Interactions Between Ocean and Successive Typhoons in the Kuroshio Region in 2018 in Atmosphere–Ocean Coupled Model Simulations

Abstract

AbstractTyphoons decrease sea surface temperature (SST) along their wakes through upwelling of subsurface water, vertical mixing in the upper ocean, and heat release from the sea surface, and these cold wakes can influence subsequent typhoons. In this study, we investigated interactions between the upper ocean and typhoons in the North Pacific subtropical gyre with focuses on Kuroshio's response and feedback using atmosphere–ocean coupled model simulations. In late August and early September 2018, typhoons SOULIK, CIMARON, and JEBI passed through the northwestern subtropical gyre. During the passages of SOULIK and CIMARON, SST decreased along their paths due to vertical mixing except in the Kuroshio region. We quantitatively revealed that the Kuroshio stayed warm because the deep mixed layer along its path and small vertical temperature gradient around the mixed layer base, which are unfavorable conditions for cooling by vertical mixing, limited the cooling effects. After SOULIK and CIMARON had passed, SST recovered through horizontal Kuroshio heat transport and radiative heating. The possibility that the SST field after SOULIK and CIMARON passages influences JEBI was also discussed. Although impacts on JEBI intensity were not identified, it is implied that the turbulent heat flux (THF; sum of the sensible and latent heat fluxes) around JEBI was modulated by the SST field: heat release from the ocean was reduced in the region with decreased SST and enhanced over the sustained high SST of the Kuroshio. Furthermore, the large THF over the Kuroshio may have caused an increase of JEBI‐associated precipitation around Japan.