562 
Observations Mohrholz (20156 
V. Maurer et al.: Evaluation of coupled and uncoupled simulations 
ROAM-NBS 
NEMO-NBS 
‘5 
0 
100 4 
“ 
8 150 +] 
DO 150 
200 + 
250 
= 100 4 
= 
je 
x. 
U 150 
30 
100 + 
150 
0 
ı1 November 2014 
——— — —— — 250 
0 400 600 800 10/1 
50 
100 + 
150 + 
hı 
100 . 
150 1 
200 — 
‚1 November 2014 11 November 2014 
—P— tt —z ———t+ 250 I ——, 
700 400 600 800 1000 0 200 400 600 800 1000 
0 
50 
100 = 
150 + 
“16 — 
- 
14 
© 
= 
Ä- 12 5 
" 
10 .& 
te 
8 
f 
A 
A 
LL, 
‚— 18 
1 16 — 
5 
Ka 
= 
ö 
14 = 
> 
17 % 
10 4 
200 + 
250 
00 * 
' February 2015 
—t—————————z— — 250 
20nN 400 600 800 1000 
7 February 2015 17 February 2015 
———— a 50 AR H—H—HE— 
200 400 600 800 1000 0 200 400 600 3800 1900n 
— 
a 
u 
15 
Fr 
A 
350 
50 = 
= 100 4 
+ 150] 
0 150 
LOO 
100 
150 + 
150 N 
200 + 
200 - 
200 - 
22 March 2015 22 March 2015 22 March 2015 
750 250 250 FL 
r 200 400 600 2800 1000 0 200 400 600 800 1000 0 200 400 600 2800 1000 
distance [km? distance [km] distance [km? 
+ 16 — 
Z 
5 
Lz 
10. 
x 8 & 
LL- 
Figure 15. Practical salinity along the Baltic thalweg for NEMO-NBS, ROAM-NBS and observational data (Mohrholz, 2016) at three time 
instances around the MBI 2014: 11 November 2014 (top panels), 7 February 2015 (middle panels) and 22 March 2015 (bottom panels). 
2015) and caused much damage and a severe storm surge 
in the North Sea. Storm ELON passed on 9 January and dis- 
solved afterwards. For 10 January 2015, 12:00 UTC, the cen- 
ter of storm FELIX with a minimum pressure of less than 
960hPa is simulated by ROAM-NBS directly to the west 
of the Norwegian coast (Fig. 16a). The location and mini- 
mum pressure agree well with the one reported by the DWD 
surface analysis (Haeseler, 2015). Accordingly, ROAM-NBS 
simulates strong westerly winds (due to surface friction, 
near-surface winds are rotated towards the low pressure cen- 
(er compared to the geostrophic wind) on 10 January with a 
maximum of up to 24m s7! (about 86 km h7!) to the north- 
west of Helgoland (Fig. 16b). Observed winds on Helgoland 
show maxima of up to 20ms”! on 9 and 10 January and 
slightly weaker maxima on 8 and 11 January (Fig. 16c), in- 
dicating that storm conditions prevailed over several days. 
The near-surface wind speed is not as well matched with the 
Geosci. Model Dev... 19. 543578, 2026 
observations by ROAM-NBS as by ERAS (Fig. 16c), but the 
maximum on 10 January is well reproduced by both. 
The storm events in January occur shortly after the Ma- 
jor Baltic inflow event in December 2014. The non-detided 
SSH results are compared against GESLAv3.0 observational 
data described in Haigh et al. (2023). Stations in the Ger- 
man Bight (Helgoland), Skagerrak (Helgeroa), and Baltic 
Sea (Travemünde) are chosen to discuss the model’s instant 
behavior exemplarily. Associated time series of the sea level 
minus the yearly mean sea level are presented in Figs. 16d 
and A8. At the station Helgoland, the warning level of 2.5 m 
for a severe storm surge in the North Sea is exceeded on 
11 January in the early morning hours. A small time shift 
can be observed compared to the wind speed maximum on 
10 January. The maximum sea level on 11 January is slightly 
better represented by the coupled model than NEMO-NBS, 
although wind speed maxima are comparable in ROAM- 
https://doi.ore/10.5194/esmd-19-543-2026