In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

Renard, Jean‐Baptiste; Dulac, François; Durand, Pierre; Bourgeois, Quentin; Denjean, Cyrielle; Vignelles, Damien; Couté, B.; Jeannot, Matthieu; Verdier, Nicolas; Mallet, Marc

doi:10.5194/acp-18-3677-2018

Cited by 63 publications

(63 citation statements)

References 95 publications

(105 reference statements)

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“…However, it is consistent with the findings of now numerous publications of individual field campaign dust size distributions, where larger particles were observed than could be explained by gravitational settling alone (Ryder et al, 2013a;Denjean et al, 2016;Stevenson et al, 2015;Gasteiger et al, 2017;Ryder et al, 2018;van der Does et al, 2018;Maring et al, 2003). Ryder et al (2013a) examined the mechanisms for transport between fresh, aged and SAL dust during 5…”

Section: The Wider Context Of Dust Size and Transportsupporting

confidence: 82%

“…For AER-D, only SEVIRI imagery was used for dust source identification since for each case HYSPLIT back trajectories indicated different 5 dust source locations, likely due to poor meteorological representation over the Sahara when convection was important . Dust ages for Fennec-SAL are not included here since their values have been found to cover an extremely large range of times (Ryder et al, 2013a).…”

Section: Estimation Of Dust Age 30mentioning

confidence: 99%

“…Firstly, Figure 10a shows Fennec-Sahara and AER-D-SAL separated by dust events. Fennec-SAL is excluded because the range of dust ages is too broad for it to be a useful addition (Ryder et al, 2013a). During AER-D-SAL, the estimated dust age varied from 0.7 to 4.6 days, while https://doi.org /10.5194/acp-2019-421 Preprint.…”

Section: The Wider Context Of Dust Size and Transportmentioning

confidence: 99%

“…For Fennec-SAL, only profile data is available (not horizontal flight legs). Therefore a logfit curve is fitted to the mean observational profile data from Ryder et al (2013a) as shown by the blue line in Figure 2 (data available in supplement). The spread of PSDs for Fennec-SAL (blue shading) is narrower compared to the other two PSDs because the minimum and maximum represent the 20 standard error of the mean as given in Ryder et al (2013a).…”

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confidence: 99%

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Coarse and Giant Particles are Ubiquitous in Saharan Dust Export Regions and are Radiatively Significant over the Sahara

Ryder¹,

Highwood²,

Walser³

et al. 2019

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 10 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. Observations are taken from the Fennec fieldwork over the Sahara and in the Saharan Air Layer (SAL) near 15 the Canary Islands, and from the AER-D fieldwork in the vicinity of the Cape Verde Islands in the SAL.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. Mass profiles show that over the Sahara 40% of dust mass was found in the giant mode, contrasting to 2 to 12% in the SAL. Size-resolved optical property 20 calculations show that in the shortwave (longwave) spectrum excluding the giant mode omits 18% (26%) of extinction over the Sahara, compared to 1-4% (2-6%) in the SAL. Excluding giant particles results in significant underestimation of both shortwave and longwave extinction over the Sahara, as well as of mass concentration, while the effects in the SAL are smaller but non-negligible. Omitting the giant mode results in a greater omission of dust longwave radiative effects compared to the shortwave, suggesting a bias towards a radiative cooling effect of dust when the giant mode is excluded and/or the coarse mode 25 is underestimated. This will be important in dust models, which typically exclude giant particles and underestimate coarse mode concentrations.A compilation of effective diameters against dust age since uplift time suggests that two regimes of dust transport exist. During the initial 1.5 days, both coarse and giant particles are rapidly deposited. During the subsequent 1.5 to 10 days, PSD barely 30 changes with transport, and the coarse mode is retained to a much greater degree than expected from estimates of gravitational

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Section: The Wider Context Of Dust Size and Transportsupporting

confidence: 82%

Section: Estimation Of Dust Age 30mentioning

confidence: 99%

Section: The Wider Context Of Dust Size and Transportmentioning

confidence: 99%

mentioning

confidence: 99%

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Coarse and Giant Particles are Ubiquitous in Saharan Dust Export Regions and are Radiatively Significant over the Sahara

Ryder¹,

Highwood²,

Walser³

et al. 2019

Preprint

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“…The Balkanski et al (2007) Kim et al (2011) from the AERosol Robotic NETwork (AERONET) at visible wavelengths. Both of the latter two produce significantly lower imaginary parts, 0.0015 and 0.0024 at 0.55 µm, respectively, widely considered to be more appropriate for accurately representing dust properties and consistent with recent observations (Rocha-Lima et al, 2018). In the longwave spectrum there is more variability between the RI datasets compared to the shortwave.…”

Section: Optical Property Calculationssupporting

confidence: 75%

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

View full text Add to dashboard Cite

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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Aerosol Size Distribution

Biagio

2022

Atmospheric Chemistry in the Mediterranean Region

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In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

Abstract: Abstract. Mineral dust from arid areas is a major component of global aerosol and has strong interactions with climate and biogeochemistry.

Cited by 63 publications

References 95 publications

Coarse and Giant Particles are Ubiquitous in Saharan Dust Export Regions and are Radiatively Significant over the Sahara

Coarse and Giant Particles are Ubiquitous in Saharan Dust Export Regions and are Radiatively Significant over the Sahara

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

Aerosol Size Distribution

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