Numerical analysis of the global transport of radionuclides from Fukushima Dai-ichi nuclear power plant accident

We analyzed the global atmospheric transport of the radioactive materials released from the accident of Fukushima Dai-ichi nuclear power plant after the Tohoku great earthquake, using our global aerosol transport model named MASINGAR (Model of Aerosol Species IN the Global AtmospheRe). In the setting of the experiment, the horizontal grid is about 60km (320x160 grids) and 40 vertical layers (from the ground surface to 0.4hPa). The horizontal wind components are nudged using global analysis of Japan Meteorological Agency (GANAL). The model treats Cs-137, Cs-134, Xe-133, and I-131 as released radionuclides. For emission fluxes of radionuclides, we used estimates by Chino et al. (2011) for Cs-137, Cs-134 and I-131 and estimates of Stohl et al. (2011) for Xe-133. The model include semi-Lagrangian advective transport, eddy diffusion, convective transport, dry and wet depositions, and radioactive decay. Reasonably good agreements between observed and simulated concentration and arrival timing of the radionuclides at available observations, although some over- or underestimation of the concentrations are found at several observational stations. We also conducted tagged tracer experiments to evaluate the emission fluxes and to identify the transport route of the radionuclides to the Pacific Ocean, North America, Europe, Russia, and Southeast Asia were identified.