Zhijin Li (JPL, United States); Lee-Lueng Fu (JPL, United States)

The Surface Water and Ocean Topography mission will launch its satellite in 2021 to measure the sea surface height with two wide swaths at a high resolution (down to 15km in some regions). 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 even 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 built to address these challenges. Here we focus on challenge (1) and present an observational system simulation experiment (OSSE) to demonstrate the design of an in situ observing system for the SWOT post-launch validation.