Experiments Commenced for Predicting Oceanic Variability Near Japan

December 20, 2001

  Dr. Toshio Yamagata (Professor of Tokyo University), Program Director, and Mr. Yasumasa Miyazawa's research group in the Climate Variations Research Program of the Frontier Research System for Global Change (a joint project of NASDA and JAMSTEC) have commenced experiments using high-resolution ocean general circulation models (OGCMs) to predict oceanic variability with particular emphasis on variations in the Kuroshio path near Japan.(reference)
  This group has developed a system for predicting the Kuroshio variability and the mesoscale eddy behavior that greatly influence the Japan coastal ocean. The system uses a high-resolution OGCM that well simulates the Kuroshio meander and the mesoscale eddy activity and sea surface height anomaly data obtained from satellite observations. The experiments that simulate the Kuroshio path in the past, and then predict "future" state from that state using the OGCM (hindcast experiments: see note), revealed that, at present, the prediction of the Kuroshio variability is feasible for up to two months in advance.
  In addition to constructing a system for experimental prediction of the oceanic variability at regular intervals, and predicting and verifying the Kuroshio path variations, this research group also intends to improve the models with the aim of practical application of systems that incorporate even more detailed predictions of coastal oceanographic conditions.

  A hindcast experiment is a simulation, referring to an experiment that predicts future conditions by simulating them from a state in the past.

  The routine predictions of oceanic variation ("ocean weather reports"), combined with the prediction results from in-situ verification, are expected to considerably contribute to the improvement of atmosphere-ocean models that predict longer-term climate change. From this practical perspective of computational science, detailed elucidation and prediction of oceanographic variability in the sea near Japan is extremely important for Japan to appropriately manage and to sustainedly develop the Exclusive Economic Zones (EEZ).

Methods and Results
  A high-resolution OGCM was developed with a horizontal resolution of about 10 km and 35 levels that resolve the detailed sea bottom topography. This OGCM has been successfully simulated for the first time in the world the variability of sea surface height caused by variations in the Kuroshio path and mesoscale eddies in the sea near Japan (fig. 1). Given the initial conditions (Kuroshio path and the location of eddies nearby) estimated using data from the satellite (NASA: TOPEX/POSEIDON) that routinely observes sea surface height variation, the OGCM simulated the variability of the Kuroshio path over the subsequent two months (fig. 2a, fig 2b).

  JAMSTEC Yokohama Institute of Earth Sciences (3173-25 Showa-machi, Kanazawa-ku, Yokohama City, Kanagawa Prefecture 236-0001, Japan) will conduct separate simulation demonstrations at the request of the press. Please direct press inquiries to the FRSGC Joint Promotion Office.

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