Civil Engineering Reference
In-Depth Information
This setup was used for runs of eight different wind directions, which were
assumed as constant over the entire simulation time of 1 day. The constant wind
directions at the height of the geostrophic wind are
• N (000
),
• NE (045
),
• E (090
),
• SE (135
),
• S (180
),
• SW (225
),
• W (270
),
• NW (315
).
Based on Ekman spiral, the wind directions in 10 m height vary slightly from the
geostrophic ones. Due to this idealized setup of METRAS, a combination with
other (ECMWF) data was not reasonable. Disadvantages of that procedure are
possibly physical abnormalities in the North Sea
s circulation due to forcing
expansion. However, such a side effect cannot be detected in the data set.
'
Setup for Case Study II: Real Meteorological Situation
For case study II, simulations of the German Bight were done with operating OWFs
and without OWFs. The simulations, presented in this topic, were done for the time
range 16-19 June 2010. This time period is chosen based on meteorological
situation and data availability for METRAS runs.
The full meteorological forcing is adopted hourly and includes forcing field of
10-m wind, surface pressure, 10-m temperature, 10-m humidity, total precipitation,
and cloud presence. The forcing fields are a hybrid between METRAS data over the
orange METRAS area in Fig.
3.6
and ECMWF data for the rest of the HAMSOM
NS domain. At the boundaries of the orange METRAS area (Fig.
3.6
), an interpo-
lation was necessary. Simulations of METRAS forcing data were done from 16 to
19 June 2010 as well. As mentioned, the model area of METRAS simulations does
not fit with HAMSOM NS; see Fig.
3.6
. Over ocean, METRAS sea surface
temperature is forced with the NOAA Optimum Interpolation Sea Surface Tem-
perature. The meteorological forcing comprises 6 hourly fields of temperature,
humidity, and the horizontal wind from ECMWF. The pressure field is then
calculated by METRAS, which simulates its own dynamic.
The meteorological forcing field for simulations under HAMSOM NS needed
some preparations. METRAS forcing data over ocean were interpolated and
projected to HAMSOM grid, and ECMWF data were horizontally interpolated
into HAMSOM grid. Also the use of a wind time step of 10 min and an hourly
residual forcing asked for the need of time interpolation of 6 hourly ECMWF data.
Although such strong timely interpolation is normally inappropriate, results show
that only the orange METRAS area is affected by OWFs, and so areas affected by
ECMWF interpolation do not influence the OWF effect analysis.
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