What can we learn on internal tides with the 1-day phase of SWOT ?

The Surface Water and Ocean Topography (SWOT) altimetry mission launched in 2022 makes 2D observations of sea surface height (SSH) using SAR radar interferometric techniques.  Compared to previous altimetry missions, SWOT extends SSH observations to 15-30 km and offers opportunities to understand better ocean dynamic processes such as mesoscale, sub mesoscale and internal tides (IT).

     This study based on SWOT observations during the Calval (1-day orbit, from mid-March to mid-July) period gives insight into the capability of SWOT to observe IT.  We analyzed the SWOT tracks crossing the Brazilian coast around the Amazon shelf.  The results show that SWOT IT observations in this region are made up of mode 1 and mode 2 but also of strong higher mode (50-2 km).  The M2 coherent IT model deduced from SWOT presents the same spatial distribution as the M2 model from Zaron et al., 2019.  Over this period, the rate of incoherent internal tidal is over 0.5 for modes 1 and 2 and almost 0.9 for higher modes.