrate that the barchan–parabolic transition emerges from localized, nonlinear airflow–sediment–vegetation feedbacks rather than from spatially uniform environmental forcing, and identify stoss-face erosion and crest-scale transport reduction as key controls on dune stabilization in semi-arid environments.