气候变化领域集成服务门户(CCPortal): Downward cloud venting of the central African biomass burning plume during the West Africa summer monsoon

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DOI	10.5194/acp-20-5373-2020
	Downward cloud venting of the central African biomass burning plume during the West Africa summer monsoon
	Dajuma A.; Ogunjobi K.O.; Vogel H.; Knippertz P.; Siluś S.; N'Datchoh E.T.; Yoboué V.; Vogel B.
发表日期	2020
ISSN	1680-7316
起始页码	5373
结束页码	5390
卷号	20 期号:9
英文摘要	Between June and September large amounts of biomass burning aerosol are released into the atmosphere from agricultural fires in central and southern Africa. Recent studies have suggested that this plume is carried westward over the Atlantic Ocean at altitudes between 2 and 4&km and then northward with the monsoon flow at low levels to increase the atmospheric aerosol load over coastal cities in southern West Africa (SWA), thereby exacerbating air pollution problems. However, the processes by which these fire emissions are transported into the planetary boundary layer (PBL) are still unclear. One potential factor is the large-scale subsidence related to the southern branch of the monsoon Hadley cell over the tropical Atlantic. Here we use convection-permitting model simulations with COSMO-ART to investigate for the first time the contribution of downward mixing induced by clouds, a process we refer to as downward cloud venting in contrast to the more common process of upward transport from a polluted PBL. Based on a monthly climatology, model simulations compare satisfactory with wind fields from reanalysis data, cloud observations, and satellite-retrieved carbon monoxide (CO) mixing ratio. For a case study on 2 July 2016, modelled clouds and rainfall show overall good agreement with Spinning Enhanced Visible and InfraRed Imager (SEVIRI) cloud products and Global Precipitation Measurement Integrated Multi-satellitE Retrievals (GPM-IMERG) rainfall estimates. However, there is a tendency for the model to produce too much clouds and rainfall over the Gulf of Guinea. Using the CO dispersion as an indicator for the biomass burning plume, we identify individual mixing events south of the coast of Côte d'Ivoire due to midlevel convective clouds injecting parts of the biomass burning plume into the PBL. Idealized tracer experiments suggest that around 15&% of the CO mass from the 2-4&km layer is mixed below 1&km within 2&d over the Gulf of Guinea and that the magnitude of the cloud venting is modulated by the underlying sea surface temperatures. There is even stronger vertical mixing when the biomass burning plume reaches land due to daytime heating and a deeper PBL. In that case, the long-range-transported biomass burning plume is mixed with local anthropogenic emissions. Future work should provide more robust statistics on the downward cloud venting effect over the Gulf of Guinea and include aspects of aerosol deposition. © 2020 author(s).
语种	英语
scopus关键词	aerosol; agricultural emission; atmospheric transport; biomass burning; computer simulation; emission inventory; Hadley cell; long range transport; monsoon; numerical model; pollutant transport; summer; Atlantic Ocean; Atlantic Ocean (Tropical); West 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/247800
作者单位	Department of Meteorology and Climate Sciences, West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL), Federal University of Technology Akure (FUTA), Ondo State, Nigeria; Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany; University Félix Houphouët Boigny, Abidjan, Cote d'Ivoire; Federal University of Technology Akure (FUTA), Ondo State, Nigeria; Université Peleforo Gon Coulibaly, Korhogo, Cote d'Ivoire
推荐引用方式 GB/T 7714	Dajuma A.,Ogunjobi K.O.,Vogel H.,et al. Downward cloud venting of the central African biomass burning plume during the West Africa summer monsoon[J],2020,20(9).
APA	Dajuma A..,Ogunjobi K.O..,Vogel H..,Knippertz P..,Siluś S..,...&Vogel B..(2020).Downward cloud venting of the central African biomass burning plume during the West Africa summer monsoon.ATMOSPHERIC CHEMISTRY AND PHYSICS,20(9).
MLA	Dajuma A.,et al."Downward cloud venting of the central African biomass burning plume during the West Africa summer monsoon".ATMOSPHERIC CHEMISTRY AND PHYSICS 20.9(2020).