The SWOT mission enables unprecedented observations of sea surface height (SSH) at smaller scales, where the ocean’s dynamic balance becomes more nuanced and ageostrophic effects become increasingly important. However, our understanding of the interplay among submesoscale processes and their expression in SSH remains limited, largely due to the challenges of resolving the full submesoscale momentum budget using traditional in-situ analyses.
To address this challenge, we assess the dynamic balance in the ocean surface layer by evaluating the terms in the Lagrangian momentum equation using satellite-tracked surface drifter trajectories. This approach enables a direct, scale-free diagnosis of the forces acting on near-surface parcels, including the pressure gradient force, wind stress, Coriolis acceleration, and friction. The resulting estimates of pressure gradients and their variability can be directly compared with concurrent SWOT observations.
We apply this analysis to data from the 2023 NASA S-MODE field campaign, which deployed over 100 drifters near a SWOT Cal/Val crossover site off the coast of California. Preliminary results highlight the spatial and temporal variability of unbalanced dynamics associated with submesoscale frontal activity and wind forcing. These findings offer new insight into the interpretation of SWOT Level 2 SSH products in dynamically active regions. Ongoing work focuses on refining these diagnostics and developing tools for the operational integration of Lagrangian and SSH observations to improve our understanding of surface current dynamics.