Enhancing SWOT Geoid Resolution in Regions Characterized by Complex Oceanic Dynamics via the mrCOSTS Method

A New Approach to Estimate Ocean Surface Velocity from High-Resolution Surface Water and Ocean Topography (SWOT) Data

This study presents a novel cyclostrophic balance correction method for estimating submesoscale ocean surface currents in the Northern Arabian Sea using surface water and ocean topography (SWOT) mission altimetry. High-resolution Ocean Color Monitor (OCM-3) data from the EOS-06 satellite reveal fine-scale eddies and filaments with high chlorophyll-a concentrations (>0.4 mg m−3), spatially coherent with geostrophic current patterns from SWOT. At these scales, the geostrophic assumption is invalid; therefore, we introduce a curvature-based cyclostrophic correction that accounts for enhanced centripetal accelerations. Validation against high-resolution model simulations shows that our approach is in better agreement with model outputs than uncorrected and previously published corrected fields, particularly in regions with strong vorticity and strain. When applied to SWOT data, the corrected velocities demonstrate spatial correspondence with chlorophyll patterns and suppress spurious gradients. Probability density functions of normalized vorticity and strain also match theoretical expectations, emphasizing the potential of SWOT for advancing submesoscale ocean dynamics.

Fine-Scale Eddies Revealed by the Surface Water and Ocean Topography (SWOT) Mission

Utilizing two-dimensional sea level anomalies from the Surface Water and Ocean Topography (SWOT) wide-swath altimeter, we conduct a global census of fine-scale eddies (with equivalent radii < 30 km) that are beyond the resolution capacity of traditional altimeters. We find that these eddies are concentrated in regions with energetic mesoscale currents such as western boundary current extensions, the Antarctic Circumpolar Current and prominent interior frontal zones. While these eddies are smaller than classical mesoscale eddies (O(100) km), they exhibit dynamics distinct from the mesoscale, including a pronounced winter peak in occurrence frequency and a striking dominance of cyclonic over anticyclonic polarities. A global composite reveals a net enhancing effect of these fine-scale eddies on surface chlorophyll-a (approximately +7% within eddy cores relative to surrounding waters). Our findings shed light on the dynamical characteristics and surface chlorophyll-a signatures of fine-scale ocean eddies, necessitating their adequate representation in next-generation ocean models.

Assessing Dynamical Contributions to SWOT Sea Surface Height in an Internal Tide Hotspot

The Surface Water and Ocean Topography (SWOT) mission has revealed high‐frequency sea surface height anomaly (SSHA) variability associated with internal gravity waves, yet comparison with in situ observations remains limited. Here, we analyze a mooring array beneath the swaths of SWOT Cal/Val south of New Caledonia, an internal tide (IT) hotspot in the southwestern tropical Pacific. SWOT agrees closely with mooring‐derived SSHA, exhibiting three times larger variance than gridded SSHA from nadir altimetry. This excess variance is mainly driven by coherent ITs, explicitly extracted from SWOT swaths, with amplitudes exceeding 10 cm. Comparison with mooring‐based estimates demonstrates centimeter‐level accuracy in the retrieved IT signal. SWOT‐derived ITs reveal substantial errors in empirical IT atlases, routinely used to correct SWOT. Particularly, absolute (relative) errors in SSHA‐derived current velocities exceed 15 cm s−1 ${\mathrm{s}}^{-1}$ (80%) in 10% of cases during SWOT Cal/Val, calling for improved methods to separate wave‐like and balanced motions.

Wide-swath satellite altimetry and novel subsurface temperature observations improve predictions in a dynamic western boundary current: System optimization and performance

Satellite Altimetry Signal Processing for Eddy Kinetic Energy Estimation in the Indonesian Seas: Toward Intelligent Ocean Monitoring

Indonesia hosts one of the most dynamically complex marine systems due to the interaction of the Indonesian Throughflow, monsoonal circulation, and complex bathymetry. These processes generate strong mesoscale variability that can be quantified using Eddy Kinetic Energy (EKE). This study proposes a satellite-altimetry-based framework for estimating EKE across the Indonesian Seas using Jason-3 observations integrated with Sea Level Anomaly (SLA) products from the Copernicus Marine Environment Monitoring Service (CMEMS). Geostrophic velocity anomalies were derived from SLA gradients and subsequently used to calculate EKE. Several preprocessing steps, including geophysical corrections, noise filtering, and anomaly normalization, were applied to improve data quality. An intelligent monitoring framework was developed to support automated data ingestion, EKE computation, and anomaly detection. Results indicate pronounced spatial variability of EKE, with elevated values observed in the Makassar Strait, Banda Sea, and southern Java waters. Seasonal analysis reveals stronger EKE during the southeast monsoon, while interannual variability demonstrates links with ENSO and the Indian Ocean Dipole. The proposed framework highlights the potential of integrating satellite altimetry and intelligent monitoring systems for operational ocean observation, environmental assessment, and coastal resilience applications.

High-resolution flood monitoring based on CYGNSS surface reflectivity: a case study of Sofala Province, Mozambique

Extreme precipitation associated with tropical cyclones frequently triggers severe flooding in low-lying coastal regions, highlighting the importance of timely and reliable flood monitoring. Conventional remote sensing approaches are often constrained by limited temporal resolution and cloud interference. To address these limitations, this study investigates the application of Cyclone Global Navigation Satellite System (CYGNSS) Level 1 observations for flood detection in Sofala Province, Mozambique, which was severely affected by Cyclone Idai in March 2019. Surface reflectivity (SR) is derived from delay Doppler map (DDM) measurements and employed to characterize surface water conditions. A threshold-based criterion is then applied to delineate inundated areas. The results are evaluated using Soil Moisture Active Passive (SMAP) soil moisture data, together with precipitation records and time series analysis. The findings indicate that SR responds sensitively to variations in surface water, enabling effective identification of flood extent. A strong consistency is observed between CYGNSS-derived results and SMAP observations, while CYGNSS additionally provides improved temporal resolution and all-weather monitoring capability. Time series analysis further reveals a clear linkage among precipitation, soil moisture dynamics, and flood evolution. Overall, this study demonstrates the effectiveness of GNSS-R observations for rapid flood monitoring, particularly in data-scarce regions.