The evaporatively driven cloud-top mixing layer

Direct numerical simulations of the turbulent temporally evolving cloud-top mixing layer are used to investigate the role of evaporative cooling by isobaric mixing locally at the stratocumulus top. It is shown that the system develops a horizontal layered structure whose evolution is determined by m...

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Author: Mellado González, Juan Pedro|||0000-0001-7506-6539
Format: article
Publication Date:2010
Country:España
Institution:Universitat Politècnica de Catalunya (UPC)
Repository:UPCommons. Portal del coneixement obert de la UPC
Language:English
OAI Identifier:oai:upcommons.upc.edu:2117/190425
Online Access:https://hdl.handle.net/2117/190425
https://dx.doi.org/10.1017/S0022112010002831
Access Level:Open access
Keyword:Atmospheric physics
Moisture
Atmospheric circulation
Turbulence
Convection (Meteorology)
Atmospheric flows
Moist convection
Turbulent mixing
Física atmosfèrica
Turbulència
Convecció (Meteorologia)
Àrees temàtiques de la UPC::Física
id ES_ebfdf97aaadf7fc304660e5a9214ba30
oai_identifier_str oai:upcommons.upc.edu:2117/190425
network_acronym_str ES
network_name_str España
repository_id_str
spelling The evaporatively driven cloud-top mixing layerMellado González, Juan Pedro|||0000-0001-7506-6539Atmospheric physicsMoistureAtmospheric circulationTurbulenceConvection (Meteorology)Atmospheric flowsMoist convectionTurbulent mixingFísica atmosfèricaTurbulènciaConvecció (Meteorologia)Àrees temàtiques de la UPC::FísicaDirect numerical simulations of the turbulent temporally evolving cloud-top mixing layer are used to investigate the role of evaporative cooling by isobaric mixing locally at the stratocumulus top. It is shown that the system develops a horizontal layered structure whose evolution is determined by molecular transport. A relatively thin inversion with a constant thickness h = ¿/we is formed on top and travels upwards at a mean velocity we 0.1(¿|bs|¿2 c ) 1/3, where ¿ is the mixture-fraction diffusivity, bs < 0 is the buoyancy anomaly at saturation conditions ¿s and ¿c is the cross-over mixture fraction defining the interval of buoyancy reversing mixtures. A turbulent convection layer develops below and continuously broadens into the cloud (the lower saturated fluid). This turbulent layer approaches a self-preserving state that is characterized by the convection scales constructed from a constant reference buoyancy flux Bs = |bs|we/¿s. Right underneath the inversion base, a transition or buffer zone is defined based on a strong local conversion of vertical to horizontal motion that leads to a cellular pattern and sheet-like plumes, as observed in cloud measurements and reported in other free-convection problems. The fluctuating saturation surface (instantaneous cloud top) is contained inside this intermediate region. Results show that the inversion is not broken due to the turbulent convection generated by the evaporative cooling, and the upward mean entrainment velocity we is negligibly small compared to the convection velocity scale w* of the turbulent layer and the corresponding growth rate into the cloud.Peer Reviewed20102010-10-1020202020-06-10journal articlehttp://purl.org/coar/resource_type/c_6501VoRhttp://purl.org/coar/version/c_970fb48d4fbd8a85info:eu-repo/semantics/articleapplication/pdfhttps://hdl.handle.net/2117/190425https://dx.doi.org/10.1017/S0022112010002831reponame:UPCommons. Portal del coneixement obert de la UPCinstname:Universitat Politècnica de Catalunya (UPC)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2Attribution-NonCommercial-NoDerivs 3.0 Spainhttp://creativecommons.org/licenses/by-nc-nd/3.0/es/info:eu-repo/semantics/openAccessoai:upcommons.upc.edu:2117/1904252026-05-27T15:37:01Z
dc.title.none.fl_str_mv The evaporatively driven cloud-top mixing layer
title The evaporatively driven cloud-top mixing layer
