HR: 0800h
AN: OS11A-0488    [Abstracts]
TI: Resolving Kuroshio/Near Boundary Interaction With Nested Numerical Models: Application to the Kyucho
AU: * Jacobson, T
EM: tivon@eps.s.u-tokyo.ac.jp
AF: Dept of Earth and Planetary Sci The University of Tokyo, Bunkyo-ku 7-3-1 Hongo, Tokyo, 113-0033 Japan
AU: Yamagata, T
EM: yamagata@eps.s.u-tokyo.ac.jp
AF: Dept of Earth and Planetary Sci The University of Tokyo, Bunkyo-ku 7-3-1 Hongo, Tokyo, 113-0033 Japan
AB: The Kyucho (lit.~swift current) is marked by sudden strong currents and an associated internal temperature rise which propagates counterclockwise at 1-2 m/s around Sagami Bay, Japan. Sagami Bay is a semicircular bay just southeast of Tokyo Bay. It has been hypothesized that the Kyucho is the manifestation of a semigeostrophic shock wave formed at the leading edge of a density current associated with the intrusion of warm Kuroshio water into Sagami Bay (T.~Yamagata, Tellus, 1980, 32, pp.~73-76; A.~Kubokawa and K.~Hanawa, J.~Ocean.~Soc.~Japan, 40, 1984, pp.~247-270). Because the Kyucho causes an average of about 2 million dollars per year of damage to fishing nets in Sagami Bay, and because it has been associated with the arrival of fishable yellowtail in Sagami Bay, Japanese researchers have been interested in the Kyucho for at least the past 75 years. It has been definitely linked to variations of the Kuroshio and to the passage of the typhoons, but little is known about the structure of the current itself or how Kyucho induced by the Kuroshio differ from those induced by typhoons. We first mention our attempts to study the Kyucho by analyzing available data: coastal station current and temperature records, recently installed HF radar surface current data, satellite SST data, and the output of the JCOPE numerical model which resolves the Kuroshio. We present some instances in which Kyucho can be linked to the advection of warm water by the Kuroshio (using the reanalysis SST product of H. Kawamura at Tohoku University). However, none of the available data has sufficient time and space resolution to clearly capture the formation and propagation of the Kyucho. In some of the near-coast HF radar data, reliability is also an issue. We therefore discuss recent work on numerical models which can resolve the details of Kyucho formation: principally, a high-resolution nested hydrostatic model based on POM which uses data from the coarser JCOPE model (Japan Coastal Ocean Predictability Experiment). It is hoped that this model will eventually be used for operational forecasting. We will also present analysis of an September-October 2004 JCOPE experiment, which will have a horizontal resolution of 3km near Sagami Bay, possibly enough to see features of the Kyucho.
DE: 4255 Numerical modeling
DE: 4512 Currents
DE: 4546 Nearshore processes
DE: 4576 Western boundary currents
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting