SAR imaging of a topography-induced current front in a tidal channel

Abstract

A quasi-linear dark-bright feature was observed on a TerraSAR-X synthetic aperture radar (SAR) image acquired in the area of Pearl River Estuary (PRE), China, on 25 October 2010. Examining the detailed local bathymetry chart, we find that the feature is collocated with major axis of Lingding Channel in the waterway of PRE. In the study, we first run a 3-D hydrodynamic model to simulate the tidal currents within PRE, and then used the simulated current and local wind data as input to run a radar simulation model to calculate the variation of normalized radar cross section induced by these parameters. Ocean model simulation shows that surface currents were parallel to the major axis of the channel at the satellite overpass time. Radar model simulation results show good agreement between the simulated and actual SAR images. The quasi-linear dark-bright feature on the SAR image was found to be due to the surface current convergence and divergence caused by the bathymetry-induced tidal current variation.