Multiscale Data Assimilation for SWOT Ocean Application

The Surface Water and Ocean Topography mission will launch its satellite in 2021 to measure the sea surface height with two wide swaths (50km) at a high resolution (2km pixel size). The 2D aspect and the high resolution of SWOT SSH measurements will improve our understanding of the mesoscale eddies and low mode internal tides, and unveil the eddies and higher mode internal tides at smaller mesoscale and submesoscale. The mission is unprecedented in producing 2D SSH measurements at such a high resolution. It also presents us with great challenges as follows. (1) Building an in-situ observing system to reconstruct the ground truth for validation purpose becomes unconventional. (2) The high-resolution measurement was done at the cost of temporal resolution. Mapping/assimilating the wide swaths data with large temporal gaps (21-day cycle) becomes a challenge especially for fast evolving small-scale processes. In this study, a multi-scale data assimilation system is introduced to address these challenges. Here we focus on the construction of the multi-scale data assimilation system and present the system sensitivities in submesoscale data assimilation. The system will be used to design an in situ observing system for the SWOT post-launch validation and future SWOT data assimilation.