An assessment of the data assimilation system developed for the SWOT satellite mission

When the Surface Water and Ocean Topography (SWOT) satellite launches in 2022, an in-situ field campaign is planned to reconstruct the ground truth for instrument calibration and validation (CalVal). It is demonstrably difficult to capture the sea surface height (SSH) features that are the focus of SWOT, with short temporal (< 20 days) and spatial scales (15 - 150 km). While the baseline field campaign comprises a linear array of 11 moorings to provide wavenumber spectral estimates required by the mission, the two-dimensional retrievals over the SWOT swath will not be directly validated. In addition, the post-launch field campaign does not include validation of the velocity reconstruction from SSH at the small-spatial and short-temporal scales. We aim to enhance the SWOT post-launch field campaign by using a multi-scale data assimilation system coupled to a primitive equation numerical model to reconstruct: (1) the 2D SSH over the SWOT swaths, and (2) the three-dimensional dynamical (velocity) fields. The objective is to assimilate the in-situ measurements from a mooring array and gliders to propagate fine-scale information off the array in creation of 2D fields for the wide-swath validation. In this talk we will present an evaluation of the data assimilation system; in the first part, we will demonstrate its performance during a 2019-2020 pre-launch field campaign using independent in-situ observations. In the second part, we will present an Observing System Simulation Experiment (OSSE) to evaluate the potential CalVal and science outcomes of the baseline post-launch field campaign design.