The mysterious long-range transport of giant mineral dust particles

Does, Michèlle van der; Knippertz, Peter; Zschenderlein, Philipp; Harrison, Giles; Stuut, Jan‐Berend

doi:10.1126/sciadv.aau2768

Cited by 178 publications

(128 citation statements)

References 54 publications

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“…Previous work demonstrated that sand or fine sand is a typical nearshore component and is deposited rapidly near the lake shore and cannot be transported to the lake center by surface runoff 40 . Furthermore, both sand and fine sand usually move by saltation across the land surface 45 , and thus they cannot reach the lake center through direct air movement unless under highly optimal conditions 46 . Notably, the bedrock debris and ice-trapped dust are dominated by fine sand and sand components ( Supplementary Fig.…”

Section: Methodsmentioning

confidence: 99%

Asian dust-storm activity dominated by Chinese dynasty changes since 2000 BP

Chen

et al. 2020

Nat Commun

108

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The Asian monsoon (AM) played an important role in the dynastic history of China, yet it remains unknown whether AM-mediated shifts in Chinese societies affect earth surface processes to the point of exceeding natural variability. Here, we present a dust storm intensity record dating back to the first unified dynasty of China (the Qin Dynasty, 221–207 B.C.E.). Marked increases in dust storm activity coincided with unified dynasties with large populations during strong AM periods. By contrast, reduced dust storm activity corresponded to decreased population sizes and periods of civil unrest, which was co-eval with a weakened AM. The strengthened AM may have facilitated the development of Chinese civilizations, destabilizing the topsoil and thereby increasing the dust storm frequency. Beginning at least 2000 years ago, human activities might have started to overtake natural climatic variability as the dominant controls of dust storm activity in eastern China.

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Section: Methodsmentioning

confidence: 99%

Asian dust-storm activity dominated by Chinese dynasty changes since 2000 BP

Chen

et al. 2020

Nat Commun

108

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“…Spectral RI data, for which the real part represents scattering and the imaginary part represents absorption, are taken from a range of sources. For the full spectrum, RI data are available from the OPAC database (Hess et al, 1998) based on values from d' Almeida et al (1991) and Shettle and Fenn (1979), Volz (1973), and Balkanski et al (2007), assuming a 1.5 % hematite content, as well as the World Meteorological Organization (WMO, 1983) and Fouquart et al (1987). For the shortwave spectrum RI data are also available from Colarco et al (2014), and for the longwave spectrum data are available from Di Biagio et al (2017), from which we have selected the Mauritania subset as it is representative of the middle of the range for their North Africa samples.…”

Section: Optical Property Calculationsmentioning

confidence: 99%

“…However, it is consistent with the findings of now numerous publications of individual field campaign dust size distributions, during which larger particles were observed than could be explained by gravitational settling alone (Ryder et al, 2013aDenjean et al, 2016;Weinzierl et al, 2017;Stevenson et al, 2015;Gasteiger et al, 2017;van der Does Table 3. Percentage contribution to total longwave scattering as well as absorption and extinction coefficient at 10.8 µm, as a function of maximum particle size considered, for the Fennec-Sahara, AER-D-SAL, and Fennec-SAL mean size distributions using the Volz et al (1973) Maring et al, 2003). Ryder et al (2013a) examined the mechanisms for transport between fresh, aged, and SAL dust during Fennec-Sahara and found that sedimentation and dispersion were able to account for the loss of the accumulation-and giant-mode changes observed between the Saharan boundary layer and the SAL during Fennec-Sahara but not for the coarse mode, which was retained to a greater degree than expected.…”

