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FVCOM Modeling Assessment of Japan’s Tsunami Event and Impacts of Radionuclides on the Pacific Ocean

March 11 2011 was a tragic day for Japan and the world. The earthquake in Tohoku, Japan caused a tsunami, and the resulting tsunami-induced inundation has placed Japan into crisis. The amount of radiation released in the nuclear accident has threatened the coastal environment with potential impacts on the Pacific Ocean. An international research team was established with the aim of studying the mechanism of the tsunami, simulating the inundation, and assessing the impact of radionuclides on the surrounding countries around the Pacific. The team members include Dr. Changsheng Chen (Physical Oceanographer), Dr. Zhigang Lai (Physical Oceanographer), and Ms. Huichan Lin (Physical Oceanographer) at University of Massachusetts-Dartmouth (UMASSD)-USA, Dr. Robert C. Beardsley(Physical Oceanographer), Dr. Jian Lin (Geologist) and Dr. Rubao Ji (Biologist) at Woods Hole Oceanographic Institution (WHOI)-USA, Dr. Jun Sasaki at Yokohama National University-Japan and Dr. Chunyan Li (Physical Oceanographer) at Louisiana State University. The ocean model used for this activity is the global-coastal nested FVCOM model system. FVCOM is an unstructured grid Finite Volume Community Ocean Model (FVCOM) developed originally by Chen et al. (2003) and is being upgraded by the UMASSD-WHOI joint FVCOM development team (Chen et al., 2006a,b). Dr. Sasaki successfully applied FVCOM to simulate the 2004 tsunami and inundation in Banda Aceh in the Indian Ocean.

We would like to share preliminary results of our particle tracer-tracking experiments. We welcome any comments and suggestions. If anyone is interested in working together with this team on this problem, please contact Dr. Chen at c1chen@umassd.edu (or phone: 508-910-6388).

Nested Global-Coastal FVCOM System

The nested global-coastal FVCOM system used for this study consists of two domains: a) the global domain (click here or image on the right to view the full-size animation of the global domain grid) and b) the coastal inundation domain. These two domains are nested through the common boundary zones off Japan's coast.

Global domain: The global domain is configured with the unstructured triangular grid in the horizontal and the generalized terrain-following coordinate in the vertical. The horizontal resolution is ~10-50 km. A total of 46 layers are specified in the vertical, with 10 uniform layers respectively in the surface and bottom boundary layers. The global-FVCOM is an ice-ocean coupled model driven by meteorological forcing, river discharges, and tidal forcing consisting of eight major tidal constituents. The global-FVCOM was developed by the team of Dr. Changsheng Chen, Dr. Gao Guoping and Dr. Zhigang Lai at UMASSD and Dr. R. C. Beardsley at WHOI (Chen et al., 200;, Gao et al., 2011).

Nested domain: The global-FVCOM used for this effort was a modified version with refined grid (5-10 km) off Japan's coast. The image on the right shows the regional domain with the refined grid in that region, where the blue dot is the location of the earthquake center. The two blue lines are the nested boundary zone used to drive the inundation model.

Inundation domain: The inundation domain is configured with the grid with horizontal resolution varying from 10 km near the boundary to 5 m in the nuclear plant area. The high resolution bathymetry and land elevation data were provided by the Japanese partnership. This model is driven by a) boundary forcing provided by the modified global-FVCOM and b) the initial setup of the earthquake-derived sea leve change. Several earthquake models are being tested.

Nuclear plant inundation domain: The inundation domain covers the nuclear power plant area with a high-resolution grid of ~5 m. The image on the right shows the enlarged figure superimposed over the Google earth map. The model resolves the detailed geometry, which is capable of resolving the water exchange between the harbor and the coastal ocean. The inundation FVCOM is capable of resolving the water transport over dams.

Grids are created by H. Lin and the global-FVCOM grid animation was made by G. Gao and C. Chen

Global Grid

 

Nested Domain

 

Inundation Domain

Nuclear Plant Inundation Domain

Preliminary Results

1. FVCOM inundation model simulated Tsunami waves

Click image or here to view a 3-D animation. Note: The right color along the coast at the initial was caused by the image process between the wet-dry boundary, which is not produced by the model.

The animation was designed by C. Chen and created by P. Xue with help from Z. Lai, G. Gao and Q. Xu.

2. FVCOM simulated inundation process in Fukushima Nuclear power plant

Click the image on the right to view the inundation process caused by the March 11 earthquake induced tsunami. The model resolution in that area is ~5 m. To make the animation viewable, we reduced the number of vectors when the animation was made.

A detailed comparison between model-predicted and observed inundation areas was made. For details, please contact Dr. Chen at UMASSD or Dr. Robert C. Beardsley.

We, a US-Japan joint research team is working on improving the local bathymetry.

The animation was designed by C. Chen and created by P. Xue with helps from Z. Lai, G. Gao and Q. Xu.

3. Particle tracer tracking experiments

a) Fixed depth tracking at 0 m, 50 m, 100 m, 200 m, 400 m, 600 m, 800 m and 1200 m. 100 neutral buoyant water particles were released at each depth at 00:00 GMT, March 12, 2011 and tracked at each fixed depth for 7 years. The flow field used in this experiment is the daily model field produced by the Global-FVCOM under the climatological meteorological forcing condition (winds, air-pressure gradient, heat flux, and precipitation minus evaporation plus tides and river discharges). The results shown here are the trajectories of particles at each depth over a 7-year period. The results suggest that radionuclides could affect the US western coast after 5 years. We also include the animations of particles at each depth here. Each dot indicates a period of one year.

At the surface (0 m), all particles would converge to the so-called Great Pacific Garbage Gyre. At 50 m, particles spread over a large region and reach the western US coast after 5 years. At 100 m, the eastward moving particles shows similar trajectories to the 50-m particles,but still slower. At 200 m, particles stay in the narrow region and move eastward. At 400 m, trajectories of particles are similar to those at 200 m. At 600 m, particles still show the same paths as those at 200 m, but move slower. At 800 m, particles spread along the Japan's coast and then flow into the Pacific Ocean. In year 7, they can enter the Bering Sea. At 1200 m, in addition to the northward movement like those at 800 m, a portion of particles move southward into the southern Asian area.

Experiments were made by Z. Lai, C. Chen and R. C. Beardsley.

Surface

50 m

100 m

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1200 m

b) Variable depth tracking with initial releases of particles at 0 m, 50 m, 100 m, 200 m, 400 m, 600 m, 800 m and 1200 m. 100 neutral buoyant water particles were released at each depth at 00:00 GMT March 12, 2011 and tracked in the three-dimensional flow field including the vertical motion. The results suggest that radionuclides in the deep water could be upwelled to the upper water column and then disperse over a broad wide region including the East China Sea and Japan Sea as well as the Bering Sea.

Experiments were made by Z. Lai, C. Chen and R. C. Beardsley

Surface

50 m

100 m

200 m

400 m

600 m

800 m

1200 m


 

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