[A-OS15] 海洋物理学一般

[AOS15-01] Where is typhoon-generated near-inertial kinetic energy going under the Tsushima oceanic front in the Sea of Japan?

*川口 悠介¹、矢部 いつか¹、和川 拓²、千手 智晴³、酒井 秋絵³、井桁 庸介² (1.東京大学・大気海洋研究所　、2.水産研究・教育機構、3.九州大学・応用力学研究所)

It is not fully understood how near-inertial kinetic energy (NIKE) is spatially distributed near Tsushima oceanic front (TOF) as a typhoon travels across the region. Underneath the main axis of the TOF, a year-round mooring of horizontal current was implemented in 2019, covering a major part of the water column. During summer, three massive typhoons (Krosa, Tapah, and Mitag) consecutively traversed the frontal area and delivered a substantial amount of NIKE into surface mixed layer. According to a mixed-layer slab model, NIKE was widely distributed near the cyclone’s track. The mooring observation exhibited the vertical distribution and pathways of surface-generated NIKE in response to the successive typhoon events. According to ray-tracing experiments based on the internal-wave theory, large-scale near-inertial waves rapidly descend to a depth of greater than 1,000 m, while mesoscale near-inertial waves slowly descend rarely going far beyond the main pycnocline. Following the passage of Tapah, we found that profound wave kinetic energy masses were nearly stationary at shallow depths coincident with vertical shear of the surface-intensified geostrophic current. It was inferred that the descending rate fell and then was amplified through the wave kinetic energy conservation when near-inertial waves came from north regions relative to the TOF.