116 T. Spangehl et al.: Intercomparing the quality of recent reanalyses for offshore wind farm planning Figure 1. Annual mean wind speed at 100 m for model based products at FINO1 grid points. Results are shown for (blue solid curve) COSMO-REA6, (blue dashed curve) COSMO-REA2, (purple dotted curve) CERRA-fc, (cyan solid curve) ERA5, (cyan dashed curve) HoKliSim-De and (red solid curve) NEWA. Results obtained from FINO1 measurements at 102 m are additionally shown (bold black dashed curve). The time period is (a) 1979–2020 and (b) 2004–2009. Table 2. Bias of annual mean wind speed [m s?1] at 100 m for model based products at FINO1 grid cells. FINO1 anemometer measurements at 102 m are used as reference. NA stands for not available. Bias of annual mean wind speed [m s?1] at 100 m at FINO1 for different products Year 2004 2005 2006 2007 2008 2009 2004–2009 COSMO-REA6 ?0.03 0.22 0.16 0.14 0.22 0.04 0.13 COSMO-REA2 NA NA NA 0.35 0.44 0.18 NA CERRA-fc ?0.01 ?0.07 0.00 ?0.08 0.19 0.01 0.01 ERA5 ?0.22 ?0.32 ?0.31 ?0.28 ?0.08 ?0.21 ?0.24 HoKliSim-De ?0.08 ?0.07 ?0.13 ?0.13 ?0.01 ?0.17 ?0.10 NEWA NA ?0.38 ?0.29 ?0.47 ?0.19 ?0.26 NA NW, NNW), where each sector covers an angle of 22.5?, are used to analyse the frequency distribution of the wind direc- tion at heights near 100 m. The analysis is performed for the time period 2004 to 2009. First, results for the whole year are discussed (Fig. 3). In a second step, the statistics of the four seasons (DJF, MAM, JJA, SON) are briefly addressed (Fig. A1). The wind rose of the observations at FINO1 shows a max- imum relative frequency of nearly 10 % at the SW sector and slightly lower relative frequencies of about 9 % at the neigh- bouring sectors SSW and WSW (Fig. 3e). Lower relative fre- Adv. Sci. Res., 20, 109–128, 2023 https://doi.org/10.5194/asr-20-109-2023