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Atmospheric and hydrospheric sciences
Model depiction of the atmospheric flows of radioactive cesium emitted from the Fukushima Daiichi Nuclear Power Station accident
Nakajima T, Misawa S, Morino Y, Tsuruta H, Goto D, Uchida J, Takemura T, Ohara T, Oura Y, Ebihara M, Satoh M
Fukushima Nuclear Power Station Accident, Aerosols; Radioactive materials, 137Cs, Chemical transport modeling, Ensemble models
Maps of observations (colored circles) and model ensemble means of atmospheric 137Cs concentration from 3/15/9h to 3/16/9h. Areas identified as plumes with concentration larger than 10 Bq m-3 are encircled and labeled with the name of the plume. JMA-MANAL wind vectors at 1000 hPa are superimposed. Movement of the P3 plume route is indicated by a thick arrow in panel (d).
In this study, a new method is proposed for the depiction of the atmospheric transportation of the 137Cs emitted from the Fukushima Daiichi Nuclear Power Station accident. This method employs a combination of the results of two aerosol model ensembles and the hourly observed atmospheric 137Cs concentration at surface level during 14–23 March 2011 at 90 sites in the suspended particulate matter monitoring network. The new method elucidates accurate transport routes and the distribution of the surface-level atmospheric 137Cs relevant to eight plume events that were previously identified. The model ensemble simulates the main features of the observed distribution of surface-level atmospheric 137Cs. However, significant differences were found in some cases, and this suggests the need to improve the modeling of the emission scenario, plume height, wet deposition process, and plume propagation in the Abukuma Mountain region. The contributions of these error sources differ in the early and dissipating phases of each event, depending on the meteorological conditions.