Beryllium 7 radionucleide as a tracer of vertical air mass transport in the troposphere

7Be is a cosmogenic radionucleide (half life 53.3 days) produced by galactic cosmic rays and solar energetic particles in the upper atmosphere and is a potentially useful tracer of the short-term atmospheric air mass motion. We have measured the surface 7Be concentration in Tokyo (35N, 139E) since 2002 with a high-volume air sampler. The present data of surface Be-7 concentrations exhibit the enhancements in spring and autumn and the seasonal enhancements are not associated with scavenging by precipitation. In order to explain the measured enhancements, we propose the possibility of the downward and upward atmospheric flows in the troposphere caused by a pair of traveling anticyclone and extratropical cyclone that passes over Japan in spring and autumn with a period of a few days.