U. Callies et al.: Surface drifters in the inner German Bight 
813 
www.ocean-sd.net/13/799/2017/ 
Ocean Sci., 13, 799-827, 2017 
Bars: distances between observed and simulated end points ot 25 h drift paths 
Coloured bars: BSHcmod+W 
0 
„ 30 
| 25 
* 20 
I 15 
« 
a s 
0 
„ 30 
| 25 
® 20 - 
| 15- 
1 
Q 5 
0 - 
„ 30 • 
| 25 
r 20 
I 15 
« 1 ° 
5 5 
0 
0 1 2 3 4 5 6 7 8 9 10111213 1 4 15 1 617 1 819 20 2122 23 24 2 5 26 2 7 28 2 9 3031 32 3 3 34 3 5 36 3738 39 4 0 414 2 43 4 4 45 4 6 47 
Drifter no. 6 
12 3 4 5 6 7 8 9 10111213 1 4 15 1 617 1 819 20 2122 23 24 2 5 26 2 7 28 2 9 3031 32 3 3 34 3 5 36 3738 39 4 0 414 2 43 4 4 45 4 6 47 4 8 49 5051 52 53 
Drifter no. 8 
3 4 5 6 7 8 9 10111213 1 4 15 1 617 1 819 20 2122 23 24 2 5 26 2 7 28 2 9 3031 32 3 3 34 3 5 36 3738 39 4 0 4142 
Drifter no. 9 
4 5 6 7 8 9 10111213 1 4 15 1 617 1 819 2 0 2122 23 24 2 5 26 
Days since 2015-05-27 (13:00 UTC) 
(b) 
^ ^ Wind vector observed at Heligoland 
(Cl) Rotation of simulations against observations (positive to the right) 
180 -r 
Drifter no. 5 
180 - 
\ mJ 
° -90 - 
-180 - 
180 
i W f 
f 
° -90- 
-180 - 
180t 
| 90 
at 0 - 
^ -90 - 
-180 ^ 
0 1 2 3 4 5 6 7 8 9 10111213 1 4 15 1 617 1 819 20 2122 23 24 2 5 26 2 7 28 2 9 3031 32 3 3 34 3 5 36 3738 39 4 0 414 2 43 4 4 45 4 6 47 
Drifter no. 6 
120212: 
ra, Q n rT|jh=uJ~L- 
1 2 3 4 5 6 7 8 9 10111213 1 4 15 1 617 1 819 20 2122 23 24 2 5 26 2 7 28 2 9 3031 32 3 3 34 3 5 36 3738 39 4 0 414 2 43 4 4 45 4 6 47 4 8 49 5051 52 53 
Drifter no. 8 
3 4 5 6 7 8 9 10 111213 1 4 15 1 617 1 819 20 2122 23 24 2 5 26 2 7 28 2 9 3031 32 3 3 34 3 5 36 3738 39 4 0 4142 
Drifter no. 9 
4 5 6 7 8 9 10 11 1213 1 4 15 1 617 1 819 2 0 2122 23 24 2 5 26 
Days since 2015-05-27 (13:00 UTC) 
Figure 10. (a) Bars indicate distances between observed end points of 25 h drift paths and corresponding simulations based on either 
BSHcmod + W or TRIM. All drift errors, coloured and labelled in terms of days since 27 May (13:00 UTC), are assigned to the centre of 
the respective 25 h period. In addition, lines show total distances travelled, (b) Wind speeds used in the two models and surface Stokes drifts 
obtained from wave model WAM. Data were extracted for the central example location (55° N and 7° E). (c) Heligoland winds, copied from 
Fig. 3. (d) Angles between observed and simulated tracer displacements. Throughout the figure, all values represent 25 h averages.