Side looking airborne radar mapping of wave refraction patterns at the mouth of the Columbia River Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/9880vt74r

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  • The ocean wave conditions at the mouth of the Columbia River have long proven a hazard to ship navigation. Over 62 major shipwrecks have occurred at, or in the vicinity of the river entrance. The wave pattern is extremely complex, varying seasonally with prevailing winds and river discharge, as well as the tidal cycle. Analysis of the cornplex wave refraction process requires repetitive wave crest mapping at critical periods such as peak ebb current, winter storms, and spring ti des. Oregon Army National Guard Mohawk aircraft equipped with the AN/APQ-94 Side Looking Airborne Radar system have overcome most of the monitoring limitations, providing scheduling flexibility, cloud penetration, and a constant angle of illumination, although the scanning nature of the system requires a correction for the progression of the wave crest between scans. This correction was accomplished by adding the resultant vectors of apparent wave refraction patterns obtained from a given flight to those of a subsequent flight flown imediately after, at a reciprocal azimuth. SLAR imagery interpretation and analysis was aided by color density slicing, which enables differences in wave steepness and height to be detected. Wave crest patterns from the imagery were traced on an equivalent scale as previous wave pattern predictions, enabling easy comparison. The use of photographic enlargements of the SLAR imagery was used in conjunction with weather and sea data, in aiding further exploitation of the imagery to aid the understanding of wave action when storm produced swell encounters strong ebb current velocities seaward of the river entrance. Analysis of the SLAR imagery of the river entrance has Increased the understanding of swell-ebb current interaction by detecting the locations and intensities of interaction and its products, the steepened/ heightened swell over the navigation channel. The imagery may well help in increasing the safety of the mouth of the Columbia River for ship navigation.
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