Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern

<p>Extratropical cyclones are known to generate extreme significant wave height (swh) values at the ocean surface in the western South Atlantic (wSA), which are highly influenced by intraseasonal scales. This work aims to investigate the importance of intraseasonal timescales (30–180 d) in the...

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Autores principales:	D. K. Sasaki, C. B. Gramcianinov, B. Castro, M. Dottori
Formato:	article
Lenguaje:	EN
Publicado:	Copernicus Publications 2021
Materias:	Meteorology. Climatology QC851-999
Acceso en línea:	https://doaj.org/article/aa497b2c314f44df8f0d7c40189b4b1a
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spelling	oai:doaj.org-article:aa497b2c314f44df8f0d7c40189b4b1a2021-12-02T14:13:14ZIntraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern10.5194/wcd-2-1149-20212698-4016https://doaj.org/article/aa497b2c314f44df8f0d7c40189b4b1a2021-12-01T00:00:00Zhttps://wcd.copernicus.org/articles/2/1149/2021/wcd-2-1149-2021.pdfhttps://doaj.org/toc/2698-4016<p>Extratropical cyclones are known to generate extreme significant wave height (swh) values at the ocean surface in the western South Atlantic (wSA), which are highly influenced by intraseasonal scales. This work aims to investigate the importance of intraseasonal timescales (30–180 d) in the regional climatology of waves and its atmospheric forcing. The variability is explained by analyzing the storm track modulation due to westerly winds. These winds present timescales and spatial patterns compatible with the intraseasonal component of the Pacific South American (PSA) patterns. The analyses are made using ECMWF’s ERA5 from 1979 to 2019 and a database of extratropical cyclones based on the same reanalysis. Empirical orthogonal function (EOF) analyses of the 10 m zonal wind and swh are used to assess the regime of westerlies and waves in the wSA. The EOF1 of the 10 m zonal wind (<span class="inline-formula"><i>u</i><sub>10</sub></span>) presented a core centered at 45<span class="inline-formula"><sup>∘</sup></span> W and 40<span class="inline-formula"><sup>∘</sup></span> S, while the EOF2 is represented by two cores organized into a seesaw pattern with a center between 30–40<span class="inline-formula"><sup>∘</sup></span> S and another to the south of 40<span class="inline-formula"><sup>∘</sup></span> S. Composites of cyclone genesis and track densities as well as swh fields were calculated based on the phases of both EOFs. In short, EOF phases presenting cores with a positive (negative) <span class="inline-formula"><i>u</i><sub>10</sub></span> anomaly provide a favorable (unfavorable) environment for cyclone genesis and track densities and, therefore, positive (negative) swh anomalies. The modulation of the cyclone tracks is significant for extreme values of the swh. The spatial patterns of the EOFs of <span class="inline-formula"><i>u</i><sub>10</sub></span> are physically and statistically consistent with 200 and 850 hPa geopotential height signals from the Pacific, indicating the importance of the remote influence of the PSA patterns over the wSA.</p>D. K. SasakiC. B. GramcianinovB. CastroM. DottoriCopernicus PublicationsarticleMeteorology. ClimatologyQC851-999ENWeather and Climate Dynamics, Vol 2, Pp 1149-1166 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Meteorology. Climatology QC851-999
spellingShingle	Meteorology. Climatology QC851-999 D. K. Sasaki C. B. Gramcianinov B. Castro M. Dottori Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern
description	<p>Extratropical cyclones are known to generate extreme significant wave height (swh) values at the ocean surface in the western South Atlantic (wSA), which are highly influenced by intraseasonal scales. This work aims to investigate the importance of intraseasonal timescales (30–180 d) in the regional climatology of waves and its atmospheric forcing. The variability is explained by analyzing the storm track modulation due to westerly winds. These winds present timescales and spatial patterns compatible with the intraseasonal component of the Pacific South American (PSA) patterns. The analyses are made using ECMWF’s ERA5 from 1979 to 2019 and a database of extratropical cyclones based on the same reanalysis. Empirical orthogonal function (EOF) analyses of the 10 m zonal wind and swh are used to assess the regime of westerlies and waves in the wSA. The EOF1 of the 10 m zonal wind (<span class="inline-formula"><i>u</i><sub>10</sub></span>) presented a core centered at 45<span class="inline-formula"><sup>∘</sup></span> W and 40<span class="inline-formula"><sup>∘</sup></span> S, while the EOF2 is represented by two cores organized into a seesaw pattern with a center between 30–40<span class="inline-formula"><sup>∘</sup></span> S and another to the south of 40<span class="inline-formula"><sup>∘</sup></span> S. Composites of cyclone genesis and track densities as well as swh fields were calculated based on the phases of both EOFs. In short, EOF phases presenting cores with a positive (negative) <span class="inline-formula"><i>u</i><sub>10</sub></span> anomaly provide a favorable (unfavorable) environment for cyclone genesis and track densities and, therefore, positive (negative) swh anomalies. The modulation of the cyclone tracks is significant for extreme values of the swh. The spatial patterns of the EOFs of <span class="inline-formula"><i>u</i><sub>10</sub></span> are physically and statistically consistent with 200 and 850 hPa geopotential height signals from the Pacific, indicating the importance of the remote influence of the PSA patterns over the wSA.</p>
format	article
author	D. K. Sasaki C. B. Gramcianinov B. Castro M. Dottori
author_facet	D. K. Sasaki C. B. Gramcianinov B. Castro M. Dottori
author_sort	D. K. Sasaki
title	Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern
title_short	Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern
title_full	Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern
title_fullStr	Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern
title_full_unstemmed	Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern
title_sort	intraseasonal variability of ocean surface wind waves in the western south atlantic: the role of cyclones and the pacific south american pattern
publisher	Copernicus Publications
publishDate	2021
url	https://doaj.org/article/aa497b2c314f44df8f0d7c40189b4b1a
work_keys_str_mv	AT dksasaki intraseasonalvariabilityofoceansurfacewindwavesinthewesternsouthatlantictheroleofcyclonesandthepacificsouthamericanpattern AT cbgramcianinov intraseasonalvariabilityofoceansurfacewindwavesinthewesternsouthatlantictheroleofcyclonesandthepacificsouthamericanpattern AT bcastro intraseasonalvariabilityofoceansurfacewindwavesinthewesternsouthatlantictheroleofcyclonesandthepacificsouthamericanpattern AT mdottori intraseasonalvariabilityofoceansurfacewindwavesinthewesternsouthatlantictheroleofcyclonesandthepacificsouthamericanpattern
_version_	1718391743340085248

Intraseasonal variability of ocean surface wind waves in the western South Atlantic: the role of cyclones and the Pacific South American pattern

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