A global wave hindcast over the period 1958-1997: Validation and climate assessment

This study describes the first 40 year global wave simulation derived from the National Centers for Environmental Prediction/National Center for Atmospheric Research Reanalysis (NRA) surface wind fields. The NRA 10 m wind fields were input into a deep water version of a proven spectral ocean wave model adapted onto a global grid of spacing 1.25 degrees in latitude by 2.5 degrees in longitude. In situ and satellite wind and wave data sets were used to evaluate the hindcast skill. The validation showed excellent agreement not only in terms of bias and scatter but over the entire frequency distribution out to 99th percentiles of both winds and waves. A global trend analysis showed statistically significant areas of both increasing and decreasing winds and waves. The increasing trend in the northeast Atlantic and decreasing trend in the central North Atlantic are particularly well defined and consistent with changes reported in previous studies, which were linked to changes in the North Atlantic Oscillation. The trend analysis highlighted the difficulty in separating creeping inhomogeneities in the NRA winds from real climate change, illustrating the need to use homogeneous in situ measured data to confirm trends derived from model output. The trends derived from the hindcast seem reasonable in the Northern Hemisphere and may provide a good upper bound to true trends in the wind and wave climate.