气候变化领域集成服务门户(CCPortal): Subsiding shells and the distribution of up- and downdraughts in warm cumulus clouds over land

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DOI	10.5194/acp-19-9769-2019
	Subsiding shells and the distribution of up- and downdraughts in warm cumulus clouds over land
	Mallaun C.; Giez A.; Mayr G.J.; Rotach M.W.
发表日期	2019
ISSN	16807316
起始页码	9769
结束页码	9786
卷号	19 期号:15
英文摘要	The mass flux of air lifted within the updraughts (updraft in American English) of shallow convection is usually thought to be compensated outside the cloud through either large-scale subsidence or stronger downdraughts in a thin shell surrounding the cloud. Subsiding shells were postulated based on large eddy simulation and are experimentally tested in this study for shallow convection over land. Isolated cumulus clouds were probed with a small research aircraft over flat land and mountainous terrain, in different wind situations and at different levels of the clouds. The average of the 191 cloud transects shows the subsiding shell as a narrow downdraught region outside the cloud boundaries. The ensemble-mean subsiding shell is narrower on the upwind side of the cloud, while it is at least half a cloud diameter wide and more humid on the downwind side. At least half of the upward mass transport in the cloud is compensated within a distance of 20% of the cloud diameter. However, this shell is not uniform. Distinct regions of downdraughts and updraughts with high variability in the vertical wind are frequent and randomly distributed in the vicinity and also within the cloud. The median diameter of the draughts directly at the cloud boundary is at least 4 times as large as inside the clouds and in the environment. Downdraughts at the cloud boundary are twice as frequent as updraughts. In contrast to the updraughts the major part of the downdraughts is situated outside of the cloud. The subsiding shell results from the distribution of these up- and downdraughts. © Author(s) 2019.
语种	英语
scopus关键词	atmospheric convection; cloud cover; cumulus; large eddy simulation; mass transport; terrain
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/144239
作者单位	Deutsches Zentrum für Luft- und Raumfahrt (DLR), Flight Experiments, Oberpfaffenhofen, Germany; University of Innsbruck, Institute of Atmospheric and Cryospheric Sciences, Innsbruck, Austria
推荐引用方式 GB/T 7714	Mallaun C.,Giez A.,Mayr G.J.,et al. Subsiding shells and the distribution of up- and downdraughts in warm cumulus clouds over land[J],2019,19(15).
APA	Mallaun C.,Giez A.,Mayr G.J.,&Rotach M.W..(2019).Subsiding shells and the distribution of up- and downdraughts in warm cumulus clouds over land.Atmospheric Chemistry and Physics,19(15).
MLA	Mallaun C.,et al."Subsiding shells and the distribution of up- and downdraughts in warm cumulus clouds over land".Atmospheric Chemistry and Physics 19.15(2019).