Size‐Resolved Dry Deposition Velocities of Dust Particles: In Situ Measurements and Parameterizations Testing

Abstract

Bulk and size-resolved particle concentrations were measured at 2.1 and 6.5 m above the soil surface during an intense dust deposition event that occurred in June 2006 in Niger. Bulk concentration measurements were performed using two tapered element oscillating microbalance instruments, and the size-resolved particle concentrations (from 0.3 to 20 μm) using two optical particle counters. The deposition fluxes derived from the bulk concentrations and those derived from the size-resolved ones are in very good agreement. The largest deposition fluxes are recorded when the dust concentrations are maximal. The temporal evolution of the dust deposition flux follows that of the dust concentration. This is not the case of the dry deposition velocities that are most of the time controlled by the wind friction velocity. The results also show that large particles are strongly sensible to rebound when the wind friction velocity is the highest. Size-resolved dry deposition velocities are compared with the rare measurements of dust deposition velocities over bare sandy soils and are confronted to existing parameterizations of the dry deposition velocity. The parameterization of Shao (2014, https://doi.org/10.5194/acp-14-12429-2014) appears to be the only one able to reproduce satisfyingly the measured dry deposition velocities on sandy soils in the 1-to 10-μm particle size range. Indeed, unlike others, this scheme considers the desert sandy surfaces as rough surfaces, allowing the interception of dust particles by the sand grains and/or by the small roughness elements present on the surface.

WRF-Chem v3.9 simulations of the East Asian dust storm in May 2017: modeling sensitivities to dust emission and dry deposition schemes

“…shown), consistent with previous studies (e.g., Bergametti et al, 2018). Figure 5b shows the surface resistance from different schemes as a function of particle diameter (Dp).…”

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

“…The development of near‐surface low‐level jets associated with dust emissions has been investigated across the Sahara (Allen et al., 2013; Bergametti et al., 2018; Fiedler et al., 2013; Kaly et al., 2015; Marsham et al., 2013; Schepanski et al., 2009), in the Bodélé depression, Chad (Todd et al., 2007; Washington et al., 2006; Washington & Todd, 2005), and in the Taklimakan, China (Ge et al., 2016). There are also observations of the frequent occurrence of LLJs with an easterly component over Etosha Pan during winter months (Clements & Washington, 2021; Zunckel, Held, et al., 1996) when strong radiative cooling at night promotes the decoupling of air aloft from the surface and nocturnal stratification of the atmosphere (Allen & Washington, 2014; Blackader, 1957).…”

“…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).…”

Desertification

“…Examples of relevant services include: drought monitoring and early warning systems, often implemented by national climate and meteorological services but also encompassing regional and global systems (Pozzi et al 2013); and the Sand and Dust Storm Warning Advisory and Assessment System (SDS-WAS), created by WMO in 2007, in partnership with the World Health Organization (WHO) and the United Nations Environment Program (UNEP). Currently, there is also a lack of ecological monitoring in arid and semi-arid regions to study surface winds, dust and sand storms, and their impacts on ecosystems and human health (Bergametti et al 2018;Marticorena et al 2010). Reliable and timely climate services, relevant to desertification, can aid the development of appropriate adaptation and mitigation options, reducing the impact of desertification under changing climate on human and natural systems (high confidence) (Beegum et al 2016;Beegum et al 2018;Cornet 2012;Haase et al 2018;Sergeant et al 2012).…”