气候变化领域集成服务门户(CCPortal): Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara

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DOI	10.5194/acp-19-15353-2019
	Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara
	Ryder C.L.; Highwood E.J.; Walser A.; Seibert P.; Philipp A.; Weinzierl B.
发表日期	2019
ISSN	16807316
起始页码	15353
结束页码	15376
卷号	19 期号:24
英文摘要	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 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. © 2019 Copernicus GmbH. All rights reserved.
语种	英语
scopus关键词	airborne survey; atmospheric transport; concentration (composition); dust; optical property; particle size; radiative transfer; size distribution; Sahara; Vulpes zerda
来源期刊	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/143965
作者单位	Department of Meteorology, University of Reading, Whiteknights, Reading, RG6 6BB, United Kingdom; University of Vienna, Faculty of Physics, Aerosol Physics and Environmental Physics, Vienna, Austria; University of Natural Resources and Life Sciences, Institute of Meteorology, Vienna, Austria
推荐引用方式 GB/T 7714	Ryder C.L.,Highwood E.J.,Walser A.,et al. Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara[J],2019,19(24).
APA	Ryder C.L.,Highwood E.J.,Walser A.,Seibert P.,Philipp A.,&Weinzierl B..(2019).Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara.Atmospheric Chemistry and Physics,19(24).
MLA	Ryder C.L.,et al."Coarse and giant particles are ubiquitous in Saharan dust export regions and are radiatively significant over the Sahara".Atmospheric Chemistry and Physics 19.24(2019).