Annual variation in the atmospheric radon concentration in Japan

Yuka Kobayashi, Yumi Yasuoka, Yasutaka Omori, Hiroyuki Nagahama, Tetsuya Sanada, Jun Muto, Toshiyuki Suzuki, Yoshimi Homma, Hayato Ihara, Kazuhito Kubota, Takahiro Mukai

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)110-118
Number of pages9
JournalJournal of Environmental Radioactivity
Publication statusPublished - 2015


  • Asian monsoons
  • Atmospheric radon
  • Atmospheric turbulence
  • Japan
  • Seasonal variation
  • Sinusoidal model


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