Analysis 02: OWF Effect on the Ocean - On the Effect of Offshore Wind Farms on the Atmosphere and Ocean Dynamics - page 100

maximum of F02 and F04 is biased by 2.7E-4 m, while F04 has the
stronger increase. In opposite to the positive part of the

The ζ

dipole, the area of lower
surface elevation more strongly affects a wider area, thus nearly the whole model
area southerly of the OWF, while changes in F01 are more concentrated at the
southeasterly part of the model area (Fig. 5.31 a1-a3). Again, F04 also dominates
the effect on the negative

ζ

ζ

dipole with 0.016 m, compared to F01 with 0.009 m

ζ

changes. The impact of the wind direction on the formation is stronger by F01 due

to a longer wake trail downstream behind the OWF. In the case of the Brostr¨m
approach (F04), that effect is more or less neglected, which leads to a ζ formation
being nearly parallel to the cross-section W-E, having only an inclination to it of
13.50 .
The occurrence of vertical motion is identified in both forcing cases, but in the
case of F04, the downwelling and upwelling are not described by two main cells—a
blurred transition of three downwelling zones and three to four upwelling zones
around the OWF are established after 1 day of simulation (Fig. 5.31 c1-c3). The
induced downwelling by the OWF in the area of the positive dipole results in

flanked upwelling and hence, again, in downwelling zones. The downwelling is

ζ

1.1E-05 m/s. But
the upwelling is about 5.43E-06 m/s weaker by F04. Due to that, the difference in
the velocity component w between F01 and F04 (Fig. 5.31 c3), the dominant
upwelling cell of F01, and the dominant downwelling areas of F04 can be
explained. In the vertical along the S-N cross section, in Fig. 5.32 , the impact on
the vertical motion in case F04 significantly includes more intensively affected
vertical layers, especially within the OWF, than F01 due to horizontal distribution
of

1.73E-05 m/s stronger for F04 than in the case of F01, having

, the u -velocity wake, and thus the distribution of vertical motion in the
horizontal. Therefore, the extrema of the w -component are placed in lower layers,
so below the thermocline for upwelling, which is for F01 above the thermocline.
Maximal differences in the w -component between F01 and F04 are in order of
5E-06 m/s for downwelling and 2E-05 m/s for upwelling, with the dominant effect
given by F01. Again, upwelling is more strongly influenced by changed external
model assumption than downwelling.
Although upwelling is weaker in case F04, in 12-m depth, and hence in layers
above, the SST pictured in Fig. 5.31 d1-d2 shows a cooling of

ζ

0.92 C. Here, the
SST is not triggered by vertical motion because the cooling is an effect of the
declination in the surface elevation.
Though the METRAS approach yields to a greater vertical motion, the effect on
temperature is, overall, more strongly influenced by F04. Besides the cooling of
SST, the use of F04 results in typical warming and cooling formations around the
OWF along the S-N cross section (Fig. 5.32 b1).
The horizontal dimension of the cells of temperature changing is wider (along S-
N section) in the case of F04. But the location of the cell s extrema nearly fits with

'

run F01.
The temperature extrema of cooling are located at 10-m depths, of warming at
14-m depths in both forcing cases. The discrepancies in the horizontal count more
than 3 km.