Ocean Dynamics 
Ö Springer 
4.2.2 Baltic Sea 
The annual averages over 2014 of the MME mean and the 
standard deviation for SSS are displayed in Fig. 17. The larg 
est deviations occur in the Kattegat and Skagerrak as well as in 
the Vistula Lagoon and Curonian Lagoon in the South with 
values higher than 2 throughout these areas. Fligh uncer 
tainties in the lagoons are probably caused by the different 
bathymetries used for the models. Deviations in the Gulf of 
Finland and Gulf of Bothnia are slightly less than 1. These 
values are accompanied by salinities below 4 indicating that 
the relative uncertainties are high in these areas. 
The daily spatial averages of SSS of the MME products 
and the individual forecasts are displayed in Fig. 18. The 
values of all forecasts vary almost simultaneously with time 
between 7 and 8.5. FCOOGETM has the greatest offset to 
the MME products. Obvious discontinuities are shown in the 
time series from DMI DKSS. The MME mean and MME 
median reflect the main features shown by the individual fore 
casts. Obvious differences between MME mean and median 
can be observed during the first half ofthe year, but in July, the 
time series converge. The spread of the ensemble members is 
quite stable during the whole year and no seasonal pattern can 
be distinguished (Fig. 18). 
4.3 Regional pattern in forecast deviation for sea surface 
current 
For the evaluation of SSC and surface transports (see Sect. 4.4), 
some transects are chosen representing the main inflow and 
outflow areas of the North Sea and Baltic Sea. The groups of 
transects are listed in Table 3. Evaluation of SSC is primarily 
done by determining the final displacement, hence the distance 
between the end points of the MME PVD and the PVD of each 
forecast yielding a matrix with distances (km) for each day and 
each transect (as illustrated in Fig. 7). The temporal mean of 
final displacements reflects the mean differences in deviation 
from the MME at each transect for each forecast. 
In Fig. 19, an example matrix for the North Sea, represent 
ed by FOAM AMM, and the temporal mean of all corre 
sponding final displacements in these regions are shown. Ver 
tical white lines in the matrix indicate no data on that day. For 
a promising statistical evaluation, a nearly gapless data set is 
essential and therefore a constant data flow is quite important. 
The greatest displacements in the matrix occur in the Norwe 
gian Coastal Current, region III. This pattern is also reflected 
in the temporal mean displacements of all forecasts, indicating 
high uncertainties in SSC magnitude and direction, which is 
possibly caused by different boundary conditions of the 
models. Regions I and II are characterized by generally lower 
values in both plots. In region III, METNOROMS exhibits 
the greatest displacements at most transects, while this fore 
cast exhibits lower values in the other areas. 
In regions I and II, FCOO GETM, SMHI HIROMB NS03, 
and BSFICMOD have also the lowest displacements at most 
transects. It should be mentioned that at Trl, Tr2, and Trl5, the 
forecasts contributing to the MME are only METUK FOAM 
and METNO ROMS. Nevertheless, the displacement of both 
forecasts is comparatively high at Tr2 in region III. 
An example matrix for the Baltic Sea (BSFI CMOD) is 
shown in Fig. 20, accompanied by the temporal mean final 
displacement of all forecasts. Fligh values are distributed evenly 
among the transects, indicating no strong regional differences. 
But, there seems to be a seasonal component which is reflected 
63°N 
60°N 
57°N 
54°N 
63°N 
60°N 
57°N 
54°N 
12°E 16°E 20°E 24°E 28°E 
12°E 16°E 20°E 
Fig. 17 Temporally averaged MME mean (left) and standard deviation (right) of SSS in the Baltic Sea in 2014 
24°E 
28°E