ERS-1 SAR observations of internal waves during the Joint US/Russia Internal Wave Remote Sensing Experiment

Images from the C-band ERS-1 SAR were acquired on two days during the Joint US/Russia Internal Wave Remote Sensing Experiment in July 1992. Images from 18 July 1992 show well-defined internal wave signatures associated with numerous internal wave packets propagating shoreward on the continental shelf. Surface winds were about 6 m/s and stable atmospheric conditions prevailed, that is, the air-water temperature difference was positive. On 25 July, under similar wind conditions but unstable atmospheric conditions, the ERS-1 SAR images are devoid of internal wave signatures. Similar results were observed in vertically-polarized, airborne radar images. Selected radar data are presented to illustrate these effects. These results demonstrate that, under some atmospheric conditions, vertically-polarised radars have significantly less capability for detecting internal wave features than horizontally-polarised radars, independent of the incidence angle of the illuminating radiation. Enhanced atmospheric clutter appears to be contributing to these differences in internal wave observability.