Abstract's details
Sub-mesoscale and coastal ocean dynamics in the North Indian Ocean using SWOT and EOS-06/OCM-3 observations
Event: 2025 SWOT Science Team Meeting
Session: Oceanography: Calibration and Validation
Presentation type: Poster
High resolution sea level observations from Surface Water and Ocean Topography (SWOT)
mission has enabled us to observe the small scale sea level and circulation features that play an
important role in dynamics of the ocean. SWOT provides sea level observations at the 2km
resolution over the 120 km swath with a middle gap of 20 km. This enables us to derive
geostrophic currents over the similar grid. At these smaller scales, there is mix of balanced
motions such as mesoscales, submesoscales and unbalanced motions such as internal waves.
Circulation features at smaller scales additionally have cyclostrophic components in addition to
the pressure gradient and coriolis, which make the geostrophic assumptions invalid. In addition
to the small-scale circulation features in the open ocean, sea level observations in the coastal
regions is also a focus of SWOT mission. Coastal areas are highly dynamic because of several
coastal processes like coastal jets, tidal circulation, high-density gradients, wind generated
dynamics, internal waves etc. SWOT observations can help to reveal some of these dynamics.
In this study, we firstly validate the SWOT sea levels observations over the Indian regions
through coastal tide gauge observations and argo floats. Validation results show an error of 3-
9cm based on multiple tide gauge observations. The coastal observations for the SWOT is also
shown to have more valid observations in the 0-8 km coastal band as compared to along-track
nadir observations. SWOT show 17% more variability with respect to the standard seal level
gridded products. The RMSD between the SWOT and standard seal level gridded products is
nearly 3.3 cm; however, there are considerable differences near the coast, where SWOT sea
levels depict significantly higher difference (~5cm RMSD). Detailed results will be presented in
the meeting.
Secondly, we analyse the covaribility of the chlorophyll form EOS-06/OCM3 and the
circulation features derived from the SWOT. A scheme to correct the SWOT circulation for the
cyclostrophic features has also proposed. We show several test cases of SWOT and chlorophyll
to show the improvements in using the proposed scheme. Detailed results will be presented in the
meeting.
Back to the list of abstractmission has enabled us to observe the small scale sea level and circulation features that play an
important role in dynamics of the ocean. SWOT provides sea level observations at the 2km
resolution over the 120 km swath with a middle gap of 20 km. This enables us to derive
geostrophic currents over the similar grid. At these smaller scales, there is mix of balanced
motions such as mesoscales, submesoscales and unbalanced motions such as internal waves.
Circulation features at smaller scales additionally have cyclostrophic components in addition to
the pressure gradient and coriolis, which make the geostrophic assumptions invalid. In addition
to the small-scale circulation features in the open ocean, sea level observations in the coastal
regions is also a focus of SWOT mission. Coastal areas are highly dynamic because of several
coastal processes like coastal jets, tidal circulation, high-density gradients, wind generated
dynamics, internal waves etc. SWOT observations can help to reveal some of these dynamics.
In this study, we firstly validate the SWOT sea levels observations over the Indian regions
through coastal tide gauge observations and argo floats. Validation results show an error of 3-
9cm based on multiple tide gauge observations. The coastal observations for the SWOT is also
shown to have more valid observations in the 0-8 km coastal band as compared to along-track
nadir observations. SWOT show 17% more variability with respect to the standard seal level
gridded products. The RMSD between the SWOT and standard seal level gridded products is
nearly 3.3 cm; however, there are considerable differences near the coast, where SWOT sea
levels depict significantly higher difference (~5cm RMSD). Detailed results will be presented in
the meeting.
Secondly, we analyse the covaribility of the chlorophyll form EOS-06/OCM3 and the
circulation features derived from the SWOT. A scheme to correct the SWOT circulation for the
cyclostrophic features has also proposed. We show several test cases of SWOT and chlorophyll
to show the improvements in using the proposed scheme. Detailed results will be presented in the
meeting.