## 5 Conclusions  
During the EUREC\({}^{4}\)A-OA/ATOMIC campaign, saildrones and research vessels were deployed in the North Brazil Current region in order to investigate mesoscale eddies and submesoscale fronts. In this study, saildrone salinity observations recorded during the campaign were compared with four different SSS products SMAP JPL, SMAP RSS 40 km, SMAP RSS 70 km and HYCOM, with the aim of highlighting the strengths and weaknesses of each product and identifying the best product for use in this area. This study represents the first validation of SMAP satellite-derived SSS using the saildrone in the river-influenced Western Tropical Atlantic, and this information can allow researchers to make informed decisions regarding the most ideal product for their application as well as highlight issues to algorithm developers. Overall, it was found that SMAP RSS 70 km outperformed its counterparts. However, SMAP RSS 40 km was better within freshening events such as a fresh tongue, with HYCOM being on the opposite spectrum, failing to identify submesocale features such as the fresh tongue. Akin to the SMAP RSS 70 km, SMAP JPL and HYCOM performed well in areas where the large-scale salinity conditions were constant, but improved input SSS fields may be required for HYCOM to reproduce smaller-scale salinity fluctuations. Finally, the results of this study can aid in the improvement of mesoscale and submesoscale SSS products, which can lead to the refinement of NWP and climate models and therefore to improved weather, ocean and climate forecasts, especially for tropical regions. An increase in SSS observations (e.g., augmented Argo floats or buoys) in the western Tropical Atlantic would allow for improved validation of SMAP and model estimates in this area. The use of the three saildrones for such a short period is insufficient to ascertain all of the SSS complexities in this location. This research paper was conceptualized by [PERSON]. Software was developed by [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON]. The validation process was executed by [PERSON] The formal analysis was done by [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON]. Resources were provided by the Caribbean Institute for Meteorology and Hydrology and Farallon Institute and the data was curated by [PERSON]. Writing-original draft preparation was executed by [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] and review and editing included [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON]. Data visualization was executed by [PERSON], [PERSON], [PERSON], [PERSON] Figure 4 was created by [PERSON], Figure 5 was created by [PERSON], Figure 7 was created by [PERSON] and Figures 3 and 6 were created by [PERSON] The project was supervised by [PERSON]. All authors have read and agreed to the published version of the manuscript. This research funding was provided by NASA Physical Oceanography grant number 80 NSSC20K1003. EUREC\({}^{4}\)A is funded with support of the European Research Council (ERC), the Max Planck Society (MPG), the German Research Foundation (DFG), the German Meteorological Weather (DWD) and the German Aerospace Center (DLR). Funding for the development of HYCOM has been provided by the National Ocean Partnership Program and the Office of Naval Research. Data assimilative products using HYCOM are funded by the U.S. Navy. The saildrone v1 data presented in this study are openly available at [[https://doi.org/10.5067/SDRON-ATOM0](https://doi.org/10.5067/SDRON-ATOM0)]([https://doi.org/10.5067/SDRON-ATOM0](https://doi.org/10.5067/SDRON-ATOM0)) (accessed on 30 April 2021). The HYCOM GOFS 3.1 data presented in this study are openly available at [[https://www.hycom.org/dataserver/gofs-3](https://www.hycom.org/dataserver/gofs-3) pt1/analysis]([https://www.hycom.org/dataserver/gofs-3](https://www.hycom.org/dataserver/gofs-3) pt1/analysis) (accessed on 17 September 2021), dataset id: GLBy0.08-expt_93.0+t83z.