Real-time Reconstruction of Surface Velocities from Satellite Observations in the Alboran Sea

Abstract

Surface currents in the Alboran Sea are characterized by a very fast evolution that is not well captured by altimetric maps due to sampling limitations. On the contrary, satellite infrared measurements provide high resolution synoptic images of the ocean at high temporal rate, allowing to capture the evolution of the flow. The capability of Surface Quasi-Geostrophic (SQG) dynamics to retrieve surface currents from thermal images was evaluated by comparing resulting velocities with in situ observations provided by surface drifters. A difficulty encountered comes from the lack of information about ocean salinity. We propose to exploit the strong relationship between salinity and temperature to identify water masses with distinctive salinity in satellite images and use this information to correct buoyancy. Once corrected, our results show that the SQG approach can retrieve ocean currents slightly better to that of near-real-time currents derived from altimetry in general, but much better in areas badly sampled by altimeters such as the area to the east of the Strait of Gibraltar. Although this area is far from the geostrophic equilibrium, the results show that the good sampling of infrared radiometers allows at least retrieving the direction of ocean currents in this area. The proposed approach can be used in other areas of the ocean for which water masses with distinctive salinity can be identified from satellite observations.

Toward an Enhanced SMOS Level-2 Ocean Salinity Product

“…These encouraging results points to the exploitation of the L2NS SSS for oceanographic applications such us the retrieval of ocean surface currents [26]- [28].…”

Can the Surface Quasi‐Geostrophic (SQG) Theory Explain Upper Ocean Dynamics in the South Atlantic?

“…Density anomaly presents a natural choice of variable for the ψ sqg reconstruction. Yet there were several studies (González‐Haro & Isern‐Fontanet, 2014; Isern‐Fontanet et al., 2006, 2020; LaCasce & Mahadevan, 2006; Turiel et al., 2008) that used SST as a proxy for surface buoyancy, because it can be measured remotely from satellite sensors. One key assumption for using SST or density for the SQG reconstruction is that these properties are in phase with SSH contours (e.g., Lapeyre & Klein, 2006), which allows the reconstruction from a SST or density snapshot.…”

“…Several studies have been conducted using different approaches of the SQG method with satellite data (e.g., Isern-Fontanet et al, 2020. Isern-Fontanet et al (2006) reconstructed surface ocean currents using microwave radiometer SST data to complement the altimeter, exploring the property that SST can be a good proxy for buoyancy under determined circumstances.…”

Editorial for the Special Issue: “Ten Years of Remote Sensing at Barcelona Expert Center”

“…The following two chapters deal with sea-surface currents. In the first, from Isern-Fontanet et al [9], the relationship between satellite salinity and temperature data to correct the buoyancy and to retrieve ocean currents by using the SQG approach is explored. The study is focused in the Alboran Sea where the altimetric maps have some limitations for capturing the ocean currents.…”