Graphical Abstract

Ishijima, K., K. Tsuboi, H. Matsueda, T. Y. Tanaka, T. Maki, T. Nakamura, Y. Niwa, and S. Hirao, 2022: Understanding temporal variations of atmospheric radon-222 around Japan using model simulations. J. Meteor. Soc. Japan, 100, 343-359.
https://doi.org/10.2151/jmsj.2022-017.
Graphical Abstract Published

Plain Language Summary: Temporal variations of atmospheric radon-222 (²²²Rn) concentrations observed at four stations in Japan were analyzed for the monthly and diurnal variations, and a series of synoptic scale high-²²²Rn events using an on-line transport model. A new calculation approach using hourly ²²²Rn values normalized to daily means enabled to extract diurnal cycles from highly variable ²²²Rn values in winter due to sporadic continental ²²²Rn outflows.

Highlights:

Diurnal cycles of absolute ²²²Rn concentrations observed and simulated are negligible or unclear, whereas d²²²Rn in November–March indicate clear diurnal cycles with notable daytime minima, mostly corresponding to PBLH maxima. At MNM, local ²²²Rn sources are not significant, and in model emissions around the station are also negligibly small.
These results suggest that variations of ²²²Rn concentrations in the near-surface atmosphere over the stations, which has been transported from the continental sources, are controlled by diurnal variations of the local PBLH.