Abstract
In order to improve our understanding of the temporal and spatial distributions of transport and depositions of the radionuclides due to the Fukushima accident, not only observational but also simulation model studies have been conducted at the Meteorological Research Institute, Japan. Observations include HV aerosol sampling, fallout sampling and β and ? radionuclides analyses. IP photos were obtained from HV filters sampled during the course of the accident and the filters were subjected for the analysis of so-called hot particles to know about the physic-chemical states of the radioactive aerosols. Model studies have employed global and regional atmospheric transport models. For the global transport the MASINGAR model, with horizontal model grid of about 0.56?SUP?o?/SUP? and 40 vertical layers (from surface to 0.4 hPa), was used. The horizontal wind components were nudged by global analysis of Japan Meteorological Agency dataset. A regional transport model MRI-PM/r has been developed. This model classifies the aerosol particles into 6 categories, and considers condensation, evaporation, cohesion, activation of cloud condensation nuclei and ice nuclei, dissolution, collision (washout), cloud microphysical processes (conversion processes among rainout, cloud water, ice clouds, raindrops, snow, hail) and dry deposition. Emission estimates by inverse modeling approach and advanced approach of ensemble simulation of atmospheric dispersion of radionuclides during the accident have been also performed.
