Abstract's details

A Significant Wave Height Correction to Account for Vertical Wave Motion Effects in SAR Altimeter Measurements

Alejandro Egido (NOAA, United States)

CoAuthors

Christopher Buchhaupt (NOAA / ESSIC, UMD, USA); François Boy (CNES, France); Claire Maraldi (CNES, France); Cadier Emeline (CLS, France); Dinardo Salvatore (CLS, France); Eric Leuliette (NOAA, USA); Thomas Moreau (CLS, France)

Event: 2022 Ocean Surface Topography Science Team Meeting

Session: Instrument Processing: Measurement and Retracking

Presentation type: Type Oral

In this paper, we propose a correction for the sea state dependent biases observed in the significant wave height (SWH) measurements obtained from high-resolution (HR) data of synthetic aperture radar (SAR) altimeters. Those biases have been linked to the effect of vertical wave motion on the radar signal, which creates a non-negligible Doppler spread that results in a loss of along-track resolution of the SAR altimeter (azimuth smearing). When this effect is not accounted for in the retracking process it results in sea state dependent biases, which can be very significant for high SWH values.

The correction has a form of a look-up table (LUT), that depends on both sea state and mean zero up-crossing period. We calculated the LUT through numerical simulations of the SAR altimeter waveforms at different sea state conditions including the azimuth smearing effect through the SAR altimeter flat sea surface response, and later retracking those waveforms with a model that does not account for the vertical wave motion. To evaluate the LUT correction we use the low-resolution mode (LRM) SWH estimated values, and the mean up-crossing wave period, that we obtain from the Meteo France Wave Advanced Model.

We evaluated the LUT correction using Sentinel-6A/MF HR and LR data and determined that the correction is able to eliminate most of the sea state dependent biases observed between both operation modes. The same results were also observed when the correction is applied to Sentinel-3A/B data, indicating the usefulness of this correction in providing consistent SWH measurements across all altimeter missions.

 

Oral presentation show times:

Room Start Date End Date
Sala Grande Tue, Nov 01 2022,10:55 Tue, Nov 01 2022,11:10
Alejandro Egido
NOAA
United States
alejandro.egido@noaa.gov