气候变化领域集成服务门户(CCPortal): Vertical variability of the properties of highly aged biomass burning aerosol transported over the southeast Atlantic during CLARIFY-2017

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DOI	10.5194/acp-20-12697-2020
	Vertical variability of the properties of highly aged biomass burning aerosol transported over the southeast Atlantic during CLARIFY-2017
	Wu H.; Taylor J.W.; Szpek K.; Langridge J.M.; Williams P.I.; Flynn M.; Allan J.D.; Abel S.J.; Pitt J.; Cotterell M.I.; Fox C.; Davies N.W.; Haywood J.; Coe H.
发表日期	2020
ISSN	1680-7316
起始页码	12697
结束页码	12719
卷号	20 期号:21
英文摘要	Seasonal biomass burning (BB) from June to October in central and southern Africa leads to absorbing aerosols being transported over the South Atlantic Ocean every year and contributes significantly to the regional climate forcing. The vertical distribution of submicron aerosols and their properties were characterized over the remote southeast Atlantic, using airborne in situ measurements made during the CLoud-Aerosol-Radiation Interactions and Forcing for Year 2017 (CLARIFY-2017) campaign. BB aerosols emitted from flaming-controlled fires were intensively observed in the region surrounding Ascension Island, in the marine boundary layer (MBL) and free troposphere (FT) up to 5 km. We show that the aerosols had undergone a significant ageing process during 7 d transit from source, as indicated by the highly oxidized organic aerosol. The highly aged BB aerosols in the far-field CLARIFY region were also especially rich in black carbon (BC), with relatively low single-scattering albedos (SSAs), compared with those from other BB transported regions. The column-weighted dry SSAs during CLARIFY were observed to be 0.85, 0.84 and 0.83 at 405, 550 and 658 nm respectively. We also found significant vertical variation in the dry SSA, as a function of relative chemical composition and size. The lowest SSA in the column was generally in the low FT layer around 2000 m altitude (averages: 0.82, 0.81 and 0.79 at 405, 550 and 658 nm). This finding is important since it means that BB aerosols across the southeast Atlantic region are more absorbing than currently represented in climate models, implying that the radiative forcing from BB may be more strongly positive than previously thought. Furthermore, in the FT, average SSAs at 405, 550 and 658 nm increased to 0.87, 0.86 and 0.85 with altitude up to 5 km. This was associated with an enhanced inorganic nitrate mass fraction and aerosol size, likely resulting from increased partitioning of ammonium nitrate to the existing particles at higher altitude with lower temperature and higher relative humidity. After entrainment into the boundary layer (BL), aerosols were generally smaller in dry size than in the FT and had a larger fraction of scattering material with resultant higher average dry SSA, mostly due to marine emissions and aerosol removal by drizzle. In the BL, the SSA decreased from the surface to the BL top, with the highest SSA in the column observed near the surface. Our results provide unique observational constraints on aerosol parameterizations used in modelling regional radiation interactions over this important region. We recommend that future work should consider the impact of this vertical variability on climate models. © 2020 Author(s).
语种	英语
scopus关键词	aerosol; atmospheric transport; biomass burning; climate forcing; climate modeling; marine atmosphere; radiative forcing; size distribution; vertical distribution; Atlantic Ocean; Atlantic Ocean (Southeast); Central Africa; Southern Africa
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/247424
作者单位	Department of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom; Met Office, Fitzroy Road, Exeter, EX1 3PB, United Kingdom; National Centre for Atmospheric Science, University of Manchester, Manchester, United Kingdom; College of Engineering Mathematics and Physical Sciences, University of Exeter, Exeter, United Kingdom; School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, United States; School of Chemistry, University of Bristol, Bristol, BS8 1TS, United Kingdom
推荐引用方式 GB/T 7714	Wu H.,Taylor J.W.,Szpek K.,et al. Vertical variability of the properties of highly aged biomass burning aerosol transported over the southeast Atlantic during CLARIFY-2017[J],2020,20(21).
APA	Wu H..,Taylor J.W..,Szpek K..,Langridge J.M..,Williams P.I..,...&Coe H..(2020).Vertical variability of the properties of highly aged biomass burning aerosol transported over the southeast Atlantic during CLARIFY-2017.ATMOSPHERIC CHEMISTRY AND PHYSICS,20(21).
MLA	Wu H.,et al."Vertical variability of the properties of highly aged biomass burning aerosol transported over the southeast Atlantic during CLARIFY-2017".ATMOSPHERIC CHEMISTRY AND PHYSICS 20.21(2020).