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DOI	10.5194/acp-21-10965-2021
	Coupled and decoupled stratocumulus-topped boundary layers: Turbulence properties
	Nowak J.L.; Siebert H.; Szodry K.-E.; Malinowski S.P.
发表日期	2021
ISSN	1680-7316
起始页码	10965
结束页码	10991
卷号	21 期号:14
英文摘要	We compare turbulence properties in coupled and decoupled marine stratocumulus-topped boundary layers (STBLs) using high-resolution in situ measurements performed by the helicopter-borne Airborne Cloud Turbulence Observation System (ACTOS) platform in the region of the eastern North Atlantic. The thermodynamically well-mixed coupled STBL was characterized by a comparable latent heat flux at the surface and in the cloud-top region, and substantially smaller sensible heat flux in the entire depth. Turbulence kinetic energy (TKE) was efficiently generated by buoyancy in the cloud and at the surface, and dissipated with comparable rate across the entire depth. Structure functions and power spectra of velocity fluctuations in the inertial range were reasonably consistent with the predictions of Kolmogorov theory. The turbulence was close to isotropic. In the decoupled STBL, decoupling was most obvious in humidity profiles. Heat fluxes and buoyant TKE production at the surface were similar to the coupled case. Around the transition level, latent heat flux decreased to zero and TKE was consumed by weak stability. In the cloud-top region, heat fluxes almost vanished and buoyancy production was significantly smaller than for the coupled case. The TKE dissipation rate inside the decoupled STBL varied between its sublayers. Structure functions and power spectra in the inertial range deviated from Kolmogorov scaling. This was more pronounced in the cloud and subcloud layer in comparison to the surface mixed layer. The turbulence was more anisotropic than in the coupled STBL, with horizontal fluctuations dominating. The degree of anisotropy was largest in the cloud and subcloud layer of the decoupled STBL. Integral length scales, of the order of 100gm in both cases, indicate turbulent eddies smaller than the depth of the coupled STBL or of the sublayers of the decoupled STBL. We hypothesize that turbulence produced in the cloud or close to the surface is redistributed across the entire coupled STBL but rather only inside the sublayers where it was generated in the case of the decoupled STBL. Scattered cumulus convection, developed below the stratocumulus base, may play a role in transport between those sublayers. © 2021 Jakub L. Nowak et al.
语种	英语
scopus关键词	atmospheric convection; boundary layer; coupling; energy dissipation; humidity; latent heat flux; marine atmosphere; stratocumulus; thermodynamics; turbulence; Atlantic Ocean; Atlantic Ocean (North)
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/246719
作者单位	Institute of Geophysics, Faculty of Physics, University of Warsaw, Pasteura 5, Warsaw, 02-293, Poland; Leibniz Institute for Tropospheric Research, Permoserstr. 15, Leipzig, 04318, Germany
推荐引用方式 GB/T 7714	Nowak J.L.,Siebert H.,Szodry K.-E.,et al. Coupled and decoupled stratocumulus-topped boundary layers: Turbulence properties[J],2021,21(14).
APA	Nowak J.L.,Siebert H.,Szodry K.-E.,&Malinowski S.P..(2021).Coupled and decoupled stratocumulus-topped boundary layers: Turbulence properties.ATMOSPHERIC CHEMISTRY AND PHYSICS,21(14).
MLA	Nowak J.L.,et al."Coupled and decoupled stratocumulus-topped boundary layers: Turbulence properties".ATMOSPHERIC CHEMISTRY AND PHYSICS 21.14(2021).