Abstract's details
Data Assimilation of Surface Geostrophic Currents Derived from SWOT data in the Northwestern Pacific Ocean and marginal seas
Event: 2025 SWOT Science Team Meeting
Session: Oceanography: Inversion/Assimilation
Presentation type: Poster
Previous studies have primarily focused on assimilating Sea Level Anomalies (SLA) observed by SWOT altimetry. However, direct assimilation of surface geostrophic currents derived from SWOT SLA data into ocean circulation models is rare. This study evaluates the impact of assimilating surface geostrophic currents derived from high resolution SWOT altimetry data into a regional ocean circulation model.
Data assimilation experiments were conducted for 2024 using the Regional Ocean Modeling System (ROMS). The Ensemble Optimal Interpolation (EnOI) method was applied, with a hindcast simulation spanning 1993–2022 used for the estimation of background error covariance. Two experiments were carried out to examine the effects of assimilating surface geostrophic currents. The control experiments assimilated satellite-observed sea surface temperature data, low resolution gridded surface geostrophic currents, and in-situ temperature and salinity profiles. The second experiment used the same configuration, but additionally assimilated high resolution surface geostrophic currents derived from SWOT altimetry.
The experiment that assimilated SWOT-derived surface geostrophic currents reproduced mesoscale eddy structures in the East Sea and the Kuroshio Extension regions, dominated by geostrophic flow. Spectrum analysis revealed that increased energy at scales between 40km and 140km, indicating that assimilating SWOT-derived surface geostrophic currents enhances representation of mesoscale eddies. The root mean square errors (RMSEs) in temperature profiles decreased by 0.36 %, while those in salinity profiles decreased by 0.01%, indicating that the assimilation of high-resolution geostrophic currents had minimal impact on the overall temperature and salinity structures. However, RMSE in temperature decreased by 23.35% in the East Sea from March to May.
These results suggest that high resolution surface geostrophic currents can improve the accuracy of mesoscale eddy representation. Nevertheless, this study applied a spatially and temporally uniform observation error. In the future work, time varying observation errors will be considered and the effects on the salinity and temperature profiles will be investigated.
This Research was supported by Korea Institute of Marine Science & Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries, Korea (RS-2025-02217872)
Back to the list of abstractData assimilation experiments were conducted for 2024 using the Regional Ocean Modeling System (ROMS). The Ensemble Optimal Interpolation (EnOI) method was applied, with a hindcast simulation spanning 1993–2022 used for the estimation of background error covariance. Two experiments were carried out to examine the effects of assimilating surface geostrophic currents. The control experiments assimilated satellite-observed sea surface temperature data, low resolution gridded surface geostrophic currents, and in-situ temperature and salinity profiles. The second experiment used the same configuration, but additionally assimilated high resolution surface geostrophic currents derived from SWOT altimetry.
The experiment that assimilated SWOT-derived surface geostrophic currents reproduced mesoscale eddy structures in the East Sea and the Kuroshio Extension regions, dominated by geostrophic flow. Spectrum analysis revealed that increased energy at scales between 40km and 140km, indicating that assimilating SWOT-derived surface geostrophic currents enhances representation of mesoscale eddies. The root mean square errors (RMSEs) in temperature profiles decreased by 0.36 %, while those in salinity profiles decreased by 0.01%, indicating that the assimilation of high-resolution geostrophic currents had minimal impact on the overall temperature and salinity structures. However, RMSE in temperature decreased by 23.35% in the East Sea from March to May.
These results suggest that high resolution surface geostrophic currents can improve the accuracy of mesoscale eddy representation. Nevertheless, this study applied a spatially and temporally uniform observation error. In the future work, time varying observation errors will be considered and the effects on the salinity and temperature profiles will be investigated.
This Research was supported by Korea Institute of Marine Science & Technology Promotion (KIMST) funded by the Ministry of Oceans and Fisheries, Korea (RS-2025-02217872)