Abstract
In this study, variations of radar backscatter features of the tidal channel in Gyeonggi Bay in the Eastern Yellow Sea were investigated using spaceborne synthetic aperture radar (SAR) images. Consistent quasi-linear bright features appeared on the SAR images. Examining the detailed local bathymetry chart, we found that the features were co-located with the major axis of the tidal channel in the region. It was also shown that modulation of the radar backscatter features changed according to the environmental conditions at the time of imaging. For the statistical analysis, the bathymetric features over the tidal channel were extracted by an objective method. In terms of shape, the extracted features had higher variability in width than in length. The analysis of the variation in intensity with the coinciding bathymetric distribution confirmed that the quasi-linear bright features on the SAR images are fundamentally imprinted due to the surface current convergence and divergence caused by the bathymetry-induced tidal current variation. Furthermore, the contribution of environmental factors to the intensity modulation was quantitatively analyzed. A comparison of the variation in normalized radar cross section (NRCS) with tidal current showed a positive correlation only with the perpendicular component of tidal current (r= 0.47). This implies that the modulation in intensity of the tidal channel signatures is mainly affected by the interaction with cross-current flow. On the other hand, the modulation of the NRCS over the tidal channel tended to be degraded as wind speed increased (r= −0.65). Considering the environmental circumstances in the study area, it can be inferred that the imaging capability of SAR for the detection of tidal channel signatures mainly relies on wind speed.
Highlights
The measurement of ocean bathymetry is essential for the support of coastal environmental research, human activities, shipping, boating, and coastal surveillance for marine safety
Since variation in a current flowing over an underwater feature induces modulations in the sea surface roughness, underwater features can be indirectly imaged onto Synthetic aperture radar (SAR) images [1,2,3,4,5,6,7,8,9,10,11,12]
This is considered a limitation to providing the statistical properties of normalized radar cross section (NRCS) modulations on SAR images for regular monitoring
Summary
The measurement of ocean bathymetry is essential for the support of coastal environmental research, human activities, shipping, boating, and coastal surveillance for marine safety. It is assumed that the direction of tidal current flow is approximately normal to the orientation of the major axis of underwater bathymetric features Models of this kind have been further improved by various researchers [2,4,14,15,16,17,18,19,20,21]. The theoretical models may provide a fundamental understanding of the SAR imaging of shallow water topography, most of the previous research has focused on apparent imaging examples under certain favorable conditions This is considered a limitation to providing the statistical properties of normalized radar cross section (NRCS) modulations on SAR images for regular monitoring. The objectives of this study are to identify tidal channel signatures from SAR images using an objective method, present the variations in the signatures in terms of radar intensity modulation, quantitatively analyze the effects of environmental factors on the NRCS, and investigate the relationship between the tidal channel signatures on SAR images and the effects of tidal current components
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
