Model behavior regarding in- and below-cloud 137Cs wet scavenging following the Fukushima accident using 1-km-resolution meteorological field data

Shuhan Zhuang; Sheng Fang; Daisuke Goto; Xinwen Dong; Yuhan Xu; Li Sheng

doi:10.1016/j.scitotenv.2023.162165

Model behavior regarding in- and below-cloud ¹³⁷Cs wet scavenging following the Fukushima accident using 1-km-resolution meteorological field data

Sci Total Environ. 2023 May 10:872:162165. doi: 10.1016/j.scitotenv.2023.162165. Epub 2023 Feb 11.

Authors

Shuhan Zhuang¹, Sheng Fang², Daisuke Goto³, Xinwen Dong¹, Yuhan Xu¹, Li Sheng⁴

Affiliations

¹ Institute of Nuclear and New Energy Technology, Collaborative Innovation Centre of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084, China.
² Institute of Nuclear and New Energy Technology, Collaborative Innovation Centre of Advanced Nuclear Energy Technology, Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084, China. Electronic address: fangsheng@tsinghua.edu.cn.
³ National Institute for Environmental Studies,16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
⁴ Earth System Modeling and Prediction Center, China Meteorological Administration, Beijing 100081, China.

PMID: 36775160
DOI: 10.1016/j.scitotenv.2023.162165

Abstract

Wet deposition remains an important source of uncertainty in modeling of the atmospheric transport of ¹³⁷Cs following the Fukushima Daiichi Nuclear Power Plant accident. Its behavior is often difficult to investigate owing to the limited resolution of meteorological field data and inconsistent model implementations. This study investigated the detailed behavior of 25 combinations of in- and below-cloud wet scavenging models using high-resolution (1 km × 1 km) meteorological input. These combinations were all implemented in the Weather Research and Forecasting-Chemistry model, thereby enabling consistent evaluation. The 1-km-resolution simulations were compared with simulations obtained previously using 3-km-resolution meteorological field data. Results revealed that rainfall of <1 mm/h is critical for simulation accuracy. The 1-km results revealed better representation of rainfall than that revealed by the 3-km results, but with spatiotemporal variability in accuracy. Owing to their sensitivity to rainfall, single-parameter wet deposition models showed improvements in performance in the 1-km simulations relative to that in the 3-km simulations. The multiparameter models showed more robust performance in terms of both simulations, and the Roselle-Mircea model presented the best performance among the 25 models considered. Wind transport showed substantial influence on the removal of atmospheric ¹³⁷Cs, and it was nonnegligible even during periods in which wet deposition was dominant. The 1-km-resolution simulations effectively reproduced local-scale ¹³⁷Cs concentrations but with deviations in timing, mainly because of biased wind direction. These findings indicate the necessity for a refined wind and dispersion model for local-scale simulation of ¹³⁷Cs concentration.

Keywords: Below-cloud scavenging; Fukushima Daiichi Nuclear Power Plant accident; In-cloud scavenging; Online-coupled modeling; WRF-Chem; Wet deposition.