TYPHOON-GENERATED EXTREME WAVE REANALYSIS BY DATA ASSIMILATION WITH FREQUENCY SPECTRUM OBSERVATIONS OF DRIFTING BUOYS

Abstract

 We developed a system to assimilate the frequency spectrum observations of drifting buoys into the spectral wave model, WAVEWATCH III. We implemented the optimal interpolation as data assimilation method. We conducted typhoon wave simulations in the Western North Pacific, targeting Typhoon NANMADOL in 2022. The accuracy of wave simulations was estimated using the Japanese coastal wave observation network. As a result, the shape of the frequency spectrum changed significantly and the significant wave height error was reduced by up to 1.2 m, and the mean period error was reduced by up to 0.8 seconds. In addition, frequency spectrum assimilation was shown to produce physically consistent improvements in wave models. Our results show that the assimilation of frequency spectrum observation data of drifting buoys can meaningfully improve the wave model for extreme typhoon waves.