Concentrations of 222RN, its short-lived daughters and 212PB and their ratios under complex atmospheric conditions and topography

Toshio Kataoka, Eiji Yunoki, Mitsuo Shimizu, Tadashige Mori, Osamu Tsukamoto, Satoshi Takahashi, Hironori Fudeyasu, Yukitaka Ohashi, Ken Sahashi, Toshihiko Maitani, Koh'ichi Miyashita, Toru Iwata, Takayuki Sasaki, Yoko Fujikawa, Akira Kudo, Roger H. Shaw

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Abstract

Atmospheric activity concentrations of 212Pb and short-lived 222Rn daughters, together with meteorological elements, have been observed continuously at three sites at Kamisaibara Village in Japan. In addition, atmospheric activity concentration of 222Rn, equilibrium-equivalent concentration of 222Rn and conditions of the lower atmosphere were observed for three intensive observation periods at Akawase, one of the three sites in Kamisaibara Village. The equilibrium-equivalent concentration of 222Rn is almost the same as the atmospheric activity concentration of short-lived 222Rn daughters. The activity concentrations of 212Pb and the short-lived 222Rn daughters and their ratio were low in the daytime owing to convective mixing, and high at night owing to the surface-based inversion during periods of no precipitation. Their variations have several patterns corresponding to the scale of the drainage wind or weak mixing. Mechanical mixing due to strong winds through both day and night during the first and second observation periods made the atmospheric activity concentrations of 212Pb and the short-lived 222Rn daughters continuously low. However, their ratios were continuously high during the first period yet continuously low during the second period. This difference can be explained by the effect of extraction of 220Rn and 222Rn due to strong winds and snow cover. There were also cases in which the ratio of the atmospheric activity concentration of 212Pb to that of the short-lived 222Rn daughters at night was equal to or less than the ratio in the daytime. This inverse trend, as in the period of no precipitation mentioned above, is considered to be due to near-neutral conditions on these nights. We find a difference in the ratio of the equilibrium-equivalent concentration of 222Rn (the activity concentration of short-lived 222Rn daughters) to the activity concentration of 222Rn during the first observation period and that during the second. The difference can be explained by snow cover on the ground. We also find differences among the ratios of the activity concentration of the short-lived 222Rn daughters to that of 222Rn during the three observation periods. These differences can be explained by the submergence of paddy fields.

Original languageEnglish
Pages (from-to)219-249
Number of pages31
JournalBoundary-Layer Meteorology
Volume107
Issue number1
DOIs
Publication statusPublished - Apr 1 2003

Keywords

  • Concentration of Pb
  • Concentration of Rn
  • Concentration of short-lived Rn daughters
  • Snow depth
  • Submergence of paddy fields

ASJC Scopus subject areas

  • Atmospheric Science

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    Kataoka, T., Yunoki, E., Shimizu, M., Mori, T., Tsukamoto, O., Takahashi, S., Fudeyasu, H., Ohashi, Y., Sahashi, K., Maitani, T., Miyashita, K., Iwata, T., Sasaki, T., Fujikawa, Y., Kudo, A., & Shaw, R. H. (2003). Concentrations of 222RN, its short-lived daughters and 212PB and their ratios under complex atmospheric conditions and topography. Boundary-Layer Meteorology, 107(1), 219-249. https://doi.org/10.1023/A:1021540506779