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b
a
Fig. 5.8 Temperature profiles of run OWFr considering 12 wind turbines for different time steps
t
at two representative positions along S-N section. (a) Temperature profiles at 6 km south to OWF
center. (b) Temperature profiles 6 km north to OWF center. Hence, (a) is placed in upwelling
region and (b) in downwelling region. Thermocline is pushed with time up and down depending on
signs of vertical velocity component
w
. The different time steps of OWF operation are 0 min,
10 min, 80 min, 160 min, 12 h, 24 h, 28 h, 36 h, 48 h, starting with the coloring from
black
to
red
5.2 Theoretical Analysis of Rising OWF Effect
on the Ocean
The effect of an offshore wind farm on the ocean includes modifications in ocean
dynamics and hydrography, as documented in Sect.
5.1
. The cause of vertical
mixing, indicated as upwelling and downwelling, is associated with changes of
the hydrographic components temperature, salinity, and density. An induced
change of the ocean
s stratification is of special relevance. Therefore, this section
aims to understand the impact on the ocean due to operating wind turbines by
analyzing the physical conditions, especially influencing vertical processes, step by
step with the help of a sensitivity study.
The preparation of the sensitivity study accounts for the following facts and
orientations:
'
i) An OWF results in up- and downwelling cells around the OWF district.
In common, local mixing of the upper ocean is predominantly forced from the
state of the atmosphere directly above it (Moum and Smyth
2001
). Main
processes for mixing are convection, wind forces, precipitation, and ice on the
upper ocean (Moum and Smyth
2001
). Here, the variable wind can be identified
as the main impulse of the OWF effect on the ocean so far. The wind is the most
important atmosphere component of this analysis because an intensified vertical
motion occurs by using a forcing covering wind as meteorological forcing only.
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