Estimation of wave field parameters from TerraSAR-X imagery in the Baltic Sea

Abstract

Current study is focused on detection of wave field parameters from SAR imagery in the Baltic Sea. Study is carried out over the Baltic Sea region where common SW and W winds induce steep waves with shorter wavelengths compared to ocean waves. As TerraSAR-X data has high spatial resolution (0.75-1.5m per pixel) compared to previous SAR sensors (e.g. ENVISAT/ASAR), it enables to detect the two-dimensional wave spectrum even in the Baltic Sea. Main objective of this work was to demonstrate the capability of detecting wave field parameter from TerraSAR-X imagery in the Baltic Sea. The wave field parameters obtained from SAR imagery was compared with in situ measurements and SWAN (Simulating Waves Nearshore) wave model. The comparison showed significant correlation between SAR derived and buoy measured wave propagation direction (r = 0.89, rmsd = 45°, bias = 8.5°) and wavelengths (r = 0.71, rmsd = 14.8m, bias 0.4m). Comparison of SAR based wave field information with SWAN wave model outputs showed also good agreement in case of wave propagation direction (r = 0.72, rmsd = 35°, bias = 14.8°) and wavelengths (r = 0.85, rmsd = 12.1m, bias = 2.4m). Peak period was also calculated from SAR based 2D wavenumber spectrum and compared with SWAN results. Case studies showed that SAR data enables to detect land shadow effects and small scale wave field variations in the coastal zones.