MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
Based on GLO12v3 operational system, the GLORYS12v1 
reanalysis at 1/12° has been developed to cover the 
altimetry period. The main specificities in GLORYS12v1 
stand in: 
using atmospheric reanalysis (ERAinterim and then 
ERA5), 
reprocessed observation data set for the full period, 
-benefit from some changes in the system, notably 
an observation errors (e.g., 3D T/S in situ seasonal 
observations errors have been computed from 
3L012v3). 
Homogeneity of the reanalysis system, atmospheric 
forcing and assimilated data set allow representation of 
ocean varilability and trend and associated uncertainties 
and errors. These results are presented in Lellouche et al,, 
‘2021) as, for example, the satisfying agreement between 
global reanalysis and satellite observations for regional 
sea level trends. Indeed, discrepancies between the 
GLORYS12v1 reanalysis and reference altimetric datasets 
remain small as they do not exceed +/- 2 mm/yr in the 
majority of the ocean observed by altimetry 
1.2 Wave forecast and reanalysis 
Wave products were added to Copernicus catalogue in 
April 2017. The global wave forecasting system of CMEMS 
is developed and operated by Meteo-France. It is based on 
state-of-the-art MFWAM model (JCOMM systematic inter- 
comparison, Bidlot et al., 2006). The first version of near 
real time system (WAVEv1) leverages the ECWAM-IFS- 
38R2 computing code with a dissipation term developed 
by Ardhuin et al., (2010). WAVEv1 was operated at 1/5° of 
resolution, with 6-hourly analysis and 3-hourly forecasted 
wind forcing from the IFS-ECMWF atmospheric system. 
WAVEv1 assimilated every 6 hours the significant wave 
height (SWH) observed by satellite (thanks to Jason 2 83, 
Saral and Cryosat altimeters). Forecasts were provided up 
to 5 days. Wave heights, period and directions of the total 
sea and its partitions (wind-sea, primary and secondary 
swells) were (and are still) distributed at a frequency of 3 h. 
In March 2018, the system was upgraded (to WAVEv2) with 
the IFS-41R2 computing code and several other features: 
„the first one concerns the resolution, which is 
improved from 1/5° to 1/10°, 
the second concerns physics, with an adjustment 
af the dissipation term and the use of a Phillips 
spectrum tail to constrain the high frequency part of 
the spectrum, 
-dispersion by oceanic currents is also introduced by 
forcing the system with daily surface currents from 
the GLO12v3 physical system (see Figure 1 for an 
indication of error on surface currents), 
the last point concerns the assimilation of Sentinel- 
1A and 1B wave spectra (Aouf et al, 2021). This is the 
first time that this type of data Is assimilated into an 
operational wave model, which in particular, makes 
possible to more accurately constrain sub-polar 
swells, 
Sentinel-3A is also added in the assimilated altimetry 
constellation. 
The validation of the global wave prediction system is 
performed using wave buoys and the independent altimeter 
HY2A, which shows values of scatter index of around 14% 
for SWH , and a SWH bias of 1 cm. Since December 2020, 
the system has been assimilating also wave heights from 
SWIM nadir CFOSAT, a Franco-Chinese satellite mission 
:WAVEv2.1). This improves scores by nearly 10%, especially 
for high latitudes. The forecast range is also extended to 10 
days. 
A new multi-year product (called WAVERYSv1) was also 
created to cover altimetry period from 1993 to present. 
It shares the same specificities as the real-time syster 
WAVEv2, except that its horizontal resolution is 1/5°. 
WAVERYSv1 has been shown to outperform the wave 
dataset of the ERA5 climate reanalysis, notably thanks 
to its better dissipation physics, the introduction of ocean 
currents and the assimilation of wave spectra over the last 
few years (Law-Chune et al, 2021). 
1.3 Biogeochemistry data assimilation 
"he biogeochemistry system, in its 1/4° configuration, 
was first commissioned at the beginning of CMEMS, in late 
2014. Since then, three major evolutions have been carriec 
gut: 
1.the upgrade of the dynamical forcing ocean, from 
the historical 1/4° to the current GLO12v3 1/12° (cf. 
section 2.1), 
2. the upgrade of the NEMO-PISCES model to version 3.6 
that includes new biogeochemical parameterizations 
(e.g., nitrogen fixation and impact of day length on 
phytoplankton growth), 
3. the activation of an Ocean Colour data assimilation 
embedded system, allowing a better control and 
confidence into the model outputs. 
‚his section provides a short synthesis of the last 2 points 
The data assimilation (hereafter DA) of satellite Ocean 
Colour maps capability has been effective since July 2019. 
Itis based on the MOi data assimilation tools (reduced order 
Kalman filter, based on the Singular Evolutive Extended 
Kalman filter formulation). The system thus, operationally 
3ssimilates daily L4 remotely sensed surface Chlorophyll. 
and produces a surface correction field of Chlorophyl 
and Nitrates (Lamouroux et al., in prep.). This correction 
is then projected vertically all along the local mixed layer. 
ın this first version of the biogeochemical assimilative 
system, only large-scale corrections (>500 km) are 
applied to the modelled Chlorophyll and nitrate. It has 
been indeed preferred to let the model develop Its own