Sand and dust storms: underrated natural hazards

Middleton, Nick; Tozer, Peter R.; Tozer, Brenton

doi:10.1111/disa.12320

Cited by 76 publications

(49 citation statements)

References 81 publications

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“…Dust is deposited to the oceans and Amazon rainforest, providing nutrients to a variety of ecosystems (Jickells et al, 2005;Yu et al, 2015). Finally, dust is a natural hazard, having a negative impact on aviation and transport (Weinzierl et al, 2012), solar energy generation, air quality, and hence human health (Middleton et al, 2018). The annual economic cost of dust storms may reach into the billions of US dollars for certain countries (Middleton, 2017).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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Abstract. 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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Section: Introductionmentioning

confidence: 99%

“…Larger particles contribute more to dust mass, which controls the impact of dust on ocean and tropical rainforest ecosystems (Jickells et al, 2005;Yu et al, 2015). A higher proportion of fine particles will lead to elevated PM 2.5 and subsequent impacts on respiratory health (Middleton, 2017).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…Dust is deposited to the oceans and Amazon rainforest providing nutrients to a variety of ecosystems (Jickells et al, 2005). Finally, dust is a natural 15 hazard, having a negative impact on aviation and transport (Weinzierl et al, 2012), solar energy generation and air quality, and hence human health (Middleton et al, 2018). The annual economic cost of dust storms may reach into the billions of US dollars for certain countries (Middleton, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…Larger particles contribute more to dust mass, which controls the impact of dust on ocean and tropical rainforest ecosystems (Jickells et al, 2005;Yu et al, 2015). A higher proportion of fine particles will lead to elevated PM2.5, and subsequent impacts on respiratory health (Middleton, 2017). 25 Dust size distribution has a strong impact on its radiative interactions (Tegen and Lacis, 1996).…”

Section: Introductionmentioning

confidence: 99%

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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“…Phys., 19, 15353-15376, 2019 www.atmos-chem-phys.net/19/15353/2019/ Table 2. Percentage contribution to total shortwave scattering as well as absorption and extinction coefficient at 0.55 µm, as a function of maximum particle size considered, for the Fennec-Sahara, AER-D-SAL, and Fennec-SAL mean size distributions using the Colarco et al (2014) , 2017;Evan et al, 2014). It is also evident that by only representing sizes up to 2.5 µm, the majority of extinction is omitted (only 27 %, 48 %, and 31 % of extinction for Fennec-Sahara, AER-D SAL, and Fennec-SAL, respectively, is captured).…”

Section: Size-resolved Optical Propertiesmentioning

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

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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Sand and dust storms: underrated natural hazards

Cited by 76 publications

References 81 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

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

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