Oceanum Global ERA5 Wave Hindcast

February 2025

Dataset description

The Oceanum global wave hindcast provides a continuous multi-decadal record of wave conditions across all ocean basins (Figure 1). Wave fields are produced using the WAVEWATCH III (WW3) third-generation spectral wave model at 0.5-degree resolution, spanning from 1979 to present at 3-hourly temporal resolution.

Wind forcing and sea ice concentration are provided by ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts. The model includes sea ice effects through coupling with ice concentration data, with wave attenuation applied in ice-covered regions. Bathymetry is derived from GEBCO 2020.

The modelling setup employs the ST4 source term parameterisations with calibrated parameters for global wave climate representation. Spectra are discretised into 24 directional bins and 31 frequency bins, covering a frequency range from 0.037 to 0.65 Hz with 10% logarithmic increments.

The dataset provides 3-hourly estimates for key ocean wave parameters (Table 2) including spectral quantities integrated over the full spectrum and for spectral partitions. Partitions are defined from an 8-second split (sea/swell) and from the Watershed method, which identifies one wind-sea partition and up to four swell partitions. Frequency-direction wave spectra are available at 26,962 strategically selected sites worldwide (black dots in Figure 1).

The global hindcast is well suited for deep water wave climate analysis anywhere on the planet. A key application is providing directional spectral boundary conditions for downscaling regional and coastal wave models. The spectra output network is designed with variable density, ranging from 2 degrees in deep water to 0.5 degrees near coastlines, ensuring appropriate resolution for boundary forcing across diverse modelling applications. The spectral data is optimised for very fast access (seconds to a few minutes), enabling efficient operational and research workflows.

Figure 1. Mean significant wave height (Hs) over the global domain from the Oceanum ERA5 wave hindcast (1979-2020). Black dots indicate spectra output locations.

Validation

The global wave hindcast has been validated against satellite altimeter observations from multiple missions including Jason-2, Jason-3, Sentinel-3A, and Sentinel-3B. Validation statistics demonstrate excellent agreement with observed wave heights across all ocean basins. The model captures seasonal and interannual variability in global wave climate, including extreme events and long-term trends. Detailed validation results are available in the full specification document.

Interactive validation results are available through the Oceanum Validation App.

Data description

Table 1. Data description.

Linked Datamesh datasources

• Oceanum global ERA5 wave hindcast parameters
• Oceanum global ERA5 wave hindcast spectra
• Oceanum global ERA5 wave hindcast statistics

Integrated parameters gridded output

Integrated wave parameters are stored 3-hourly over the domain at the native model resolution. Table 2 describes long names and units of key gridded output parameters.

Table 2. Gridded output parameters.

Variable names link to the corresponding NERC Vocabulary Server standard name where available. All parameters are defined on the time, latitude and longitude coordinates.

Spectra output

Frequency-direction wave spectra are stored hourly at the spectra output sites within the domain. Table 3 describes the spectra output variables, using the exact variable names served by Datamesh.

Table 3. Spectra output variables.

Variable names link to the corresponding NERC Vocabulary Server standard name where available. Spectra are defined on the time, site, freq and dir coordinates; lon and lat are per-site data variables giving each site’s location.

www.oceanum.science