[A-CG38] 海洋と大気の波動・渦・循環の力学

[ACG38-01] Near-inertial and double-inertial internal waves under the influence of quasi-geostrophic disturbances in the Sea of Japan: A case study of Typhoon Tapah

*川口 悠介¹、矢部 いつか¹ (1.東京大学・大気海洋研究所　)

キーワード：近慣性波、2f波、台風、対馬暖流、メソ渦、日本海

Distinct signatures of near-inertial and multiple inertial internal waves in response to travelling cyclones are often observed in the frontal region of the Sea of Japan. However, it is not well known how they are generated, propagated, and dissipated under the influence of the Tsushima Warm Current (TWC), which flows into the middle of the sea. In this study, we investigated the behavior of near-inertial and double-inertial internal waves (NIWs and DIWs, respectively) using a three-dimensional numerical model that resolved meso- and fine-scale features. The model used the realistic wind forcing of Typhoon Tapah, which passed the sea in September 2019. To clarify the influence of the TWC, experiments with (WITH TWC) and without (NO TWC) warm water inflow through the Tsushima Strait were conducted and compared. Compared to NO TWC, WITH TWC, with many meanders and mesoscale eddies, simulated the enhancement of the NIWs and the emergence of DIWs. In the WITH TWC experiment, mesoscale features with a negative relative vorticity near the cyclone track favorably captured the NIWs and held them persistently. Within the mesoscales, the DIWs grew quickly and radiated towards the outer regions, mostly poleward, and eventually dissipated within several days. The modal dispersion relation explains the wave nature: NIWs generally favored a high vertical mode (the 3^rd to 5^th), so their lateral travelling was too sluggish to escape the mesoscale features. DIWs had the lowest vertical mode and were fast enough to exit the source region. The updated knowledges of the wave behaviors benefit the understanding of ocean mixing at remote places from the cyclone’s track.