Abstract's details

First look at SWOT nadir and KaRIn data in regional seas with 1-day sampling

Rosemary Morrow (CTOH / LEGOS, France)


Florence Birol (LEGOS / CTOH, France); Fabien Blarel (LEGOS/CTOH, France); Robin Chevrier (CLS Group / LEGOS, France); Fabien Leger (LEGOS / CTOH, France); Fernando Nino (LEGOS / CTOH, France); Oscar Vergara (CLS Group / LEGOS, France)

Event: 2023 Ocean Surface Topography Science Team Meeting

Session: Science III: Mesoscale and sub-mesoscale oceanography

Presentation type: Type Forum only

Contribution: PDF file


The NASA/CNES Surface Water Ocean Topography (SWOT) mission, with partners from the Canadian and UK Space Agencies, was launched in December 2023. SWOT carries a unique altimetric payload, including a Ku-band Jason-class nadir altimeter and a Ka-band SAR-interferometric (KaRIn) wide-swath altimeter providing 2 swaths 50-km wide; the ensemble spans 120 km across track. During the first 7 months of the mission, SWOT was in a widely spaced daily orbit for Calibration and Validation purposes. The first 3 months were for instrument checkout, but from April 2023 through to 11 July 2023, data with stable parameters were acquired for scientific validation. This daily sampling is unprecedented in the history of satellite altimetry observations, and allows us to explore the rapidly evolving regional ocean signals.

Over the regional and coastal seas, the Jason-class SWOT nadir data are available at 1 Hz and 20 hz (350 m) alongtrack and the SWOT ocean products are available in 2D across the swaths at 2 km and 250 m resolution. The daily sampling SWOT orbit provides a unique opportunity to evaluate how the evolution of rapidly evolving regional 2D SSH dynamics are captured in the nadir data at 1-day and 10-days, and to identify and separate the SSH structures of meandering geostrophic fronts / filaments and propagating eddies. In this study from the CTOH/Toulouse, we will concentrate our analyses on a few different regions. Accurate SSH and derived geostrophic currents depend on the instrument signal-to-noise but also the accuracy of altimetric corrections including high-frequency DAC, tides and internal-tides: these are currently tuned and improved in coastal and regional seas for alongtrack nadir data, and this needs to be extended across the SWOT swaths at 2km and 250 m-resolution. These points will be demonstrated and highlighted in our study. This is a first look, but our aim is to study these rapidly evolving dynamics with SWOT in regional seas, and also to understand how their signature and structure are represented in the historical time series of 10-day or 27/35-day nadir altimeter sampling.

Rosemary Morrow