Response of Near-Inertial Internal Waves to Various Typhoon-Tracks Around the Tango Peninsula, Japan

Abstract

Response of near-inertial internal waves (NIIWs) to various typhoon-tracks was investigated by analysis of mooring data observed around the Tango Peninsula during eight typhoons. Spectral shapes, energy levels and propagation property of NIIWs were different by typhoon tracks. Amplifications of NIIWs were especially large and the NIIWs propagated with the coast on the right having the characteristic of an internal Kelvin wave along the coast when typhoon have passed northeastward over the Japan Sea. Slab model analysis showed that the amplifications of NIIWs after passage of typhoon were almost induced by rapid temporal variation of local wind, however, duration time and second amplification of NIIWs after passage of typhoons were not explained. To clarify the formation mechanisms of observed properties of NIIWs and response of coastal water to various typhoon-tracks, numerical experiments using multilayer level model with idealized wind stress and realistic topography were performed. Model results showed that the NIIWs energy around the Tango Peninsula were amplified after passage of typhoon by southward propagation of NIIWs generated off the western coast of Noto Peninsula or off Tango Peninsula. In the case which typhoon advanced northward off Kyushu, nevertheless large amplitude NIIWs were generated at wide region in the western side of Oki Island, its energy generated there has not reach around the Tango Peninsula was found. Consequently, the NIIWs energy are greatly strengthen in the wide region around the Tango Peninsula, when the typhoon passed north east ward off the Japan Sea and the NIIWs were widely generated in the eastern side of Noto Peninsula and off the Tango Peninsula. Moreover, slab model and numerical model results showed that amplification of NIIWs can be occur when typhoon is advancing slowly and its radius are large even though the typhoon passed over not Japan Sea but the Honshu.