Day 4

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Paper title Simulation of Doppler shift from sea surface: preparation for the next-generation ocean observation satellite
Authors
  1. Huimin Li NUIST Speaker
  2. Bertrand Chapron Ifremer - LOPS
  3. Wenming Lin Nanjing University of Information Science and Technology
  4. Baochang Liu NUIST
  5. Yijun He NUIST
Form of presentation Poster
Topics
  • A8. Ocean
    • A8.10 Ocean Doppler: Challenges and Opportunities for Future Missions of Global Ocean Surface Currents
Abstract text Ocean surface current is yet poorly observed by satellite remote sensing in comparison to other sea surface variables, such as the surface temperature, the surface winds and waves field, among others. Over the recent years, a rich of radar missions dedicated to the ocean current mapping at the global scale have emerged. Most of the proposed techniques take advantage of the Doppler shift obtained by the phase-resolving radars, which is associated with the sea surface motion. Both observational and simulation efforts have demonstrated that apart from the satellite motion, the total Doppler shift is composed of contributions from the surface winds, ocean waves, in addition to the underlying ocean surface current. The knowledge of concurrent wind and wave component is essential for the removal of their impact to acquire the geophysical Doppler shift. Such Doppler shift residual could be directly converted to the line-of-sight current velocity. Successful applications of this technique to observe major ocean current have been illustrated based on the single-antenna synthetic aperture radar systems, which proves the feasibility of Doppler shift method for further exploitation. A radar mission designed for concurrent measurements of wind, waves and current is under development. As the preparatory studies for this mission, we conduct the simulation of Doppler shift from sea surface with a wide variety of sea state conditions and different radar configurations (polarization, radar frequency and incidence angles et al.). Results illustrate that the contribution of winds and waves constitutes a major part of total Doppler shift, particularly when the underlying surface current is relatively weak. This further evidences the necessity to remove the wind/wave component for accurate retrieval of surface current in the future operational processing. Given the variable sensitivity of polarization to the ocean waves, dual-polarized Doppler shift brings more information than single-polarized channel, which could be promoted in the radar system configuration. The simulation study strengthens our confidence on this pending mission to enhance the observational capability of ocean surface current on top of other concepts.