TY - JOUR
T1 - Variation of atmospheric radon concentration with bimodal seasonality
AU - Omori, Yasutaka
AU - Tohbo, Izumi
AU - Nagahama, Hiroyuki
AU - Ishikawa, Yoichi
AU - Takahashi, Masato
AU - Sato, Hiroaki
AU - Sekine, Tsutomu
N1 - Funding Information:
The authors would like to thank P.F. Biagi, K. Hattori, and D. Ouzounov for their fruitful discussions and the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and READY website. This paper was improved by valuable comments from three anonymous reviewers, which we also acknowledge. This study was conducted as a part of the Global Center-Of-Excellence program, “Global Education and Research Center for Earth and Planetary Dynamics”, of Tohoku University. Y. Omori is financially supported by the JSPS Research Fellowship for Young Scientists. I. Tohbo acknowledges financial help from the Support Program Graduate School Education by Graduate School of Science, Tohoku University.
Copyright:
Copyright 2009 Elsevier B.V., All rights reserved.
PY - 2009/10
Y1 - 2009/10
N2 - Atmospheric radon (222Rn) concentration has been measured on the Oshika Peninsula, northeastern Japan, since July 2005 to assess fluctuations of natural gamma-ray dose rate. The radon concentration shows a typical diurnal cycle with a minimum in daytime and a maximum in nighttime generated by the different strength in atmospheric convection, which is well observed in the world. On seasonal time scale, monthly change of the daily minimums has a monomodal seasonality with a maximum in winter and a minimum in summer, while monthly changes of the daily averages and maximums exhibit a bimodal one with maximum both in winter and summer. The origins of air masses arriving to the measuring site characterized by the Asian monsoonal cycle appear to explain the monomodal seasonality rather than the bimodal one. In addition, the atmospheric stability is not strong enough to cause the radon increase in summer. These results suggest that the bimodal cycle is possibly decomposed of two phases: one is attributed to the seasonal difference in radon inflow by atmospheric circulation and the other in radon exhalation from the earth surface.
AB - Atmospheric radon (222Rn) concentration has been measured on the Oshika Peninsula, northeastern Japan, since July 2005 to assess fluctuations of natural gamma-ray dose rate. The radon concentration shows a typical diurnal cycle with a minimum in daytime and a maximum in nighttime generated by the different strength in atmospheric convection, which is well observed in the world. On seasonal time scale, monthly change of the daily minimums has a monomodal seasonality with a maximum in winter and a minimum in summer, while monthly changes of the daily averages and maximums exhibit a bimodal one with maximum both in winter and summer. The origins of air masses arriving to the measuring site characterized by the Asian monsoonal cycle appear to explain the monomodal seasonality rather than the bimodal one. In addition, the atmospheric stability is not strong enough to cause the radon increase in summer. These results suggest that the bimodal cycle is possibly decomposed of two phases: one is attributed to the seasonal difference in radon inflow by atmospheric circulation and the other in radon exhalation from the earth surface.
KW - Atmospheric radon concentration
KW - Seasonal variation
KW - The Asian monsoonal cycle
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U2 - 10.1016/j.radmeas.2009.10.077
DO - 10.1016/j.radmeas.2009.10.077
M3 - Article
AN - SCOPUS:70949098832
VL - 44
SP - 1045
EP - 1050
JO - Radiation Measurements
JF - Radiation Measurements
SN - 1350-4487
IS - 9-10
ER -