[A-CG38] 海洋と大気の波動・渦・循環の力学

[ACG38-P05] Kuroshio path inferred from satellite-derived sea surface topography between the islands of Luzon and Kyushu in the northwestern Pacific

*Ying-Chih Fang¹、Wei-Teh Li¹ (1.Department of Oceanography, College of Marine Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan)

キーワード：Kuroshio path, Mesoscale eddies, High-frequency radars, Surface currents

Variability of Kuroshio paths (KPs) in the northwestern Pacific has been locally investigated in the region between the islands of Kyushu and Luzon. We optimally track KPs by applying an automatic front-detecting method based on maximum geostrophic velocity along a given satellite-derived dynamic height isoline. Our results are robust and consistent with previous studies, showing highly variable KPs east of Luzon and Taiwan. An immediate explanation is the impingement of westward-propagating mesoscale cyclonic and anticyclonic eddies. We observe patterns along the KPs with anticyclones (cyclones) enhancing (weakening) the Kuroshio. The KPs are relatively stable at ~28^oN, in comparison to more variable KPs at the lower latitudes. Most of the variability stems from energy with timescales of ~30-160 d and 1 yr. Temporal variability of surface geostrophic velocities along the KPs is examined in detail, showing substantial deviations from upstream to downstream regions along the KP. There exists surface velocity reduction at ~26^oN and south of ~23^oN. More sustained and identifiable KPs and stronger surface currents at ~1 m s^-1 are characteristic of the region from midway along the shelfbreak in the East China Sea to the Tokara Strait. Such regional differences result from the relatively smaller impact of mesoscale eddies that are largely blocked by the Ryukyu Islands. Our optimally determined KPs are in line with strong surface currents of > 0.8 m s^-1 observed by the shored-based high-frequency radars (HFR) along the east coast of Taiwan. Interpretation of vortex-like flow patterns in the HFR data is corroborated by the calculated KPs, which provide supportive evidence showing that the measured surface current pattern is related to mesoscale eddies outside the radar footprint. Our work may help interpret and diagnose complicated HFR observations east of Taiwan.