Impacts of mesh refinement on the simulation of a long-range transported extreme dust storm over East Asia in the global variable-resolution model (iAMAS v2.6.3)

Abstract. Long-range transported dust storms challenge regional high-resolution models because lateral boundary conditions constrain the consistent representation of dust emission, transport, and deposition. Here we use the integrated Atmospheric Model Across Scales (iAMAS v2.6.3), a global variable-resolution physics-chemistry coupled model, to simulate the extreme East Asian dust storm from 13 to 18 March 2021. Three experiments adopt a globally quasi-uniform 50 km mesh (U50 km) and two source-refined meshes at 16–50 km (V16 km) and 4–50 km (V4 km). Evaluated against reanalysis and ground-based observations, the simulations reproduce the large-scale synoptic evolution, while mesh refinement captures more detailed near-surface dynamical features and terrain-channeled winds through improved topographic representation. The model reasonably represents 10-m wind speed, surface PM₁₀ concentrations, and aerosol optical depth. Relative to U50 km, total dust emissions over East Asia increase by 35.24 % in V16 km and 54.98 % in V4 km, as refined meshes resolve localized friction-velocity enhancement and nonlinear saltation-threshold exceedances. By altering emission evolution and its interaction with atmospheric circulation, mesh refinement also affects the spatial distribution of transported dust. The contrast between V16 km and V4 km reveals regional heterogeneity in downwind dust mass loading, with V4 km capturing localized wet-scavenging enhancement not evident in V16 km and reducing dust loading over the Yangtze River Delta by 30.49 % relative to U50 km. This research emphasizes the importance of mesh refinement for representing long-range transported dust storms and provides a basis for future evaluations of multiple dust emission schemes in global variable-resolution models.