Numerical investigation on characteristics of long wave components amplified under the 2018 Typhoons Jebi and Trami observed along the coast of Wakayama, Japan

Abstract

ABSTRACT The tide gauge data at Shirahama in Tanabe Bay on the Wakayama coast during Typhoons Jebi and Trami in 2018 showed two dominant oscillation components with periods of approximately 40–45 min and 7 min. We investigated the characteristics of the unique resonances using wavelet analysis and numerical simulations. Through the numerical simulation of storm surges by Jebi and Trami and the modeling of Trami with different tracks, we found that oscillations having a period of 40–45 min were primarily induced by the resonance in large areas, including Tanabe Bay and Kii Strait, which is north of the bay. The amplification of this large-scale resonance was sensitive to the forward speed and angle of the typhoon tracks. In addition, Green’s functions were developed to investigate local resonant characteristics in Tanabe Bay. The spatial distributions of the amplitude and phase difference of Green’s functions at different locations showed that the observed 7-min oscillations were amplified by the resonance of two adjacent small inlets at the Shirahama tide gauge station. The resonance between these two local inlets produced a long-lasting ~7-min oscillation observed at the tide gauge.