Model intercomparison of atmospheric Cs from the Fukushima Daiichi Nuclear Power Plant accident; Simulations based on identical input data

Sato, Yosuke*; Takigawa, Masayuki*; Sekiyama, Tsuyoshi*; Kajino, Mizuo*; Terada, Hiroaki   ; Nagai, Haruyasu  ; Kondo, Hiroaki*; Uchida, Junya*; Goto, Daisuke*; Qulo, D.*; Mathieu, A.*; Qurel, A.*; Fang, S.*; Morino, Yu*; von Schoenberg, P.*; Grahn, H.*; Brnnstrm, N.*; Hirao, Shigekazu*; Tsuruta, Haruo*; Yamazawa, Hiromi*; Nakajima, Teruyuki*

A model intercomparison of the atmospheric dispersion of Cs emitted following the Fukushima Daiichi Nuclear Power Plant accident was conducted by 12 models to understand the behavior of Cs in the atmosphere. The same meteorological data, horizontal grid resolution, and an emission inventory were applied to all the models to focus on the model variability originating from the processes included in each model. The multi-model ensemble captured 40% of the observed Cs events, and the figure-of-merit in space for the total deposition of Cs exceeded 80. Our analyses indicated that the meteorological data were most critical for reproducing the Cs events. The results also revealed that the differences among the models were originated from the deposition and diffusion processes when the meteorological field was simulated well. However, the models with strong diffusion tended to overestimate the Cs concentrations.