Abstract
This study estimated the accumulative probability curves and the annual and monthly statistics, such as the maximum, median, mean, and minimum values, of the 20-min-mean wave powers around Japan by using the significant wave database of the deepwater GPS buoys and shallow-water coastal wave gauges on NOWPHAS, and then examined the seasonal and inter-annual variations on these statistics. The examination led the following major conclusions; (a) During a year or a month an individual wave power can exceed the mean vaule over the duration with a probability of 20-40%; (b) The annual and monthly maximum and minimum values estimated from daily mean wave power datasets become around half and twice, respectively, as much as those from 20-min-mean ones; (c) A several-year-long dataset is recommended for the certain determination of wave power statistics because the inter-annual variations on the statistics are large; (d) The mean wave power and the median direction are almost constant among GPS buoys off the Pacific and Sea of Japan coast, respectively; and (e) These statistics on the coastal wave gauges are strongly affected by their surrounding bathymetry. Moreover, this study calibrated the signinfciant waves that are estimated by using the WAM model, and interpolated the mean wave powers in the months when the measurements are not available owing to the Great Tohoku Disaster effects.
