Refined S-6 sea state bias correction models and a multi-frequency EM bias assessment using C-, Ku-, and Ka-band data
Event: 2022 Ocean Surface Topography Science Team Meeting
Session: Instrument Processing: Propagation, Wind Speed and Sea State Bias
Presentation type: Type Oral
This study will report on results from two parallel sea state bias correction model investigations. Ongoing verification of sea level measurements from the Sentinel-6 Michael Freilich mission suggests the possibility of systematic range bias and noise due to the use of preliminary sea state bias correction models based on tandem comparisons with Jason-3 altimeter data. New C- and Ku-band sea state bias models built using Side-B altimeter data from S-6 will be presented including an assessment of revised global range measurement comparison against Jason-3 and against the present S-6 GDRF06 version datasets. One goal of this work is to reduce apparent geographically-correlated error between Jason-3 and S-6 sea level measurements. Part two of this work will use SARAL/AltiKa and Jason altimeter range data to reconsider what these long-term three frequency radar measurements can explain about the underlying physical controls of the altimeter sea state bias. The altimeter data are co-registered with global wave model data to investigate their relative dependence on the expected primary control, long-wave wave steepness, using bulk statistical wave parameters including the significant slope and wave age. The data clearly illustrate that the range bias changes due to steepness decreases as the radar frequency increases, with one operational example being the greater need for ancillary long-wave information when using a C-band altimeter vs. a Ka-band system. We also document a varied impact of the near-surface wind change between the C-, Ku- and Ka-band measurements.