spellingShingle The evaporatively driven cloud-top mixing layer
Mellado González, Juan Pedro|||0000-0001-7506-6539
Atmospheric physics
Moisture
Atmospheric circulation
Turbulence
Convection (Meteorology)
Atmospheric flows
Moist convection
Turbulent mixing
Física atmosfèrica
Turbulència
Convecció (Meteorologia)
Àrees temàtiques de la UPC::Física
title_short The evaporatively driven cloud-top mixing layer
title_full The evaporatively driven cloud-top mixing layer
title_fullStr The evaporatively driven cloud-top mixing layer
title_full_unstemmed The evaporatively driven cloud-top mixing layer
title_sort The evaporatively driven cloud-top mixing layer
dc.creator.none.fl_str_mv Mellado González, Juan Pedro|||0000-0001-7506-6539
author Mellado González, Juan Pedro|||0000-0001-7506-6539
author_facet Mellado González, Juan Pedro|||0000-0001-7506-6539
author_role author
dc.subject.none.fl_str_mv Atmospheric physics
Moisture
Atmospheric circulation
Turbulence
Convection (Meteorology)
Atmospheric flows
Moist convection
Turbulent mixing
Física atmosfèrica
Turbulència
Convecció (Meteorologia)
Àrees temàtiques de la UPC::Física
topic Atmospheric physics
Moisture
Atmospheric circulation
Turbulence
Convection (Meteorology)
Atmospheric flows
Moist convection
Turbulent mixing
Física atmosfèrica
Turbulència
Convecció (Meteorologia)
Àrees temàtiques de la UPC::Física
description Direct numerical simulations of the turbulent temporally evolving cloud-top mixing layer are used to investigate the role of evaporative cooling by isobaric mixing locally at the stratocumulus top. It is shown that the system develops a horizontal layered structure whose evolution is determined by molecular transport. A relatively thin inversion with a constant thickness h = ¿/we is formed on top and travels upwards at a mean velocity we 0.1(¿|bs|¿2 c ) 1/3, where ¿ is the mixture-fraction diffusivity, bs < 0 is the buoyancy anomaly at saturation conditions ¿s and ¿c is the cross-over mixture fraction defining the interval of buoyancy reversing mixtures. A turbulent convection layer develops below and continuously broadens into the cloud (the lower saturated fluid). This turbulent layer approaches a self-preserving state that is characterized by the convection scales constructed from a constant reference buoyancy flux Bs = |bs|we/¿s. Right underneath the inversion base, a transition or buffer zone is defined based on a strong local conversion of vertical to horizontal motion that leads to a cellular pattern and sheet-like plumes, as observed in cloud measurements and reported in other free-convection problems. The fluctuating saturation surface (instantaneous cloud top) is contained inside this intermediate region. Results show that the inversion is not broken due to the turbulent convection generated by the evaporative cooling, and the upward mean entrainment velocity we is negligibly small compared to the convection velocity scale w* of the turbulent layer and the corresponding growth rate into the cloud.
publishDate 2010
dc.date.none.fl_str_mv 2010
2010-10-10
2020
2020-06-10
dc.type.none.fl_str_mv journal article
http://purl.org/coar/resource_type/c_6501
VoR
http://purl.org/coar/version/c_970fb48d4fbd8a85
dc.type.openaire.fl_str_mv info:eu-repo/semantics/article
format article
dc.identifier.none.fl_str_mv https://hdl.handle.net/2117/190425
https://dx.doi.org/10.1017/S0022112010002831
url https://hdl.handle.net/2117/190425
https://dx.doi.org/10.1017/S0022112010002831
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.source.none.fl_str_mv reponame:UPCommons. Portal del coneixement obert de la UPC
instname:Universitat Politècnica de Catalunya (UPC)
instname_str Universitat Politècnica de Catalunya (UPC)
reponame_str UPCommons. Portal del coneixement obert de la UPC
collection UPCommons. Portal del coneixement obert de la UPC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,301603

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