Ocean Dynamics and Climate in the Western Pacific

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The present international cooperative research on the ocean dynamics and climate issues in the western Pacific Ocean was promoted as a part of ODC (Ocean Dynamics and Climate) program under the IOC/WESTPAC.In particular, we facilitated cooperative researches using an oceanic general circulation model, exchange of observed data, the arrangement of observation plans among the related countries. The following are the main outcomes of the present research program.1) A high-resolution Indo-Pacific oceanic general circulation model (OGCM) demonstrates that the seasonal variation of the sea level around Southeast Asia is governed by the local monsoonal winds and the equatorial Kelvin Jets generated remotely during the transition period of the monsoon in the central and eastern Indian Ocean. It also shows that the semiannual aspect appeared in the transport through the Lombok Strait results from the reduction of the posotive pressure gradient across the strait due to the propagation of the Kel … More vin Jets along the southern coast of Indonesia. To detect the surface current fields associated with those jets, surface drifting buoys are deployed off southern coast of Indonesia in November 1993 based on the result of model buoy trajectories simulated in the OGCM.2) We are successful in reproducing a detailed three-dimensional structure of Kuroshio south of Japan by use of a high-resolution OGCM which can predict the surface elevation explicitly. An analysis of a torque balance for the depth integrated transport indicates that the Kuroshio transport over the continental slope area west of Ryukyu Islands is strongly affected by an interaction between the ocean and the solid earth through the bottom pressure torque.3) We analyzed the variations on intraseasonal to decadal time scale in temperature field in the western Pacific taken from satellites and/or hydrographic observations. Based on the analysis, we developed a new statistical method that can compute horizontal velocity fields from the temperature variability data.4) A coupled atmosphere-ocean model composed of the 2 1/2 layr ocean model developed in Nova University and a simple Gill-type atmospheric model or an atmospheric GCM is constructed and tested for the response of the equatorial ocean to the atmospheric intraseasonal disturbances and the monsoonal winds. During the development of the coupled model, we invited Professors McCreary and Lukas mainly to the University of Tokyo to review the research on the oceanic climate variability in the Indian and western Pacific Oceans, and organized a real time research network through the Internet to facilitate mutual communication among each country.5) At the JSC/Pacific Ocean Panel (chaired by Dr.Halpern), which was held at the Jet Propulsion Lab.in Los Angels, the present project was introduced as a core forerunner of a future intensive research program in the western Pacific under GCOS/GOOS and WCRP/CLIVAR.6) The results of the present project were presented at the ODC-2 session at the IOC/WESTPAC Symposium that was held in November 1994 at Bali, Indonesia. At the same symposium, we organized a workshop entitled "Special Session of Western Boundary Currents", and discussed in detail the oceanic climate variability in the western Pacific and the adjacent regions and on a future plan of the research in the regions. Papers presented at the workshop will be published in J.Geophy.Res.special issue edited by the principal investigator of the current program (T.Yamagata).7) Principal investigator is going to organize a symposium as a chief convenor, which focuses on the decadal and interdecadal oceanic climate variability, at the IUGG/IAPSO Meeting in August 1995 at Honolulu, Hawaii. Less