Near‐surface dust flux enrichment in small particles during erosion events

Abstract Mineral dust in the atmosphere impacts Earth's radiative budget and biogeochemical cycles. Sorting of dust‐sized particles within the first few meters above the soil during wind erosion is still unknown. In particular, the sensitivity of the size distribution of dust flux to wind intensity has been questioned for years. This sensitivity is reanalyzed here using a novel erosion model developed in a turbulent airflow model. Starting from air free of dust, the suspension of small dust (1.5μm) needs several hours to reach a stationary state against about 20 min for coarser dust (> 5μm). During this nonstationary phase, a continuous enrichment of the near‐surface dust flux in small particles is simulated, enrichment enhanced with wind intensity. This is explained by the lower deposition velocity of small dust particles, a process usually ignored in interpretation of field data but that plays a crucial role in sorting dust particles.