{"id":{"repo_id":"soton","oai_identifier":"oai:eprints.soton.ac.uk:63136"},"canonical_url":"https://search.dev.ndltd.org/etd/soton/oai:eprints.soton.ac.uk:63136","repository":{"repo_id":"soton","name":"University of Southampton","base_url":"https://eprints.soton.ac.uk/cgi/oai2"},"display":{"title":"Diagnostics of diapycnal diffusion in z-level ocean models","abstract":"In general ocean circulation models (OGCMs) diapycnal diffusion arises not
only from the discretisation of the explicit diffusion, but also by numerically
induced diffusion, caused, e.g., by common discretisations of advective
transport.
In the present study, three different diagnostics to analyse the mean
diapycnal diffusivities of individual tracers (vertically and horizontally) are
introduced: (i) The divergence method based on the work of Ledwell
et al. (1998) infers the mean diapycnal diffusivity from the
advection-diffusion equation. (ii) The tracer flux method based on the work
of Griffies et al. (2000), that determines the diapycnal flux crossing an
isopycnal layer, is modified for the analysis of mean diapycnal diffusivities
of a passive tracer. (iii) The variance method based on the work of
Morales Maqueda and Holloway (2006) is a more general approach
as the diapycnal diffusion is analysed by the variance decay of the total
tracer concentration.
These methods can be used for the analysis of the diffusivity of passive
tracer independent of the model set-up, e.g. the advection scheme used, but
support only information about mean diapycnal diffusivity of that tracer
field rather than for each individual layer. The applicability of these
methods is tested in a set of 1- and 2-dimensional case studies. The effect
of vertical advection and of diverging and converging isopycnals is shown
separately. In all three methods used, the transformation of the tracer onto
isopycnals leads to errors in the diagnosed diffusivities. It turns out that
the tracer flux method is the most robust method and therefore the method
of choice. In order to keep the errors as small as possible, longer time mean
values should be analysed.","abstract_html":"In general ocean circulation models (OGCMs) diapycnal diffusion arises not<br/>only from the discretisation of the explicit diffusion, but also by numerically<br/>induced diffusion, caused, e.g., by common discretisations of advective<br/>transport.<br/>In the present study, three different diagnostics to analyse the mean<br/>diapycnal diffusivities of individual tracers (vertically and horizontally) are<br/>introduced: (i) The divergence method based on the work of Ledwell<br/>et al. (1998) infers the mean diapycnal diffusivity from the<br/>advection-diffusion equation. (ii) The tracer flux method based on the work<br/>of Griffies et al. (2000), that determines the diapycnal flux crossing an<br/>isopycnal layer, is modified for the analysis of mean diapycnal diffusivities<br/>of a passive tracer. (iii) The variance method based on the work of<br/>Morales Maqueda and Holloway (2006) is a more general approach<br/>as the diapycnal diffusion is analysed by the variance decay of the total<br/>tracer concentration.<br/>These methods can be used for the analysis of the diffusivity of passive<br/>tracer independent of the model set-up, e.g. the advection scheme used, but<br/>support only information about mean diapycnal diffusivity of that tracer<br/>field rather than for each individual layer. The applicability of these<br/>methods is tested in a set of 1- and 2-dimensional case studies. The effect<br/>of vertical advection and of diverging and converging isopycnals is shown<br/>separately. In all three methods used, the transformation of the tracer onto<br/>isopycnals leads to errors in the diagnosed diffusivities. It turns out that<br/>the tracer flux method is the most robust method and therefore the method<br/>of choice. In order to keep the errors as small as possible, longer time mean<br/>values should be analysed.","abstract_has_math":false,"creators":["Getzlaff, Julia"],"institution":"University of Southampton","degree_name":"Ph.D.","degree_level":"doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2008,"date_issued":"2008-03","date_published":"2008-03","updated_at":"2026-07-24T04:35:54Z","subjects":[],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Getzlaff, Julia"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2008-03"]},{"key":"dc:date.issued","label":"Date","values":["2008-03"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Ocean and Earth Science (pre 2011 reorg)","School of Ocean and Earth Science"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Southampton"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://eprints.soton.ac.uk/63136/"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["Ph.D."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://eprints.soton.ac.uk/63136/1/Getzlaff_2008_PhD.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In general ocean circulation models (OGCMs) diapycnal diffusion arises not
only from the discretisation of the explicit diffusion, but also by numerically
induced diffusion, caused, e.g., by common discretisations of advective
transport.
