25
exceeding ADCP currents. However, with the exception of the surface layer, for ebb
currents the difference between the data sets is less significant.
From March 20, until June 6, 2000, an ADCP was deployed in the Baltic Sea at 54° 38.6'
N, 13° 30.0' E at a water depth of 25 m. The position is located at the outer boundary of
Tromper Wiek, a bight at the northern part of the island of Rügen. The circulation pattern
within the Tromper Wiek is highly variable with much lower velocities than in the North
Sea and without or with only hardly detectable tidal currents. The model data used for
this validation are not layer data, but interpolated data for 5, 10, 15, and 20 m depth. The
corresponding ADCP bin depths can be read from Table 6 which summarises current
statistics of both data sets. The significant difference between model and measurement
is the magnitude of current velocity. The model’s velocities are much too low while
current directions proved to be roughly comparable.
One reason for the differences between modelled and measured velocities may be an
inadequate description of nature in this near-coastal area by the discrete model
topography. However, compared to the North Sea, currents in the Baltic Sea are
determined much more by baroclinic features. As will be shown in chapter 5.5, simulation
of long-term salinity distribution and stratification still is a major problem in the model.
Table 6: Current statistics Tromper Wiek, BSHcmod (M) and ADCP data (A)
sd
m
U
cm/s
V
cm/ s
v s
cm/ s
V v
cm/ s
dir
O
k E
(cm/ s
k M
) 2
U'U'
v'v'
(cm/s)
u'v'
2
k E /k,
M
5.0
-0.9
1.6
4.9
1.9
330
15.9
1.7
11
21
-7
9.1
A
5.3
-3.3
4.6
10.2
5.7
325
56.4
16.2
45
68
-13
3.5
M
10.0
-0.7
0.8
2.6
1.1
319
4.8
0.6
2
7
-3
7.6
A
9.3
-2.7
3.9
8.6
4.8
325
38.9
11.4
26
52
-9
3.4
M
15.0
-0.6
0.4
2.4
0.7
307
3.8
0.3
3
4
-2
14.6
A
15.3
-2.1
2.6
7.6
3.4
321
33.7
5.7
23
45
-8
5.9
M
20.0
-0.5
0.3
2.6
0.6
305
4.8
0.2
7
3
-1
29.1
A
19.3
-1.6
2.3
7.3
2.8
324
33.7
3.9
27
40
-13
8.6
sd = sampling depth, dir = current direction
