WAVERYS : A CMEMS global wave reanalysis during the altimetry period

<p><strong>As part of the Copernicus Marine Core service, WAVERYS is the multi-year wave reanalysis that aims to provide global wave data with a grid resolution of 1/5°. The wave reanalysis covers the period of 1993-2018 and provides 3-hourly classical integrated wave parameters describing the sea state at the ocean surface. The wave model used is the V4 version of the model MFWAM, which is driven by atmospheric forcing (winds and ice fraction) from ECMWF ERA5 reanalysis. This latter has showed a significant improvement regarding to the previous reanalysis ERA-Interim. WAVERYS includes the assimilation of altimeters wave data available during the period starting from Topex-Poseidon until Sentinel-3A missions. Directional wave spectra from Synthetic Aperture Radar (SAR) of Sentinel-1A and 1B missions are also assimilated. This is the first time that such directional wave spectra are used in a global wave reanalysis.</strong></p><p><strong>Further, WAVERYS uses a 3 hour surface current forcing provided by ocean reanalysis GLORYS12 implemented by Mercator-Ocean in the frame of Copernicus Marine Service with a grid resolution of 1/12°. The wave reanalysis is high skilled for ocean regions with dominant wave-currents interactions. Preliminary validation tests have shown improvement by 15% in scatter index for large scale high currents areas. This paper will give detailed characteristics of the wave system and will insist on the benefits of taking into account ocean currents and a physics calibrated for realistic swell propagation.</strong></p><p> </p>

Quality Assessment and Practical Interpretation of the Wave Parameters Estimated by HF Radars in NW Spain

High-frequency (HF) radars are efficient tools for measuring vast areas and gathering ocean parameters in real-time. However, the accuracy of their wave estimates is under analysis. This paper presents a new methodology for analyzing and validating the wave data estimated by two CODAR SeaSonde radars located on the Galician coast (NW Spain). Approximately one and a half years of wave data (January, 2014–April, 2015) were obtained for ten range cells employing two different sampling times used by the radar software. The resulting data were screened by an updated method, and their abundance and quality were described for each radar range cell and different wave regime; the latter were defined using the spectral significant wave height (Hm0) and mean wave direction (Dm) estimated by two buoys and three SIMAR points (SImulación MARina in Spanish, from the wave reanalysis model by Puertos del Estado (PdE)). The correlation between the results and the particularities of the different sea states (broadband or bimodal), the wind and the operation of the devices are discussed. Most HF radar wave parameters’ errors occur for waves from the NNE and higher than 6 m. The best agreement between the Vilán radar and the Vilano-Sisargas buoy wave data was obtained for the dominant wave regime (from the northwest) and the southwest wave regime. However, relevant contradictions regarding wave direction were detected. The possibilities of reducing the wave parameters’ processing time by one hour and increasing the numbers of range cells of the radars have been validated.

AUTOMATIC CALIBRATION OF A WAVE MODEL WITH AN EVOLUTIONARY BAYESIAN METHOD

Bayesian Inference has been widely applied with success in science and engineering. One of its main uses is the inference of model parameters in order to reconcile model outputs with evidence provided by measures. In this article we propose this application for coastal engineering problems. Specifically, it is proposed to infer the parameters of a numerical wave model used to downscale wave reanalysis data to a coastal site. The proposed method is applied to a case study on the Uruguayan Atlantic coast, where a few month wave measure data series is available and needs to be extended in order to be used on an engineering project. The wave model used is SWAN and the data in deep waters and the wind data were obtained from the ERA-Interim reanalysis. At first, the method was tested with one and two parameters, since in these cases it is possible to compare the obtained results with a plot of the target function. Finally it was used to calibrate four parameters of the wave model and assess the uncertainty introduced by the selection of a set of parameters.

On the feasibility of the use of wind SAR to downscale waves on shallow water

On the recent years wave reanalysis have become popular as a powerful source of information for wave climate research and engineering applications. These wave reanalysis provide continuous time-series of offshore wave parameters, nevertheless on coastal areas or shallow water waves are poorly described because spatial resolution is not detailed. By means of wave downscaling it is possible to increase spatial resolution in high temporal coverage simulations, using forcing from wind and offshore wave databases. Meanwhile the reanalysis wave databases are enough to describe the wave climate on the limit of simulations, wind reanalysis at an adequate spatial resolution to describe the wind structure near the coast are not frequently available. Remote Sensing Synthetic Aperture Radar (SAR) has the ability to detect sea surface signatures and estimate wind field at high resolution (up to 300 m) and high frequency. In this work a wave downscaling is done on the northern Adriatic sea, using an hybrid methodology and Global wave and wind reanalysis as forcing. The wave fields produced were compared to wave fields produced with SAR winds that represent the two dominant wind regimes in the area: the Bora (ENE direction) and Sirocco (SE direction). Results show a good correlation between the waves forced with reanalysis wind and SAR wind. In addition, a validation of reanalysis is shown. This research demonstrates how Earth Observation products, as SAR wind fields, can be successfully up-taken into oceanographic modeling, producing similar downscaled wave field when compared to waves forced with reanalysis wind.