First SMOS Sea Surface Salinity dedicated products over the Baltic Sea

Abstract. This paper presents the first Soil Moisture and Ocean Salinity (SMOS) Sea Surface (SSS) dedicated products over Baltic Sea. The SSS retrieval from L-band brightness temperature (TB) measurements this basin is really challenging due to important technical issues, such as land–sea ice–sea contamination, high contamination by radio-frequency interference (RFI) sources, low sensitivity of TB at changes in cold waters, poor characterization dielectric constant models for range basin. For these reasons, exploratory research algorithms used level 0 up 4 has been required develop products. work performed framework European Space Agency regional initiative Baltic+ Dynamics. Two have generated period 2011–2019 are freely distributed: Level 3 (L3) product (daily 9 d maps a 0.25∘ grid; https://doi.org/10.20350/digitalCSIC/13859, González-Gambau et al., 2021a) (L4) 0.05∘ https://doi.org/10.20350/digitalCSIC/13860, 2021b)​​​​​​​, which computed applying multifractal fusion L3 with SST maps. accuracy typically around 0.7–0.8 psu. L4 an improved spatiotemporal resolution respect 0.4 Regions highest errors limited coverage located Arkona Bornholm basins Gulfs Finland Riga. impact assessment shown that they can help understanding salinity dynamics They complement temporally spatially very sparse situ measurements, covering data gaps region, also be useful validation numerical models, particularly areas where sparse.