118 T. Spangehl et al.: Intercomparing the quality of recent reanalyses for offshore wind farm planning Figure 3. Wind rose of hourly wind speed and direction at 100 m for model based products at FINO1 grid points. Results are shown for (a) COSMO-REA6, (b) CERRA-fc, (c) ERA5 and (d) HoKliSim-De. Results obtained from (e) hourly FINO1 measurements (10 min averages) of wind speed at 102 m and wind direction at 91 m are additionally shown. The time period is 2004–2009. quencies are apparent decreasing from 6 % at W to about 5 % at NNW. Most of the sectors from N over E to S show relative frequencies of less than 5 %. Here only the S sector and the E sector show values slightly above the 5 % level. Sector E depicts a secondary maximum of about 6 %. The wind rose of COSMO-REA6 (Fig. 3a) is in line with observations (Fig. 3e). Differences of less than 1 percent are seen for most sectors. COSMO-REA6 slightly underesti- mates the frequent occurrence of the south-westerly wind di- rections seen in observations, especially for sector SSW. By contrast, the occurrence of wind directions at sectors W to NNW is somewhat more frequent in COSMO-REA6. In ad- dition, the relative maximum at sector E is less pronounced in COSMO-REA6 and shifted to sector ESE. Wind speeds above 15 m s?1 are predominately found for south-westerly Adv. Sci. Res., 20, 109–128, 2023 https://doi.org/10.5194/asr-20-109-2023