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DOI	10.5194/acp-19-9595-2019
	Observation of absorbing aerosols above clouds over the south-east Atlantic Ocean from the geostationary satellite SEVIRI-Part 1: Method description and sensitivity
	Peers F.; Francis P.; Fox C.; Abel S.J.; Szpek K.; Cotterell M.I.; Davies N.W.; Langridge J.M.; Meyer K.G.; Platnick S.E.; Haywood J.M.
发表日期	2019
ISSN	16807316
起始页码	9595
结束页码	9611
卷号	19 期号:14
英文摘要	High-temporal-resolution observations from satellites have a great potential for studying the impact of biomass burning aerosols and clouds over the south-east Atlantic Ocean (SEAO). This paper presents a method developed to simultaneously retrieve aerosol and cloud properties in aerosol above-cloud conditions from the geostationary instrument Meteosat Second Generation/Spinning Enhanced Visible and Infrared Imager (MSG/SEVIRI). The above-cloud aerosol optical thickness (AOT), the cloud optical thickness (COT) and the cloud droplet effective radius (CER) are derived from the spectral contrast and the magnitude of the signal measured in three channels in the visible to shortwave infrared region. The impact of the absorption from atmospheric gases on the satellite signal is corrected by applying transmittances calculated using the water vapour profiles from a Met Office forecast model. The sensitivity analysis shows that a 10 % error on the humidity profile leads to an 18.5 % bias on the above-cloud AOT, which highlights the importance of an accurate atmospheric correction scheme. In situ measurements from the CLARIFY-2017 airborne field campaign are used to constrain the aerosol size distribution and refractive index that is assumed for the aforementioned retrieval algorithm. The sensitivities in the retrieved AOT, COT and CER to the aerosol model assumptions are assessed. Between 09:00 and 15:00 UTC, an uncertainty of 40 % is estimated on the above-cloud AOT, which is dominated by the sensitivity of the retrieval to the single-scattering albedo. The absorption AOT is less sensitive to the aerosol assumptions with an uncertainty generally lower than 17 % between 09:00 and 15:00 UTC. Outside of that time range, as the scattering angle decreases, the sensitivity of the AOT and the absorption AOT to the aerosol model increases. The retrieved cloud properties are only weakly sensitive to the aerosol model assumptions throughout the day, with biases lower than 6 % on the COT and 3 % on the CER. The stability of the retrieval over time is analysed. For observations outside of the backscattering glory region, the time series of the aerosol and cloud properties are physically consistent, which confirms the ability of the retrieval to monitor the temporal evolution of aerosol above-cloud events over the SEAO. © 2019 Author(s).
语种	英语
scopus关键词	aerosol; albedo; cloud cover; geostationary satellite; refractive index; sensitivity analysis; SEVIRI; size distribution; Atlantic Ocean; Atlantic Ocean (Southeast)
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/144244
作者单位	College of Engineering, Mathematics, and Physical Sciences, University of Exeter, Exeter, United Kingdom; Met Office, Fitzroy Road, Exeter, United Kingdom; NASA Goddard Space Flight Center, Greenbelt, MD, United States
推荐引用方式 GB/T 7714	Peers F.,Francis P.,Fox C.,et al. Observation of absorbing aerosols above clouds over the south-east Atlantic Ocean from the geostationary satellite SEVIRI-Part 1: Method description and sensitivity[J],2019,19(14).
APA	Peers F..,Francis P..,Fox C..,Abel S.J..,Szpek K..,...&Haywood J.M..(2019).Observation of absorbing aerosols above clouds over the south-east Atlantic Ocean from the geostationary satellite SEVIRI-Part 1: Method description and sensitivity.Atmospheric Chemistry and Physics,19(14).
MLA	Peers F.,et al."Observation of absorbing aerosols above clouds over the south-east Atlantic Ocean from the geostationary satellite SEVIRI-Part 1: Method description and sensitivity".Atmospheric Chemistry and Physics 19.14(2019).