Section: The Wider Context Of Dust Size and Transportmentioning

confidence: 99%

Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara

Ryder¹,

Highwood²,

Walser

et al. 2020

Preprint

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Mineral dust is an important component of the climate system, interacting with radiation, clouds, and biogeochemical systems and impacting atmospheric circulation, air quality, aviation, and solar energy generation. These impacts are sensitive to dust particle size distribution (PSD), yet models struggle or even fail to represent coarse (diameter (d) > 2.5 µm) and giant (d > 20 µm) dust particles and the evolution of the PSD with transport. Here we examine three state-of-the-art airborne observational datasets, all of which measured the full size range of dust (d = 0.1 to > 100 µm) at different stages during transport with consistent instrumentation. We quantify the presence and evolution of coarse and giant particles and their contribution to optical properties using airborne observations over the Sahara (from the Fennec field campaign) and in the Saharan Air Layer (SAL) over the tropical eastern Atlantic (from the AER-D field campaign).Observations show significantly more abundant coarse and giant dust particles over the Sahara compared to the SAL: effective diameters of up to 20 µm were observed over the Sahara compared to 4 µm in the SAL. Excluding giant particles over the Sahara results in significant underestimation of mass concentration (40 %), as well as underestimates of both shortwave and longwave extinction (18 % and 26 %, respectively, from scattering calculations), while the effects in the SAL are smaller but non-negligible. The larger impact on longwave extinction compared to shortwave implies a bias towards a radiative cooling effect in dust models, which typically exclude giant particles and underestimate coarse-mode concentrations.A compilation of the new and published effective diameters against dust age since uplift time suggests that two regimes of dust transport exist. During the initial 1.5 d, both coarse and giant particles are rapidly deposited. During the subsequent 1.5 to 10 d, PSD barely changes with transport, and the coarse mode is retained to a much greater degree than expected from estimates of gravitational sedimentation alone. The reasons for this are unclear and warrant further investigation in order to improve dust transport schemes and the associated radiative effects of coarse and giant particles in models.

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“…Understanding the processes contributing to volcanic lightning has been the focus of most studies of electrostatic phenomena at volcanoes; however, quantifying the effect of charge on ash and particle transport processes is an overlooked, although increasingly important problem (e.g., van der Does et al, 2018). Charging of droplets and particles can affect the fall speed of particles, changes aggregation rates, and enhances washout of particles, all of which are potentially important in accurately modeling the long-range transport of volcanic plumes.…”

Section: Implications Of Plume Chargingmentioning

confidence: 99%

“…Renewed interest in understanding the behavior of charged aerosol clouds (including volcanic plumes and dust clouds) has arisen due to realization that existing long-range particle transport models do not accurately predict the transport of large particles (Ryder et al, 2013;van der Does et al, 2018;Weinzierl et al, 2017). Charging modifies the fall speeds of small particles in the atmospheric electric field, changes aggregation rates, and enhances the washout of particles by rainfall (Harrison & Carslaw, 2003).…”

Section: Introductionmentioning

confidence: 99%

First In Situ Observations of Gaseous Volcanic Plume Electrification

Nicoll

Airey

Cimarelli

et al. 2019

Geophysical Research Letters

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Volcanic plumes become electrically charged, often producing spectacular displays of lightning. Previous research has focused on understanding volcanic lightning, primarily the large electric fields produced by charging of ash particles. Here we report on the previously overlooked phenomenon of volcanic plume electrification in the absence of detectable ash. We present the first in situ vertical profile measurements of charge, thermodynamic, and microphysical properties inside predominantly gaseous plumes directly above an erupting volcano. Our measurements demonstrate that substantial charge (at least ±8,000 pC/m3) is present in gaseous volcanic clouds without detectable ash. We suggest that plume charging may be enhanced by the emission of radon gas from the volcano, which causes ionization. This presents a hitherto unrecognized, but likely to be common, mechanism for charge generation in volcanic plumes, which is expected to modulate plume characteristics and lifetime. This process is currently neglected in recognized mechanisms of volcanic plume electrification.

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The mysterious long-range transport of giant mineral dust particles

Abstract: Strong winds, turbulence, convective uplift, and electric charge may keep giant particles aloft.

Cited by 178 publications

References 54 publications

Asian dust-storm activity dominated by Chinese dynasty changes since 2000 BP

Asian dust-storm activity dominated by Chinese dynasty changes since 2000 BP

Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara

First In Situ Observations of Gaseous Volcanic Plume Electrification

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