Long-distance transport of radioactive plume by nocturnal local winds

Abstract

Radioactive plumes can spread far and wide depending on wind conditions. The plumes often frequently reached the Tokyo metropolitan area, which is approximately 200 km away from the Fukushima Daiichi nuclear power plant, under spatially heterogeneous wind fields in March 2011. To reduce exposure to radioactive plumes, the behaviour of the plumes must be known. However, the transport mechanism of radioactive plumes is not fully understood. Using a regional climate model, we show that multiple diurnal cycle processes play a key role in the frequent transport of radioactive plumes to the Tokyo metropolitan area. The observed data and hindcast results indicate that the radioactive plume moves along the local winds, which comprise the northeasterly local wind (NELW) associated with the meso-scale low-pressure system (meso-low) and the northerly sea wind (NSW) during the night. The long-term analysis and sensitivity simulations also show the nocturnal processes that the NELW caused by the meso-low and the NSW are formed east of the Tokyo metropolitan area and from Fukushima offshore east of the Tokyo metropolitan area, respectively, when neither winter monsoons nor extra-tropical cyclones are predominant. These findings indicate that the radioactive plumes could reach faraway places frequently via nocturnal local processes.

Estimation of Dietary Intake of Radionuclides and Effectiveness of Regulation after the Fukushima Accident and in Virtual Nuclear Power Plant Accident Scenarios

“…As described in Methods, validation of the regional trade of foods and the transport model was reported elsewhere [6,12]. A unit of μSv month −1 was used since the dose might be subject to temporary change.…”

“…Details and the validity of the transport model were reported previously [12]. Two emission conditions were used: actual and maximum emission conditions.…”

Precipitation Redistribution Method for Regional Simulations of Radioactive Material Transport During the Fukushima Daiichi Nuclear Power Plant Accident

“…GPV‐MSM presents the results of the mesoscale climate model, whose domain covers the islands of Japan and its near seas, and it is provided by JMA. In this study, applying GPV‐MSM data is based on the study by Yoshikane et al (). The GPV‐MSM data used in this study are provided by the GPV Data Archiving in Kitsuregawa laboratories, IIS, The University of Tokyo.…”

“…According to the previous studies, the formation process of the highly concentrated distribution of 137 Cs in the Kanto region from 20 March through 23 March, hereafter called the hot spot, was such that the radioactive plume was transported from the FDNPP to the south by a northerly wind, passed through the metropolitan area via a northeasterly wind, and was deposited by precipitation (Kinoshita et al, ; Morino et al, ; Srinivas et al, ; Terada et al, ). In addition, the more precise process was investigated by Yoshikane et al (). They found that the northeasterly wind was associated with a mesoscale low‐pressure system, and they concluded that the transportation of the radioactive materials was related to the diurnal regional climate cycle in this area (Yoshikane et al, ).…”

“…In addition, the more precise process was investigated by Yoshikane et al (). They found that the northeasterly wind was associated with a mesoscale low‐pressure system, and they concluded that the transportation of the radioactive materials was related to the diurnal regional climate cycle in this area (Yoshikane et al, ). However, the numerical calculations using atmospheric transport models had uncertainties that depended on each model's scheme and data set.…”