Ocean Downscaled Modeling Activities in Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

Sergey M. Varlamov

Ocean Downscaled Prediction Research Team, Research Institute for Global Change, JAMSTEC, Yokohama, 2360001, JAPAN, E-mail: vsm@jamstec.go.jp.

JAMSTEC is one of largest marine science research institutions in Japan. Its activities cover observations of world oceans and earth, including ocean drilling program for understanding of processes in solid earth such as earthquakes, researches in global climate variability and global changes, atmospheric and ocean dynamics analysis and simulation using one of largest in Japan supercomputer system “Earth Simulator” etc.

One direction of JAMSTEC activities is realization of Japan Coastal Ocean Predictability Experiment (JCOPE) program that includes development of real-time ocean assimilation and modeling systems for analysis and prediction of ocean circulation and its variability, surface and internal wave dynamics etc as.

In frame of this program, a general prototype of tide-resolving regional ocean modeling system was designed, developed and number of regional subsystems are operated for regions all around the globe. Regions of interest include coastal waters around Japan and number of areas perspective for exploration of natural resources and renewable ocean energy. Structure of such regional modeling system would be described on an example of Japan coastal ocean prediction system.

The core of regional system is an ocean circulation model (JCOPE-T) that is a generalized sigma coordinates model nested to the non-tidal assimilation JCOPE model. Tides are introduced at open boundaries and as a body force. Example regional model has horizontal resolution of 1/36 degree and 46 vertical levels. It is forced by surface fluxes estimated by bulk formulas using analyses and forecasts of Japan Meteorological Agency and USA National Centers for Environmental Prediction. Hourly JCOPE-T model results are provided to customers and used for research purposes. One of model applications was drift estimation of radioactive substances following the 2011 Fukushima Dai-Ichi nuclear power station accident.

Using these modeling systems, recently analyzed are results from modification of ocean vertical mixing scheme to popular in Japan Nakanishi-Niino version of Mellor-Yamada model developed based on Large Eddy Simulation results. Level 3 mixing model is used in JMA atmospheric non-hydrostatic models, when level 2.5 model is tested with different ocean circulation models. Results show some improvement in modeling of surface mixed layer without any surface wave breaking parameterization. Other our group research works include validation of impact from direct bi-directional coupling of surface waves and ocean circulation models, validation of internal waves with satellite observations etc.