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Study on retrievals of ocean wave spectrum by spaceborne SAR in ice-covered areas
  • Bingqing Huang,
  • Xiaoming Li
Bingqing Huang
Aerospace Information Research Institution, Chinese Academy of Sciences
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Xiaoming Li
Aerospace Information Research Institute, Chinese Academy of Sciences (CAS)

Corresponding Author:lixm@radi.ac.cn

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Interaction between ocean waves and sea ice may play an important role in sea ice retreat in the Arctic. However, it is difficult to quantify the change of ocean waves propagating in ice as nearly no available measurements. Although SAR has shown the capability of imaging ocean waves in ice-covered areas, there are few attempts to retrieve two-dimensional ocean wave spectra (OWS) by SAR. In this study, we applied the previously developed nonlinear inversion scheme, i.e., the MPI scheme, to retrieve OWS by the Sentinel-1 SAR data acquired in the Barents Sea, where waves penetrate deeply in ice. We compared the retrieved spectra by different combinations of modulation transfer functions (MTFs) used in the MPI scheme, i.e., the same MTFs as those used in retrievals in open water, neglecting both the hydrodynamic and tilt modulations in the MTFs, and neglecting the hydrodynamic modulation but remaining the tilt modulation (a new one fitted in this study for HH-polarized SAR data over ice) in the MTFs. As no in situ measurements (e.g., by directional buoys) available, we compared the simulated SAR image spectra based on the retrievals with the observational SAR image spectra to quantify their respective performances. The comparisons suggest that neglecting hydrodynamic modulation can significantly improve the retrievals. Remaining tilt modulation can further improve the retrievals, particularly for range-travelling waves. The study enhances the understanding of principles of SAR imaging waves in ice and provides basics for retrievals of ocean wave spectra by SAR data in ice-covered areas.