Die Küste, 81 (2014), 255-271 
268 
Wind speed 
Wind direction 
340 
330 
„320 
a? 
<D 
8 * 310 ' 
T3 
■I 300 o 
O 
© 
=5 ° 
290 
280 
Mean wave direction 
o 
o 
o 
o 
• Finol 
° Helgoland Sued 
♦ UFS/TW Ems 
° UFSDB 
0 Helgoland 
270 
Figure 6: In blue wind speed and wind direction (in 10 m height) over time used by the drift 
model (GME+LME model data) at the simulated container positions. The dots in magenta show 
wind speed, wind direction, significant wave height and mean wave direction as measured at the 
station Finol (54° 0.86’ N, 006° 35,03’ E). The wind measurements of Finol are in 33 m height. 
The magenta circles show significant wave height and mean wave direction from the wave buoy 
at Flelgoland Sued (54° 10.783’ N, 007° 53,467’ E). Wind speed and direction measurements at 
light vessel TW Ems (54° 10,0’ N, 006° 20.8’ E) in magenta crosses and at Flelgoland in magenta 
diamonds. 
SeatrackWeb uses parameterized Stokes drift from the model wind. This means that the 
displacement due to waves is computed from wind speed and direction. If die wind and 
wave direction match well (what is usually the case in fresh wind sea), the Stokes drift has 
the correct direction and size. In conditions when the wind and wave directions are dif 
ferent the parameterized Stokes drift cannot catch this change in direction. Probably this 
is die reason why the simulated container positions are more northwards than die ob 
served ones.