114 T. Spangehl et al.: Intercomparing the quality of recent reanalyses for offshore wind farm planning Metop/ASCAT based monthly average wind speed of the WIND_GLO_PHY_CLIMATE_L4_REP_012_003 product was used. The WIND_GLO_PHY_CLIMATE_L4_REP _012_003 product was withdrawn in the Novem- ber 2022 release of CMEMS and was replaced by WIND_GLO_PHY_CLIMATE_L4_MY_012_003 (Coper- nicusMarineService, personal communication, 2023). This new product contains monthly averaged ERA5 stress- equivalent wind fields (components), corrected for persistent biases based on scatterometer observations. These bias corrections are calculated for the wind components and have been demonstrated to provide improved surface wind fields. Bias corrections for wind speed have been calculated as well, but compared to the vector components, their statistical and physical interpretation is more complex and requires further study. For this reason, wind speed has not been included in the monthly product (yet) (CopernicusMarineService, personal communication, 2023). As is documented in the WIND_GLO_PHY_CLIMATE_L4_MY_012_003 product QUID for the vector components, differences between the hourly and the monthly bias correction are small (QUID, CopernicusMarineService, personal communication, 2023). Therefore, the present study uses the hourly wind speed com- ponents provided by WIND_GLO_PHY_L4_MY_012_006, https://doi.org/10.48670/moi-00185, to calculate monthly averaged wind speed as outlined above. 2.5.1 Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS), version 4.0+extension This dataset contains gridded Thematic Climate Data Records (TCDR) (1987–2014, Andersson et al., 2017)+ extension (2015–2020) of wind speed at 10 m from the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data (HOAPS) climatology compiled by the Satellite Application Facility on Climate Monitor- ing (CM SAF). HOAPS is a completely satellite-based climatology of precipitation, evaporation, freshwater budget, latent heat flux, total column water vapour, near-surface spe- cific humidity and near-surface wind speed over the global ice-free oceans. All variables are derived from recalibrated and intercalibrated measurements from SSM/I and SSMIS passive microwave radiometers, except for the SST, which is taken from AVHRR measurements (Andersson et al., 2010). The near-surface wind speed is retrieved with a 1D-Var retrieval scheme. The data is provided as monthly averages on a regular latitude/longitude grid with a spatial resolution of 0.5× 0.5?. 2.6 Methodology Model grid points used for evaluation with FINO measure- ments are selected according to a nearest neighbour approach (Table 1). For comparison with the mast measurements the Table 1. Coordinates of grid point assigned to FINO1, nominal hor- izontal resolution and model of different products are shown. More- over, coordinates of FINO1 station tower are shown. NA stands for not applicable. Product Lon [?] Lat [?] 1x [km] Model FINO1 6.5876 54.0149 NA NA COSMO-REA6 6.6151 54.0033 6 COSMO COSMO-REA2 6.5864 54.0161 2 COSMO CERRA-fc 6.5731 53.9950 5.5 HARMONIE ERA5 6.5000 54.0000 31 IFS HoKliSim-De 6.6018 53.9604 2.8 COSMO-CLM NEWA 6.5662 54.0156 3 WRF model data is vertically interpolated to a height of 100 m above mean sea level (a.m.s.l). Linear vertical interpolation is used for COSMO-REA6. To enable direct comparability with available model out- put data 10 min averages of the FINO measurements at full hours are used (results for time period 2004–2009 presented in Sect. 3.1). Moreover, the dates of the model data are cho- sen to match the available FINO observations, i.e. data at dates where observations are missing are discarded in the model data base. Distribution parameters of the hourly wind speed data are obtained by fitting a Weibull distribution function to the wind speed histogram (1 m s?1 histogram bins used). For compar- ison with the satellite-based reference data 10 m wind speed from models is used. All model-based products are regridded to the geographical grid of the reference data used. Box-plots are created for monthly averages of the grid box data. 3 Results Results are presented separately for the evaluation using in- situ measurements of FINO1 and satellite-based data as ref- erence. Evaluation using FINO data concentrates on assess- ment of temporarily high resolved data at heights near 100 m. Evaluation using satellite-based data focuses on monthly av- erages of gridded data for an investigation area around the German EEZ of the North Sea. 3.1 Evaluation using in-situ measurements at FINO1 as reference The quality of the different reanalyses is assessed by com- parison with in-situ measurements of the wind speed and wind direction at FINO1. For the wind speed the measure- ments of the top anemometer at 102 m a.m.s.l. are used. Wind direction is measured at 91 m a.m.s.l. The FINO1 re- search platform is located in the southern part of Germany’s EEZ in the North Sea, ca. 45 km (ca. 24 nautical miles) north of the Isle Borkum in a water depth of about 30 m of the shelf sea. The exact coordinates are 54?00?53.5?? N, Adv. Sci. Res., 20, 109–128, 2023 https://doi.org/10.5194/asr-20-109-2023