Major Research Proposal for improvement of prediction accuracy of swell

The design of port and harbor facilities basically uses observed wave data. We need to estimate waves with a wave hindcasting model if there is no available observation data. However, the third-generation wave hindcasting model WAM, which has been used in practice for many years, may fail to estimate wave periods with sufficient precision in certain cases. The Technical Standards and Commentaries for Port and Harbor Facilities in Japan was revised in May 2018. As a result, we also needed to consider only swells in addition to the conventional wave conditions that do not distinguish between wind waves and swells. In the future, it is required to improve the estimation accuracy of swell.
 

Therefore, in this study, we will examine the estimation precision of the third-generation wave hindcasting model WAM and WW3 by comparing the model output to observed wave data at multiple NOWPHAS stations, and develop a wave hindcasting system that will be applicable to the coast of Japan.
 

In FY 2018, we compared the wave statistics estimated using WAM and WW3 in previous fiscal years to actual observation data collected from several NOWPHAS locations, and saw that WW3 had a slightly better precision on average between those locations, but WAM was more accurate in certain cases.
 

In addition, we focused on swells (Yori-mawari-nami) in Toyama Bay and examined the estimation accuracy, which suggested that it would be difficult to perform high-precision estimation using the third-generation wave hindcasting models that are currently available.
 

Furthermore, we developed a wave hindcasting system for the coast of Japan based on WW3, which automatically performs all required computational tasks including pre-processing of ocean wind and other input data, execution of wave estimation, creation of graphs, etc. to illustrate the estimation result, and all other post-processing, by simply specifying an estimation period.
 

We plan to continuously improve the accuracy of wave estimation and hope that it will help create better designs of port, harbor, and coastal facilities and also prevent disasters in coastal areas.