Meteorological Notes for Understanding the Transport of Beryllium-7 in the Troposphere

By using information of beryllium-7 (7Be) and its transport, we can obtain important information of the atmospheric transport process which cannot be obtained by atmospheric physical quantities alone. However, in proceeding with the 7Be transport study, one difficulty comes from an integrated research between health physics and meteorology. This review is an attempt to overcome this difficulty, describing meteorological aspects in the 7Be transport process toward health physicists. We stress that (a) 7Be particles do not come from straight above but from far away, and (b) the way of thinking is different depending on timescale. In (a), backward trajectories are calculated, showing that trajectories strongly depend on season. In winter, spring, and autumn, particles generally come from high altitudes in high latitudes, which can be understood by using the notion of potential temperature. In (b), 7Be concentrations are largely influenced by daily disturbances in short timescales, showing large daily variations. In long timescales, they take almost equilibrium values with seasonal variations. We discuss extremely high and low concentrations as examples of short timescales, and seasonality as examples of long timescales. In all the examples, it is important to consider where 7Be particles come from and what happens along the trajectories.