Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates
The present study reconciles theoretical differences between the Lagrangian diffusivity and effective diffusivity in a transformed spatial coordinate based on the contours of a quasi-conservative tracer. In the transformed coordinate, any adiabatic stirring effect, such as shear-induced dispersion,...
Published in: | Journal of Physical Oceanography |
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AMER METEOROLOGICAL SOC
2019
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ftchacadscgigcas:oai:ir.gig.ac.cn:344008/49935 2023-05-15T18:25:32+02:00 Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates Qian, Yu-Kun Peng, Shiqiu Liang, Chang-Xia 2019-06-01 http://ir.gig.ac.cn/handle/344008/49935 https://doi.org/10.1175/JPO-D-18-0251.1 英语 eng AMER METEOROLOGICAL SOC JOURNAL OF PHYSICAL OCEANOGRAPHY http://ir.gig.ac.cn/handle/344008/49935 doi:10.1175/JPO-D-18-0251.1 Oceanography SURFACE CIRCULATION STOCHASTIC-MODELS EDDY DIFFUSIVITY LATERAL DIFFUSIVITY SOUTHERN-OCEAN PART II TRANSPORT STATISTICS PACIFIC SEA 期刊论文 2019 ftchacadscgigcas https://doi.org/10.1175/JPO-D-18-0251.1 2020-12-22T07:22:31Z The present study reconciles theoretical differences between the Lagrangian diffusivity and effective diffusivity in a transformed spatial coordinate based on the contours of a quasi-conservative tracer. In the transformed coordinate, any adiabatic stirring effect, such as shear-induced dispersion, is naturally isolated from diabatic cross-contour motions. Therefore, Lagrangian particle motions in the transformed coordinate obey a transformed zeroth-order stochastic (i.e., random walk) model with the diffusivity replaced by the effective diffusivity. Such a stochastic model becomes the theoretical foundation on which both diffusivities are exactly unified. In the absence of small-scale diffusion, particles do not disperse at all in the transformed contour coordinate. Besides, the corresponding Lagrangian autocorrelation becomes a delta function and is thus free from pronounced overshoot and negative lobe at short time lags that may be induced by either Rossby waves or mesoscale eddies; that is, particles decorrelate immediately and Lagrangian diffusivity is already asymptotic nomatter how small the time lag is. The resulting instantaneous Lagrangian spreading rate is thus conceptually identical to the effective diffusivity that only measures the instantaneous irreversible mixing. In these regards, the present study provides a new look at particle dispersion in contour-based coordinates. Report Southern Ocean Guangzhou Institute of Geochemistry: GIG OpenIR (Chinese Academy of Sciences) Pacific Southern Ocean Journal of Physical Oceanography 49 6 1521 1539 |
institution |
Open Polar |
collection |
Guangzhou Institute of Geochemistry: GIG OpenIR (Chinese Academy of Sciences) |
op_collection_id |
ftchacadscgigcas |
language |
English |
topic |
Oceanography SURFACE CIRCULATION STOCHASTIC-MODELS EDDY DIFFUSIVITY LATERAL DIFFUSIVITY SOUTHERN-OCEAN PART II TRANSPORT STATISTICS PACIFIC SEA |
spellingShingle |
Oceanography SURFACE CIRCULATION STOCHASTIC-MODELS EDDY DIFFUSIVITY LATERAL DIFFUSIVITY SOUTHERN-OCEAN PART II TRANSPORT STATISTICS PACIFIC SEA Qian, Yu-Kun Peng, Shiqiu Liang, Chang-Xia Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates |
topic_facet |
Oceanography SURFACE CIRCULATION STOCHASTIC-MODELS EDDY DIFFUSIVITY LATERAL DIFFUSIVITY SOUTHERN-OCEAN PART II TRANSPORT STATISTICS PACIFIC SEA |
description |
The present study reconciles theoretical differences between the Lagrangian diffusivity and effective diffusivity in a transformed spatial coordinate based on the contours of a quasi-conservative tracer. In the transformed coordinate, any adiabatic stirring effect, such as shear-induced dispersion, is naturally isolated from diabatic cross-contour motions. Therefore, Lagrangian particle motions in the transformed coordinate obey a transformed zeroth-order stochastic (i.e., random walk) model with the diffusivity replaced by the effective diffusivity. Such a stochastic model becomes the theoretical foundation on which both diffusivities are exactly unified. In the absence of small-scale diffusion, particles do not disperse at all in the transformed contour coordinate. Besides, the corresponding Lagrangian autocorrelation becomes a delta function and is thus free from pronounced overshoot and negative lobe at short time lags that may be induced by either Rossby waves or mesoscale eddies; that is, particles decorrelate immediately and Lagrangian diffusivity is already asymptotic nomatter how small the time lag is. The resulting instantaneous Lagrangian spreading rate is thus conceptually identical to the effective diffusivity that only measures the instantaneous irreversible mixing. In these regards, the present study provides a new look at particle dispersion in contour-based coordinates. |
format |
Report |
author |
Qian, Yu-Kun Peng, Shiqiu Liang, Chang-Xia |
author_facet |
Qian, Yu-Kun Peng, Shiqiu Liang, Chang-Xia |
author_sort |
Qian, Yu-Kun |
title |
Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates |
title_short |
Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates |
title_full |
Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates |
title_fullStr |
Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates |
title_full_unstemmed |
Reconciling Lagrangian Diffusivity and Effective Diffusivity in Contour-Based Coordinates |
title_sort |
reconciling lagrangian diffusivity and effective diffusivity in contour-based coordinates |
publisher |
AMER METEOROLOGICAL SOC |
publishDate |
2019 |
url |
http://ir.gig.ac.cn/handle/344008/49935 https://doi.org/10.1175/JPO-D-18-0251.1 |
geographic |
Pacific Southern Ocean |
geographic_facet |
Pacific Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
JOURNAL OF PHYSICAL OCEANOGRAPHY http://ir.gig.ac.cn/handle/344008/49935 doi:10.1175/JPO-D-18-0251.1 |
op_doi |
https://doi.org/10.1175/JPO-D-18-0251.1 |
container_title |
Journal of Physical Oceanography |
container_volume |
49 |
container_issue |
6 |
container_start_page |
1521 |
op_container_end_page |
1539 |
_version_ |
1766207049524314112 |