8.10
Detection of extreme ocean waves
Susanne Lehner, German Aerospace Center, Remote Sensing Technology Center, Wessling, Germany; and W. Rosenthal, H. Dankert, J. Horstmann, and J. Schulz-Stellenfleth
Within the last several years a considerable number of large ships, as well as off and onshore structures, have been lost or damaged. The causes of these accidents are in many cases reported as rogue waves. These are individual extreme waves of exceptional wave height and shape.
This paper deals with the detection, investigation and explanation of the rogue wave phenomena. In addition to conventional buoy data and standard spectral analysis, spatial radar data from marine radars and satellite imagery was used. The task included the detection of rogue waves, and extreme wave groups from the data, as well as the investigation on wave statistics with respect to those extreme wave events.
Two different radar concepts were used: Space borne Synthetic Aperture Radar (SAR) and Wave Monitoring System II (WaMoS II), a wave measuring device based on standard marine radar technology. These radar systems are described in more detail in subsequent sections of this paper.
Traditionally, rogue waves and wave groups have been studied by means of time series analysis of buoy records, which provide reliable information about the temporal variability of such phenomena at a fixed ocean position (e.g. the buoy deployment point). Radar systems instead provide spatial information of the sea surface at a given time and thus show a synoptic picture of the spatial structure of the ocean waves. Satellites observe the ocean surface continuously on a global scale thus showing extreme events during hurricanes or in the southern oceans, where most of the extreme events were found during this study. A new quality of observation comes from the fact that crossing seas can easily be observed.
In the case of nautical radar by every turn of the radar antenna, temporal information is acquired, too. In the frame of the project nautical radars were mounted on platforms to collect long term statistics, e.g. at oil platforms or on ships navigating through dangerous ocean areas like the Alghulas Current.
The work was performed in the framework of the European project MAXWAVE.
.Session 8, Upper ocean - lower atmosphere - surface wave interactions
Friday, 13 August 2004, 8:30 AM-12:15 PM, New Hampshire Room
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