Measurement of waves, wave groups and wind fields using nautical radar-image sequences

In this thesis, which is based on three journal papers, novel techniques are developed for retrieving individual waves, wave groups, and wind fields, spatially and temporally from nautical radar-image sequences. The images with a spatial extension of #approx#4 km x 4 km and a spatial resolution of #approx#10 m were recorded by the Wave Monitoring System (WaMoS), developed at GKSS Research Centre. Wave groups are derived by the first new method, based on the determination of the spatial-temporal envelope function. The wave groups are investigated regarding their spatial-temporal development, their extension and phase velocities for two sites, one in shallow water, the other one in deep water. High-resolution wind fields with a spatial resolution of up to 100 m are retrieved by the second method. The wind directions are extracted from the wind-induced streaks, which are approximately in line with the mean wind direction. The wind speeds are derived from the radar backscatter, taking into consideration the local wind direction and the air-sea surface temperature difference. The wind measurements are validated by comparing to in-situ measurements. For the investigation of single waves and wave groups an inversion scheme is introduced for determining ocean surface elevation image sequences from the radar-image sequences. This method is based on the local determination of the tilt angle of the ocean surface. The results are compared to three in-situ sensors for validation. (orig.)SIGLEAvailable from TIB Hannover: RA 3251(04/4) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman