MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
‚igure 3: Example of the daily L4 Sea Surface Temperature product in 2020, including satellite observations from Seviri on MSG, VIIRS NPP, 
/URS N20, SLSTRs on Sentinel-3A and S3B. GOES16. GOES17, Himawari, MSG Indian Ocean, AVHRR on Metop-B, AMSRE 2 and GMI. 
1.3 Baltic Sea products 
The operational Baltic Sea SST product is a Level 4 gap-free 
field covering the North Sea and Baltic Sea with a spatial 
resolution of 1/50°. In 2015, inputs to the operational 
product were level 2, swath based Metop, NOAA AVHRR 
SSTs observations supplemented with Geostationary 
SEVIRI observations. A dynamical and spatially varying 
bias adjustment scheme was introduced in 2015 when 
SST products were referenced to each other, resulting in 
improved performance for SST fields. 
The launch of the Copernicus Sentinel-3A and 3B 
satellites provided a significant amount of additional SST 
observations. Sentinel-3A data were Included In 2018 
and the Sentinel-3B was included in 2019 together with 
NOAA 20 SST observations. The inclusion of additional 
satellite SST products has led to a significant increase in 
the performance of the operational product over the last 5 
vears, when compared to in situ observations. 
A new product was introduced in the Baltic Sea SST 
portfolio in 2019 as per user requests from the CMEMS 
Baltic Sea Monitoring Forecasting Center (BAL-MFC). The 
product was a level 3 supercollated (L3S) field consisting 
of aggregated and referenced satellite observations that 
were averaged but not interpolated to fill gaps. The product 
ıs now being routinely assimilated in the CMEMS BAL-MFC 
3cean model runs. An example of a L3S field is shown in 
Tigure 4