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2.50 2.60 2.70 2.80 2.90 3.00 3.10 3.20 3.30 3.40 3.50
uv10(m/s)
temp (
°
C)
relH (%)
Fig. 6.2 Fields of 10-m (a) temperature, (b) humidity, and (c) wind speed after 1 day of METRAS
simulation. Results belong to run with constant wind direction
N
as a representative example for all
wind directions. Due to wind direction, the extrema can vary slightly; the important point is that in
10-m heights, the conditions are nearly homogenous over ocean. Outside of METRAS model area
(Fig.
3.6
), the METRAS data at boundaries were expanded over ocean
fields, and 10-m horizontal wind field of reference run without wind turbines. The
important point of that representation is that over ocean the 10-m fields of temper-
ature, humidity, and wind are homogenous. Hence, changes in those fields only
occur due to operating OWFs.
After 24 h of simulation, the reference runs have a 10-m temperature of 14-
15
C over ocean, humidity is of 90 %, and wind speeds are of 3 m/s. Cut-in of wind
turbines is set to 2.5 m/s, cut-off is set to 17.0 m/s in hub height. The wind field at
hub height does not reach velocities greater than 17.0 m/s. Thus, it is assumed that
the wind turbine parameterization is never avoided. In the following, differences
between OWFr and REFr are presented for each defined wind direction after 1 day
of simulation.
The changes of the horizontal wind velocity
are shown in Fig.
6.3
. Most of the
EEZ area is influenced by a reduction of wind speed between 10 and 60 %. An
intensified wake is formed especially within OWF areas. An increased wind speed
of around 17 % up to 26 % occurs at the constraints of the wind farms depending on
the wind direction. So also in the more realistic case of scenario
B1-2030much
, the
structure of wake and wake
s flanks can be identified. While the wind wake is strict
locally limited over the OWF district, the wind increase also influences coasts and
land depending on wind direction. In case of a wind coming from the coasts, that is,
the south, southeast, and east directions, the wake length in wind direction is longer
and broader over the ocean.
As mentioned in Chap.
4
, here the use of the METRAS approach for wind wake
simulation is necessary because, obviously, the Brostr¨m approach cannot cover
such special formation for OWFs.
The changes of temperatures in 10 m
are depicted in Fig.
6.4
. Here, the
temperature increases by about 3-5 % and partly also decreases by about
1 %-4 %. The rise in the temperature is especially located in lees of wind farm
areas and also within OWFs and comprises a bigger zone than cooled areas.
'
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