Surface drifters in the German Bight: model validation considering windage and Stokes drift
Six surface drifters (drogued at about 1 m depth) deployed in the inner German Bight (North Sea) were tracked for between 9 and 54 days. Corresponding simulations were conducted offline based on surface currents from two independent models (BSHcmod and TRIM). Inclusion of a direct wind drag (0.6...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-09-01
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| Series: | Ocean Science |
| Online Access: | https://www.ocean-sci.net/13/799/2017/os-13-799-2017.pdf |
| _version_ | 1818481780735344640 |
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| author | U. Callies N. Groll J. Horstmann H. Kapitza H. Klein S. Maßmann F. Schwichtenberg |
| author_facet | U. Callies N. Groll J. Horstmann H. Kapitza H. Klein S. Maßmann F. Schwichtenberg |
| author_sort | U. Callies |
| collection | DOAJ |
| description | Six surface drifters (drogued at about 1 m depth) deployed
in the inner German Bight (North Sea) were tracked for between 9
and 54 days. Corresponding simulations were conducted
offline based on surface currents from two independent models
(BSHcmod and TRIM). Inclusion of a direct wind drag (0.6 %
of 10 m wind) was needed for successful simulations based on
BSHcmod currents archived for a 5 m depth surface
layer. Adding 50 % of surface Stokes drift simulated with
a third-generation wave model (WAM) was tested as an alternative
approach. Results resembled each other during most of the
time. Successful simulations based on TRIM surface currents
(1 m depth) suggest that both approaches were mainly needed
to compensate insufficient vertical resolution of hydrodynamic
currents.
<br><br>
The study suggests that the main sources of simulation errors were
inaccurate Eulerian currents and lacking representation of sub-grid-scale
processes. Substantial model errors often occurred under low
wind conditions. A lower limit of predictability (about
3–5 km day<sup>−1</sup>) was estimated from two drifters that were
initially spaced 20 km apart but converged quickly and
diverged again after having stayed at a distance of 2 km or
less for about 10 days. In most cases, errors in simulated
25 h drifter displacements were of similar order of
magnitude. |
| first_indexed | 2024-12-10T11:39:37Z |
| format | Article |
| id | doaj.art-9bff733aaf4a4bab977dabaf92ea8c7f |
| institution | Directory Open Access Journal |
| issn | 1812-0784 1812-0792 |
| language | English |
| last_indexed | 2024-12-10T11:39:37Z |
| publishDate | 2017-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Ocean Science |
| spelling | doaj.art-9bff733aaf4a4bab977dabaf92ea8c7f2022-12-22T01:50:18ZengCopernicus PublicationsOcean Science1812-07841812-07922017-09-011379982710.5194/os-13-799-2017Surface drifters in the German Bight: model validation considering windage and Stokes driftU. Callies0N. Groll1J. Horstmann2H. Kapitza3H. Klein4S. Maßmann5F. Schwichtenberg6Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, GermanyInstitute of Coastal Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, GermanyInstitute of Coastal Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, GermanyInstitute of Coastal Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, GermanyFederal Maritime and Hydrographic Agency (BSH), Bernhard-Nocht-Str. 78, 20359 Hamburg, GermanyFederal Maritime and Hydrographic Agency (BSH), Bernhard-Nocht-Str. 78, 20359 Hamburg, GermanyFederal Maritime and Hydrographic Agency (BSH), Bernhard-Nocht-Str. 78, 20359 Hamburg, GermanySix surface drifters (drogued at about 1 m depth) deployed in the inner German Bight (North Sea) were tracked for between 9 and 54 days. Corresponding simulations were conducted offline based on surface currents from two independent models (BSHcmod and TRIM). Inclusion of a direct wind drag (0.6 % of 10 m wind) was needed for successful simulations based on BSHcmod currents archived for a 5 m depth surface layer. Adding 50 % of surface Stokes drift simulated with a third-generation wave model (WAM) was tested as an alternative approach. Results resembled each other during most of the time. Successful simulations based on TRIM surface currents (1 m depth) suggest that both approaches were mainly needed to compensate insufficient vertical resolution of hydrodynamic currents. <br><br> The study suggests that the main sources of simulation errors were inaccurate Eulerian currents and lacking representation of sub-grid-scale processes. Substantial model errors often occurred under low wind conditions. A lower limit of predictability (about 3–5 km day<sup>−1</sup>) was estimated from two drifters that were initially spaced 20 km apart but converged quickly and diverged again after having stayed at a distance of 2 km or less for about 10 days. In most cases, errors in simulated 25 h drifter displacements were of similar order of magnitude.https://www.ocean-sci.net/13/799/2017/os-13-799-2017.pdf |
| spellingShingle | U. Callies N. Groll J. Horstmann H. Kapitza H. Klein S. Maßmann F. Schwichtenberg Surface drifters in the German Bight: model validation considering windage and Stokes drift Ocean Science |
| title | Surface drifters in the German Bight: model validation considering windage and Stokes drift |
| title_full | Surface drifters in the German Bight: model validation considering windage and Stokes drift |
| title_fullStr | Surface drifters in the German Bight: model validation considering windage and Stokes drift |
| title_full_unstemmed | Surface drifters in the German Bight: model validation considering windage and Stokes drift |
| title_short | Surface drifters in the German Bight: model validation considering windage and Stokes drift |
| title_sort | surface drifters in the german bight model validation considering windage and stokes drift |
| url | https://www.ocean-sci.net/13/799/2017/os-13-799-2017.pdf |
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