Abstract
We investigated the use of C-band RADARSAT Constellation Mission (RCM) synthetic aperture radar (SAR) for retrieval of ocean surface wind speeds by using four new channels (right circular transmit, vertical receive (RV); right circular transmit, horizontal receive (RH); right circular transmit, left circular transmit (RL); and right circular transmit, right circular receive (RR)) in compact polarimetry (CP) mode. Using 256 buoy measurements collocated with RADARSAT-2 fine beam quad-polarized scenes, RCM CP data was simulated using a “CP simulator”. Provided that the relative wind direction is known, our results demonstrate that wind speed can be retrieved from RV, RH and RL polarization channels using existing C-band model (CMOD) geophysical model function (GMF) and polarization ratio (PR) models. Simulated RR-polarized radar returns have a strong linear relationship with speed and are less sensitive to relative wind direction and incidence angle. Therefore, a model is proposed for the RR-polarized synthetic aperture radar (SAR) data. Our results show that the proposed model can provide an efficient methodology for wind speed retrieval.
Highlights
Ocean surface winds are an important parameter for studies related to sea surface variables and processes in the lower atmospheric boundary layer, e.g., the water mass circulation and the coupling of atmospheric and oceanic systems
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For RH-and RL-polarized wind speed retrieval, the CMOD5 function with Z2011 polarization ratio (PR) model are recommended as the optimal combination, with an RMSE of 2.48 m/s (RH-polarized) and 2.31 m/s
Summary
Ocean surface winds are an important parameter for studies related to sea surface variables and processes in the lower atmospheric boundary layer, e.g., the water mass circulation and the coupling of atmospheric and oceanic systems. No similar wind field retrieval models exist for horizontal transmit, horizontal receive (HH)-polarized SAR data To remedy this difficulty, the polarization ratio (PR) was proposed to map the expected NRCS at VV-polarized mode to HH-polarized values for the same wind direction and speed. The limitation of conventional quad-polarized SAR systems is mainly the acquisition of SAR images with both wide swath coverage and high spatial resolution, and insufficient wind data for operational use in terms of covering the vast global ocean On account of these drawbacks, there is intense ongoing study of compact polarimetry (CP) for the remote sensing of Earth observations including oceanography because of its large spatial coverage and its diverse information content [22]. Based on the generated CP parameters, the potential ability of wind speed retrievals from RCM will be considered in ongoing studies
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