Time series analysis of atmospheric 222Rn concentrations and meteorological factors in Japan

The aim of this study is to examine a phenomenon of material transports in the atmosphere. To consider the meteorological factors contributing to the variation of atmospheric 222Rn concentration, time series analysis (1) which contained the trend model, the power spectrum and the correlation function has been applied to the relationship of 222Rn concentrations observed at Kanazawa, Nagoya and Ogasawara-Hahajima with meteorological factors. The analyzing period was from December 8 to 17, 1995. During this period two low pressures passed above Japan, and we observed then rapid increases of 222Rn concentrations at Ogasawara-Hahajima. We confirmed from the time series analysis at Nagoya that the 222Rn concentrations correlated with atmospheric pressure, temperature and wind speed. In addition, relative humidity shows a similar cyclic variation. In addition to this analysis, we examined the isentropic backward trajectory of air mass at Ogasawara-Hahajima. It gives a good account of the relation between the 222Rn concentrations and transport direction of air mass. The trajectory analysis enables us to discuss the long distance transport of 222Rn in relation to snow depth on the continent. (author)