CoAuthors

Don Chambers (University of South Florida, United States)

The SWOT error budget for sea surface height measurements are predicated on a significant wave height (SWH) of 2 meters. Within this range, the surface wave error on the swath falls below the noise floor, and is assumed it can be ignored. However, there are many locations within the oceans where this SWH is an under-estimation. Specifically, within the Southern Ocean the SWH regularly varies between 4-8 meters, and often reaches 12 meters. The resulting regional under-estimation of modeled SWH may contaminate the signal returned by KaRIN especially after onboard processing.
Ocean general circulation models (OGCM) often do not represent sea surface heights for wavelengths < 20 km, which is potentially observable by SWOT. To remedy this, we create our own sea surfaces which include sub-mesoscale energy and wave motions. We create our own sea surfaces using spectral techniques, creating two different surfaces that will then be added together. For generation of the sub-mesoscale surface we utilize a spectral extension method to continue the sea surface height spectra through the noise floor. To generate the wave surface, we utilize the various wave spectra that are representative of different ocean wave states, e.g. realistic to the Southern Ocean and in line with the current SWOT technical documentation. The sub-mesoscale and wave layers are then added together at high resolution (~5 km for sub-mesoscale, ~5 m for waves) and then sampled using a simplified point target response function and averaged into a 5 km x 5km swath that is identical to the OGCM sampled swath from the SWOT simulator. We then compare the spectra, kinetic energy, and statistics of the resulting swaths. We present here a quantification of wave error on SWOT sea surface height measurements