MERCATOR OCEAN JOURNA, 
SEPTEMBER 2021 
Basin coverage in the Mediterranean Sea with multi sensor 
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2019. B) introduction of OLCI S3A in 201%: C) introduction of NOAA VIIIRS 20 in 2019 
1.2.2 Sentinel data streams 
Since 2018, the Sentinel-3A/OLCI datasets have been added 
to the CMEMS catalogue with a spatial resolution of 1 km 
(consistent with the other OCTAC datasets) and with the first 
11 ofthe 21 OLCI spectral bands. The OLCI data stream was 
‚ncluded in the NRT/DT/REP processing chains of multi- 
sensor products for Global Ocean and Regional Seas 
«Figure 2). In May 2021, OLCI datasets at 300 m resolution 
were added to the catalogue combining the Sentinel-3A and 
B missions. This increased the product coverage and 
resolution of the whole regional seas, as well as the global 
level data up to 200 km along from the coastline (Figure 4) 
For the OLCI “single-sensor” product and the 300 meters 
product, the Global Chlorophyll-a product stored in the 
EUMETSAT level-2 is used (i.e., O0C4Me algorithm). In 
February 2021, EUMETSAT switched for NRT product to a 
new algorithm based on a blended 0C4Me/CI-Hu approach. 
Sentinel-2 MS! datasets products are available in the 
catalogue since May 2021. These high-resolution products 
are delivered on a daily and monthly basis for coastal 
waters (20 km strip from the coastline) for all Europear. 
Seas with a spatial resolution of 100 m (Figure 5). Europear 
Seas have very specific optical characteristics and 
zhallenges. Diverse atmospheric conditions and fast 
zhanging water types in space and time are addressed by 
zombining different algorithms for Atmospheric Correction 
(Brockmann et al., 2016; Keukelaere et al., 2018; Novoa et 
al., 2018, Vanhellemont, 2019) and in-water retrieval (Gons 
et al., 2002; Nechad et al., 2010). The selection and merging 
of algorithms are based on criteria that characterize the 
water colour (Lavigne et al. 2021). Delivered parameters 
are water-leaving reflectances, turbidity (e.g., Figure 5), 
suspended matter concentration, backscatter and 
Chlorophyll concentration.