In the present study, three different diagnostics to analyse the mean
diapycnal diffusivities of individual tracers (vertically and horizontally) are
introduced: (i) The divergence method based on the work of Ledwell
et al. (1998) infers the mean diapycnal diffusivity from the
advection-diffusion equation. (ii) The tracer flux method based on the work
of Griffies et al. (2000), that determines the diapycnal flux crossing an
isopycnal layer, is modified for the analysis of mean diapycnal diffusivities
of a passive tracer. (iii) The variance method based on the work of
Morales Maqueda and Holloway (2006) is a more general approach
as the diapycnal diffusion is analysed by the variance decay of the total
tracer concentration.
These methods can be used for the analysis of the diffusivity of passive
tracer independent of the model set-up, e.g. the advection scheme used, but
support only information about mean diapycnal diffusivity of that tracer
field rather than for each individual layer. The applicability of these
methods is tested in a set of 1- and 2-dimensional case studies. The effect
of vertical advection and of diverging and converging isopycnals is shown
separately. In all three methods used, the transformation of the tracer onto
isopycnals leads to errors in the diagnosed diffusivities. It turns out that
the tracer flux method is the most robust method and therefore the method
of choice. In order to keep the errors as small as possible, longer time mean
values should be analysed."]},{"key":"dc:format","label":"Dc Format","values":["text"]},{"key":"dc:title","label":"Title","values":["Diagnostics of diapycnal diffusion in z-level ocean models"]}]}],"canonical_facts":{"dc:creator":["Getzlaff, Julia"],"dc:date":["2008-03"],"dc:date.issued":["2008-03"],"dc:description.abstract":["In general ocean circulation models (OGCMs) diapycnal diffusion arises not
only from the discretisation of the explicit diffusion, but also by numerically
induced diffusion, caused, e.g., by common discretisations of advective
transport.
In the present study, three different diagnostics to analyse the mean
diapycnal diffusivities of individual tracers (vertically and horizontally) are
introduced: (i) The divergence method based on the work of Ledwell
et al. (1998) infers the mean diapycnal diffusivity from the
advection-diffusion equation. (ii) The tracer flux method based on the work
of Griffies et al. (2000), that determines the diapycnal flux crossing an
isopycnal layer, is modified for the analysis of mean diapycnal diffusivities
of a passive tracer. (iii) The variance method based on the work of
Morales Maqueda and Holloway (2006) is a more general approach
as the diapycnal diffusion is analysed by the variance decay of the total
tracer concentration.
These methods can be used for the analysis of the diffusivity of passive
tracer independent of the model set-up, e.g. the advection scheme used, but
support only information about mean diapycnal diffusivity of that tracer
field rather than for each individual layer. The applicability of these
methods is tested in a set of 1- and 2-dimensional case studies. The effect
of vertical advection and of diverging and converging isopycnals is shown
separately. In all three methods used, the transformation of the tracer onto
isopycnals leads to errors in the diagnosed diffusivities. It turns out that
the tracer flux method is the most robust method and therefore the method
of choice. In order to keep the errors as small as possible, longer time mean
values should be analysed."],"dc:format":["text"],"dc:identifier.uri":["https://eprints.soton.ac.uk/63136/1/Getzlaff_2008_PhD.pdf"],"dc:publisher.department":["Ocean and Earth Science (pre 2011 reorg)","School of Ocean and Earth Science"],"dc:publisher.institution":["University of Southampton"],"dc:relation.isreferencedby":["https://eprints.soton.ac.uk/63136/"],"dc:title":["Diagnostics of diapycnal diffusion in z-level ocean models"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["doctoral"],"dc:type.qualificationname":["Ph.D."]},"updated_at":"2026-07-24T04:35:54Z"}