Space-time structure of long ocean swell fields
The space-time structure of long-period ocean swell fields is investigated, with particular attention given to features in the direction orthogonal to the propagation direction. This study combines space-borne synthetic aperture radar (SAR) data with numerical model hindcasts and time series recorde...
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ftarchimer:oai:archimer.ifremer.fr:13647 2023-05-15T17:40:00+02:00 Space-time structure of long ocean swell fields Delpey, Matthias T. Ardhuin, Fabrice Collard, Fabrice Chapron, Bertrand 2010-12 application/pdf https://archimer.ifremer.fr/doc/00025/13647/10881.pdf https://doi.org/10.1029/2009JC005885 https://archimer.ifremer.fr/doc/00025/13647/ eng eng Amer Geophysical Union https://archimer.ifremer.fr/doc/00025/13647/10881.pdf doi:10.1029/2009JC005885 https://archimer.ifremer.fr/doc/00025/13647/ 2010 American Geophysical Union info:eu-repo/semantics/openAccess restricted use Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2010-12 , Vol. 115 , N. C12037 , P. 13 p. text Publication info:eu-repo/semantics/article 2010 ftarchimer https://doi.org/10.1029/2009JC005885 2021-09-23T20:19:06Z The space-time structure of long-period ocean swell fields is investigated, with particular attention given to features in the direction orthogonal to the propagation direction. This study combines space-borne synthetic aperture radar (SAR) data with numerical model hindcasts and time series recorded by in situ instruments. In each data set the swell field is defined by a common storm source. The correlation of swell height time series is very high along a single great circle path with a time shift given by the deep water dispersion relation of the dominant swells. This correlation is also high for locations situated on different great circles in entire ocean basins. Given the Earth radius R, we define the distance from the source R alpha and the transversal angle beta so that alpha and beta would be equal the colatitude and longitude for a storm centered on the North Pole. Outside of land influence, the swell height field at time t, H-ss(alpha, beta, t) is well approximated by a function H-ss,H-0(t - R alpha/C-g)/root(alpha sin(alpha)) times another function r(2) (beta), where C-g is a representative group speed. Here r(2) (beta) derived from SAR data is very broad, with a width at half the maximum that is larger than 70 degrees, and varies significantly from storm to storm. Land shadows introduce further modifications so that in general r(2) is a function of beta and alpha. This separation of variables and the smoothness of the H-ss field, allows the estimation of the full field of H-ss from sparse measurements, such as wave mode SAR data, combined with one time series, such as that provided by a single buoy. A first crude estimation of a synthetic H-ss field based on this principle already shows that swell hindcasts and forecasts can be improved by assimilating such synthetic observations. Article in Journal/Newspaper North Pole Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) North Pole Journal of Geophysical Research 115 C12 |
institution |
Open Polar |
collection |
Archimer (Archive Institutionnelle de l'Ifremer - Institut français de recherche pour l'exploitation de la mer) |
op_collection_id |
ftarchimer |
language |
English |
description |
The space-time structure of long-period ocean swell fields is investigated, with particular attention given to features in the direction orthogonal to the propagation direction. This study combines space-borne synthetic aperture radar (SAR) data with numerical model hindcasts and time series recorded by in situ instruments. In each data set the swell field is defined by a common storm source. The correlation of swell height time series is very high along a single great circle path with a time shift given by the deep water dispersion relation of the dominant swells. This correlation is also high for locations situated on different great circles in entire ocean basins. Given the Earth radius R, we define the distance from the source R alpha and the transversal angle beta so that alpha and beta would be equal the colatitude and longitude for a storm centered on the North Pole. Outside of land influence, the swell height field at time t, H-ss(alpha, beta, t) is well approximated by a function H-ss,H-0(t - R alpha/C-g)/root(alpha sin(alpha)) times another function r(2) (beta), where C-g is a representative group speed. Here r(2) (beta) derived from SAR data is very broad, with a width at half the maximum that is larger than 70 degrees, and varies significantly from storm to storm. Land shadows introduce further modifications so that in general r(2) is a function of beta and alpha. This separation of variables and the smoothness of the H-ss field, allows the estimation of the full field of H-ss from sparse measurements, such as wave mode SAR data, combined with one time series, such as that provided by a single buoy. A first crude estimation of a synthetic H-ss field based on this principle already shows that swell hindcasts and forecasts can be improved by assimilating such synthetic observations. |
format |
Article in Journal/Newspaper |
author |
Delpey, Matthias T. Ardhuin, Fabrice Collard, Fabrice Chapron, Bertrand |
spellingShingle |
Delpey, Matthias T. Ardhuin, Fabrice Collard, Fabrice Chapron, Bertrand Space-time structure of long ocean swell fields |
author_facet |
Delpey, Matthias T. Ardhuin, Fabrice Collard, Fabrice Chapron, Bertrand |
author_sort |
Delpey, Matthias T. |
title |
Space-time structure of long ocean swell fields |
title_short |
Space-time structure of long ocean swell fields |
title_full |
Space-time structure of long ocean swell fields |
title_fullStr |
Space-time structure of long ocean swell fields |
title_full_unstemmed |
Space-time structure of long ocean swell fields |
title_sort |
space-time structure of long ocean swell fields |
publisher |
Amer Geophysical Union |
publishDate |
2010 |
url |
https://archimer.ifremer.fr/doc/00025/13647/10881.pdf https://doi.org/10.1029/2009JC005885 https://archimer.ifremer.fr/doc/00025/13647/ |
geographic |
North Pole |
geographic_facet |
North Pole |
genre |
North Pole |
genre_facet |
North Pole |
op_source |
Journal Of Geophysical Research-oceans (0148-0227) (Amer Geophysical Union), 2010-12 , Vol. 115 , N. C12037 , P. 13 p. |
op_relation |
https://archimer.ifremer.fr/doc/00025/13647/10881.pdf doi:10.1029/2009JC005885 https://archimer.ifremer.fr/doc/00025/13647/ |
op_rights |
2010 American Geophysical Union info:eu-repo/semantics/openAccess restricted use |
op_doi |
https://doi.org/10.1029/2009JC005885 |
container_title |
Journal of Geophysical Research |
container_volume |
115 |
container_issue |
C12 |
_version_ |
1766140770599829504 |