Available direct model output from the DWD-BSH model chain 
7 
2 Available direct model output from the DWD-BSH model chain 
In situations of rapidly changing wind conditions, numerical model systems combining atmospheric 
and circulation models have been found to provide better results than empirical methods. Such model 
systems covering the German Bight have been in operational use at Bundesamt für Seeschifffahrt und 
Hydrographie (BSH) since 1981 (SOETJE and BROCKMANN, 1983). In 1990, the model was extended 
to cover the entire area of the North Sea and Baltic Sea. Today, 3D hydrodynamic-numerical ocean and 
shelf sea models predict numerous physical variables (Dick et al., 2001), among them water levels. If 
only water levels are of interest, a 2D model is sufficient. It requires considerably less computation time 
than the 3D model. The lower computation time is an important advantage for MOS because it 
allows timely inclusion of all forcing data provided by atmospheric models. The BSH receives hourly 
predictions of meteorological parameters from the GME/COSMO-EU modelling chain of DWD four 
times a day (MAJEWSKI et al., 2002; STEPPELER et al., 2003). 
340' 345' 350" 355' 0' 5' 10' 15' 20' 25' 30' 
340' 345' 350' 355’ D' 5' 10' 15' 20' 25' 30’ 
Fig. 3: Model areas of BSH’s numerical water level forecast system 
The analysis for the MOS equations was made on the basis of a data set covering the period from 
January 2008 to July 2009, using the 0 and 12 h runs of the 2D model (DMO: 2Dv4). The model system 
currently used in BSH-MOS, version 4, presently has the following configuration: 
- Meteorological input data from GME/COSMO-EU 
- Double nested [3D: triple] 
- Northeast Atlantic model (20 km grid size) 
- North Sea model (5.5 km), [3D: North and Baltic Seas model] 
[- 3D: coastal model, German Bight and Western Baltic (0.9 km)] 
- 4 runs per day (starting at 0, 6, 12, and 18 UTO), [3D: 1 daily run (12 UTC)] 
The 3D model configuration is given alternatively or additionally in square brackets. 
In the forecasting modus, new surge prediction data from DMO-2D in the v4 version (2Dv4) enter the 
MOS equations every six hours.