Review of model intercomparison projects (MIPs) of atmospheric dispersion model for Cs emitted from Fukushima Daiichi Nuclear Power Plant; MIPs with identical source term and meteorological data

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

Two Model Intercomparison of Projects (MIPs) of atmospheric dispersion model targeting on Cs released from Fukushima Daiichi Nuclear Power Plant (FDNPP) on March 2011 were conducted. Both MIPs were conducted using an identical source term of Cs, identical meteorological data, and the same horizontal grid resolution (3 km and 1 km) to exclude the uncertainties of the model originated from them. Our analyses indicated that most of the model well simulated the atmospheric Cs obtained from the operational aerosol sampling of the national suspended particle matter network. Our analyses also indicated that meteorological data were most critical for reproducing the atmospheric Cs events, and the extent of the horizontal diffusion and the deposition were critical if the meteorological field was reasonably simulated. The comparison of the results between the two MIPs elucidated that the fine grid resolution is required to simulate atmospheric Cs in the vicinity of FDNPP, but the use of the fine grid resolution does not always improve the performance of the models especially for areas distant from the FDNPP. The results of both MIPs elucidated that the good performance of some models improved the performance of the multimodel, highlighting the advantage of using a multimodel ensemble.