Abstract's details
High-Resolution Observations from the FaSt-SWOT Campaigns: Validation and Fine-Scale Signal Analysis
Event: 2025 SWOT Science Team Meeting
Session: Oceanography: Velocities
Presentation type: Oral
During the SWOT fast-sampling phase, two field campaigns were conducted (April-May 2023) to perform a multi-platform in situ experiment in the western Mediterranean Sea in the frame of the FaSt-SWOT project. In situ observations combining ship-based instruments and autonomous platforms (surface drifters and gliders) together with complementary satellite data (SST, ocean colour, and conventional nadir altimetric products) provided a comprehensive view of the surface dynamics in our study area. These measurements allowed us to characterize a small-scale eddy observed by SWOT, and to trace its evolution.
In this study, we focus on two complementary components that provide continuous, high-resolution observations during and beyond the FaSt-SWOT campaigns:
(1) glider-based observations, which resolve the vertical and temporal evolution of a targeted eddy;
(2) surface drifter trajectories, which provide detailed insights into surface circulation, vorticity and the validity of the geostrophic assumption.
Two gliders were programmed to repeatedly perform back-and-forth sections over a 3-week period, with a 1-day delay between them. This strategy provided the opportunity to evaluate the temporal variability of ocean fields at a frequency comparable to SWOT’s fast-sampling phase repeat cycle, offering valuable insights into the evolution of fine-scale structures. Quantification of temporal variability from both gliders shows a good agreement, laying the groundwork for further analyses of high-frequency signals present in both SWOT absolute dynamic topography and glider-derived dynamic height.
Using surface currents from 40 surface (~1 m depth) and 6 subsurface (~15 m depth) drifters, we infer Differential Kinematic Properties (DKP) like vorticity, to compare them with the SWOT-derived counterparts. These results allow us to confirm the validity of the geostrophic assumption in our study region, with Rossby numbers < 1. The extended continuity of the drifter dataset beyond the campaign period enables further evaluation of the SWOT-derived velocity fields and the surface dynamics these represent. Compared to nadir altimetric products (e.g. the DUACS-OI dataset), SWOT velocities show significant improvements.
The in situ observations confirm SWOT’s significantly improved capability in detecting sea level signature of small-scale eddies and their temporal variability. Beyond Cal/Val activities, this FaSt-SWOT dataset helps to better characterize and understand the fine-scale dynamics in this region, characterized by a small Rossby radius of deformation. We also highlight the implications of SWOT swath corrections on characterizing small mesoscale structures, and underscore how wide-swath altimetry introduces both new challenges and transformative opportunities for understanding previously unresolved dynamics.
Back to the list of abstractIn this study, we focus on two complementary components that provide continuous, high-resolution observations during and beyond the FaSt-SWOT campaigns:
(1) glider-based observations, which resolve the vertical and temporal evolution of a targeted eddy;
(2) surface drifter trajectories, which provide detailed insights into surface circulation, vorticity and the validity of the geostrophic assumption.
Two gliders were programmed to repeatedly perform back-and-forth sections over a 3-week period, with a 1-day delay between them. This strategy provided the opportunity to evaluate the temporal variability of ocean fields at a frequency comparable to SWOT’s fast-sampling phase repeat cycle, offering valuable insights into the evolution of fine-scale structures. Quantification of temporal variability from both gliders shows a good agreement, laying the groundwork for further analyses of high-frequency signals present in both SWOT absolute dynamic topography and glider-derived dynamic height.
Using surface currents from 40 surface (~1 m depth) and 6 subsurface (~15 m depth) drifters, we infer Differential Kinematic Properties (DKP) like vorticity, to compare them with the SWOT-derived counterparts. These results allow us to confirm the validity of the geostrophic assumption in our study region, with Rossby numbers < 1. The extended continuity of the drifter dataset beyond the campaign period enables further evaluation of the SWOT-derived velocity fields and the surface dynamics these represent. Compared to nadir altimetric products (e.g. the DUACS-OI dataset), SWOT velocities show significant improvements.
The in situ observations confirm SWOT’s significantly improved capability in detecting sea level signature of small-scale eddies and their temporal variability. Beyond Cal/Val activities, this FaSt-SWOT dataset helps to better characterize and understand the fine-scale dynamics in this region, characterized by a small Rossby radius of deformation. We also highlight the implications of SWOT swath corrections on characterizing small mesoscale structures, and underscore how wide-swath altimetry introduces both new challenges and transformative opportunities for understanding previously unresolved dynamics.