Strong winds in a coupled wave-atmosphere model during a North Atlantic storm event: evaluation against observations

Strong winds may be biased in atmospheric models. Here the ECMWF coupled wave-atmosphere model is used (1) to evaluate strong winds against observations, (2) to test how alternative wind stress parameterizations could lead to a more accurate model. For the period of storms Kaat and Lilli (23 to 27 January 2014), we compared simulated winds with in-situ – moored buoys and platforms - and satellite observations available from the North Atlantic. Five wind stress parameterizations were evaluated. The first result is that moderate simulated winds (5-20 m s-1) match with all observations. However, for strong winds (above 20 m s-1), mean differences appear, as much as -7 m s-1 at 30 m s-1. Significant differences also exist between observations, with buoys and ASCAT-KNMI generally showing lower wind speeds than the platforms and other remote sensing data used in this study (AMSR2, ASCAT-RSS, WindSat, SMOS and JASON-2). It is difficult to conclude which dataset should be used as a reference. Even so, buoy and ASCAT-KNMI winds are likely to underestimate the real wind speed. The second result is that common wave-age dependent parameterizations produce unrealistic drags and are not appropriate for coupling, whereas a newly empirically-adjusted Charnock parameterization leads to higher winds compared to the default ECMWF parameterization. This proposed new parameterization may lead to more accurate results in an operational context.

Keyword(s)

air-sea exchanges, northeast Atlantic, winds, IFS, sea state, roughness length, drag coefficient, wind stress

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Pineau-Guillou Lucia, Ardhuin Fabrice, Bouin Marie-Noelle, Redelsperger Jean-Luc, Chapron Bertrand, Bidlot Jean-Raymond, Quilfen Yves (2018). Strong winds in a coupled wave-atmosphere model during a North Atlantic storm event: evaluation against observations. Quarterly Journal Of The Royal Meteorological Society. 144 (711 Part.B). 317-332. https://doi.org/10.1002/qj.3205, https://archimer.ifremer.fr/doc/00410/52118/

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