Japan Geoscience Union Meeting 2023

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[J] Oral

A (Atmospheric and Hydrospheric Sciences ) » A-CG Complex & General

[A-CG43] Kuroshio Large Meander

Sun. May 21, 2023 9:00 AM - 10:15 AM 201A (International Conference Hall, Makuhari Messe)

convener:Hatsumi Nishikawa(Atmosphere and Ocean Research Institute, University of Tokyo), Hidetaka Hirata(Rissho University), Toru Miyama(Japan Agency for Marine-Earth Science and Technology, Application Laboratory), KUSAKA AKIRA(National Research and Development Agency, Japan Fisheries Research and Education Agency. Fisheries Resources Institute), Chairperson:Hatsumi Nishikawa(Atmosphere and Ocean Research Institute, University of Tokyo), Hidetaka Hirata(Rissho University), Toru Miyama(Japan Agency for Marine-Earth Science and Technology, Application Laboratory), KUSAKA AKIRA(National Research and Development Agency, Japan Fisheries Research and Education Agency. Fisheries Resources Institute)


9:30 AM - 9:45 AM

[ACG43-03] Numerical Experiments on Wintertime Atmospheric Response to the Kuroshio Large Meander

*Yoshi N Sasaki1, Ryunosuke Ito1 (1.Hokkaido University)

Keywords:Kuroshio, air-sea interaction

The Kuroshio large meander causes a negative sea surface temperature (SST) anomaly associated with a cold-core eddy off the Kii Peninsula and a positive SST anomaly along the coast of the Tokai region. To clarify the atmospheric response in winter to these SST anomalies associated with the Kuroshio large meander, we conducted a control experiment using a regional atmospheric model with real SSTs and sensitivity experiments in which the SST boundary conditions were replaced with those for the large meander and non-large-meander periods, respectively. The results of these sensitivity experiments show that during the large meander period, a positive sea level pressure (SLP) anomaly and divergence of sea surface winds are found above the cold-core eddy. In contrast, the convergence of sea surface winds occurs to the north and south of the cold-core eddy. This positive SLP anomaly over the cold-core eddy has been reported in previous studies and is explained by a pressure adjustment mechanism due to the cooling by the negative SST anomaly of the cold-core eddy. Interestingly, the sea surface wind anomalies north of the cold-core eddy continue to the Kanto coast, with northerly wind anomalies occurring during the large meander period. This northerly wind anomaly is seen from the surface to 950 hPa and exists to blow into the positive SST anomaly along the coast of the Tokai region. Because this northerly wind anomaly is not located over an SST anomaly, this northerly wind anomaly cannot be explained by the pressure adjustment mechanism. Similar low-level winds blowing into positive SST anomalies along the coast of the Tokai region are also observed in the ERA5 product. In addition, the precipitation decreased over the cold-core eddy during the large meander period. This is consistent with the downward wind caused by the positive SLP anomalies over the cold-core eddy during the large meander period. On the other hand, from the Tokai region coast to the Kanto coast to its north, there was no significant change in precipitation, but the frequency of precipitation increased significantly. This precipitation change may be due to the aforementioned northerly wind anomalies.