Global Ocean Wind‐Wave Model Hindcasts Forced by Different Reanalyzes: A Comparative Assessment

Four global wind wave hindcasts based on the third-generation spectral wave model WAVEWATCH III forced by ERA5, ERA-Interim, National Centers of Environmental Prediction and Climate Forecast System Reanalysis (CFSR) and MERRA2 reanalyzes for 1980-2019 are presented. Absolute magnitudes of both 10-m wind speeds and significant wave heights are the largest in the CFSR and CFSR-based hindcast respectively, particularly in the extratropical regions. The differences in annual extremes between CFSR and ERA5 (and corresponding hindcasts) amount to 2.4 ms(-1) for wind speeds and 1.2 m for wave heights. CFSR and CFSR-based hindcast also stand out with respect to remaining datasets, showing mostly negative trends in both mean and extreme characteristics. ERA5-, ERA-Interim-, and MERRA2-based hindcasts show annual positive trends in wave heights in 1980-2019, in particular in the Southern Ocean (up to 0.15 m decade(-1) for extreme wave heights in MERRA2-based hindcast) as well as in the central Pacific, equatorial and tropical Atlantic, and Indian Oceans. All four hindcasts agree on the positive linear trends in the North Atlantic midlatitudes and subtropics, western South Atlantic midlatitudes and the tropical South Pacific, and the negative trends in the eastern North Pacific midlatitudes. Areas with significant linear trends in wave heights generally coincide with those for wind speeds, however, they have larger spatial coverage. The interannual variability in significant wave heights is the most consistent across different hindcasts in the eastern midlatitudes of both hemispheres. The performed hindcasts provide a useful background for studies on both present and future wave climates.