Numerical simulation of wind waves on the Río de la Plata: evaluation of four global atmospheric databases

The performance of NCEP/NCAR I, NCEP/DOE II, JRA-25 and ERA-Interim global databases, implemented as atmospheric forcings of the SWAN model in the Río de la Plata region, was quantitatively tested by calculating the bias, the mean square root error, the determination coefficient and the slope of the line fitted between observed and simulated wave parameters (significant wave height, mean period and direction). Even though statistical estimators showed no evident differences for wave periods and directions some noticeable differences were observed for simulated significant wave heights depending on the forcing used. The lowest bias (0.22 m) was obtained when the SWAN model was forced by ERA-Interim. With regard to the mean square root errors, the lowest values were obtained when NCEP/NCAR I (0.16 m) and NCEP/DOE II (0.19 m) were used as forcing. In addition, the best slope for simulated heights (0.79) was obtained using NCEP/DOE II. Computed determination coefficients for heights, periods and directions were very similar (0.89-0.93) for all the simulations carried out in this study. Energetic and severe wave events were given special consideration. The most energetic wave episode recorded in the Río de la Plata mouth (24 August, 2005) was analyzed and discussed in particular. It was concluded that during energetic atmospheric conditions the best agreement is achieved by implementing NCEP/DOE II as forcing. In the light of these results it is concluded that NCEP/DOE II is the most suitable atmospheric forcing to simulate wave heights with the SWAN model in the Río de la Plata region.Na região do Rio de la Plata, o desempenho das reanálises globais do NCEP/NCAR I, NCEP/DOE II, JRA-25 e ERAInterim implementadas como forçantes atmosféricas do modelo SWAN foram quantitativamente acessados através do viés, erro quadrático médio, coeficiente de determinação e inclinação da reta. Estes índices foram obtidos dos parâmetros de ondas observados e simulados (alturas significativas de ondas, período principal e direção). Embora as estimativas estatísticas não mostrem diferenças evidentes para períodos e direções, algumas diferenças notáveis foram obtidas para altura de ondas simuladas, dependendo do vento utilizado. O menor viés para altura significativa (0.22 m) foi obtido quando o SWAM foi forçado com a ERAInterim, enquanto o NCEP/NCAR I (0.16 m) e NCEP/DOE II (0.19 m) forneceram menor erro quadrático médio. A melhor inclinação da reta entre simulação e observação de altura significativa (0.79) foi obtida usando NCEP/DOE II. No período de estudo, o maior episódio de onda registrado na boca do Río de la Plata foi analisado e discutido. Neste evento de condições atmosféricas energéticas o melhor ajuste foi alcançado utilizando os ventos do NCEP/DOE II como forçante. Conclui-se que a base de dados NCEP/DOE II é forçante atmosférica mais adequada para simular alturas significativas de ondas com o modelo SWAN na região estudada

Assessing accuracy in the estimation of spectral content in wave energy resource on the French Atlantic test site SEMREV

International audienceThis paper presents a detailed assessment of the spectral accuracy of state of the art numerical estimations of wave energy at the SEMREV French Atlantic test site, by comparison with in-situ measurements. Power density frequency spectra from HOMERE [Boudiere et al. (2013)], the most up-to-date highly refined hindcast dataset, are compared with several measurements from three wave buoys located either offshore or onsite. The spectral signature of the error exhibits a highly non-linear site dependent behavior. Examined in conjunction with usual comparisons of standard integral parameters, this provides meaningful insight into the epistemic uncertainties and errors in different part of the wave energy spectrum. Notably, a complementary analysis of the mean available energy as a function of frequency illustrates the varying degree of impact that inaccuracies in the estimation could have on production by WECs, which are often designed to harvest energy from specific frequency bandwidths. It notably also enlighten the frequency domains where the input forcing and the accounting or parameterization of processes may still lack accuracy