Characterizing uncertainty on ocean swell heights from CFOSAT/Sentinel-1 observations, wave modelling and in-situ measurements

Nowadays, directional ocean swell spectra and thereby partitioned swell heights Hss are being routinely acquired by spaceborne radars: Sentinel-1A/B SARs and the real aperture radar sensor CFOSAT SWIM. In this era, questions may interest the community: what are their quantitative uncertainties? Is it possible to characterize the uncertainties in buoy Hss which are usually regarded as ground-truth? Here, a triple colocation error model is exploited to quantify the absolute uncertainties in the Hss observed from SAR, SWIM and WW3 modelling. Furthermore, we propose a buoy Hss error estimation model by combining dual and triple collocation using data derived from buoys, two space-borne radars and modelling. Our findings imply that the reference value uncertainties should be taken into account when understanding direct satellite Hss validation against buoy in situ. Alse, the biases of CFOSAT and Sentinel-1 Hss are important for optimizing the synergetic use and merging of these remotely-sensed Hss in the near future and typical example will be presented.