Study on the Increase in Annual Maximum Significant Wave Height Due to the Intensification of Typhoons Using NOWPHAS Wave Observation Data

As the effects of global climate change are causing increasingly severe weather disasters, it has been reported that the annual maximum significant wave height, which is important in the calculation of design waves for offshore structures that will be in service for a long period of time, is increasing year by year. Therefore, we analyzed wave observation data for Japan up to the year 2020 and identified the type of meteorological disturbance when the maximum significant annual wave height was observed. Among the wave observation sites on the Pacific side of Honshu, 87% of the sites showed an increase in maximum significant annual wave height. Among these, typhoons were mainly responsible for the increase in annual maximum significant wave heights, especially at the stations located south of the bay mouth. Analysis of the RSMC best track data shows that the number of typhoons per year tends to decrease, while the intensity of individual typhoons tends to increase. Since typhoons are greatly affected by sea surface temperature (SST), we compared the 100-year SST increase in the southern Japanese archipelago with the global average and found that the SST increase is twice as large as the global average. Therefore, typhoon intensity is expected to increase in the long term, and the annual maximum significant wave height on the Pacific side of Honshu is expected to increase accordingly.