Validation of Coastal Wind and Wave Fields by High Resolution Satellite Data

Kurzfassung

Methods to derive wind speed and the sea state from Synthetic Aperture Radar (SAR) satellite data are presented and applied for use in high resolution numerical modelling for coastal application. The new radar satellite TerraSAR-X (TS-X) images the sea surface with a high resolution up to 1m. So not only the wind field and integrated sea state parameters but also individual ocean waves with wavelengths down to 30m are detectable. Two-dimensional information of the ocean surface retrieved using TS-X data is validated for different oceanographic applications: derivation of fine resolved wind fields (XMOD algorithm) and integrated sea state parameters (XWAVE algorithm). The algorithms are capable to take into account fine-scale effects in coastal areas. he wind and sea state information retrieved from SAR data are applied as an input for a wave numerical spectral model (wind forcing and boundary condition of sea state) running at fine spatial horizontal resolution of 100m. The results are compared to collocated buoy measurements. The sea state simulated by increased and decreased wind speed and comparison against waves simulated using original TS-X derived wind shows sensitivity of waves on local wind variation and thus the importance of local wind effects on wave behaviour in coastal areas. Examples for the German Bight, North Sea are shown. The TS-X satellite scenes render well developed ocean wave patterns of well developed swell at the sea surface. Refraction of individual long swell waves at a water depth shallower than about 70m is caused by the influence of underwater topography in coastal areas which is imaged on the radar scenes. A technique was developed for tracking of wave rays depending on changing of swell wavelength and direction. We estimate the wave energy flux along the wave tracks from deep water to the coastal line based on SAR information: wave height and wavelength are derived from TS-X data.