Deutsche Hydrographische Zeitschrift - German Journal of Hydrography
470
-50 0 50 100 150
Fig.4 Progressive vector diagram of ADCP measure
ments (a) and model data (b) 15.6.1999 15:45 -
10.8.1999 08:30. The start position is marked
with a big cross, time marks (X) are given every
5 days. The numbers at the tracks give the sam
pling depth (bin center, respectively layer center)
in metres.
5.2 Residual currents
Figure 5 shows the vertical mean profiles of
speed 1 ’, magnitude, and current direction for ADCP
and model data. Taking into account the different
vertical resolutions -2m ADCP bins versus 4 to 8
m model layers - there is considerable agreement
between both data sets. The profiles of speed and
magnitude are very similar. In the lower half of the
water column there are some differences in current
direction. The shear at 20 m depth appears to be
much sharper in the ADCP data and there are sig
nificant differences between 20 and about 30 m
depth, while the near-bottom current directions are
again very similar. Table 3 gives some basic current
statistics, and Table 4 quantifies the relationship be
tween both data sets. The correlation coefficients r,
given for the zonal and meridional current compo
nent, range between 0.87 and 0.96; only in the first
magnitude =
n i = 1
layer does the correlation of the meridional compo
nent amount to just 0.67. Here we must consider the
fact that the model values are vertical means over
the complete layer, while the ADCP data represent
only the range between 5 and 7 m depth due to the
above-mentioned side lobe effects. At all depths
there is a slightly higher correlation of the zonal cur
rent components as compared to the meridional
components.
E
ji
Q.
CD
"D
direction [dear]
0 60 120 180 240 300 360
0,0 20.0 40.0
magnitude,vec. speed [cm/s]
direction [degr]
0 60 120 180 240 300 360
magnitude,vec. speed [cm/s]
Fig. 5 Vertical mean profiles of current speed (broken li
ne), magnitude (solid line), and current direction
(*) for ADCP (above) and model data (below).
See also Table 3.
