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Figure A2. Seasonal mean biases of daily minimum and maximum temperature of ROAM-NBS against E-OBS, averaged over 1979-2020. 
some cases, neighbouring countries were combined into one 
:ime series (GB and Ireland, Spain and Portugal, Norway and 
Sweden, and the Baltic states including Estonia, Latvia and 
Lithuania). In general, both ICON-CLM and ROAM-NBS 
reproduce the mean trends as well as the year-to-year vari- 
ability of the references (E-OBS and ERAS5) very well. As 
shown before, a cold bias can be discerned which is largest 
in Spain and Portugal and also clearly visible for GB and Ire- 
land. In the eastern part of the domain, e.g. in Ukraine, the 
summertime warm bias is dominant. In all cases, ROAM- 
NBS and ICON-CLM are very similar. 
A2 Mean ocean conditions 
To complement the evaluation of SST bias evolution in win- 
er and summer, biases and absolute time series for SST 
ıntegrals over the same regions (whole domain, Open At- 
lantic, North Sea, Baltic Sea) are presented for all seasons in 
Fig. A4. In support of the mean profile validation of salin- 
ity and temperature, a Hovmöller diagram is provided in 
Fig. A5, to illustrate the temporal evolution of these variables 
at stations SMHIBY5S and SMHIBY15. See Fig. 10a for the 
locations of the stations. Corresponding time series of sur- 
face and bottom salinity at stations SMHIBY2, SMHIBY5, 
and SMHIBY15 are provided in Fig. A6. Furthermore, ex- 
‚ending the analysis of detided sea surface height (SSH), 
Fig. A7 presents a scatter plot comparison of bias-adjusted 
SSH at the tidal station Plymouth for NEMO-NBS versus 
ROAM-NBS. Both model configurations exhibit very high 
correlation with the GESLAv3.0 observational dataset. 
Geosci. Model Dev... 19. 543578, 2026 
A3 Variability and extremes 
Time series within the same time period as reviewed in 
Sect. 4.2 are provided for two additional stations: Hel- 
geroa and Travemünde. The results show a good agree- 
ment of ROAM-NBS and NEMO-NBS in the Skagerrak and 
Baltic Sea, where the maximum SSH is better represented 
by ROAM-NBS at Helgeroa, whereas at Travemünde the 
SSH maximum is overestimated by both NEMO-NBS and 
ROAM-NBS with a slightly better fit by NEMO-NBS. The 
marine heatwaves are additionally evaluated in Fig. A9 at 
the station UFS Deutsche Bucht to assess NEMO-NBS’s and 
ROAM-NBS’s performance in the North Sea. In Fig. A10, 
the seasonal climatology and corresponding 90th percentile 
threshold are presented for ROAM-NBS, NEMO-NBS, the 
Copernicus reanalysis and in-situ observation data for the 
station Leuchtturm Kiel. 
https://doi.org/10.5194/smd-19-543-2026