Effect of Unusual Wave Height Data in 2004 on the Estimate of Return Wave Heightaround the Coasts of Japan

Abstract

Least-squares-based extreme value analyses are conducted for annual maximum (AM) and peaks-over-threshold (POT) wave height data, extracted from measurements carried out over a period of 16 to 36 years at 37 coastal stations around Japan. The main findings are as follows:(1) a statistically significant trend is not detectedat almost all stations, (2) a POT analysis yields a more proper estimate of the 50-year return wave height (RWH) than an AM analysis, (3) the inclusion of unusual wave height data in 2004 and 2005 into the POT data increases the estimatesof both RWH and its confidence interval, (4) neither separating storm types nor censoring the data improves the efficiency of the RWH estimated in the POT analysis.