Development of three-dimensional numerical model for Rn and its decay products coupled with a mesoscale meteorological model, 1; Model description and validation

Nishizawa, Masato; Nagai, Haruyasu  ; Chino, Masamichi; Moriizumi, Jun*; Yoshioka, Katsuhiro*; Okura, Takehisa ; Yamazawa, Hiromi*; Iida, Takao*; Mukai, Hitoshi*; Tojima, Yasunori*; Oda, Nobukazu*; Shimano, Fujio*

A three-dimensional Eulerian numerical model for Rn and its decay products coupled with a mesoscale meteorological model has been developed and applied to the reproduction of the daily and monthly variations of Rn concentration, the monthly variation of Pb deposition in Japan and the temporal variation of dose rate after the cold front passage in the coastal area of the Japan Sea for the verification of model capability. The results are as follows: (1) The model reproduced the monthly variation of surface Rn concentration in remote islands, but underestimated inland concentration due to coarse vertical resolution near the surface of the model. (2) The model reproduced the seasonal variation of the observed and the long-term yearly averaged Pb depositions as long as precipitations are predicted precisely. (3) The model reproduced the rise of dose rate in precipitation accompanied with the cold front passage. In particular, Rn decay products in melted snow and graupel contributed the rise of dose rate.