The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves
Empirical rules for both entrainment and detrainment are developed from LES of the Southern Ocean boundary layer when the turbulence, stratification, and shear cannot be assumed to be in equilibrium with diurnal variability in surface flux and wave (Stokes drift) forcing. A major consequence is the...
Published in: | Journal of Physical Oceanography |
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Format: | Article in Journal/Newspaper |
Language: | English |
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2021
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Online Access: | https://doi.org/10.1175/JPO-D-20-0308.1 |
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ftncar:oai:drupal-site.org:articles_25118 2024-04-14T08:19:59+00:00 The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves Large, William G. (author) Patton, Edward G. (author) Sullivan, Peter P. (author) 2021-10 https://doi.org/10.1175/JPO-D-20-0308.1 en eng Journal of Physical Oceanography--0022-3670--1520-0485 Large Eddy Simulation of the Southern Ocean--10.5065/87n8-9r86 articles:25118 doi:10.1175/JPO-D-20-0308.1 ark:/85065/d7n01b3w Copyright 2021 American Meteorological Society (AMS). article Text 2021 ftncar https://doi.org/10.1175/JPO-D-20-0308.1 2024-03-21T18:00:26Z Empirical rules for both entrainment and detrainment are developed from LES of the Southern Ocean boundary layer when the turbulence, stratification, and shear cannot be assumed to be in equilibrium with diurnal variability in surface flux and wave (Stokes drift) forcing. A major consequence is the failure of downgradient eddy viscosity, which becomes more serious with Stokes drift and is overcome by relating the angle between the stress and shear vectors to the orientations of Lagrangian shear to the surface and of local Eulerian shear over 5m. Thus, the momentum flux can be parameterized as a stress magnitude and this empirical direction. In addition, the response of a deep boundary layer to sufficiently strong diurnal heating includes boundary layer collapse and the subsequent growth of a morning boundary layer, whose depth is empirically related to the time history of the forcing, as are both morning detrainment and afternoon entrainment into weak diurnal stratification. Below the boundary layer, detrainment rules give the maximum buoyancy flux and its depth, as well a specific stress direction. Another rule relates both afternoon and nighttime entrainment depth and buoyancy flux to surface layer turbulent kinetic energy production integrals. These empirical relationships are combined with rules for boundary layer transport to formulate two parameterizations; one based on eddy diffusivity and viscosity profiles and another on flux profiles of buoyancy and of stress magnitude. Evaluations against LES fluxes show the flux profiles to be more representative of the diurnal cycle, especially with Stokes drift. Article in Journal/Newspaper Southern Ocean OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) Southern Ocean Journal of Physical Oceanography |
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Open Polar |
collection |
OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) |
op_collection_id |
ftncar |
language |
English |
description |
Empirical rules for both entrainment and detrainment are developed from LES of the Southern Ocean boundary layer when the turbulence, stratification, and shear cannot be assumed to be in equilibrium with diurnal variability in surface flux and wave (Stokes drift) forcing. A major consequence is the failure of downgradient eddy viscosity, which becomes more serious with Stokes drift and is overcome by relating the angle between the stress and shear vectors to the orientations of Lagrangian shear to the surface and of local Eulerian shear over 5m. Thus, the momentum flux can be parameterized as a stress magnitude and this empirical direction. In addition, the response of a deep boundary layer to sufficiently strong diurnal heating includes boundary layer collapse and the subsequent growth of a morning boundary layer, whose depth is empirically related to the time history of the forcing, as are both morning detrainment and afternoon entrainment into weak diurnal stratification. Below the boundary layer, detrainment rules give the maximum buoyancy flux and its depth, as well a specific stress direction. Another rule relates both afternoon and nighttime entrainment depth and buoyancy flux to surface layer turbulent kinetic energy production integrals. These empirical relationships are combined with rules for boundary layer transport to formulate two parameterizations; one based on eddy diffusivity and viscosity profiles and another on flux profiles of buoyancy and of stress magnitude. Evaluations against LES fluxes show the flux profiles to be more representative of the diurnal cycle, especially with Stokes drift. |
author2 |
Large, William G. (author) Patton, Edward G. (author) Sullivan, Peter P. (author) |
format |
Article in Journal/Newspaper |
title |
The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves |
spellingShingle |
The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves |
title_short |
The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves |
title_full |
The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves |
title_fullStr |
The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves |
title_full_unstemmed |
The diurnal cycle of entrainment and detrainment in LES of the Southern Ocean driven by observed surface fluxes and waves |
title_sort |
diurnal cycle of entrainment and detrainment in les of the southern ocean driven by observed surface fluxes and waves |
publishDate |
2021 |
url |
https://doi.org/10.1175/JPO-D-20-0308.1 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
Journal of Physical Oceanography--0022-3670--1520-0485 Large Eddy Simulation of the Southern Ocean--10.5065/87n8-9r86 articles:25118 doi:10.1175/JPO-D-20-0308.1 ark:/85065/d7n01b3w |
op_rights |
Copyright 2021 American Meteorological Society (AMS). |
op_doi |
https://doi.org/10.1175/JPO-D-20-0308.1 |
container_title |
Journal of Physical Oceanography |
_version_ |
1796298151817117696 |