Variability of wave height in the Sea of Japan

Abstract

The Sea of Japan is a semi-enclosed sea located in the northwest Pacific area. There has been no study conducted to examine the relationship between the interannual variability of the wind field and the spatial variability of wave height in the Sea of Japan. We examined the relationship between the spatiotemporal variability of the wave height and the wind field in the Japan Sea using monthly mean ERA5 reanalysis data. Firstly, it is demonstrated that the ERA5 wave height closely matches that of moored buoys. Following that, we investigated the relationship between the wave height and the wind anomaly distribution using empirical orthogonal function (EOF) and self-organizing map (SOM) analysis. This is the first study to examine the spatial variation of wave height using the SOM. The EOF’s first mode is a mode that oscillates in the central region of the Sea of Japan, while the second mode is a north-south dipole mode. In each season, the wave height anomaly EOF mode had a significant correlation with a variety of climatic indices. Although the correlation between EOF of wave height anomaly and EOF of wind speed anomaly was not high throughout the year, the correlation between them was high for each season. The SOM revealed a pattern consistent with the EOF analysis’s first and second modes. Throughout the year, the relationship between wave height and wind speed anomaly patterns is not strong. The link, however, varies with the seasons. The frequency of patterns with increased wave height anomalies in the central Japan Sea has increased in recent years. This is consistent with the EOF first mode’s long-term trend.