Statistics of Heavy Weather Actual Ocean Wave Data in North Sea and Japan Sea with Reference to Abnormal Waves

摘要

Wind and wave data acquired at North Sea offshore Norway and Japan Sea offshore Yura, Japan are analysed to some details such as; 1. Distributions of sea surface elevation 2. Sea surface spectra 3. Wave height distributions 4. Wave period distributions 5. Expected distribution of ratio of the highest wave against significant wave within 20 minutes Discrepancies from well known linear random theory are examined. The existence of so called abnormal or freak type waves are also closely inquired. We found several cases of such an interesting phenomenon in moderate sea rather than in heavy weathers. It is related quantitatively to the statistical parameters of the stochastic process. We slightly mention the synoptic natures of these two sites. We debt the Norwegian data to STATOIL company and NTNU in Trondheim. On the other hand Yura data were measured by SRI.