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Composite Structure of Plumes in Stratus-Topped Boundary Layers

Moeng, C.H. and Schumann, U. (1991) Composite Structure of Plumes in Stratus-Topped Boundary Layers. Journal of the Atmospheric Sciences, 48, pp. 2280-2291. DOI: 10.1175/1520-0469(1991)048<2280:CSOPIS>2.0.CO;2

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Official URL: http://ams.allenpress.com/perlserv/?request=get-archive&issn=1520-0469

Abstract

Knowledge of convective plumes within the clear convective boundary layer (CBL) is quite advanced owing to direct measurements, tank experiments, and large-eddy simulation studies. As a result, modeling of the CBL is relatively successful. Progress for the stratus-topped boundary layer (STBL), however, is slow. This study compares the plume structure of the surface-heated CBL with that of the cloud-top-cooled STBL in the hope of extending our knowledge of the CBL to the STBL. A conditional sampling technique is applied to the STBL flow fields that are generated through large-simulations, so that the structures of typical updrafts and downdrafts may be derived. For the purpose of comparing the surface-heated CBL and the cloud-top-cooled STBL, an idealized STBL is simulated where the turbulence is maintained solely by cloud-top radiative cooling. The principal difference between the CBL and this idealized STBL lies in the origin of the plumes: primary plumes in the CBL are generated at a rigid surface, while those in the STBL are generated at the entraining interface. It was found that in the idealized STBL, the compensating updrafts are nearly as strong as the top-cooling-generated downdrafts, and they contribute a significant amount to the heat, moisture, and momentum transports. This differs very much from the CBL, where the compensating downdrafts are much weaker than the surface-heating-generated updrafts and contribute much less to the transports. The mechanism that results in such an asymmetry between the CBL and STBL is examined, and suggestions on how the asymmetry affects the entrainment process are made.

Item URL in elib:https://elib.dlr.de/31607/
Document Type:Article
Title:Composite Structure of Plumes in Stratus-Topped Boundary Layers
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Moeng, C.H.NCAR, Boulder, CO, USAUNSPECIFIED
Schumann, U.UNSPECIFIEDUNSPECIFIED
Date:1991
Journal or Publication Title:Journal of the Atmospheric Sciences
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Volume:48
DOI :10.1175/1520-0469(1991)048<2280:CSOPIS>2.0.CO;2
Page Range:pp. 2280-2291
Status:Published
Keywords:convective boundary layer, CBL, stratus-topped boundary layer, STBL
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Atmosphären- und Klimaforschung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics
Deposited By: DLR-Beauftragter, elib
Deposited On:02 Apr 2006
Last Modified:31 Jul 2019 19:17

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