Evaluation of the ERA5 Significant Wave Height against NDBC Buoy Data from 1979 to 2019

Significant wave height (SWH) is a vital parameter in marine science research and engineering application. The up-to-date reanalysis product ERA5 SWH brings new possibilities to the long-term analysis. However, a systematic assessment of ERA5 SWH on a large scale is still lacking. This paper presents an evaluation of ERA5 SWH against observations from 103 buoys in the North American Atlantic and Pacific sourced by the National Data Buoy Center over the period 1979 to 2019. Overall, the ERA5 SWH has a good agreement with the in-situ observations, with a bias of −0.058 m, root mean squared error of 0.325 m, correlation coefficient of 0.961 and scatter index of 18.54%. The accuracy of ERA5 SWH is satisfactory under the most typical sea states (0.5 m < SWH < 4 m). The monthly analysis shows the performance of ERA5 SWH in summer is the best. The water depth and offshore distance have also been identified to impact the reliability of ERA5 SWH. Although the statistics vary at different locations, the performances of ERA5 SWH at most stations are reasonable. In addition, an evident improvement in the validity over time is observed, which can be attributed to the assimilation of the altimeter wave height.