A Study of Internal Wave Propagation in the Strait of Gibraltar Using Shore-Based Marine Radar Images

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Abstract
An X-band marine radar on Windmill Hill, Gibraltar, was used to monitor the propagation of internal waves in the Strait of Gibraltar during March, April, and June 1986. Surface roughness features of the waves were observed out to a range of ∼15 km. From photographic images of the radar screen, the positions of image features were measured manually using a digitizing table, and these data were then computer processed to give wave arrival times and phase speeds. During most tidal cycles, an internal undular bore generated at Camarinal Sill was observed to pass eastward (A-waves). These occurred throughout the experiments although less frequently near neap tides. The time of travel to Gibraltar varied significantly, so that the bore arrived between four and nine hours after high water. Arrival times were found to be closely related to the amplitude of the upper layer tidal current. This current had a strong diurnal component, which was manifested as an inequality between the arrival times of success... Abstract An X-band marine radar on Windmill Hill, Gibraltar, was used to monitor the propagation of internal waves in the Strait of Gibraltar during March, April, and June 1986. Surface roughness features of the waves were observed out to a range of ∼15 km. From photographic images of the radar screen, the positions of image features were measured manually using a digitizing table, and these data were then computer processed to give wave arrival times and phase speeds. During most tidal cycles, an internal undular bore generated at Camarinal Sill was observed to pass eastward (A-waves). These occurred throughout the experiments although less frequently near neap tides. The time of travel to Gibraltar varied significantly, so that the bore arrived between four and nine hours after high water. Arrival times were found to be closely related to the amplitude of the upper layer tidal current. This current had a strong diurnal component, which was manifested as an inequality between the arrival times of success...

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