2025 年 21 巻 p. 124-131
Typhoons AMPIL and SHANSHAN (2024) slowed down as they approached and moved parallel to the Kuroshio Current. Both typhoons reached peak intensity at relatively high latitudes while they were moving northward. Various atmospheric and oceanic datasets were used to investigate atmospheric and oceanic thermodynamic similarities and differences between AMPIL and SHANSHAN. In addition, numerical simulations and sensitivity experiments for high sea surface temperature (SST) in the Kuroshio Current region were performed with a nonhydrostatic atmosphere model and an atmosphere-wave-ocean coupled model to understand related intensification mechanism. The 26°C isotherm was relatively deep and the upper-ocean heat content was relatively high where AMPIL and SHANSHAN intensified. Despite the different atmospheric environments, such as the vertical wind shear and the relative humidity at the 600-hPa altitude, AMPIL and SHANSHAN were able to develop and maintain the maximum intensity at relatively high latitudes during when the TCs moved slowly near the Kuroshio Current region. The results of the sensitivity experiments suggest that high SSTs in the Kuroshio Current region possibly contribute to the development and maintenance of the maximum intensity of AMPIL and SHANSHAN through high latent heat fluxes outside the radius of maximum wind speed and the inner-core axisymmetrization.
