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Fukushima Tracers in Global RTOFS

NCEP/NWS deployed particle tracing to predict the movement of radionuclides in the ocean shortly after the Japanese nuclear disaster near Fukushima.

The full three-dimensional tracer computations capability of HYCOM has also been implemented to predict the dispersion of radionuclides in a nested North-West Pacific sub-region model within Global RTOFS. The boundary conditions of the nested sub-region are updated daily from the nowcast fields of the global model. These tracer forecasts have been implemented at NCEP Central Operations.

IMPORTANT NOTE: These results only track initial releases of radionuclides from the Fukushima Dai'Ichi Nuclear Power Plant over the time period of 12 March 2011 through 26 April 2011. No subsequent discharges from the facility are considered in this simulation.

Posters were presented at the Fourth Session of the Joint WMO-IOC Technical Commission for Oceanography and Marine Meteorology, 23-31 May 2012, Yeosu, Republic of South Korea, (PDF available here). and the Fall 2012 meeting of the American Geophysical Union, 3-7 December 2012, San Francisco, USA (PDF available here).

To view the tracer images:

  1. Select a View: (SSH is Sea Surface Height, Cs-137 is Cesium-137)
  2. Pick the From and To dates
  3. Press Start
The dates are selectable from April 27, 2011 to the near present.

Changing the view or the dates will reload the viewer. Note, selecting a long date range can result in a very slow browser or even a browser crash. We recommend limiting the loops to about a month or two at a time.

The Cesium-137 radioactivity is given in units of Bequerels (Bq), One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second.

From: To:

Simulation of Cs-137 through RTOFS_EP_WPA, after the Fukushima-Daichii nuclear accident.

A numerical simulation for the time evolution of the 3-dimensional Cs-137 concentration after the Fukushima-Daichii nuclear plant accident was performed, and is referred as RTOFS_EP_WPA (RTOFS Episodic Tracer for the Western Pacific).

The simulation uses the HYCOM model, in the domain 134°E-30°W, 15°N-60°N, at 1/12° horizontal resolution, with 32 vertical layers, nested to the daily nowcast archives of the Global RTOFS model, a global operational ocean prediction model at EMC, in strong partnership with the Navy). The regional simulation is run in forecast mode (with no data assimilation inside the domain). The HYCOM source is version 2.2.36tr, with atmospheric deposition of tracers.

Cs-137 is added as an atmospheric deposition to the top layer of the ocean model, with the horizontal and time evolution provided by NOAA's HYSPLIT-NSC (V.3) for Cs-137, based on Cs-137 source by Japan's Nuclear Safety Commission's. HYSPLIT-NSC covers the whole period of deposition, March 12-April 21, 2011, with a total deposition of 5.4 PBq over the ocean (1 PBq=1015 Becquerels).

At model day April 26 2011, the direct ocean discharge of Cs-137 from waters released from the plant was added as simulated by NOS' ROMS coastal model (Lanerole, Patchen, et al, 2012 Ocean Sciences meeting, Salt Lake City), normalized to 4.5 PB of total direct discharge.

The 3-D Cs-137 concentration is followed in a simulation to estimate the importance of patches in the Pacific Ocean.

Results from the simulation were presented in:

  • Tolman, H., Z. Garraffo, A. Mehra, I. Rivin, H-C Kim, T. Spindler, 2012: "Ocean plume and tracer modeling for the Fukushima-Dai'ichi event", 2012 Ocean Sciences meeting, Salt Lake City.

  • Garraffo Z.D, H-C. Kim, A. Mehra, T. Spindler, H. Tolman, 2012: "Tracer modeling with the Hybrid Coordinates Ocean Model (HYCOM)", 2012 Ocean Sciences meeting, Salt Lake City.