T. Spangehl et al.: Intercomparing the quality of recent reanalyses for offshore wind farm planning 
1413 
(2023), COSMO-CLM is evaluated and used to study cluster- 
scale wake effects of wind farms in the North Sea. 
A horizontal grid spacing of 0.0275° (—3km) is used 
together with 50 vertical levels and 25s time stepping. 
The simulation starts in December 1969 with 13 months 
spin-up time and is extended regularly close to real- 
ime. Currently, the most commonly used variables of this 
dataset are available for the time period 1971-2019 on the 
DWD node of the ESGF (Earth System Grid Federation) 
as version V2022.01 (https://esgf.dwd.de/projects/dwd-cps/ 
hoklisim-v2022-01, last access: 6 November 2023, Brienen 
et al., 2022). The model domain covers 461x481 grid points 
and is centered around Germany. The forcing at the lat- 
eral boundaries has been updated every hour for the ERA5S 
period in a direct nesting approach. For ERA40, 6-hourly 
boundary data from an intermediate nesting simulation at 
0.11° (— 12km) have been used, which had been run using 
the same configuration as in the EURO-CORDEX-CMIP5S 
simulations with COSMO-CLM (see e.g. Kotlarski et al., 
2014; Vautard et al., 2021). For this study, the wind com- 
ponents which have been interpolated inside the model to the 
100m a.g.1. are investigated. 
different heights, are measured. In addition, a complete set of 
hydrographic data is collected. Moreover, the forces induced 
by wind and waves are measured in the foundation area (Lei- 
ding et al., 2016). 
In the present study measurements of wind speed and di- 
rection at FINO1 are used. Wind direction data is taken from 
the highest measurement level available for this parameter at 
91 ma.m.s.l. (above mean sea level). The wind speed time se- 
ries stems from the top anemometer at 102 ma.m.s.l. At this 
height the effect of the mast on the wind speed measurement 
is assumed to be small. The mast effect is corrected by apply- 
ing a mast correction to the wind speed data (Leiding et al.. 
2016). The mast correction depends on the wind direction. 
The simultaneous wind direction measurement of the wind 
vane at 91 m is included in each corrected wind speed value 
in order to be able to carry out the mast correction (UL Inter- 
national GmbH, personal communication, 2022). Moreover, 
measurements are influenced by a lightning protection cage 
which leads to slightly lower wind speeds in 4 narrowly pro- 
nounced wind direction sectors (Leiding et al., 2016). Here 
we estimate the overall error for all wind directions to be less 
than 1%. The time series of wind speed and direction con- 
sist of 10 min averages. Hourly data at full hours is used to 
enable comparability with available model output data. Ad- 
ditional information on measurement uncertainties and data 
availability is indicated by Leiding et al. (2016). 
2.2.2 NEWA (New European Wind Atlas) 
The New European Wind Atlas (NEWA) covers the 30-year 
period from 1989 to 2018. The Weather Research and Fore- 
casting (WRF) model was used together with ERAS as driv- 
ing reanalysis for a series of one-way nested simulations. The 
simulation’s design is optimised to represent wind speed dis- 
tributions in complex terrain. Three nested domains with a 
resolution of 27, 9 and 3km were used. Spectral nudging 
was applied in the outer domain to incorporate the observed 
large-scale atmospheric patterns. The simulations consist of 
7 d periods using a spin-up of 24h to achieve equilibrium of 
the mesoscale flow with the terrain. In the vertical the model 
incorporates 61 levels with the model top at 50 hPa. Data is 
available for 30 min intervals for wind energy relevant pa- 
rameters. Details are given by Hahmann et al. (2020) and 
Dörenkämper et al. (2020). Data for 2005-2018 is publicly 
available via the website https://map.neweuropeanwindatlas. 
eu/ (last access: 6 November 2023). The WRF model output 
was further downscaled to create the microscale atlas. In the 
present study the mescoscale data at 3 km resolution is used. 
2.4 Satellite observations 
25 
Copernicus Marine Environment Monitoring Service 
or Copernicus Marine Service (CMEMS) 
Monthly averaged near-surface wind speed is 
obtained from CMEMS. The CMEMS wind 
product WIND_GLO_PHY_L4_MY_012_006, 
https://doi.org/10.48670/moi-00185, is used. The prod- 
uct incorporates scatterometer Observations to correct for 
persistent biases in hourly ERA5 model fields. Bias correc- 
tions are based on scatterometer observations from Metop-A. 
Metop-B, Metop-C ASCAT (0.125°) and QuikSCAT Sea- 
Winds (0.25°). The bias corrections are calculated over 20 d 
centered around the time of interest. Therefore, averaging 
hourly wind speeds from this product over a month includes 
some observations (10d) from both the previous and next 
month (PUM, CopernicusMarineService, personal com- 
munication, 2023). The product provides stress-equivalent 
Level-4 wind components at 10m at 0.125 and 0.25° 
horizontal spatial resolution and covers the period from 
August 1999 to February 2023. "The stress-equivalent 
wind does not rely on the assumption of neutral stability 
(de Kloe et al., 2017). In the present study data at 0.125° 
horizontal spatial resolution is used. Hourly near-surface 
wind speed is calculated from components. Monthly values 
are obtained from the hourly wind speed by arithmetic 
averaging. In a previous version of the manuscript the 
2.3 FINO observations 
2.3.1 FINO (Ger. Forschungsplattformen in Nord- und 
Ostsee) 
The FINO research platforms facilitate the exploration of off- 
shore conditions and help to determine the effects of off- 
shore wind energy development on marine flora and fauna. 
Masts have been erected on the working platforms of FINO1, 
FINO2 and FINO3, on which the most important meteoro- 
logical parameters, in particular wind speed and direction at 
attos://doi.org/10.5194/asr-20-109-- u2 
Adv. Sei. Res., 20, 109-128. 2023