2023 Volume 79 Issue 17 Article ID: 23-17021
To improve its accuracy, we developed a system to assimilate the drifting buoy observations into the spectral wave model, WAVEWATCH III. We implemented Optimal Interpolation as data assimilation method. We conducted typhoon wave simulations in the Western North Pacific, targeting the typhoon waves in the summer of 2022. The accuracy of wave simulations was estimated using the Japanese coastal wave observation network. At first, we conducted the initialized experiment in which the initial condition is assimilated with drifting buoy observations, and the model runs for three days without assimilation. As a result, the model improves immediately after data assimilation (initial condition), and the improvement continues for 71 hours. Next, we conducted a sequential data assimilation experiment in which the assimilation process was operated every 1 hour. The sequential data assimilation reduced the wave model error by up to 2.72 m when drifting buoys observed extreme typhoon waves near the center. Even when the assimilation process is operated every 3 hours, the wave model error was reduced by up to 2.36 m. Our results show that the assimilation of drifting buoys observation data can meaningfully improve the wave model for extreme typhoon waves.
