title: Annual variation in the atmospheric radon concentration in Japan.
abstract: Anomalous atmospheric variations in radon related to earthquakes have been observed in hourly exhaust-monitoring data from radioisotope institutes in Japan. The extraction of seismic anomalous radon variations would be greatly aided by understanding the normal pattern of variation in radon concentrations. Using atmospheric daily minimum radon concentration data from five sampling sites, we show that a sinusoidal regression curve can be fitted to the data. In addition, we identify areas where the atmospheric radon variation is significantly affected by the variation in atmospheric turbulence and the onshore-offshore pattern of Asian monsoons. Furthermore, by comparing the sinusoidal regression curve for the normal annual (seasonal) variations at the five sites to the sinusoidal regression curve for a previously published dataset of radon values at the five Japanese prefectures, we can estimate the normal annual variation pattern. By fitting sinusoidal regression curves to the previously published dataset containing sites in all Japanese prefectures, we find that 72% of the Japanese prefectures satisfy the requirements of the sinusoidal regression curve pattern. Using the normal annual variation pattern of atmospheric daily minimum radon concentration data, these prefectures are suitable areas for obtaining anomalous radon variations related to earthquakes.
authors.affiliation: Kobe Pharmaceutical University, 4-19-1, Motoyamakitamachi, Higashinada-ku, Kobe City, Hyogo, 658-8558, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Kobe Pharmaceutical University, 4-19-1, Motoyamakitamachi, Higashinada-ku, Kobe City, Hyogo, 658-8558, Japan. Electronic address: yasuoka@kobepharma-u.ac.jp.
authors.forename: Yumi
authors.initials: Y
authors.lastname: Yasuoka
authors.affiliation: Fukushima Medical University, 1, Hikarigaoka, Fukushima City, Fukushima, 960-1295, Japan.
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Omori
authors.affiliation: Tohoku University, 6-3, Aza Aoba, Aramaki, Aoba-ku, Sendai City, Miyagi, 980-8578, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nagahama
authors.affiliation: Hokkaido University of Science, Maeda 7-15-4-1, Teine-ku, Sapporo City, Hokkaido, 006-8585, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sanada
authors.affiliation: Tohoku University, 6-3, Aza Aoba, Aramaki, Aoba-ku, Sendai City, Miyagi, 980-8578, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Muto
authors.affiliation: Fukushima Medical University, 1, Hikarigaoka, Fukushima City, Fukushima, 960-1295, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Suzuki
authors.affiliation: Fukushima Medical University, 1, Hikarigaoka, Fukushima City, Fukushima, 960-1295, Japan.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Homma
authors.affiliation: Wakayama Medical University, 811-1, Kimiidera, Wakayama City, Wakayama, 641-8509, Japan.
authors.forename: Hayato
authors.initials: H
authors.lastname: Ihara
authors.affiliation: The Institute of Medical Science, The University of Tokyo (retired), 4-6-1, Shirokanedai, Minato-ku, Tokyo, 108-8639, Japan.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Kubota
authors.affiliation: Kobe Pharmaceutical University, 4-19-1, Motoyamakitamachi, Higashinada-ku, Kobe City, Hyogo, 658-8558, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Mukai
mesh_terms: D000396:Air Pollutants, Radioactive / Q000032:analysis*; D055866:Earthquakes; D007564:Japan; D008962:Models, Theoretical; D011834:Radiation Monitoring; D011886:Radon / Q000032:analysis*; D012621:Seasons
chemical_list: D000396:Air Pollutants, Radioactive; D011886:Radon
keywords: Asian monsoons; Atmospheric radon; Atmospheric turbulence; Japan; Seasonal variation; Sinusoidal model