[A-CG44] Kuroshio Large Meander

[ACG44-P03] Response of frontal structure associated with an explosively developing extratropical cyclone to the variability of the Kuroshio Path

*Hidetaka Hirata¹, Ryuichi Kawamura², Masami Nonaka³ (1.Rissho University, 2.Kyushu University, 3.Japan Agency for Marine-Earth Science and Technology)

Keywords:Kuroshio, extratropical cyclone, frontal structure

To examine the influence of the variability of the Kuroshio path on the frontal structure of an explosively developing extratropical cyclone, we conduced sensitivity numerical experiments to sea surface temperature (SST) anomalies using a regional cloud-resolving model. We paid attention to an explosive cyclone, which developed to the south of Japan in January 2017, and examined its response to warm and cold SST anomalies associated with the Kuroshio Straight (KST) and Large Meander (KLM) path. The results derived from the numerical experiments showed that the SST anomalies influenced the atmospheric thermal structure near the surface around the south of Japan prior to the development of the cyclone. In the KST experiment, the horizontal gradient of potential temperature near the surface was enhanced zonally along the KST path. In the KLM experiment, the meandering structure of the potential temperature gradient was evident along the KLM path. We also found the differences in the fontal structure of the cyclone between the two experiments when it passed to the south of Japan. A surface atmospheric front, which formed to the north of a warm front, intensified off the coast of Shikoku in the KST experiment compared with the KLM experiment. In contrast, the warm front strengthened when the cyclone approached the KLM region in the KLM experiment compared with the KST experiment. These differences in the frontal structure seem to be due to the differences in the atmospheric thermal structure before the cyclone development. Moreover, frontal precipitation was stronger off the coast of Shikoku in the KST experiment than in the KST experiment. The enhanced front off the coast of Shikoku in the KST experiment is likely to be related to this precipitation intensification. These results suggest that the variability of the Kuroshio path affects the frontal structure of the cyclone and associated precipitation.