Preprints
https://doi.org/10.5194/wcd-2021-29
https://doi.org/10.5194/wcd-2021-29

  26 May 2021

26 May 2021

Review status: this preprint is currently under review for the journal WCD.

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

Dalton Kei Sasaki1, Carolina Barnez Gramcianinov2, Belmiro Castro1,, and Marcelo Dottori1 Dalton Kei Sasaki et al.
  • 1Departamento de Oceanografia Física, Química e Geológica, Instituto Oceanográfico, Universidade de São Paulo, Praça do Oceanográfico, 191, Cidade Universitária, São Paulo, SP, Brazil
  • 2Departamento de Ciências Atmosféricas, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, Cidade Universitária, São Paulo, SP, Brazil
  • deceased, 11 October 2020

Abstract. Extratropical cyclones are known to generate extreme significant wave height (swh) values in the western South Atlantic (wSA), which are highly influenced by intraseasonal scales. This work aims to investigate the importance of intraseasonal time scales (30–180 days) in the regional wave climate and its atmospheric forcing. The variability is explained by analyzing the storm track modulation due to westerlies winds. These winds present time-scales and spatial patterns compatible with the intraseasonal component of the Pacific South–American (PSA) patterns. The analysis 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) analysis of the 10 m zonal wind and swh are used to assess the westerlies and waves regime in the wSA. The EOF1 of u10 presented a core centred at 45° W and 40° S, while the EOF2 is represented by two cores organized into a see-saw pattern with a center between 30° S–40° S and another to the south of 40° S. Composites of cyclone genesis and track densities, and swh fields were calculated based on the phases of both EOFs. In short, EOF phases presenting cores with a positive (negative) u10 anomaly provides a favorable (unfavorable) environment for cyclone genesis and track densities and, therefore, positive (negative) swh anomalies. The modulation of the cyclones track are significant for extreme values of the swh. The spatial patterns of the EOFs of u10 are physically and statistically consistent with 200 hPa and 850 hPa geopotential height signals from the Pacific, indicating the importance of the remote influence of the PSA patterns over the wSA.

Dalton Kei Sasaki et al.

Status: open (until 07 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on wcd-2021-29', Anonymous Referee #1, 10 Jun 2021 reply
  • RC2: 'Comment on wcd-2021-29', Anonymous Referee #2, 23 Jun 2021 reply

Dalton Kei Sasaki et al.

Dalton Kei Sasaki et al.

Viewed

Total article views: 201 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
151 43 7 201 3 3
  • HTML: 151
  • PDF: 43
  • XML: 7
  • Total: 201
  • BibTeX: 3
  • EndNote: 3
Views and downloads (calculated since 26 May 2021)
Cumulative views and downloads (calculated since 26 May 2021)

Viewed (geographical distribution)

Total article views: 187 (including HTML, PDF, and XML) Thereof 187 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 24 Jun 2021
Download
Short summary
Extratropical cyclones are relevant in the western South Atlantic and influence the climate of ocean surface wave. Propagating atmospheric features from the South Pacific to the South Atlantic are relevant to the cyclones and waves and its intensified westerlies lead to more cyclones and, as a consequence, to higher wave heights. The opposite happens with its weakening. These features are similar to the so-called Pacific South-American patterns and present periods between 30–180 days.