[AAS01-P04] Analysis of high Radon-222 concentration events using NICAM
Keywords:NICAM, Radon-222, Event
Frequency of the occurrence of high 222Rn events at the monitoring stations on remote islands in both hemispheres are comparable between the observations and models. Seasonal changes of the frequency are also well reproduced by models, with the correlation coefficients almost exceeding 0.6. These results imply that NICAM is capable of simulating synoptic atmospheric fluctuations for 222Rn transport. Temporal changes of 222Rn around the event are reasonably simulated by d56 and d14, but d223 cannot reproduce the peak sharpness observed, due to the coarse horizontal resolution. Meridional distributions of 222Rn and equivalent potential temperature around the stations for the event time show comparable gradients in d56 and d14, especially indicating tight trapping of 222Rn behind the front at a station in the southeast of Japan. On the other hand, less enhancement of 222Rn, by up to 20 %, accompanied by the milder slopes on the both sides around the station are seen for d223. Throughout analyses of high 222Rn events in this study, d56 and d14 show comparable performance, also mostly reproducing the observed temporal variability. Although there is no observation data to validate spatial distribution of 222Rn around cold front, it is probably reasonable from our analysis that the horizontal resolution of better than 50-60km is required for simulating atmospheric 222Rn variations.