Evaluation of SMOS L4 Sea Surface Salinity Product in the Western Iberian Coast

Abstract

Salinity is one of the oldest parameters being measured in oceanography and one of the most important to study in the context of climate change. However, its quantification by satellite remote sensing has been a relatively recent achievement. Currently, after over ten years of data gathering, there are still many challenges in quantifying salinity from space, especially when it is intended for coastal environments study. That is mainly due to the spatial resolution of the available products. Recently, a new higher resolution (5 km) L4 SMOS sea surface salinity (SSS) product was developed by the Barcelona Expert Center (BEC). In this study, the quality of this product was tested along the Western Iberian Coast through its comparison with in situ observations and modelled salinity estimates (CMEMS IBI Ocean Reanalysis system). Moreover, several parameters such as the temperature and depth of in situ measurements were tested to identify the variables or processes that induced higher errors in the product or influenced its performance. Lastly, a seasonal and interannual analysis was conducted considering data between 2011 to 2019 to test the product as a potential tool for long-term studies. The results obtained in the present analysis showed a high potential of using the L4 BEC SSS SMOS product in extended temporal and spatial analyses along the Portuguese coast. A good correlation between the satellite and the in situ datasets was observed, and the satellite dataset showed lower errors in retrieving coastal salinities than the oceanic model. Overall, the distance to the coast and the closest rivers were the factors that most influenced the quality of the product. The present analysis showed that great progress has been made in deriving coastal salinity over the years and that the SMOS SSS product is a valuable contribution to worldwide climatological studies. In addition, these results reinforce the need to continue developing satellite remote sensing products as a global and cost-effective methodology for long-term studies.

Response of phytoplankton to coastal upwelling: The importance of temporal and spatial scales

“…This study has provided a broad view of the spatiotemporal variability of the environmental conditions related to the upwelling-downwelling events on the WIC, through a new and extensive quasi-synoptic oceanographic dataset, that has not been done since the 1980 (Moita 2001). A clear north-south gradient was observed along the Portuguese coast for surface temperature and salinity, corroborating previous studies (Ferreira et al 2019;Santos da Silva 2020;Biguino et al 2022).…”

“…The campaign between February and March 2020 (AQ4) was named early spring given that the phytoplankton growing season in this region is considered to start in February (Brito et al 2012) and March is part of the spring conditions (e.g., Bode et al 2017). The surface seawater was sampled using Niskin bottles coupled to a rosette and combined with a multiparametric probe (Ocean Seven 320 Plus WOCE-CTD, IDRONAUT) equipped with temperature ( C), pressure (dbar), conductivity (ms cm À1 ) and turbidity (FTU, SEAPOINT OEM) sensors (for processing details see Biguino et al 2022). In situ meteorological parameters, that is, wind speed (m s À1 ) and direction (degrees), were obtained from the onboard anemometer during the campaigns (Fig.…”