Designing an in-situ observing system for the CalVal of the SWOT sea-surface height meausrement
Event: 2016 Ocean Surface Topography Science Team Meeting
Session: Tides, internal tides and high-frequency processes
Presentation type: Type Poster
The future Surface Water and Ocean Topography (SWOT) satellite will be able to measure a two-dimensional swath of sea surface height (SSH) by carrying a radar interferometer. One of the grand challenges of the SWOT mission is the calibration and validation (Cal/Val) of satellite measurements. The purpose of this study to design an in-situ observing system for the SWOT ocean Cal/Val, to validate the SSH measurement error wavenumber spectrum. We have explored the performance of Underway CTD (UCTD), Pressure-Inverted-Echo-Sounder (PIES), and moored measurement of temperature and salinity using the global 1/48th degree resolution ECCO2 simulation. The results show that, if observed perfectly, in-situ hydrographic measurement of the upper 2000 meters together with bottom pressure are sufficient to infer the true SSH. However, in reality, UCTD suffers from the aliasing of the high frequency (<1 day) motions due to the slow speed of the towing vessel. The reconstruction of SSH from PIES has uncertainties of about 5 cm. PIES works well when SSH variance is much larger than its uncertainties but becomes less useful for submesoscale or weak mesoscale variability. Moored measurement is expensive but can resolve the high frequency motions and reproduce synoptic SSH structure with less than 30% error. It is concluded that the backbone of an in-situ observing system for the SWOT ocean Cal/Val is an array of moorings.