High-resolution wave climate hindcast around Japan and its spectral representation

Abstract

A 34-year high-resolution ocean surface wave climate hindcast around Japan is presented, and the wave climate around Japan is examined from a spectral point of view. The spectral wave model is forced by the sea surface wind data obtained from the JRA-55 atmospheric reanalysis. The wave climate hindcast is validated by comparing it with buoy observations around Japan. The correlation coefficient of the significant wave height is 0.9. The correlation coefficient of the mean wave period is 0.8 for the Japan Sea and Pacific side of eastern Japan and 0.7–0.8 for the Pacific side of western Japan. The wave climate is represented by temporal-mean two-dimensional wave spectra. The characteristics of the spectral wave climate are investigated by classifying them into three types. Distinctive characteristics of the mean wave spectra along the Japan Sea are narrower band widths for both the period and direction. The mean wave spectra along the Pacific side of eastern Japan are characterized by swells with a spectral peak propagating from the northeast. The distinctive spectral features corresponding to the Pacific side of western Japan are bi-modal peaks with long-period components typically generated by typhoons. The variability in the monthly mean wave spectra is examined using an empirical orthogonal function (EOF) analysis. In the winter, it is found that the wave height variability (EOF 1st mode) is related to wave direction variability (EOF 2nd mode) at locations 1000 km apart via the sea level pressure variance over the North Pacific. In the summer, the EOF 1st mode corresponding to the Pacific side locations is dominated by the variability in typhoon-generated swells. The spectral wave climate representation provides new insight into the wave climate around Japan with clear relationships between the atmospheric conditions, the wave height, direction, and period.