Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations
<p>Recently, <span class="cit" id="xref_text.1"><a href="#bib1.bibx31">Jánosi et al.</a> (<a href="#bib1.bibx31">2019</a>)</span> introduced the concept of a “vortex proxy” based on an observation of strong correlatio...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2022-09-01
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| Series: | Ocean Science |
| Online Access: | https://os.copernicus.org/articles/18/1361/2022/os-18-1361-2022.pdf |
| _version_ | 1798033378241413120 |
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| author | I. M. Jánosi I. M. Jánosi H. Kantz J. A. C. Gallas J. A. C. Gallas M. Vincze M. Vincze |
| author_facet | I. M. Jánosi I. M. Jánosi H. Kantz J. A. C. Gallas J. A. C. Gallas M. Vincze M. Vincze |
| author_sort | I. M. Jánosi |
| collection | DOAJ |
| description | <p>Recently, <span class="cit" id="xref_text.1"><a href="#bib1.bibx31">Jánosi et al.</a> (<a href="#bib1.bibx31">2019</a>)</span> introduced the concept of a “vortex proxy” based on an observation of strong correlations between integrated kinetic energy and integrated enstrophy over a large enough surface area. When mesoscale vortices are assumed to exhibit a Gaussian shape, the two spatial integrals have particularly simple functional forms, and a ratio of them defines an effective radius of a “proxy vortex”. In the original work, the idea was tested over a restricted area in the Californian Current System. Here we extend the analysis to global scale by means of 25 years of AVISO altimetry data covering the (ice-free) global ocean. The results are compared with a global vortex database containing over 64 million mesoscale eddies. We demonstrate that the proxy vortex representation of surface flow fields also works globally and provides a quick and reliable way to obtain coarse-grained vortex statistics. Estimated mean eddy sizes (effective radii) are extracted in very good agreement with the data from the vortex census. Recorded eddy amplitudes are directly used to infer the kinetic energy transported by the mesoscale vortices. The ratio of total and eddy kinetic energies is somewhat higher than found in previous studies. The characteristic westward drift velocities are evaluated by a time-lagged cross-correlation analysis of the kinetic energy fields. While zonal mean drift speeds are in good agreement with vortex trajectory evaluation in the latitude bands 30–5<span class="inline-formula"><sup>∘</sup></span> S and 5–30<span class="inline-formula"><sup>∘</sup></span> N, discrepancies are exhibited mostly at higher latitudes on both hemispheres. A plausible reason for somewhat different drift velocities obtained by eddy tracking and cross-correlation analysis is the fact that the drift of mesoscale eddies is only one component of the surface flow fields. Rossby wave
activities, coherent currents, and other propagating features on the ocean surface apparently contribute to the zonal transport of
kinetic energy.</p> |
| first_indexed | 2024-04-11T20:29:27Z |
| format | Article |
| id | doaj.art-8e2bd70bc63e434f9dedf599c21f7cfc |
| institution | Directory Open Access Journal |
| issn | 1812-0784 1812-0792 |
| language | English |
| last_indexed | 2024-04-11T20:29:27Z |
| publishDate | 2022-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Ocean Science |
| spelling | doaj.art-8e2bd70bc63e434f9dedf599c21f7cfc2022-12-22T04:04:33ZengCopernicus PublicationsOcean Science1812-07841812-07922022-09-01181361137510.5194/os-18-1361-2022Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlationsI. M. Jánosi0I. M. Jánosi1H. Kantz2J. A. C. Gallas3J. A. C. Gallas4M. Vincze5M. Vincze6Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, GermanyUniversity of Public Service, Faculty of Water Sciences, Department of Water and Environmental Policy,Ludovika tér 2, 1083 Budapest, HungaryMax Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, GermanyMax Planck Institute for the Physics of Complex Systems, Nöthnitzer Str. 38, 01187 Dresden, GermanyInstituto de Altos Estudos da Paraíba, Rua Silvino Lopes 419-2502, 58039-190 João Pessoa, Brazilvon Kármán Laboratory for Environmental Flows, Eötvös Loránd University, Pázmány Péter s. 1/A, 1117 Budapest, HungaryMTA-ELTE Theoretical Physics Research Group, Pázmány Péter s. 1/A, 1117 Budapest, Hungary<p>Recently, <span class="cit" id="xref_text.1"><a href="#bib1.bibx31">Jánosi et al.</a> (<a href="#bib1.bibx31">2019</a>)</span> introduced the concept of a “vortex proxy” based on an observation of strong correlations between integrated kinetic energy and integrated enstrophy over a large enough surface area. When mesoscale vortices are assumed to exhibit a Gaussian shape, the two spatial integrals have particularly simple functional forms, and a ratio of them defines an effective radius of a “proxy vortex”. In the original work, the idea was tested over a restricted area in the Californian Current System. Here we extend the analysis to global scale by means of 25 years of AVISO altimetry data covering the (ice-free) global ocean. The results are compared with a global vortex database containing over 64 million mesoscale eddies. We demonstrate that the proxy vortex representation of surface flow fields also works globally and provides a quick and reliable way to obtain coarse-grained vortex statistics. Estimated mean eddy sizes (effective radii) are extracted in very good agreement with the data from the vortex census. Recorded eddy amplitudes are directly used to infer the kinetic energy transported by the mesoscale vortices. The ratio of total and eddy kinetic energies is somewhat higher than found in previous studies. The characteristic westward drift velocities are evaluated by a time-lagged cross-correlation analysis of the kinetic energy fields. While zonal mean drift speeds are in good agreement with vortex trajectory evaluation in the latitude bands 30–5<span class="inline-formula"><sup>∘</sup></span> S and 5–30<span class="inline-formula"><sup>∘</sup></span> N, discrepancies are exhibited mostly at higher latitudes on both hemispheres. A plausible reason for somewhat different drift velocities obtained by eddy tracking and cross-correlation analysis is the fact that the drift of mesoscale eddies is only one component of the surface flow fields. Rossby wave activities, coherent currents, and other propagating features on the ocean surface apparently contribute to the zonal transport of kinetic energy.</p>https://os.copernicus.org/articles/18/1361/2022/os-18-1361-2022.pdf |
| spellingShingle | I. M. Jánosi I. M. Jánosi H. Kantz J. A. C. Gallas J. A. C. Gallas M. Vincze M. Vincze Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations Ocean Science |
| title | Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations |
| title_full | Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations |
| title_fullStr | Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations |
| title_full_unstemmed | Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations |
| title_short | Global coarse-grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations |
| title_sort | global coarse grained mesoscale eddy statistics based on integrated kinetic energy and enstrophy correlations |
| url | https://os.copernicus.org/articles/18/1361/2022/os-18-1361-2022.pdf |
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