MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
also added to the SL-TAC catalogue. The global CNES_ 
2LS18 MDT field was introduced in 2020 and used in 
the SL-TAC production since Dec 2019. Compared to 
the previous version (CNES-CLS13), the new CNES_ 
2LS18 MDT has showed Improved performance 
averywhere and most significantly in coastal areas 
and in strong western boundary currents. The Root 
Mean Square Deviation (RMSD) have been reduced 
by 10% within 100 km of coasts for the CNES-CLS18 
'Mulet et al., 2021). In 2020, two regional MDT fields 
were also specifically estimated for Copernicus 
Marine Service applications in the Mediterranean and 
Black Sea. They were, for the first time, computed 
using a first guess based on the geoid model rather 
than a numerical model as done in previous versions. 
"he avallability of additional in-situ measurements 
zompared to previous versions, also enhanced the 
Juality of new regional MDTs. Their error has been 
estimated between 5 and 6& cm in mean dynamic 
height and between 10.5 and 11.65 cm/s for the 
3ssociated mean geostrophic current (Jousset et al,, 
2020). These regional MDTs have been used in the SL- 
7AC regional production since May 2021, 
monthly mean sea level anomalies gridded fields 
were also introduced in the REP series in 2020, 
‚in 2019, regional products, initially defined for the 
Mediterranean Sea and Black Sea were extended to 
the whole European Seas, including the North East 
Atlantic and Baltic Seas in order to better address 
different regional MFCs, 
-a specific field, giving an information of the formal 
mapping error of the geostrophic current was 
introduced in the gridded NRT products in 2020. This 
evolution will be completed in REP/DT series during 
year 2021, 
-the C3S altimeter products were introduced in the 
CMEMS catalogue in late 2018, 
- specific products’ format and _nomenclature 
evolutions were implemented in order to contribute 
to the CMEMS catalogue standards homogenization 
The SL-TAC products are now all delivered in NetCDF 
cf1.6 standards, 
‘romin a user-oriented perspective, the collaboration 
with MFCs (the most direct users of SL-TAC), was 
ensured through the organization of meetings and 
discussions with MFCs assimilation experts. These 
meetings were a place to discuss about different 
issues regarding altimeter sea level products (e.g., 
products resolution, physical content, observation 
errors, reference surface) and to design and 
test new experimental products before possible 
implementation. 6 of such meetings were organizec 
during the 2015-2020 period. 
50° N 
30° N 
0° 
30°5 
60°,5 
90° 
0 
10 
45°E 90° 135°E 180° 135°W" 930° W" 45° 
A 
LLC — ——— — 
300 400 (X) A000 700 
igure 2: Effective spatial resolution, in kilometers, of the DUACS-DT2018 maps for the Global Ocean aridded product. From Ballarotta et al. (2019)