MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
Secondly, a first integration schedule was drawn, showing 
the importance of relying on a common atmospheric 
forcing produced operationally (ERA5 from Copernicus 
Climate Change service, available since 2019). This 
schedule also highlighted three datasets that were limiting 
the extension In time of “best estimate” MYPs up to 3 
months before present: 
- ERA5 (best estimate stops 3 months before present), 
- sea level anomalies (orbital corrections available 3-4 
months before present), 
in situ (delayed time quality control induces a 6-month 
delay). 
In consequence, the current implementation of regular and 
timely deliveries of in situ CORA products, together with 
-eprocessed sea level anomaly time extensions in January 
and June each year, were organized with the technical 
coordination. In parallel, automatic “time extension mode” 
is progressively implemented for most REP. When this is in 
alace, regular updates of reanalyses can be scheduled 
every 6 months, for the best estimate MYPs to reach 1 year 
before real time. 
2. CONTINUITY AND TIMELINESS: TOWARD 
INTERIM PRODUCTION, UP TO ONE MONTH 
BEFORE PRESENT 
In order to provide reliable trends together with consistent 
and recent information on the ocean state, MYPs have to be 
zontinuous in time and ideally reach one month before 
oresent. Starting 3 months before present, ERA5T 
atmospheric fields continue the ERA5 reanalysis by using 
the same atmospheric reanalysis system and leveraging 
near real-time upstream data. In consequence, the ERA5/ 
ERAST series allows the provision of a continuous 
atmospheric forcing over the past decades up to one month 
before present, which in turn can be used by the Marine 
Service MYPs. If not homogeneous in terms of quality, 
ERA5/ERAST is homogeneous In terms of technica 
zharacteristics (grid, variables, frequency, main settings) 
As shown in Figure 3, one objective of the cross-cutting 
MYP activity was to collaborate with the Marine Service 
producers to propose such continuous MYPs, making an 
optimal use of the ERAS5/ERAST suite. Depending on 
upstream dependencies, production centres will be 
implementing scenario (A) or (B) between 2021 and 2024. 
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Best estimate production 
using high quality reprocessed / quality controlled inputs 
2 Alnterim production 
S using DT/NRT Inputs 
A. Interim Initialization Is “rolline” 
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Best estimate production 
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Interim production 
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7} 
- Schematic of the organization of the Marine Service multi-vear interim production