Real time tide resolving ocean prediction system for Japanese coastal waters

The Japan Coastal Ocean Predictability Experiment (JCOPE) group of JAMSTEC weekly operates the 1/12 degree North-Western Pacific Ocean JCOPE modeling system focused on reproduction and prediction of Kuroshio current behavior south-east of Japan. Recently, for more detailed resolution of ocean variability in coastal waters around Japan, it was developed and is routinely operated the 1/36 degree regional tide-resolving ocean model that is the one way nested to the larger scale North-Western Pacific Ocean JCOPE modeling system.

Both models are based on POM code and use generalized sigma vertical coordinate system. Regional model covers part of East China Sea, Japan Sea and Pacific Ocean including coastal waters around the largest Japanese Islands (except Northern Hokkaido). Simulated are Kuroshio current south-east of Japan, Oyashio cold current spreading southward along the eastern Hokkaido and Hohshu, Tsushima and Tsugaru currents in the straits connecting Japan Sea with the East-China Sea and Pacific ocean etc.

Regional model explicitly simulates tidal processes that are specified by boundary conditions and by tidal gravitational force for major tidal constituents (up to 16 main short-term tidal harmonics). Boundary conditions are specified using both information from the nesting non-tidal model and tidal volume fluxes and sea level anomalies at the model boundaries. Tidal information around Japan is provided by tidal model of Japan National Astronomic Observatory (Matsumoto et. al).

The tidal sea level variability is well reproduced in Japan coastal waters except that some overestimation of tidal amplitude is found in the semi-enclosed Seto Inland Sea.

Tidal motion over the sloping topography generates strong internal tidal waves which represent an important part of the short-term ocean variability. These waves are reproduced by nested regional model. Prediction of internal tides seems to be possible close to the generation zones over the continental slopes, when off-shore and far away from the generation zones the deterministic predictability of these processes is under the question due to the complex dependence of wave propagation features from the oceanic conditions.

Close to the tidal frequencies are found inertial oscillations that potentially could be predicted locally following significant disturbances of oceanic circulation caused by passage of strong atmospheric disturbances: fronts, typhoons etc. To achieve this goal, model's meteorological forcing is provided by best of available meteorological weather prediction models: JMA non-hydrostatic MSM system (spacial data resolution ~10 km, hourly forecasts up to 33 h updated every 3 h) followed by JMA GSM (0.2*0.25 degree) and/or by NCEP GFS data (~0.3125 degree resolution short-term forecasts followed by ~0.625 degree resolution medium range forecasts).

North-Western Pacific JCOPE system uses the 3DVAR assimilation method with the incremental assimilation update and assimilates satellite SST and SSH anomalies as well as latest available Japan Fisheries Research Agency (JFRA) in-city T and S profiles data. Regional model runs daily and uses weak nudging of the time-filtered T and S fields to these of the external model (with the 10 days nudging time scale). Modeling results in the experimental mode are provided to researchers and potential users through the interactive WEB site at http://www.jamstec.go.jp/frcgc/jcope/vwp/ (registration is required).