Abstract
Following the Fukushima Daiichi Nuclear Power Plant accident on March 11, 2011, large amounts of 137Cs were released and transported through the atmosphere, leading to great radioactivity deposition in Japan. WRF-Chem model is often used to simulate the long-range transport of pollutants and has been widely applied in radionuclides release after the nuclear accident, i.e., the Fukushima accident. With microphysics, boundary layer schemes and many other schemes proposed and integrated into the source code, the WRF-Chem model has been upgrading all the time. However, few studies have adopted the latest version of WRF-Chem for simulation, and most work has been done based on WRF-Chem of version before 4.0. In order to get access to more proposed schemes available only in the new version of WRF-Chem and evaluate the performance of WRF-Chem in radionuclide transport modeling, the simulation of 137Cs transport in the Fukushima accident based on WRF-Chem 4.2 has been conducted. In this paper, the in-cloud (Roselle) and below-cloud (Baklanov) schemes, which have been proven to perform well in WRF-Chem 3.5, were integrated into WRF-Chem 4.2. The results of WRF-Chem 4.2 have been evaluated comprehensively with respect to cumulative deposition and atmospheric concentration. As the results indicated, WRF-Chem 4.2 reproduces the high deposition area in Fukushima and Nakadori well and reaches the good performance criteria with a RANK over 2. However, it presents an overestimated cumulative deposition amount and overestimated the further Gunma and Tochigi. As for concentration simulation, WRF-Chem 4.2 shows a RANK2 slightly over 1 and the plume events are not captured well. Further improvement should be done on the parameterizations of WRF-Chem 4.2.
