Rain, Wind, and Dust Connections in the Sahel

Abstract

Between 1,000 and 4,000 Tg of mineral dust are injected yearly by wind erosion into the atmosphere (e.g., Boucher et al., 2013;Huneeus et al., 2011), making dust as one of the most emitted particulate species. As a consequence, the dust cycle has significant impacts on the Earth's environment and is now recognized as a key actor in the Earth System Science (e.g., Shao et al., 2011). In dust source regions, mainly arid and semiarid areas, the movement of windblown sediments modulates the geomorphology of landscapes (e.g., Greeley & Iversen, 1985;Livingstone & Warren, 1996) and can also lead to an impoverishment of naturally vegetated areas and cultivated soils (e.g.,

Quantifying Mechanisms of Aeolian Dust Emission: Field Measurements at Etosha Pan, Namibia

“…The short duration but high intensity dust emissions (See Table S2 in Supporting Information S1), and the presence of deep convective cloud associated with CPO‐driven events, makes them difficult to detect from remote sensing observation (Allen et al., 2015; Caton Harrison et al., 2021). However, the recognition of CPOs driving dust emissions at Etosha and other sites of significant dust activity is important because the small‐scale processes which generate them are not well constrained by emissions models (Bergametti et al., 2022), and so their contribution to total atmospheric aerosol load is therefore under‐represented globally (Caton Harrison et al., 2021; Marsham et al., 2013).…”

“…In quantifying the significance of LLJs and CPOs over a complete annual cycle we have also been able to capture clear seasonal differences in their operation. The occurrence of CPO‐driven dust emissions is noteworthy given that the associated meteorological processes that drive CPOs are poorly represented in dust emissions models (Bergametti et al., 2022; Marsham et al., 2013). We quantify the relative magnitude of dust events and show they are heavily dominated by a few large events, where nearly 31% of all horizontal dust flux is seen to be generated by the six largest events, and a single event accounts for as much as 8%.…”

“…For each 10-min logging period the wind velocity (u) measured at a height of 3.18 m was used to calculate the Dust Uplift Potential (DUP), an indicator of the power of the wind available for generating dust emission in excess of the critical threshold for erosion, u t (Bergametti et al, 2022;:…”

“…For each 10‐min logging period the wind velocity ( u ) measured at a height of 3.18 m was used to calculate the Dust Uplift Potential (DUP), an indicator of the power of the wind available for generating dust emission in excess of the critical threshold for erosion, u t (Bergametti et al., 2022; Marsham et al., 2011): $$$\mathrm{D}\mathrm{U}\mathrm{P}=\left(\mathit{1}+\frac{{u}_{t}}{u}\right)\left(\mathit{1}-\frac{{u}_{t}^{\mathit{2}}}{{u}^{\mathit{2}}}\right)\,\mathrm{f}\mathrm{o}\mathrm{r}\,u\, > \,{u}_{t};\,\mathrm{o}\mathrm{t}\mathrm{h}\mathrm{e}\mathrm{r}\mathrm{w}\mathrm{i}\mathrm{s}\mathrm{e}\,0$$$ …”

“…Of note is that the events identified using the 0.5 mg/m 3 threshold in the austral winter (July–September) qualitatively match with those observed using remote sensing imagery (e.g., Figure 1). The analytical boundaries employed here for identifying individual events are therefore considered practical and allow reasonable comparison with other studies of dust emission where aerosol concentration has been measured on an event basis across a variety of averaging times and at widely varying distances from source (e.g., Bergametti et al., 2018, 2022; Draxler et al., 2001; Gong & Zhang, 2008; Kaly et al., 2015; Klose et al., 2019; Lee et al., 2009; Marticorena et al., 2017; Rajot et al., 2008; Wang et al., 2008).…”