Synthetic Aperture Radar (SAR) Imagery of Storm-Induced Seas Around the Goto Islands, Japan

摘要

High-quality, 3-m-resolution aircraft synthetic aperture radar (SAR) imagery of coastal seas around the Goto Islands was obtained on August 31, November 19, and November 27, 1982. The August data were taken during 10-17 m per sec (SE) winds associated with a typhoon that generated 200-m-long waves propagating toward 354 T. The November 19 data are from a calm period of winds less than 1.5 m per sec from the southwest; no sea returns were obtained with the exception of small oceanic fronts. The November 27 data are from a fall-season monsoonal surge of 9.5 per sec winds from the northwest, generating 80-100-m-long waves propagating SSW (142-204 T). Sea and swell diffraction/refraction patterns are clearly discernible, as well as wave-current interactions, shallow-water fronts, and surface wind effects. A computer program has been developed that, using SAR-derived wavelength and surface wind data, estimates wave period, clearity, wave height, wind shear velocity, drag coefficient, and dynamic roughness length. SAR-derived wind directions agree closely with coastal station and ship of opportunity data. The quality of the radar sea return has been found to be critically dependent on antenna depression angle, wind speed, and surface roughness. The system used was the AN/UPD-4 radar mapping set operated on wavelengths of 3 cm (X band, 9.68 GHz). (Author)