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_012_003 product was withdrawn in the Novem-
ver 2022 release of CMEMS and was replaced by
WIND_GLO_PHY_CLIMATE_L4_MY_012_003 (Coper-
ıicusMarineService, personal communication, 2023). This
aew product contains monthly averaged ERAS Sstress-
equivalent wind fields (components), corrected for persistent
viases 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,
out compared to the vector components, their statistical and
ohysical 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,
attps://doi.org/10.48670/moi-00185, to calculate monthly
averaged wind speed as outlined above.
2.5.1 Hamburg Ocean Atmosphere Parameters and
F]uxes 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 10m
from the Hamburg Ocean Atmosphere Parameters and
Fluxes from Satellite Data (HOAPS) climatology compiled
oy the Satellite Application Facility on Climate Monitor-
ıng (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
:aken 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 x 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 commparison with the mast measurements the
Adv. Sci. Res... 20. 109-128. 2027
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[°] Ax [km] Model
FINO1 6.5876 54.0149
ZOSMO-REA6 6.6151 54.0033
COSMO-REA2 6.5864 54.0161
CERRA-fe 6.5731 53.9950
ERA5S5 6.5000 54.0000
HoKliSim-De 6.6018 53.9604
NEWA 6.5662 54.0156
model data is vertically interpolated to a height of 100m
above mean sea level (a.m.s.1). 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 ms”! 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.
2 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.
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 ma.m.s.l. are used.
Wind direction is measured at 91 ma.m.s.l. The FINO1 re-
search platform is located in the southern part of Germany’s
EEZ in the North Sea, ca. 45km (ca. 24 nautical miles)
north of the Isle Borkum in a water depth of about 30m
of the shelf sea. The exact coordinates are 54°00’53.5” N.
https://doi.org/10.5194/asr-20-109-2023
