MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
The OCTAC provides users across the scientific and 
operational oceanography communities, commercial 
providers focused on the use of marine resources, and 
public agencies focused on environmental monitoring, with 
Interests in data across oceanic, shelf and coastal waters. 
Depending on their applications, these users require 
different spatial resolutions (i.e., -1 km in ocean, 300 m 
over the shelf, down to 10's of metres in coastal waters). 
To meet these needs, OCTAC provides in a timely and 
sustained manner a set of Essential Ocean Variables (EOVs) 
that can be retrieved from Ocean Colour radiometry. These 
include Chlorophyll-a concentration (CHL), Inherent Optical 
BE 
1016 
2017 
IRT 
ingle-sensor 
MODIS „1KS 
3/01 
s3A IKM 
Properties (I0Ps), and PFTs/PSCs (Phytoplankton 
Functional Types and Size Classes), as well as the 
radiometry in itself (GOOS, 2018). 
Since 2015, CMEMS has been providing single-sensor as 
well as multi-sensor products (Table 1) at 1 km resolution 
for European seas, and at 4 km resolution for the Global 
Ocean. In 2017-2018, the single-sensor MODIS and VIIRS 
datasets were retired and the single-sensor Sentinel-3A/ 
OLCI was introduced. In May 2021, OLCI datasets at 300 m 
vesolution combining Sentinel-3A and B, as well as the 
Sentinel-2/MSI datasets at 100 m, were added to the 
catalogue (Figure 2). 
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‚Do 
*ure £: Overview of the OCTAC catalogue evolution from 2015 to 202 
1. MAIN ACHIEVEMENTS FROM 2015 
TO 2021 AND STATUS AT THE END OF 
CODERNICUS 1 
The OCTAC comprises three OC production centres that 
generate global and regional higher-level combined 
products, thus bridging the gap between space agencies 
providing ocean colour data and users needing added- 
value information (not yet available from space agencies). 
These higher-level combined products provide added- 
value to standard products delivered by the space agencies, 
in terms of both harmonization and accuracy. 
Firstly, observations from multiple missions are processed 
together to ensure homogenized and inter-calibrated 
datasets with higher spatial coverage than the single- 
sensor data streams. Second, regional satellite products 
provide higher accuracy at basin level than the standard 
Ocean Colour data. Indeed, the regionalization of processing 
chains takes into account bio-optical characteristics of 
aach regional sea (Atlantic, Arctic, Baltic, Mediterranean 
and Black Sea) for production and data validation (e.g., 
D’Alimonte and Zibordi, 2003; Brewin et al., 2018; Kaliyama 
et al., 2018; Pitarch et al., 2016; Volpe et al., 2007; 2019). 
Moreover, blended Chlorophyll products are generated 
with the appropriate algorithm across the open ocean and 
zoastal waters based on the occurring water types 
(Hieronymi et al., 2015; Kajiyama et al., 2018; Le Traon et 
al., 2017; Volpe et al., 2019). 
For each ocean region, the OCTAC delivers two types of 
products: CHL and OPTICS. CHL includes the phytoplankton