Statistical analysis and inference from the in-situ data of the sea of Japan with reference to abnormal and/or freak waves

摘要

In the last paper (ISOPE'99) the author found the fairly strong correlation between Abnormality Index, that is, H{sub}max/H{sub}s (AI) and the kurtosis of the sea surface deflection distribution by the analysis of actual sea waves data acquired both in the North Sea of offshore Norway as well as the North Pacific Ocean 500 nautical miles southeast of the Japanese Islands. The analysis is now carried out for Yura site data taken by Ship Research Institute during 1987 and 1990 in which we have the same tendency as for AI. Some of the short term statistical analysis are presented such as surface deflection, wave height distribution and joint distribution of wave height and period. Long term nature of the distribution of AI is examined and a statistical test is performed for the fitting to the theoretical curve. The regressions between wave height statistics H{sub}s, H{sub}(rms) etc are calculated and compared with theoretical or empirical relations proposed so far. Finally, some examples of observed Freak waves are presented.