气候变化领域集成服务门户(CCPortal): Variability in lidar-derived particle properties over West Africa due to changes in absorption: Towards an understanding

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DOI	10.5194/acp-20-6563-2020
	Variability in lidar-derived particle properties over West Africa due to changes in absorption: Towards an understanding
	Veselovskii I.; Hu Q.; Goloub P.; Podvin T.; Korenskiy M.; Derimian Y.; Legrand M.; Castellanos P.
发表日期	2020
ISSN	16807316
起始页码	6563
结束页码	6581
卷号	20 期号:11
英文摘要	Measurements performed in western Africa (Senegal) during the SHADOW field campaign are analyzed to show that spectral dependence of the imaginary part of the complex refractive index (CRI) of dust can be revealed by lidar-measured particle parameters. Observations in April 2015 provide good opportunity for such study, because, due to high optical depth of the dust, exceeding 0.5, the extinction coefficient could be derived from lidar measurements with high accuracy and the contribution of other aerosol types, such as biomass burning, was negligible. For instance, in the second half of April 2015, AERONET observations demonstrated a temporal decrease in the imaginary part of the CRI at 440nm from approximately 0.0045 to 0.0025. This decrease is in line with a change in the relationship between the lidar ratios (the extinction-to-backscattering ratio) at 355 and 532nm (S355 and S532). For instance in the first half of April, S355/S532 is as high as 1.5 and the backscatter Ångström exponent, Aβ, is as low as -0.75, while after 15 April S355/S532 = 1.0 and Aβ is close to zero. The aerosol depolarization ratio δ532 for the whole of April exceeded 30% in the height range considered, implying that no other aerosol, except dust, occurred. The performed modeling confirmed that the observed S355/S532 and Aβ values match the spectrally dependent imaginary part of the refractive index as can be expected for mineral dust containing iron oxides. The second phase of the SHADOW campaign was focused on evaluation of the lidar ratio of smoke and estimates of its dependence on relative humidity (RH). For five studied smoke episodes the lidar ratio increases from 44±5 to 66±7 sr at 532 nm and from 62±6 to 80±8 sr at 355 nm, when RH varied from 25% to 85 %. Performed numerical simulations demonstrate that observed ratio S355/S532, exceeding 1.0 in the smoke plumes, can indicate an increase in the imaginary part of the smoke particles in the ultraviolet (UV) range. © 2020 Copernicus GmbH. All rights reserved.
关键词	absorption aerosol lidar optical depth refractive index relative humidity smoke spatial variation Senegal
语种	英语
来源机构	Atmospheric Chemistry and Physics
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/131988
推荐引用方式 GB/T 7714	Veselovskii I.,Hu Q.,Goloub P.,et al. Variability in lidar-derived particle properties over West Africa due to changes in absorption: Towards an understanding[J]. Atmospheric Chemistry and Physics,2020,20(11).
APA	Veselovskii I..,Hu Q..,Goloub P..,Podvin T..,Korenskiy M..,...&Castellanos P..(2020).Variability in lidar-derived particle properties over West Africa due to changes in absorption: Towards an understanding.,20(11).
MLA	Veselovskii I.,et al."Variability in lidar-derived particle properties over West Africa due to changes in absorption: Towards an understanding".20.11(2020).