[A-CG43] Kuroshio Large Meander

[ACG43-02] Impact of sea surface temperature anomalies associated with the Kuroshio large meander on a distant typhoon intensity

*Keita Fujiwara¹, Ryuichi Kawamura², Masami Nonaka³ (1.Disaster Prevention Research Institute, Kyoto University, 2.Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University, 3.Application Laboratory, Japan Agency for Marine-Earth Science and Technology)

Keywords:typhoon, Kuroshio large meander

This study investigated how the local sea surface temperature (SST) anomalies (SSTA) associated with the Kuroshio large meander (KLM) remotely influenced the intensity of Typhoon Neoguri during its northward-moving phase over the ocean south of Japan on October 2019. A control run (CTL run) with the observed SSTA and several SST sensitivity experiments were performed, using a cloud-resolving regional model with a high horizontal resolution of 2 km. The SSTA during the KLM event was characterized by the cold SSTA south of the Kii Peninsula and warm SSTA off the Tokai region. The SST sensitivity runs included the NW run without warm SSTA south of the Tokai coast, the NC run without cold SSTA south of the Kii Peninsula, and the NWC run without warm and cold SSTA over these regions.

The surface evaporation off the Tokai area in the NW run was suppressed by approximately 25% as compared with the CTL run, leading to the decrease in water vapor within the lower troposphere over the domain where the SSTA was modified. The forward trajectory analyses captured the intrusion of the relatively dry air around the modified SST region into the vicinity of Neoguri. As a result, the central pressure of Neoguri during its mature phase was 5 hPa higher in the NW run than the CTL run. In contrast, the NC run enhanced the surface evaporation over the ocean south of the Kii Peninsula, moistening the atmospheric boundary layer around the excluded cold SSTA area. The situation increased the moisture transports into the distant typhoon, contributing to deepening the central pressure during the mature phase by approximately 1 hPa, as compared with the CTL run. The NWC run was similar to the NW run rather than the NC run in terms of the changes in typhoon intensity and moisture influx from the Kuroshio, because the warm SSTA was significantly pronounced during the KLM event on October 2019. These simulations revealed that the local SSTA created by the KLM has the potential to remotely influence the development of a typhoon approaching the Kuroshio in boreal fall.