V. Maurer et al.: Evaluation of coupled and uncoupled simulations 
(a) SW net surface 
(b) pr 
50° 
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50°N 
CC 
40°) 
10° 
x 
30°1 
Knall 
50° 
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ii 
MAM 
56. 
„an 
SON 
W°N 
& 
A 
/c) LW net surface 
sO°h. 
Ö°h 
NS. 
3°: 
AQ°N 
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60°N - 
-A°M 
40°N 
30° N 
KON 
NN 
A0°N 
AM 
cr 
‚or 
40° 
30° 
(d) pr 
S0°N gu 
S0°N 
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US 
E 30° 
60°N ' 
105 
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30°) 
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a 
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Figure A1. Seasonal mean biases of surface shortwave net radiation for ROAM-NBS against CERES (a), of precipitation against E-OBS (b), 
of surface longwave net radiation against CERES (c), and of precipitation against IMERG (d), all averaged over 2001-2020. 
is much larger than the differences between the simulations 
(Fig. 6a). Especially in winter, the coupling slightly increases 
the negative precipitation bias, related to the negative SST 
bias of NEMO-NBS and ROAM-NBS and, with that, de- 
creased evaporation in ROAM-NBS (see Sect. 3.2.2), but 
che effect is small. The tuning of evaporation by laminar re- 
sistances over the ocean can increase precipitation and was 
found to be beneficial for most biases over land, but it was 
disregarded as it resulted in a strong overestimation of evap- 
oration over the ocean compared to satellite observations. In 
the future, an increase of precipitation efficiency over the 
ocean should be tested. 
https:/doi.org/10.5194/egmd-19-543-2026 
Complementing Fig. 5, the seasonal bias maps for ROAM- 
NBS against E-OBS are shown in Fig. A2 for tasmin and 
tasmax. They confirm that the tasmin bias is small and non- 
systematic compared to the more systematic cold bias for 
tasmax. One slightly outstanding pattern in the tasmin bias 
is red pattern in Scandinavia in winter (DJF). However, it 1s 
unclear if this also might be over-emphasized by the compar- 
ison against E-OBS as it does not show up that clearly when 
comparing against ERA5 (not shown). 
To give an insight into the temporal evolution of temper- 
atures within the evaluation period, time series of yearly av- 
eraged tas are given in Fig. A3 for different countries. In 
Geosci. Model Dev... 19. 543-578, 2026