Advection and dispersion analysis of radon and its progenies in the East Asian region, and the relation with the winter thunderstorm activity

. A transport model of radon and its progeny nuclides for the Asian region was developed based on RAMS and HYP ACT models to determine the mechanism for occurrences of lightning during the winter season in the coastal areas of the Sea of Japan. Using this model, radon dispersion from September 2002 to October 2003 was evaluated. The analyzed concentration distribution clarifies that seasonal winds carry a large amount of radon from the Asian continent to the coastal area of the Sea of Japan. A large concentration of the continent-originated radon stays in the area between the ground and the altitude of 3 km msl. This result suggests that regions with strong electric fields in winter thunderclouds may be filled with a large concentration of radon. Furthermore, it suggests that beta and gamma rays emitted by radon progenies cause electromagnetic showers in this region.