Seasonal forecasts provide valuable insights into upcoming conditions, offering forecast horizons of up to seven months. However, uncorrected seasonal forecasts often exhibit substantial biases and drifts, when compared to reference data like, e.g., ERA5. This makes post-processing essential for their use in analysis and downstream modelling. This dataset provides bias-corrected and downscaled seasonal forecasts from the ECMWF SEAS5 system for precipitation and 2-meter temperature, covering the global land surface at 0.25° resolution. Using the Bias Correction and Spatial Disaggregation (BCSD) method, forecasts are corrected for biases and temporal drifts and include all SEAS5 ensemble members over the full hindcast period (1981–2016) and until 2024. The dataset supports lead times up to seven months and is suitable for a wide range of applications in water, energy, and agricultural sectors. Forecast quality has been evaluated using Brier Skill Scores and CRPSS, showing strong skill for temperature across most regions and for precipitation in tropical and humid areas.

The hydrodynamic model Trim-NP (2.6) was used to get an impression of the spatial distribution of water levels at the coast during historical severe storm tides. For these events, the atmospheric reanalysis products from the Twentieth Century Reanalysis project (20CR), (Compo et al., 2011; Slivinski et al., 2019) and from the ECMWF (ERA5 and UERRA-HARMONIE) (Hersbach et al., 2018, Copernicus Climate Change Service, 2019) are used to force the model. Additionally, the German weather service (DWD) developed reanalysis data for storm surge events for the project OptempS-MohoWif (Kristandt et al., 2014). These reanalysis data are calculated three days before the event and two days after. Based on the comparison between tide gauge observations and model output, we can estimate, the skill of the reanalyses in simulating severe storms. All model runs are forced by finite element solutions tidal atlases FES2004 at the lateral boundaries (Lyard et al., 2006). Further information about the reanalyses: https://psl.noaa.gov/data/20thC_Rean/ https://www.ecmwf.int/en/research/climate-reanalysis/reanalysis-climate-monitoring https://www.ecmwf.int/en/forecasts/dataset/uncertainties-ensembles-regional-reanalysis Copernicus Climate Change Service, Climate Data Store, (2019): Complete UERRA regional reanalysis for Europe from 1961 to 2019. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). DOI: 10.24381/cds.dd7c6d66 (Accessed on 01-APR-2023) The file name of the data sets is composed as follows. trim_<grid>.<variable>.<forcing>_<year>_<run>.nc grid: 2 ( 6.4 km resolution) and 4 (1.6km resolution) variables: u10(x_wind), v10(y_wind) und e(sea_surface_height_above_sea_level) forcing: 20CR versions(v2c und v3) and (UERRA, ERA5) for ECMWF and OptemptS Year: 1825, 1949, 1953, 1962, 1967, 1976, 1999, 2013 run: only used for the 20CR project with 56 (v2c) and 80 (v3) ensemble members Depending on whether the forcing data was available, data are generated.