[AAS04-P31] Variations of atmospheric Radon-222 concentration observed at JMA stations
In this study, we analyze the observed and model simulated atmospheric 222Rn concentration, to understand the transport process of land-origin atmospheric tracer as well as to validate the GSAM-TM. For example, the model well reproduces high 222Rn peaks, which are frequently observed at Minamitorishima (MNM; 24.28°N, 153.98°E) and Chichijima (CCJ; 27.09°N, 142.19°E) in winter to spring. Especially in winter, there are many cases that a high peak is first observed at CCJ and one day after at MNM. They are mainly produced by a cold front moving eastward with dense 222Rn behind the frontal line. The peak height at MNM is about two-thirds of that at CCJ. It is slightly smaller than that expected from decay by the 3.8 days half-life (about four-fifths), because dense 222Rn trapped by the front is diluted mainly by diffusion while transported. The model also well reproduces such peak attenuation degree. More details and results of 222Rn-age tracer simulations as well as of other JMA station will also be discussed in our presentation.
Acknowledgements. We sincerely thank all members of the JMA for operating 222Rn measurement systems at JMA monitoring stations