CoAuthors

Lee-Lueng Fu (Caltech/JPL, USA)

The Surface Water and Ocean Topography (SWOT) mission aims to measure the sea surface height (SSH) at a high spatial resolution using Ka-band Radar Interferometer (KaRIN). The primary oceanographic objective is to characterize the ocean eddies at a spatial resolution of 15 km for 68% of the ocean. This resolution is derived from the signal to noise ratio between the wavenumber spectrum of the conventional altimeter (projected to submesoscale) and the SWOT SSH errors. While the 15km threshold is useful as a global approximation of the spatial scales resolved by SWOT (SWOT-scale), it can be misleading for regional studies. Here we revisit the problem using a high-resolution (~2km) tide-resolving global ocean simulation and map the SWOT-scale as a function of latitude-longitude and season. The results show that the SWOT-scale has a strong geographic and seasonal dependence. In general, it is smaller (<15km) in low latitudes, increases to ~30km in mid-latitudes; and is larger in local winter than in summer. Internal gravity waves and internal tides have a significant contribution to the scale variation. These characteristics provide a guideline for interpreting the satellite fidelity with ocean physics in consideration, which in turn sheds light on developing the future SWOT data assimilation system.