气候变化领域集成服务门户(CCPortal): Environmental sensitivities of shallow-cumulus dilution

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DOI	10.5194/acp-21-14039-2021
	Environmental sensitivities of shallow-cumulus dilution - Part 2: Vertical wind profile
	Drueke S.; Kirshbaum D.J.; Kollias P.
发表日期	2021
ISSN	1680-7316
起始页码	14039
结束页码	14058
卷号	21 期号:18
英文摘要	This second part of a numerical study on shallowcumulus dilution focuses on the sensitivity of cloud dilution to changes in the vertical wind profile. Insights are obtained through large-eddy simulations of maritime and continental cloud fields. In these simulations, the speed of the initially uniform geostrophic wind and the strength of geostrophic vertical wind shear in the cloud and subcloud layer are varied. Increases in the cloud-layer vertical wind shear (up to 9ms-1 km-1) lead to 40 %-50% larger cloud-core dilution rates compared to their respective unsheared counterparts. When the background wind speed, on the other hand, is enhanced by up to 10ms-1 and subcloud-layer vertical wind shear develops or is initially prescribed, the dilution rate decreases by up to 25 %. The sensitivities of the dilution rate are linked to the updraft strength and the properties of the entrained air. Increases in the wind speed or vertical wind shear result in lower vertical velocities across all sets of experiments with stronger reductions in the cloud-layer wind shear simulation (27 %-47 %). Weaker updrafts are exposed to mixing with the drier surrounding air for a longer time period, allowing more entrainment to occur (i.e., the "coreexposure effect"). However, reduced vertical velocities, in concert with increased cloud-layer turbulence, also assist in widening the humid shell surrounding the cloud cores, leading to entrainment of more humid air (i.e., the "core- shell dilution effect"). In the experiments with cloud-layer vertical wind shear, the core-exposure effect dominates and the cloud-core dilution increases with increasing shear. Conversely, when the wind speed is increased and subcloud-layer vertical wind shear develops or is imposed, the core-shell dilution effect dominates to induce a buffering effect. The sensitivities are generally stronger in the maritime simulations, where weaker sensible heat fluxes lead to narrower, more tilted, and, therefore, more suppressed cumuli when cloudlayer shear is imposed. Moreover, in the experiments with subcloud wind shear, the weaker baseline turbulence in the maritime case allows for a larger turbulence enhancement, resulting in a widening of the transition zones between the cores and their environment, leading to the entrainment of more humid air. © Author(s) 2021.
语种	英语
scopus关键词	cloud classification; cloud microphysics; cumulus; dilution; sensitivity analysis; wind profile; wind shear
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/246566
作者单位	Department of Atmospheric and Oceanic Sciences, McGill University, Montréal, QC, Canada; School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY, United States
推荐引用方式 GB/T 7714	Drueke S.,Kirshbaum D.J.,Kollias P.. Environmental sensitivities of shallow-cumulus dilution - Part 2: Vertical wind profile[J],2021,21(18).
APA	Drueke S.,Kirshbaum D.J.,&Kollias P..(2021).Environmental sensitivities of shallow-cumulus dilution - Part 2: Vertical wind profile.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(18).
MLA	Drueke S.,et al."Environmental sensitivities of shallow-cumulus dilution - Part 2: Vertical wind profile".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.18(2021).