Source-Limited Dust Emission in the Tarim Basin, China: Landform-Specific Parameterisation and Wind-Flux Hysteresis

Abstract: Dust emissions from the Tarim Basin, China, are governed by strong surface heterogeneity and finite sediment supply, two pivotal controls that can induce source depletion and wind-flux hysteresis during dust events. In this study, we adopt the source-limited dust emission (SLDE) scheme proposed by Shao (2025) and develop a landform-specific parameterization that couples remotely sensed surface units with field-measured particle-size data. Specifically, we generate a mutually exclusive seven-class geomorphology map in Google Earth Engine via a hierarchical decision tree, which integrates multi-source datasets including topography (MERIT DEM), vegetation coverage (MODIS NDVI), surface water occurrence (JRC Global Surface Water), and Sentinel-1 backscatter texture characteristics. The resultant geomorphological units comprise mobile dunes, vegetated hummock dunes, fixed/semi-fixed sandy lands, interdune areas, gobi/deflation surfaces, fluvial-lacustrine sediments, and mountain/loess terrains. For each unit, class-specific particle-size distributions are compiled from in-situ measurements and converted into discretized lookup tables, which serve as static input parameters for the SLDE scheme. Initial diagnostic experiments at both column and point scales, driven by hourly 10-m wind data from ERA5-Land (for the April 2020 case study), reveal distinct dust emission regimes across different landform types. On supply-limited surfaces-notably gobi/deflation and fluvial-lacustrine units-our simulations demonstrate that dust flux declines markedly under sustained high-wind conditions as the near-surface sediment reservoir becomes depleted, leading to pronounced hysteresis in the wind-flux relationship. The effective emission efficiency decreases from nearly unity at the onset of dust events to ~0.1 by the late stages, even when wind speeds remain above the threshold friction velocity for dust emission. In contrast, transport-limited behavior dominates in regions with ample sediment supply. These findings establish a physically interpretable framework for deriving SLDE parameters from geomorphological classifications and particle-size properties. Ongoing gridded simulations will quantify the extent to which sediment depletion reshapes the spatial contribution of key deflation zones, as well as the event-integrated dust emission budget, relative to results derived under conventional transport-limited assumptions.

Keywords: Source-limited dust emission; Source depletion; Wind-Flux Hysteresis; Particle size distribution