Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> It is increasingly recognized that atmospheric-boundary-layer stability (ABLS) plays an important role in eolian processes. While the effects of ABLS on particle emission have attracted much attention and been investigated in several studies, those on particle deposition have so far been less well studied. By means of large-eddy simulation, we investigate how ABLS influences the probability distribution of surface shear stress and hence particle deposition. Statistical analysis of the model results reveals that the shear stress can be well approximated using a Weibull distribution, and the ABLS influences on particle deposition can be estimated by considering the shear stress fluctuations. The model-simulated particle depositions are compared with the predictions of a particle-deposition scheme and measurements, and the findings are then used to improve the particle-deposition scheme. This research represents a further step towards developing deposition schemes that account for the stochastic nature of particle processes.

Highlights

  • Dry deposition is the removal of particulates and gases at the air-surface interface by turbulent transfer and gravitational settling (Sehmel, 1980; Droppo, 2006; Hicks et al, 2016)

  • The current particledeposition schemes only consider the mean behavior of wind, and how this mean behavior varies with atmospheric boundary-layer stability (ABLS) via the Monin-Obukhov similarity theory, (Monin et al, 2007; Monin and Obukhov, 1954), but not the fluctuations of the associated shear stress and how they vary with ABLS. 60 We argue that focusing only on the effects of ABLS on mean wind is insufficient to model particle deposition accurately

  • The present study was designed to determine the effect of atmospheric boundary layer (ABL) stability on dust particle deposition

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Summary

Introduction

Dry deposition is the removal of particulates and gases at the air-surface interface by turbulent transfer and gravitational settling (Sehmel, 1980; Droppo, 2006; Hicks et al, 2016). The turbulent wind flow in a particle-deposition scheme is reflected in the turbulent shear stress (or vertical momentum flux) It is well-known that apart from gravitational settling, particle deposition is driven by 45 turbulent diffusion which is intimately related to the vertical momentum transfer in the atmospheric boundary layer (ABL) (Wyngaard, 2010). We address the following three issues: (1) How ABLS affects the probability distribution of surface shear stress; (2) How ABLS impacts on particle deposition; and (3) How the ZS14 scheme can be improved to account for the ABLS effect. On this basis, an improvement to the ZS14 scheme ( applicable to other schemes) is proposed.

WRF-LES/D
Particle-deposition scheme of ZS14
Simulation Set-up
Results
Improvement to dust deposition scheme
Conclusion
370 Code and data availability
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