Short term variations of ⁷Be, ¹⁰Be concentrations in atmospheric boundary layer

To compare meteorological conditions, short term variations of atmospheric concentrations of ⁷Be (T_1/2 = 53.3 days) and ¹⁰Be (T_1/2 = 1.5 × 10⁶ years) were investigated at Tokyo and Fukuoka, Japan, and Pacific Ocean nearby Japan. Atmospheric concentrations of ⁷Be and ¹⁰Be at anticyclone condition were higher than that at cyclone condition to a factor of 2-10. Because of being influenced by re-suspended components from soil (¹⁰Be/⁷Be > 1000), temporal variability of ¹⁰Be/⁷Be was high in daytime and low in nighttime. But when corrected for re-suspended component using Al concentration as an indicator of soil the ¹⁰Be/⁷Be ratio was constant. Comparing ⁷Be and ¹⁰Be concentrations with ²¹²Pb concentration as soil-generated component, we make a conclusion that high ⁷Be and ¹⁰Be concentration air mass is brought into boundary layer by high convection at daytime. Those diurnal variations were not observed in marine boundary layer. When cyclone passed through Fukuoka to Tokyo, which is 12 h behind, ⁷Be and ¹⁰Be concentrations also decreased with 12 h lag between Fukuoka and Tokyo. The ¹⁰Be/⁷Be ratio was constant during anticyclone to cyclone condition, and between Tokyo and Fukuoka. We conclude that after stratospheric aerosols enter into the upper troposphere they reside there for a certain period and mix uniformly in horizontal strata; later they are transported down to lower troposphere by anticyclone and penetrate into ground level air at daytime by convective strong mixing of boundary layer.